Radiology Review Manual
6th Edition

Musculoskeletal System
Differential Diagnosis of Musculoskeletal Disorders
Differential-Diagnostic Gamut of Bone Disorders
Conditions to be considered = “dissect bone disease with a DIATTOM”
  • Dysplasia + Dystrophy
  • Infection
  • Anomalies of development
  • Tumor + tumorlike conditions
  • Trauma
  • Osteochondritis + ischemic necrosis
  • Metabolic disease
DYSPLASIA = disturbance of bone growth
DYSTROPHY = disturbance of nutrition
Limping child
1–4 Years
    • Developmental dysplasia of hip
    • Toddler’s fracture
    • Nonaccidental trauma
    • Other fractures
    • Foreign body
    • Diskitis
    • Septic arthritis
    • Osteomyelitis
    • Transient synovitis of hip
4–10 Years
    • Septic arthritis
    • Osteomyelitis
    • Transient synovitis of hip
    • Diskitis
    • Juvenile rheumatoid arthritis
    • Legg-Perthes disease
10–15 Years
    • Stress fracture
    • Osteochondritis dissecans
    • Osgood-Schlatter disease
    • Juvenile rheumatoid arthritis
    • Ankylosing spondylitis
    • Septic arthritis
    • Osteomyelitis
    • Epiphyseolysis of femoral head
Delayed bone age
    • Familial
    • IUGR
    • Hypopituitarism
    • Hypothyroidism
    • Hypogonadism (Turner syndrome)
    • Cushing disease, steroid therapy
    • Diabetes mellitus
    • Rickets
    • Malnutrition
    • Irradiation of brain (for cerebral tumor / ALL)
    • Congenital heart disease
    • Renal disease
    • GI disease: celiac disease, Crohn disease, ulcerative colitis
    • Anemia
    • Bone marrow transplantation (<5 years of age)
    • Trisomies
    • Noonan disease
    • Cornelia de Lange syndrome
    • Cleidocranial dysplasia
    • Lesch-Nyhan disease
    • Metatrophic dwarfism
Bone sclerosis
Diffuse Osteosclerosis
mnemonic: 5 M’S To PROoF
  • Metastases
  • Myelofibrosis
  • Mastocytosis
  • Melorheostosis
    Metabolic: hypervitaminosis D, fluorosis, hypothyroidism, phosphorus poisoning
  • Sickle cell disease
  • Tuberous sclerosis
  • Pyknodysostosis, Paget disease
  • Renal osteodystrophy
  • Osteopetrosis
  • Fluorosis
Constitutional Sclerosing Bone Disease
  • Engelmann-Camurati disease
  • Infantile cortical hyperostosis
  • Melorheostosis
  • Osteopathia striata
  • Osteopetrosis
  • Osteopoikilosis
  • Pachydermoperiostosis
  • Pyknodysostosis
  • Van Buchem disease
  • P.2

  • Williams syndrome
Sclerosing Bone Dysplasia
    • = failure in resorption + remodeling of primary immature spongiosa by osteoclasts
    • accumulation of calcified cartilage matrix packing the medullary cavit
    Target sites: tubular + flat bones, vertebrae, skull base, ethmoids, ends of clavicle
    • Osteopetrosis
    • Pyknodysostosis
    • = errors in resorption + remodeling of secondary spongiosa
    • focal densities / striations
    • Enostosis
    • Osteopoikilosis
    • Osteopathia striata
    • = disequilibrium between periosteal bone formation + endosteal bone resorption
      Target sites: cortex of tubular + flat bones, calvaria, bones of upper face, tympanic parts of temporal bone, vomer, medial pterygoid
    • Progressive diaphyseal dysplasia
    • Hereditary multiple diaphyseal sclerosis (Ribbing disease)
    • Hyperostosis corticalis generalisata
      • Van Buchem disease
      • Sclerosteosis (Truswell-Hansen disease)
      • Worth disease
      • Nakamura disease
    • Diaphyseal dysplasia with anemia
    • Oculodento-osseous dysplasia
    • Trichodento-osseous dysplasia
    • Kenny-Caffey syndrome
    • predominantly endochondral disturbance
      • Dysosteosclerosis
      • Metaphyseal dysplasia (Pyle disease)
      • Craniometaphyseal dysplasia
      • Frontometaphyseal dysplasia
    • predominantly intramembranous defects
      • Melorheostosis
      • Craniodiaphyseal dysplasia
      • Lenz-Majewski hyperostotic dwarfism
      • Progressive diaphyseal dysplasia
Solitary Osteosclerotic Lesion
    • Bone island
    • Old bone infarct
    • Aseptic / ischemic / avascular necrosis
    • trauma: callus formation in stress fracture
    • benign tumor: fibrous cortical defect / nonossifying fibroma, brown tumor; bone cyst
    • malignant tumor: lytic metastasis after radiation, chemo-, hormone therapy
    (low-grade chronic infection / healing infection)
    • Osteoid osteoma
    • Chronic / healed osteomyelitis: bacterial, tuberculous, fungal
    • Sclerosing osteomyelitis of Garré
    • Granuloma
    • Brodie abscess
    • Osteoma
    • Osteoblastoma
    • Ossifying fibroma
    • Healed fibrous cortical defect
    • Enchondroma / osteochondroma
    • Osteoblastic metastasis (prostate, breast)
    • Lymphoma
    • Sarcoma: osteo-, chondro-, Ewing sarcoma
    • Sclerotic phase of Paget disease
    • Fibrous dysplasia
Cortical Sclerotic Lesion in Child
  • Osteoid osteoma
  • Stress fracture
  • Chronic osteomyelitis
  • Healed fibrous cortical defect
Multiple Osteosclerotic Lesions
    • Osteopoikilosis
    • Enchondromatosis = Ollier disease
    • Melorheostosis
    • Multiple osteomas: associated with Gardner syndrome
    • Osteopetrosis
    • Pyknodysostosis
    • Osteopathia striata
    • Chondrodystrophia calcificans congenita= congenital stippled epiphyses
    • Multiple epiphyseal dysplasia = Fairbank disease
    • Mastocytosis = urticaria pigmentosa
    • Tuberous sclerosis
Bone-within-bone Appearance
= endosteal new bone formation
  • Normal
    • thoracic + lumbar vertebrae (in infants)
    • growth recovery lines (after infancy)
  • Infantile cortical hyperostosis (Caffey)
  • Sickle cell disease / thalassemia
  • Congenital syphilis
  • Osteopetrosis / oxalosis
  • Radiation
  • Acromegaly
  • Paget disease
  • Gaucher disease

mnemonic: BLT PLT RSD RSD
  • Bismuth ingestion
  • Lead ingestion
  • Thorium ingestion
  • Petrosis (osteopetrosis)
  • Leukemia
  • Tuberculosis
  • Rickets
  • Scurvy
  • Dtoxicity (vitamin D)
  • RSD (reflex sympathetic dystrophy)
Dense Metaphyseal Bands
mnemonic: DENSE LINES
  • D-vitamin intoxication
  • Elemental arsenic and heavy metals (lead, bismuth, phosphorus)
  • Normal variant
  • Systemic illness
  • Estrogen to mother during pregnancy
  • Leukemia
  • Infection (TORCH), Idiopathic hypercalcemia
  • Never forget healed rickets
  • Early hypothyroidism (cretinism)
  • Scurvy, congenital Syphilis, Sickle cell disease
    also: methotrexate therapy
= decrease in bone quantity maintaining normal quality
  • increased radiolucency of bone:
    • vertical striations in vertebral bodies
    • accentuation of tensile + compressive trabeculae of proximal femur
    • reinforcement lines (= bone bars) crossing marrow cavity about knee
    • cortical resorption of 2nd metacarpal:
      • measuring outer cortical diameter (W) and width of medullary cavity (m) at midportion of bone and reporting combined cortical thickness (CCT)
    • subperiosteal tunneling
    • Osteoporosis = decreased osteoid production
    • Osteomalacia = undermineralization of osteoid
    • Hyperparathyroidism
    • Multiple myeloma / diffuse metastases
    • Drugs
    • Mastocytosis
    • Osteogenesis imperfecta
= reduced bone mass of normal composition secondary to
  • osteoclastic resorption (85%) (trabecular, endosteal, intracortical, subperiosteal)
  • osteocytic resorption (15%)
Incidence: 7% of all women aged 35–40 years; 1 in 3 women > age 65 years
    • Osteogenesis imperfecta
      • The only osteoporosis with bending!
    • Homocystinuria
  • IDIOPATHIC (bone loss begins earlier + proceeds more rapidly in women)
    1. Juvenile osteoporosis: <20 years
    2. Adult osteoporosis: 20–40 years
    3. Postmenopausal osteoporosis: >50 years (40–50% lower trabecular bone mineral density in elderly than in young women)
    4. Senile osteoporosis: >60 years progressively decreasing bone density at a rate of 8% in females; 3% in males
    • scurvy; protein deficiency (malnutrition, nephrosis, chronic liver disease, alcoholism, anorexia nervosa, kwashiorkor, starvation), calcium deficiency
    • Cushing disease, hypogonadism (Turner syndrome, eunuchoidism), hyperthyroidism, hyperparathyroidism, acromegaly, Addison disease, diabetes mellitus, pregnancy, paraneoplastic phenomenon in liver tumors
    • decrease / same / increase in spinal trabecular bone; rapid loss in appendicular skeleton
  • IMMOBILIZATION = disuse osteoporosis
    • infiltration by lymphoma / leukemia (ALL), multiple myeloma, diffuse metastases, marrow hyperplasia secondary to hemolytic anemia
    • heparin (15,000–30,000 U for >6 months), methotrexate, corticosteroids, excessive alcohol consumption, smoking, Dilantin
    • Sudeck dystrophy, transient osteoporosis of hip, regional migratory osteoporosis of lower extremities
  • serum calcium, phosphorus, alkaline phosphatase frequently normal
  • hydroxyproline may be elevated during acute stage
    • measures primarily cortical bone of appendicular bones, single-energy I-125 radioisotope source
      Site: distal radius (= wrist bone density), os calcis
      Dose: 2–3 mrem
      Precision: 1–3%
    • radioactive energy source with two photon peaks; should be reserved for patients <65 years of age because of interference from osteophytosis + vascular calcifications
      Site: vertebrae, femoral neck
      Dose: 5–10 mrem
      Precision: 2–4%
    • = area projectional technique for quantitative bone density measurement

      Site: distal radius, calcaneus
      Dose: low
      Precision: 0.5–2%
    • Most widely used & most precise technique!
    • = quantitative digital radiography
    • = beams with two distinct energy levels allow identification of trabecular from cortical bone
    • • has replaced dual-photon absorptiometry and is produced by x-ray tube with higher radiation flux than radioisotope source
    Site: lumbar spine, femoral neck, whole body, forearm
    Dose: <3 mrem; Precision: 1–2%
    Data collected:
    • BMD (bone marrow density) value (g/cm2)
    • %BMD compared to young adults
    • %BMD compared to age-matched adults
    • T-score (SD of young-adult mean)
    • Z-score (SD of age-matched mean)
    • = determines true volumetric density (mg/cm3)
    • • high-turnover cancellous bone is important for vertebral strength and has high responsiveness
    • • trabecular bone + low-turnover compact bone can be measured separately
    • compared to external bone mineral reference phantom scanned simultaneously with patient to calibrate CT attenuation measurements
    • 10-mm–thick section with gantry angle correction through center of vertebral body
      Site: vertebrae L1–L3, other sites
      Use: assessment of vertebral fracture risk; measurement of age-related bone loss; follow-up of osteoporosis + metabolic bone disease
      (a) single energy: 300–500 mrem; 6–25% precision
      (b) dual energy: 750–800 mrem;5–10% precision
    • Most sensitive technique!
    = exact 3-dimensional localization of target volumes with multisection data acquisition capability covering a large volume of bone
    Site: distal radius
    Location: axial skeleton (lower dorsal + lumbar spine), proximal humerus, neck of femur, wrist, ribs
    • Radiographs are insensitive prior to bone loss of 25–30%
    • Bone scans do NOT show a diffuse increase in activity
      Diagnosis T-score Management Follow-up
      Normal >1 prevention 3 years
      Osteopenia <-1 and >-2.5 prevention or therapy 2 years
      Osteopororis <-2.5 therapy 1 year
    • decreased number + thickness of trabeculae
    • cortical thinning (endosteal + intracortical resorption)
    • juxtaarticular osteopenia with trabecular bone predominance
    • delayed fracture healing with poor callus formation
    • (DDx: abundant callus formation in osteogenesis imperfecta + Cushing syndrome)
      Cx: (1) Fractures at sites rich in labile trabecular bone (eg, vertebrae, wrist) in postmenopausal osteoporosis
      (2) Fractures at sites containing cortical + trabecular bone (eg, hip) in senile osteoporosis
      Rx: calcitonin, sodium fluoride, diphosphonates, parathyroid hormone supplements, estrogen replacement
Osteoporosis of Spine
  • diminished radiographic density
  • vertical striations (= marked thinning of transverse trabeculae with relative accentuation of vertical trabeculae along lines of stress)
  • accentuation of endplates
  • “picture framing” (= accentuation of cortical outline with preservation of external dimensions secondary to endosteal + intracortical resorption)
  • compression deformities with protrusion of intervertebral disks:
    • biconcave vertebrae
    • Schmorl nodes
    • wedging
    • decreased height of vertebrae
  • absence of osteophytes
= accumulation of excessive amounts of uncalcified osteoid with bone softening + insufficient mineralization of osteoid due to
  • high remodeling rate: excessive osteoid formation + normal / little mineralization
  • low remodeling rate: normal osteoid production + diminished mineralization
  • dietary deficiency of vitamin D3 + lack of solar irradiation
  • deficiency of metabolism of vitamin D:
    • chronic renal tubular disease
    • chronic administration of phenobarbital (alternate liver pathway)
    • diphenylhydantoin (interferes with vitamin D action on bowel)
  • decreased absorption of vitamin D:
    • malabsorption syndromes (most common)
    • partial gastrectomy (self-restriction of fatty foods)
  • decreased deposition of calcium in bone
    • diphosphonates (for treatment of Paget disease)
Histo: excess of osteoid seams + decreased appositional rate
  • bone pain / tenderness; muscular weakness
  • serum calcium slightly low / normal
  • decreased serum phosphorus
  • elevated serum alkaline phosphatase

  • uniform osteopenia
  • fuzzy indistinct trabecular detail of endosteal surface
  • coarsened frayed trabeculae decreased in number + size
  • thin cortices of long bone
  • bone deformity from softening:
    • hourglass thorax
    • bowing of long bones
    • acetabular protrusion
    • buckled / compressed pelvis
    • biconcave vertebral bodies
  • increased incidence of insufficiency fractures
  • pseudofractures = Looser zones
  • mottled skull
Localized / Regional Osteopenia
  • Disuse osteoporosis / atrophy
    Etiology: local immobilization secondary to
    • fracture (more pronounced distal to fracture site)
    • neural paralysis
    • muscular paralysis
  • Reflex sympathetic dystrophy = Sudeck dystrophy
  • Regional migratory osteoporosis, transient regional osteoporosis of hip
  • Rheumatologic disorders
  • Infection: osteomyelitis, tuberculosis
  • Osteolytic tumor
  • Lytic phase of Paget disease
  • Early phase of bone infarct and hemorrhage
  • Burns + frostbite
Bone Marrow Edema
= hypointense on T1WI + hyperintense on T2WI relative to fatty marrow
  • Trauma
    • “bone bruise”
    • radiographically occult acute fracture
    • recent surgery
  • Infection = osteomyelitis
  • Aseptic arthritis
  • Osteonecrosis = early stage of AVN
  • Neuropathic osteoarthropathy
  • Reflex sympathetic dystrophy (some cases)
  • Transient osteoporosis of hip
  • Infiltrative neoplasm
Transverse Lucent Metaphyseal Lines
mnemonic: LINING
  • Leukemia
  • Illness, systemic (rickets, scurvy)
  • Normal variant
  • Infection, transplacental (congenital syphilis)
  • Neuroblastoma metastases
  • Growth lines
Frayed Metaphyses
mnemonic: CHARMS
  • Congenital infections (rubella, syphilis)
  • Hypophosphatasia
  • Achondroplasia
  • Rickets
  • Metaphyseal dysostosis
  • Scurvy
Bone tumor
Role of Radiologist
  • Is there a lesion?
  • Is it a bone tumor?
  • Is the tumor benign or malignant?
  • Is a biopsy necessary?
  • Is the histologic diagnosis consistent with the radiographic image?
Assessment of Aggressiveness
    • Diagnosis certain: no further work-up necessary
    • Asymptomatic lesion with highly probable benign diagnosis may be followed clinically
    • Symptomatic lesion with highly probable benign diagnosis may be treated without further work-up
    • not clearly categorized as benign or malignant; needs staging work-up
  • MALIGNANT: needs staging work-up
    Staging work-up:  
    Bone scan: identifies polyostotic lesions (eg, multiple myeloma, metastatic disease, primary osteosarcoma with bone-forming metastases, histiocytosis, Paget disease)
    Chest CT: identifies metastatic deposits + changes further work-up and therapy
Local staging with MR imaging:
  • Margins: encapsulated / infiltrating
  • Compartment: intra- / extracompartmental
  • Intraosseous extent + skip lesions
  • Soft-tissue extent (DDx: hematoma, edema)
  • Joint involvement
  • Neurovascular involvement
Local assessment with CT imaging:
  • matrix / rim calcifications
Tumorlike Conditions
  • Solitary bone cyst
  • Juxtaarticular (“synovial”) cyst
  • Aneurysmal bone cyst
  • Nonossifying fibroma; cortical defect; cortical desmoid
  • Eosinophilic granuloma
  • Reparative giant cell granuloma
  • Fibrous dysplasia (monostotic; polyostotic)
  • Myositis ossificans
  • “Brown tumor” of hyperparathyroidism
  • Massive osteolysis
Pseudomalignant Appearance
  • Osteomyelitis
  • Aggressive osteoporosis
Pattern of Bone Destruction

    Cause: (a) slow-growing usually benign tumor
    (b)rarely malignant: plasma cell myeloma, metastasis
    (c) infection: granulomatous osteomyelitis
    • well-defined smooth / irregular margin
    • short zone of transition
    Cause: (a) rapidly growing malignant bone tumor
    (b) osteomyelitis
    • less well defined / demarcated lesional margin
    • longer zone of transition
    mnemonic: H LEMMON
    • Histiocytosis X
    • Lymphoma
    • Ewing sarcoma
    • Metastasis
    • Multiple myeloma
    • Osteomyelitis
    • Neuroblastoma
    Cause: aggressive bone tumor with rapid growth potential (eg, Ewing sarcoma)
    • poorly demarcated lesion imperceptibly merging with uninvolved bone
    • long zone of transition
Size, Shape, and Margin of Bone Lesion
  • Primary malignant tumors are larger than benign tumors
  • elongated lesion (= greatest diameter of >1.5 times the least diameter): Ewing sarcoma, histiocytic lymphoma, chondrosarcoma, angiosarcoma
  • sclerotic margin (= reaction of host tissue to tumor)
Tumor Position in Transverse Plane
    • Enchondroma
    • Solitary bone cyst
    • Giant cell tumor
    • Osteogenic sarcoma, chondrosarcoma, fibrosarcoma
    • Chondromyxoid fibroma
    • Nonossifying fibroma
    • Osteoid osteoma
    • Juxtacortical chondroma / osteosarcoma
    • Osteochondroma
    • Parosteal osteogenic sarcoma
Tumor Position in Longitudinal Plane
    • Chondroblastoma (prior to closure of growth plate)
    • Intraosseous ganglion, subchondral cyst
    • Giant cell tumor (originating in metaphysis)
    • Clear cell chondrosarcoma
    • Fibrous dysplasia
    • Abscess
    mnemonic: CAGGIE
    • Chondroblastoma
    • Aneurysmal bone cyst
    • Giant cell tumor
    • Geode
    • Infection
    • Eosinophilic granuloma
      • [after 40 years of age throw out “CEA” and insert metastases / myeloma]
    • Nonossifying fibroma (close to growth plate)
    • Chondromyxoid fibroma (abutting growth plate)
    • Solitary bone cyst
    • Osteochondroma
    • Brodie abscess
    • Osteogenic sarcoma, chondrosarcoma
    • Round cell tumor (eg, Ewing sarcoma)
    • Nonossifying fibroma
    • Solitary bone cyst
    • Aneurysmal bone cyst
    • Enchondroma
    • Osteoblastoma
    • Fibrous dysplasia
    mnemonic: FEMALE
    • Fibrous dysplasia
    • Eosinophilic granuloma
    • Metastasis
    • Adamantinoma
    • Leukemia, Lymphoma
    • Ewing sarcoma
Tumors Localizing to Hematopoietic Marrow
  • Metastases
  • Plasma cell myeloma
  • Ewing sarcoma
  • Histiocytic lymphoma
Diffuse Bone Marrow Abnormalities in Childhood
    • metastatic disease
      • Neuroblastoma (in young child)
      • Lymphoma (in older child)
      • Rhabdomyosarcoma (in older child)
    • primary neoplasm
      • Leukemia
    • = Red cell hyperplasia = reconversion
      • severe anemia: sickle cell disease, thalassemia, hereditary spherocytosis
      • chronic severe blood loss
      • marrow replacement by neoplasia
      • treatment with granulocyte-macrophage colony stimulating factor
    • Myeloid depletion = aplastic anemia
    • Myelofibrosis
Age Incidence of Malignant Bone Tumors
  • 80% of bone tumors are correctly determined on the basis of age alone!

Sarcomas by Age
mnemonic: Every Other Runner Feels Crampy Pain On Moving
Ewing sarcoma 0 –10 years
Osteogenic sarcoma 10–30 years
Reticulum cell sarcoma 20–40 years
Fibrosarcoma 20–40 years
Chondrosarcoma 40–50 years
Parosteal sarcoma 40–50 years
Osteosarcoma 60–70 years
Metastases 60–70 years
Age [years] Tumor
0.1 Neuroblastoma
0.1–10 Ewing tumor in tubular bones (diaphysis)
10 –30 Osteosarcoma (metaphysis); Ewing tumor in flat bones
30 –40 Reticulum cell sarcoma (similar histology to Ewing tumor); fibrosarcoma; malignant giant cell tumor (similar histology to fibrosarcoma); parosteal sarcoma; lymphoma
>40 Metastatic carcinoma; multiple myeloma; chondrosarcoma
Round Cell Tumors
  • arise in midshaft
  • osteolytic lesion
  • reactive new bone formation
  • no tumor new bone
mnemonic: LEMON
  • Leukemia, Lymphoma
  • Ewing sarcoma, Eosinophilic granuloma
  • Multiple myeloma
  • Osteomyelitis
  • Neuroblastoma
Malignancy with Soft-tissue Involvement
mnemonic: My Mother Eats Chocolate Fudge Often
  • Metastasis
  • Myeloma
  • Ewing sarcoma
  • Chondrosarcoma
  • Fibrosarcoma
  • Osteosarcoma
Tumor Matrix of Bone Tumors
Cartilage-forming Bone Tumors
  • centrally located ringlike / flocculent / flecklike radiodensities
    • Enchondroma
    • Parosteal chondroma
    • Chondroblastoma
      Average Age for Occurrence of Benign and Malignant Bone Tumors
    • P.8

    • Chondromyxoid fibroma
    • Osteochondroma
    • Chondrosarcoma
    • Chondroblastic osteosarcoma
Bone-forming Tumors
  • inhomogeneous / homogeneous radiodense collections of variable size + extent
    • Osteoma
    • Osteoid osteoma
    • Osteoblastoma
    • Ossifying fibroma
    • Osteogenic sarcoma
Fibrous Connective Tissue Tumors
    • cortical
      • Benign cortical defect
      • Avulsion cortical irregularity
    • medullary
      • Herniation pit
      • Nonossifying fibroma
      • Ossifying fibroma
      • Congenital generalized fibromatosis
    • corticomedullary
      • Nonossifying fibroma
      • Ossifying fibroma
      • Fibrous dysplasia
      • Cherubism
      • Desmoplastic fibroma
      • Fibromyxoma
    • Fibrosarcoma
Tumors of Histiocytic Origin
    • Giant cell tumor
    • Benign fibrous histiocytoma
    • Malignant fibrous histiocytoma
Tumors of Fatty Tissue Origin
    • Intraosseous lipoma
    • Parosteal lipoma
    • Intraosseous liposarcoma
  • Lipomas follow the signal intensity of subcutaneous fat in all sequences!
Tumors of Vascular Origin
<1% of all bone tumors
    • Hemangioma
    • Glomus tumor
    • Lymphangioma
    • Cystic angiomatosis
    • Hemangiopericytoma
    • Malignant hemangiopericytoma
    • Angiosarcoma = hemangioendothelioma
Metastatic sites: lung, brain, lymph nodes, other bones
Tumors of Neural Origin
    • Solitary neurofibroma
    • Neurilemoma
    • Neurogenic sarcoma = malignant schwannoma
Intraosseous lesion
Bubbly Bone Lesion
  • Fibrous dysplasia, Fibrous cortical defect
  • Osteoblastoma
  • Giant cell tumor
  • Myeloma (plasmacytoma), Metastases from kidney, thyroid, breast
  • Aneurysmal bone cyst / Angioma
  • Chondromyxoid fibroma, Chondroblastoma
  • Histiocytosis X, Hyperparathyroid brown tumor, Hemophilia
  • Infection (Brodie abscess, Echinococcus, coccidioidomycosis)
  • Nonossifying fibroma
  • Enchondroma, Epithelial inclusion cyst
  • Simple unilocular bone cyst
Infectious Bubbly Lesion
  • Brodie abscess (Staph. aureus)
  • Coccidioidomycosis
  • Echinococcus
  • Atypical mycobacterium
  • Cystic tuberculosis
Blowout Lesion
    • Carcinoma of thyroid, kidney, breast
    • Fibrosarcoma
    • Multiple myeloma (sometimes)
    • Aneurysmal bone cyst
    • Hemophilic pseudotumor
Nonexpansile Unilocular Well-demarcated Bone Defect
  • Fibrous cortical defect
  • Nonossifying fibroma
  • Simple unicameral bone cyst
  • Giant cell tumor
  • Brown tumor of HPT
  • Eosinophilic granuloma
  • Enchondroma
  • Epidermoid inclusion cyst
  • Posttraumatic / degenerative cyst
  • Pseudotumor of hemophilia
  • Intraosseous ganglion
  • P.9

  • Histiocytoma
  • Arthritic lesion
  • Endosteal pigmented villonodular synovitis
  • Fibrous dysplasia
  • Infectious lesion
Nonexpansile Multilocular Well-demarcated Bone Defect
  • Aneurysmal bone cyst
  • Giant cell tumor
  • Fibrous dysplasia
  • Simple bone cyst
Expansile Unilocular Well-demarcated Osteolysis
  • Simple unicameral bone cyst
  • Enchondroma
  • Aneurysmal bone cyst
  • Juxtacortical chondroma
  • Nonossifying fibroma
  • Eosinophilic granuloma
  • Brown tumor of HPT
Poorly Demarcated Osteolytic Lesion without Periosteal Reaction
    • Metastases from any primary neoplasm
    • Multiple myeloma
    • Hemangioma
    • Chondrosarcoma
    • Giant cell tumor
    • Metastasis from kidney / thyroid
Poorly Demarcated Osteolytic Lesion with Periosteal Reaction
  • Osteomyelitis
  • Ewing sarcoma
  • Osteosarcoma
Mixed Sclerotic and Lytic Lesion
Mixed Bone Lesion with Button Sequestrum
  • bone opacity surrounded by a well-defined lucent area
    • Osteomyelitis
    • Eosinophilic granuloma
    • Fibrosarcoma, desmoplastic fibroma, MFH
    • Lymphoma
  • uncommon:
    • partially calcified intraosseous lipoma, tuberculous osteitis, radiation necrosis, metastatic carcinoma, fibrous dysplasia, dermoid & epidermoid cyst, hemangioma, meningioma
Mixed Bone Lesion without Sequestrum
  • Osteomyelitis
  • Tuberculosis
  • Ewing sarcoma
  • Metastasis
  • Osteosarcoma
Trabeculated Bone Lesion
1. Giant cell tumor: delicate thin trabeculae
2. Chondromyxoid fibroma: coarse thick trabeculae
3. Nonossifying fibroma: lobulated
4. Aneurysmal bone cyst: delicate, horizontally oriented trabeculae
5. Hemangioma: striated radiating trabeculae
Lytic Bone Lesion Surrounded by Marked Sclerosis
mnemonic: BOOST
  • Brodie abscess
  • Osteoblastoma
  • Osteoid osteoma
  • Stress fracture
  • Tuberculosis
Multiple Lytic Lesions
mnemonic: FEEHMI
  • Fibrous dysplasia
  • Enchondromas
  • Eosinophilic granuloma
  • Hyperparathyroidism (brown tumors), Hemangiomas
  • Metastases, Multiple myeloma
  • Infection
Multiple Lytic Lesions in Child
  • Histiocytosis X
  • Metastatic neuroblastoma / leukemia
  • Fibrous dysplasia
  • Enchondromatosis
  • Rare: cystic angiomatosis, multifocal osteomyelitis
Lytic Bone Lesion in Patient <30 Years of Age
mnemonic: CAINES
  • Chondroblastoma
  • Aneurysmal bone cyst
  • Infection
  • Nonossifying fibroma
  • Eosinophilic granuloma
  • Solitary bone cyst
Lytic Bone Lesion on Both Sides of Joint
mnemonic: SAC
  • Synovioma
  • Angioma
  • Chondroid lesion
Multiple Bone Lesions & Soft-tissue Tumor
  • Neurofibromatosis & fibroxanthomas
  • Maffucci syndrome = enchondromatosis & hemangioma
  • Mazabraud syndrome = fibrous dysplasia & myxoma
  • Metastases
    • Multiple myeloma
    • Malignant melanoma
    • Lymphoma
Osteoblastic Bone Lesion
    • Bone island
    • Osteoma
    • Osteoid osteoma
  • P.10

    • Osteosarcoma
    • Parosteal sarcoma
Widespread Osteosclerotic Lesions
  • Metastases: prostate, breast, lung, bladder, pancreas, stomach, colon, carcinoid, brain
  • Paget disease
  • Sarcoma
  • Myelofibrosis
  • Mastocytosis
    = abnormalities of cartilage / bone growth and development
    • identifiable at birth:
      • usually lethal: achondrogenesis, fibrochondrogenesis, thanatophoric dysplasia, short rib syndrome
      • usually nonlethal: chondrodysplasia punctata, camptomelic dysplasia, achondroplasia, diastrophic dysplasia, chondroectodermal dysplasia, Jeune syndrome, spondyloepiphyseal dysplasia congenita, mesomelic dysplasia, cleidocranial dysplasia, oto-palato-digital syndrome
    • identifiable in later life: hypochondroplasia, dyschondrosteosis, spondylometaphyseal dysplasia, acromicric dysplasia
    • abnormal bone density: osteopetrosis, pyknodysostosis, Melnick-Needles syndrome
    = malformation of individual bones singly / in combination
    • with cranial + facial involvement:craniosynostosis, craniofacial dysostosis (Crouzon), acrocephalosyndactyly, acrocephalopolysyndactyly, branchial arch syndromes (Treacher-Collins, Franceschetti, acrofacial dysostosis, oculo-auriculo-vertebral dysostosis, hemifacial microsomia, oculo-mandibulo-facial syndrome
    • with predominant axial involvement:vertebral segmentation defects (Klippel-Feil), Sprengel anomaly, spondylocostal dysostosis, oculovertebral syndrome
    • with predominant involvement of extremities:acheiria (= absence of hands), apodia (= absence of feet), polydactyly, syndactyly, camptodactyly, Rubinstein-Taybi syndrome, pancytopenia-dysmelia syndrome (Fanconi), Blackfan-Diamond anemia with thumb anomaly, thrombocytopenia-radial aplasia syndrome, cardiomelic syndromes (Holt-Oram), focal femoral deficiency, multiple synostoses
    = disorders with multifocal resorption of bone
    (a) calcium / phosphorus: hypophosphatasia
    (b) complex carbohydrates: mucopolysaccharidosis
Micromelia = shortening involves entire limb (eg, humerus, radius + ulna, hand)
Rhizomelia = shortening involves proximal segment (eg, humerus)
Mesomelia = shortening involves intermediate segment (eg, radius + ulna)
Acromelia = shortening involves distal segment (eg, hand)
Micromelic Dwarfism
= disproportionate shortening of entire leg
  • Mild micromelic dwarfism
    • Jeune syndrome
    • Ellis-van Creveld syndrome= chondroectodermal dysplasia
    • Diastrophic dwarfism
  • Mild bowed micromelic dwarfism
    • Camptomelic dysplasia
    • Osteogenesis imperfecta, type III
  • Severe micromelic dwarfism
    • Thanatophoric dysplasia
    • Osteogenesis imperfecta, type II
    • Homozygous achondroplasia
    • Hypophosphatasia
    • Short-rib polydactyly syndrome
    • Fibrochondrogenesis
Acromelic Dwarfism
= distal shortening (hands, feet)
  • Asphyxiating thoracic dysplasia
Rhizomelic Dwarfism
= shortening of proximal segments (humerus, femur)
mnemonic: MA CAT
  • Metatrophic dwarfism
  • Achondrogenesis (most severe shortening)
  • Chondrodysplasia punctata (autosomal recessive)
  • Achondroplasia, heterozygous
  • Thanatophoric dysplasia
  • Failure of
    • articular cartilage: spondyloepiphyseal dysplasia
    • ossification center: multiple epiphyseal dysplasia
    • proliferating cartilage: achondroplasia
    • spongiosa formation: hypophosphatasia
    • spongiosa absorption: osteopetrosis
    • periosteal bone: osteogenesis imperfecta
    • endosteal bone: idiopathic osteoporosis
  • Excess of
    • articular cartilage: dysplasia epiphysealis hemimelica
    • hypertrophic cartilage: enchondromatosis
    • spongiosa: multiple exostosis
    • periosteal bone: progressive diaphyseal dysplasia
    • endosteal bone: hyperphosphatemia
Lethal Bone Dysplasia
in order of frequency:
  • Thanatophoric dysplasia
  • Osteogenesis imperfecta type II
  • P.11

  • Achondrogenesis type I + II
  • Jeune syndrome (may be nonlethal)
  • Hypophosphatasia, congenital lethal form
  • Chondroectodermal dysplasia (usually nonlethal)
  • Chondrodysplasia punctata, rhizomelic type
  • Camptomelic dysplasia
  • Short-rib polydactyly syndrome
  • Homozygous achondroplasia
  • Lethal short-limbed dysplasias typically are manifest on sonograms before 24 weeks MA!
Nonlethal Dwarfism
  • Achondroplasia (heterozygous)
  • Asphyxiating thoracic dysplasia
  • Chondroectodermal dysplasia
  • Chondrodysplasia punctata
  • Spondyloepiphyseal dysplasia (congenital)
  • Diastrophic dwarfism
  • Metatrophic dwarfism
  • Hypochondroplasia
Late-onset Dwarfism
  • Spondyloepiphyseal dysplasia tarda
  • Multiple epiphyseal dysplasia
  • Pseudoachondroplasia
  • Metaphyseal chondrodysplasia
  • Dyschondrosteosis
  • Cleidocranial dysostosis
  • Progressive diaphyseal dysplasia
Hypomineralization in Fetus
    • Osteogenesis imperfecta
    • Hypophosphatasia
    • Achondrogenesis
Large Head in Fetus
  • Achondroplasia
  • Thanatophoric dysplasia
Narrow Chest in Fetus
  • Short-rib polydactyly syndrome
  • Asphyxiating thoracic dysplasia
  • Chondroectodermal dysplasia
  • Camptomelic dysplasia
  • Thanatophoric dwarfism
  • Homozygous achondroplasia
  • Achondrogenesis
  • Hypophosphatasia
  • Thanatophoric dysplasia
  • Osteogenesis imperfecta type II
  • Achondroplasia
  • Morquio syndrome
Bowed Long Bones in Fetus
  • Camptomelic syndrome
  • Osteogenesis imperfecta
  • Thanatophoric dysplasia
  • Hypophosphatasia
Bone Fractures in Fetus
  • Osteogenesis imperfecta
  • Hypophosphatasia
  • Achondrogenesis
Limb reduction anomalies
Amelia = absence of limb
Hemimelia = absence of distal parts
Phocomelia = proximal reduction with distal parts attached to trunk
Aplasia / Hypoplasia of Radius
mnemonic: The Furry Cat Hit My Dog
  • Thrombocytopenia–absent radius syndrome
  • Fanconi anemia
  • Cornelia de Lange syndrome
  • Holt-Oram syndrome
  • Myositis ossificans progressiva (thumb only)
  • Diastrophic dwarfism (“hitchhiker’s thumb”)
Pubic Bone Maldevelopment
mnemonic: CHIEF
  • Cleidocranial dysostosis
  • Hypospadia, epispadia
  • Idiopathic
  • Exstrophy of bladder
  • F for syringomyelia
Bone overgrowth
Bone Overdevelopment
  • Marfan syndrome
  • Klippel-Trenaunay syndrome
  • Nerve territory-oriented macrodactyly
    • Macrodystrophia lipomatosa
    • Fibrolipomatous hamartoma with macrodactyly
Erlenmeyer Flask Deformity
= expansion of distal end of long bones, usually femur
  • Gaucher disease, Niemann-Pick disease
  • Hemolytic anemia: thalassemia, sickle cell
  • Osteopetrosis
  • Heavy metal poisoning
  • Metaphyseal dysplasia = Pyle disease
  • Rickets
  • Fibrous dysplasia
  • Down syndrome
  • Achondroplasia
  • Rheumatoid arthritis
  • Hypophosphatasia
  • Leukemia
mnemonic: TOP DOG
  • Thalassemia
  • Osteopetrosis
  • Pyle disease
  • Diaphyseal aclasis
  • Ollier disease
  • Gaucher disease

Periosteal reaction / periostitis
1. Trauma, hemophilia  
2. Infection  
3. Inflammatory: arthritis
4. Neoplasm  
5. Congenital: physiologic in newborn
6. Metabolic: hypertrophic osteoarthropathy, thyroid acropachy, hypervitaminosis A
7. Vascular: venous stasis
Solid Periosteal Reaction
  • = reaction to periosteal irritant
  • even + uniform thickness >1 mm
  • persistent + unchanged for weeks
  • thin: eosinophilic granuloma, osteoid osteoma
  • dense undulating: vascular disease
  • thin undulating: pulmonary osteoarthropathy
  • dense elliptical: osteoid osteoma; long-standing malignant disease (with destruction)
  • cloaking: storage disease; chronic infection
Interrupted Periosteal Reaction
= pleomorphic, rapidly progressing process undergoing constant change
  • buttressing = periosteal bone formation merges with underlying cortex: eosinophilic granuloma
  • laminated = “onion skin”: acute osteomyelitis; malignant tumor (osteosarcoma, Ewing sarcoma)
  • radiating spicules = “sunburst”: osteosarcoma; Ewing sarcoma; chondrosarcoma; fibrosarcoma; leukemia; metastasis; acute osteomyelitis
  • perpendicular spicules = “hair-on-end”: Ewing sarcoma
  • amorphous: malignancy (deposits may represent extension of tumor / periosteal response); osteosarcoma
  • Codman triangle: hemorrhage; malignancy (osteosarcoma, Ewing sarcoma); acute osteomyelitis; fracture
Symmetric Periosteal Reaction in Adulthood
  • Venous stasis (lower extremity)
  • Hypertrophic osteoarthropathy
  • Pachydermoperiostosis
  • Thyroid acropachy
  • Fluorosis
  • Rheumatoid arthritis
  • Psoriatic arthritis
  • Reiter syndrome
  • Idiopathic-degenerative
Periosteal Reaction in Childhood
  • benign
    • Physiologic (up to 35%): symmetric involvement of diaphyses during first 1–6 months of life
    • Nonaccidental trauma = battered child syndrome
    • Infantile cortical hyperostosis: <6 months of age
    • Hypervitaminosis A
    • Scurvy
    • Osteogenesis imperfecta
    • Congenital syphilis
  • malignant
    • Multicentric osteosarcoma
    • Metastases from neuroblastoma + retinoblastoma
    • Acute leukemia
  • Physiologic, Prostaglandin
  • Eosinophilic granuloma
  • Rickets
  • Infantile cortical hyperostosis
  • Osteomyelitis
  • Scurvy
  • Trauma
  • Ewing sarcoma
  • A-hypervitaminosis
  • Leukemia + neuroblastoma
  • Syphilis
  • Osteosarcoma
  • Child abuse
  • Kinky hair syndrome
  • Sickle cell disease
Periosteal Reaction in Infant
  • before 6 months of age
    • Infantile cortical hyperostosis
    • Physiologic
    • Extracorporeal membrane oxygenation
  • after 6 months of age
    • Hypervitaminosis A
    • Scurvy
    • Rickets
  • anytime during infancy
    • Nonaccidental trauma
    • Syphilis
    • Metastatic neuroblastoma / leukemia
    • Prostaglandin therapy: within 40 days
    • Sickle cell dactylitis
DDx: motion artifact
  • [en, Greek = in; thesis, Greek = position]
  • Enthesis = osseous attachment of tendon composed of 4 zones, ie, tendon itself + unmineralized fibrocartilage + mineralized fibrocartilage + bone
  • Degenerative disorder
  • Seronegative arthropathies: ankylosing spondylitis, Reiter disease, psoriatic arthritis
  • Diffuse idiopathic skeletal hyperostosis
  • Acromegaly
  • Rheumatoid arthritis (occasionally)
Location: at site of tendon + ligament attachment
  • bone proliferation (enthesophyte)
  • calcification of tendon + ligament
  • erosion
Bone trauma
Childhood Fractures
  • Greenstick fracture
  • Bowing fracture
  • P.13

  • Traumatic epiphyseolysis
  • Battered child syndrome
  • Epiphyseal plate injury
Pseudarthrosis in Long Bones
  • Nonunion of fracture
  • Fibrous dysplasia
  • Neurofibromatosis
  • Osteogenesis imperfecta
  • Congenital: clavicular pseudarthrosis
Exuberant Callus Formation
  • Steroid therapy / Cushing syndrome
  • Neuropathic arthropathy
  • Osteogenesis imperfecta
  • Congenital insensitivity to pain
  • Paralysis
  • Renal osteodystrophy
  • Multiple myeloma
  • Battered child syndrome
Premature Epiphyseal Ossification
  • @ Proximal femoral and humeral epiphyses
    • Jeune asphyxiating thoracic dysplasia
    • Ellis-van Creveld chondroectodermal dysplasia
Epiphyseal / Apophyseal Lesion
  • Chondroblastoma
  • Brodie abscess
  • Fungal / tuberculous infection
  • Langerhans cell histiocytosis
  • Osteoid osteoma
  • Chondromyxoid fibroma
  • Enchondroma
  • Bone cyst
  • Foreign-body granuloma
Subarticular Lesion
  • Giant cell tumor
  • Solitary subchondral cyst
  • Intraosseous ganglion
  • Brodie abscess
  • Clear cell chondrosarcoma
Stippled Epiphyses
  • Normal variant
  • Avascular necrosis
  • Hypothyroidism
  • Chondrodysplasia punctata
  • Multiple epiphyseal dysplasia
  • Spondyloepiphyseal dysplasia
  • Hypoparathyroidism
  • Down syndrome
  • Trisomy 18
  • Fetal warfarin syndrome
  • Homocystinuria (distal radial + ulnar epiphyses = pathognomonic)
  • Zellweger cerebrohepatorenal syndrome
Physeal / Metaphyseal Widening & Irregularity
  • Rickets
  • Hypophosphatasia
  • Metaphyseal chondroplasia
Epiphyseal Overgrowth
  • Juvenile rheumatoid arthritis
  • Hemophilia
  • Healed Legg-Perthes disease
  • Tuberculous arthritis
  • Pyogenic arthritis (chronic)
  • Fungal arthritis
  • Epiphyseal dysplasia hemimelica
  • Fibrous dysplasia of epiphysis
  • Winchester syndrome
= SLIPPED EPIPHYSIS(zone of maturing hypertrophic cartilage affected, not zone of proliferation)
  • Idiopathic / juvenile epiphyseolysis
    Age: 12–15 years (? puberty-related hormonal dysregulation)
    • adiposogenital type; tall stature
  • Renal osteodystrophy
  • Hyperparathyroidism in chronic renal disease
  • Hypothyroidism
  • Radiotherapy
Approach to Arthritis
mnemonic: ABCDE’S
  • Alignment
  • Bone mineralization
  • Cartilage loss
  • Distribution
  • Erosion
  • Soft tissues
Signs of Arthritis
Prevalence of arthritis: 15% of population in USA
Conventional x-ray:
  • narrowing of radiologic joint space:
    • uniform = inflammatory arthritis
    • nonuniform = degenerative arthritis
  • evidence of disease on both sides of joint:
    • osteopenia
    • subchondral sclerosis
    • erosion
    • subchondral cyst formation
    • malalignment
  • joint effusion
  • joint bodies
  • increase in regional blood flow (active disease)
  • distribution of disease
  • irregularity + narrowing of articular cartilage
  • Gd-DTPA enhancement of synovium (active disease)

Classification of Arthritides
    • Tuberculous
    • Pyogenic
    • Lyme arthritis
    • Fungal arthritis: Candida, Coccidioides immitis, Blastomyces dermatitidis, Histoplasma capsulatum, Sporothrix schenckii, Cryptococcus neoformans, Aspergillus fumigatus
      N.B.: Tuberculous + fungal arthritis shows prominent osteoporosis + slower rate of destruction + less joint narrowing than a pyogenic infection (Phemister triad)
    • Rheumatoid arthritis
    • Ankylosing spondylitis
    • Psoriatic arthritis
    • Rheumatic fever
    • Sarcoidosis
    • Gout
    • Chondrocalcinosis
    • Ochronosis
    • Hemophilic arthritis
    • Secondary osteoarthritis
    • Neurotrophic arthritis
    • Pigmented villonodular synovitis
      • Ulcerative colitis (in 10–20%)
      • Crohn disease (in 5%): peripheral arthritis increases with colonic disease
      • Whipple disease (in 60–90% transient intermittent polyarthritis: sacroiliitis, spondylitis)
        Resection of diseased bowel is associated with regression of arthritic symptomatology!
      Infectious agents: Salmonella, Shigella, Yersinia
    • after intestinal bypass surgery
Spondyloarthritis and Positive HLA-B 27 Histocompatibility Complex
1. Ankylosing spondylitis 95%
2. Reiter disease 80%
3. Arthropathy of inflammatory bowel disease 75%
4. Psoriatic spondylitis 70%
5. Normal population 10%
Destructive Monoarthritis
  • Any destructive monoarthritis should be regarded as infection until proved otherwise!
  • Septic arthritis
  • Monoarticular presentation of a systemic arthritis
    • Rheumatoid arthritis
    • Gout
    • Amyloidosis
    • Seronegative arthritis
  • Joint tumor
    • PVNS
    • Synovial chondromatosis
    • Articular hemangioma
Nonseptic Monoarthritis
  • Gout
  • Milwaukee shoulder
  • Rapidly destructive articular disease
  • Amyloid arthropathy
  • Hemophilic arthropathy
  • Primary synovial osteochondromatosis
  • Pigmented villonodular synovitis
  • Neuropathic arthropathy
  • Foreign-body synovitis
Arthritis without Demineralization
  • Gout
  • Neuropathic arthropathy
  • Psoriasis
  • Reiter disease
  • Pigmented villonodular synovitis
mnemonic: PONGS
  • Psoriatic arthritis
  • Osteoarthritis
  • Neuropathic joint
  • Gout
  • Sarcoidosis
Arthritis with Demineralization
mnemonic: HORSE
  • Hemophilia
  • Osteomyelitis
  • Rheumatoid arthritis, Reiter disease
  • Scleroderma
  • Erythematosus, systemic lupus
Deforming Nonerosive Arthropathy
  • Collagen-vascular disease, especially SLE
  • Rheumatoid arthritis (rare)
  • Rheumatic fever (Jaccoud arthritis) (rare)
Arthritis with Periostitis
  • Juvenile rheumatoid arthritis
  • Psoriatic arthritis
  • Reiter syndrome
  • Infectious arthritis
Premature Osteoarthritis
mnemonic: COME CHAT
  • Calcium pyrophosphate dihydrate arthropathy
  • Ochronosis
  • Marfan syndrome
  • Epiphyseal dysplasia
  • Charcot joint = neuroarthropathy
  • Hemophilic arthropathy
  • Acromegaly
  • Trauma
Synovial Disease with Decreased Signal Intensity
= hemosiderin deposition

  • Pigmented villonodular synovitis
  • Rheumatoid arthritis
  • Hemophilia
mnemonic: WHIP A DOG
  • Wilson disease
  • Hemochromatosis, Hemophilia, Hypothyroidism, 1° Hyperparathyroidism (15%), Hypophosphatasia, Familial Hypomagnesemia
  • Idiopathic (aging)
  • Pseudogout (CPPD)
  • Arthritis (rheumatoid, postinfectious, traumatic, degenerative), Amyloidosis, Acromegaly
  • Diabetes mellitus
  • Ochronosis
  • Gout
mnemonic: 3 C’s
Crystals CPPD, sodium urate (gout)
Cations calcium (any cause of hypercalcemia), copper, iron
Cartilage degeneration osteoarthritis, acromegaly, ochronosis
Subchondral Cyst
    Etiology: bone necrosis allows pressure-induced intrusion of synovial fluid into subchondral bone; in conditions with synovial inflammation
    Cause: 1. Osteoarthritis
    2. Rheumatoid arthritis
    3. Osteonecrosis
    4. CPPD
  • size of cyst usually 2–35 mm
  • may be large + expansile (especially in CPPD)
    DDx: (1) Giant cell tumor
    (2) Pigmented villonodular synovitis
    (4) Intraosseous ganglion
    5) Hemophilia
Loose Intraarticular Bodies
  • Osteochondrosis dissecans
  • Synovial osteochondromatosis
  • Chip fracture from trauma
  • Severe degenerative joint disease
  • Neuropathic arthropathy
Intraarticular Process with Cortical Erosion
  • Pigmented villonodular synovitis
  • Synovial osteochondromatosis
  • Rheumatoid arthritis
  • Gout
  • Synovial hemangioma
  • Lipoma arborescens
Erosions of DIP Joints
  • Inflammatory osteoarthritis
  • Psoriatic arthritis
  • Gout
  • Multicentric reticulohistiocytosis
  • Hyperparathyroidism
  • Frostbite
  • Septic arthritis
Articular Disorders of Hand and Wrist
  • Osteoarthritis = degenerative joint disease
    • = abnormal stress with minor + major traumatic episodes
      Target areas: DIP, PIP, 1st CMC, trapezioscaphoid; bilateral symmetric / asymmetric
    • joint space narrowing
    • subchondral eburnation
    • marginal osteophytes + small ossicles
    • radial subluxation of 1st metacarpal base
    • Radiocarpal joint normal unless history of trauma
  • Erosive osteoarthritis = inflammatory osteoarthritis
    Age: predominantly middle-aged / postmenopausal women
    • • acute inflammatory episodes
      Target areas: DIP, PIP, 1st CMC, trapezioscaphoid; bilateral symmetric / asymmetric
    • central erosions combined with osteophytes= subchondral “gull wing” erosions
    • joint space narrowing + sclerosis
    • rare ankylosis
  • Psoriatic arthritis
    • = rheumatoid variant / seronegative spondyloarthropathy; peripheral manifestation in monarthritis / asymmetric oligoarthritis / symmetric polyarthritis
      Target areas: all hand + wrist joints (commonly distal); bi- / unilateral asymmetric polyarticular changes
    • “mouse ears” marginal erosions
    • intraarticular osseous excrescences
    • new bone formation ± fusion
    • osteoporosis may be absent
  • Rheumatoid arthritis
    • = synovial proliferative granulation tissue = pannus
      Target areas: PIP (early in 3rd), MCP (earliest changes in 2nd + 3rd), all wrist joints (early in RC, IRU), ulnar styloid; both hands in relative symmetric fashion
    • fusiform soft-tissue swelling
    • regional periarticular osteoporosis
    • diffuse loss of joint space
    • marginal + central poorly defined erosions
    • joint deformities
  • Gouty arthritis
    • monosodium urate crystals in synovial fluid
    • asymptomatic periods from months to years
      Target areas: commonly CCMC + all hand joints
    • development of chronic tophaceous gout= lobulated soft-tissue masses
    • well-defined eccentric erosions with overhanging edge (often periarticular) + sclerotic margins
    • preservation of joint spaces
    • absence of osteoporosis
    • most extensive changes in common carpometacarpal compartment:

      • scalloped erosions of bases of ulnar metacarpals
  • Calcium pyrophosphate dihydrate crystal deposition disease = CPPD
    Target areas: MCP (2nd, 3rd), radiocarpal; bilateral symmetric / asymmetric changes
    • chondrocalcinosis + periarticular calcifications:
      • calcification of triangular fibrocartilage
    • “degenerative changes” in unusual locations:
      • narrowing ± obliteration of space between distal radius and scaphoid ± fragmentation of surfaces
      • scapholunate separation
      • destruction of trapezioscaphoid space
    • no erosions
    • + large osteophytes = hemochromatosis
  • SLE
    • = myositis, symmetric polyarthritis, deforming nonerosive arthropathy, osteonecrosis
      Target areas: PIP, MCP
    • reversible deformities
  • Scleroderma = progressive systemic sclerosis (PSS)
    Target areas: DIP, PIP, 1st CMC
    • tuft resorption
    • soft-tissue calcifications
Arthritis Involving Distal Interphalangeal Joints
mnemonic: POEM
  • Psoriatic arthritis
    Articulations of Hand and Wrist
  • Osteoarthritis
  • Erosive osteoarthritis
  • Multicentric reticulohistiocytosis
Ankylosis of Interphalangeal Joints
mnemonic: S - Lesions
  • Psoriatic arthritis
  • Ankylosing spondylitis
  • Erosive osteoarthritis
  • Still disease
Joint anatomy:
  • ligamentous portion (superior 2/3 to 1/2 of joint):
    formed by interosseous sacroiliac ligament
  • synovial component (inferior 1/3 to 1/2 of joint):
    the sacral surface is lined by 3–5 mm-thick hyaline cartilage; the iliac surface of joint is lined by 1–mm-thick fibrocartilage
  • 2–5 mm normal joint width
    Positioning: oblique view + modified Ferguson view = AP projection with 23° cephalad angulation
  • findings predominate on the iliac side (thinner cartilage)
    • Ankylosing spondylitis
      • small regular erosion = loss of definition of white cortical line on iliac side (initially)
        Distribution Pattern of Arthritic Lesions (adapted from Donald Resnick, M.D.)
      • P.17

      • subchondral sclerosis + subsequent ankylosis
      • ossification of interosseous ligaments
    • Enteropathic arthropathy
      • same signs as in ankylosing spondylitis
    • Rheumatoid arthritis (in late stages)
      • joint space narrowing without reparation
      • osteoporosis
      • ankylosis may occur
    • Deposition arthropathy: gout, CPPD, ochronosis, acromegaly
      • slow loss of cartilage
      • subchondral reparative bone + osteophytes
    • Osteitis condensans ilii
    DDx: Hyperparathyroidism (subchondral bone resorption on iliac side resembling erosion + widening of joint)
    • Psoriatic arthritis
      • large extensive erosion
      • subchondral sclerosis + occasional ankylosis
    • Reiter syndrome
    • Juvenile rheumatoid arthritis
    • Infection
    • Osteoarthritis from abnormal mechanical stress
      • no erosions
      • irregular narrowing of joint space with subchondral sclerosis
      • osteophytes at anterosuperior / -inferior aspect of joint (may resemble ankylosis)
      DDx: psoriatic arthritis, Reiter syndrome, trauma, gout, pigmented villonodular synovitis, osteitis condensans ilii
Sacroiliac Joint Widening
mnemonic: CRAP TRAP
  • Colitis
  • Rheumatoid arthritis
  • Abscess (infection)
  • Parathyroid disease
  • Trauma
  • Reiter syndrome
  • Ankylosing spondylitis
  • Psoriasis
Sacroiliac Joint Fusion
mnemonic: CARPI
  • Colitic spondylitis
  • Ankylosing spondylitis
  • Reiter syndrome
  • Psoriatic arthritis
  • Infection (TB)
Widened Symphysis Pubis
mnemonic: EPOCH
  • Exstrophy of the bladder
  • Prune belly syndrome
  • Osteogenesis imperfecta
  • Cleidocranial dysostosis
  • Hypothyroidism
Arthritis of Interphalangeal Joint of Great Toe
  • Psoriatic arthritis
  • Reiter disease
  • Gout
  • Degenerative joint disease
Thoracic Deformity
Funnel Chest = Pectus Excavatum
  • = posterior depression of sternum compressing heart against spine
  • Most frequently an isolated anomaly!
May be associated with:
  • prematurity, homocystinuria, Marfan syndrome, Noonan syndrome, fetal alcohol syndrome
    • depressed position of sternum (LATERAL)
    • indistinct right heart border mimicking right middle lobe process (FRONTAL)
    • decreased heart density (FRONTAL)
    • leftward displacement of heart mimicking cardiomegaly (FRONTAL)
    • horizontal course of posterior portion of ribs
    • accentuated downward course of anterior portions of ribs (FRONTAL)
Barrel Chest
  • = large sagittal diameter of thorax
    Cause: COPD, emphysema
  • lateral segments of ribs elongated + straight pointing vertical (FRONTAL)
  • square shape on cross section (CT)
Congenital Rib Anomalies
Prevalence: 1.4%
  • Cervical rib (0.2–1–8%)
    • usually asymptomatic
    • thoracic outlet syndrome (due to elevation of floor of scalene triangle with decrease of costoclavicular space):
        Osteoarthritis Ankylosing spondylitis ilii Osteitis condensans
      Age older younger younger
      Sex M, F M > F F > M
      Distribution bi- / unilateral symmetric bilateral symmetric bilateral
      Sclerosis iliac mild focal iliac ± extensive iliac triangular
      Erosions absent common absent
      Intraarticular ankylosis rare common absent
      Ligamentous ossification less common common absent

      • 10–20% of symptomatic patients have a responsible cervical rib
      • 5–10% of complete cervical ribs cause symptoms
      May be associated with: Klippel-Feil anomaly
    • uni- / bilateral
    • may fuse with first ribs anteriorly
    • adjacent transverse process angulated inferiorly
      Cx: aneurysmal dilatation of subclavian a.
      DDx: elongated transverse process of 7th cervical vertebra; hypoplastic 1st thoracic rib
  • Forked / bifid rib (0.6%) = duplication of anterior portion
    Location: 4th rib (most often)
    May be associated with: Gorlin basal cell nevus syndrome
    • A single bifid rib is most commonly a normal incidental finding!
  • Rib fusion (0.3%)
    May be associated with: vertebral segmentation anomalies
    Location: 1st + 2nd rib / several adjacent ribs
    Site: posterior / anterior portion
  • Bone bridging = focal joining by bone outgrowth
    Cause: congenital / posttraumatic
    Location: anywhere along one pair of ribs / several adjacent ribs
    • complete bridging / pseudarthrosis
  • Rudimentary / hypoplastic rib (0.2%)
    Location: 1st rib (usually)
    • transverse process angulated superiorly
      DDx: cervical rib
  • Pseudarthrosis of 1st rib (0.1%)
    • radiolucent line through midportion with dense sclerotic borders
  • Intrathoracic / pelvic rib (rare)
  • Abnormal number of ribs
    • supernumerary: trisomy 21, VATER syndrome
    • 11 pairs: normal individuals (5–8%); trisomy 21 (33%); cleidocranial dysplasia; camptomelic dysplasia
Short Ribs
  • Thanatophoric dysplasia
  • Jeune asphyxiating thoracic dysplasia
  • Ellis-van Creveld chondroectodermal dysplasia
  • Short rib-polydactyly syndromes (Saldino-Noonan, Majewski, Verma-Naumoff)
  • Achondroplasia
  • Achondrogenesis
  • Mesomelic dwarfism
  • Spondyloepiphyseal dysplasia
  • Enchondromatosis
Rib Lesions
    • Fibrous dysplasia (most common benign lesion)
      • predominantly posterior location
    • Osteochondroma / exostosis: at costochondral / costovertebral junction
      Associated with: spontaneous hemothorax
    • Langerhans cell histiocytosis (eosinophilic granuloma)
    • Benign cortical defect
    • Hemangioma of bone
    • Enchondroma: at costochondral / costovertebral junction
    • Giant cell tumor
    • Aneurysmal bone cyst
    • Osteoblastoma
    • Osteoid osteoma
    • Chondroblastoma
    • Enostosis = bone island (0.4%)
    • Paget disease
    • Brown tumor of HPT
    • Xanthogranuloma
    • Chondrosarcoma (calcified matrix): most common
    • Plasmacytoma
    • Lymphoma
    • Osteosarcoma (rare)
    • Fibrosarcoma
    • Primitive neuroectodermal tumor (= Askin tumor)
    — in adult: 1. Metastasis (most common malignant lesion)
    2. Multiple myeloma
    3. Desmoid tumor
    — in child: 1. Ewing sarcoma (most common malignant tumor affecting ribs of children + adolescents)
    2. Metastatic neuroblastoma
    • Healing fracture
    • Radiation osteitis
      DDx: pulmonary nodule
    • = osteomyelitis
Expansile Rib Lesion
mnemonic: O FEEL THE CLAMP
  • Osteochondroma (25% of all benign rib tumors)
  • Fibrous dysplasia
  • Eosinophilic granuloma
  • Enchondroma (7% of all benign rib tumors)
  • Lymphoma / Leukemia
  • Tuberculosis
  • Hematopoiesis
  • Ewing sarcoma
  • Chondromyxoid fibroma
  • Lymphangiomatosis
  • Aneurysmal bone cyst
  • Metastases
  • Plasmacytoma
Abnormal Rib Shape
Rib Notching on Inferior Margin
  • = minimal concave scalloping / deep ridges along the neurovascular groove with reactive sclerosis
  • Minor undulations in the inferior ribs are normal!
  • The medial third of posterior ribs near transverse process of vertebrae may be notched normally!

      Cause: intercostal aa. function as collaterals to descending aorta / lung
      • Aorta: coarctation (usually affects ribs 4–8; rare before age 8 years), thrombosis
      • Subclavian artery: Blalock-Taussig shunt
      • Pulmonary artery: pulmonary stenosis, tetralogy of Fallot, absent pulmonary artery
    Cause: enlargement of intercostal veins
    • AV malformation of chest wall
    • Superior vena cava obstruction
    • Intercostal neuroma
    • Neurofibromatosis type 1
    • Poliomyelitis / quadriplegia / paraplegia
    • Hyperparathyroidism
    • Thalassemia
    • Melnick-Needles syndrome
Unilateral Rib Notching on Inferior Margin
  • Postoperative Blalock-Taussig shunt(subclavian to pulmonary artery)
  • Coarctation between origin of innominate a. + L subclavian a.
  • Coarctation proximal to aberrant subclavian a.
Rib Notching on Superior Margin
  • Rheumatoid arthritis
  • Scleroderma
  • Systemic lupus erythematosus
  • Hyperparathyroidism
  • Restrictive lung disease
  • Marfan syndrome
Dysplastic Twisted Ribbon Ribs
  • Osteogenesis imperfecta
  • Neurofibromatosis
Bulbous Enlargement of Costochondral Junction
  • Rachitic rosary
  • Scurvy
  • Achondroplasia
  • Hypophosphatasia
  • Metaphyseal chondrodysplasia
  • Acromegaly
Wide Ribs
  • Marrow hyperplasia (anemias)
  • Fibrous dysplasia
  • Paget disease
  • Achondroplasia
  • Mucopolysaccharidoses
Slender Ribs
  • Trisomy 18 syndrome
  • Neurofibromatosis
Dense Ribs
  • Tuberous sclerosis
  • Osteopetrosis
  • Mastocytosis
  • Fluorosis
  • Fibrous dysplasia
  • Chronic infection
  • Trauma
  • Subperiosteal rib resection
Hyperlucent Ribs
Congenitally Lucent Ribs
  • Osteogenesis imperfecta
  • Achondrogenesis
  • Hypophosphatasia
  • Camptomelic dysplasia
Acquired Lucent Ribs
  • Cushing disease
  • Acromegaly
  • Scurvy
Absence of Outer End of Clavicle
  • Rheumatoid arthritis
  • Hyperparathyroidism
  • Posttraumatic osteolysis
  • Metastasis / multiple myeloma
  • Cleidocranial dysplasia
  • Gorlin basal cell nevus syndrome
Penciled Distal End of Clavicle
mnemonic: SHIRT Pocket
  • Scleroderma
  • Hyperparathyroidism
  • Infection
  • Rheumatoid arthritis
  • Trauma
  • Progeria
Destruction of Medial End of Clavicle
mnemonic: MILERS
  • Metastases
  • Infection
  • Lymphoma
  • Eosinophilic granuloma
  • Rheumatoid arthritis
  • Sarcoma
Wrist & hand
Carpal Angle
= angle of 130° formed by tangents to proximal row of carpal bones
    • Turner syndrome
    • Hurler syndrome
    • Morquio syndrome
    • Madelung deformity
    • Down syndrome
    • Arthrogryposis
    • Bone dysplasia with epiphyseal involvement

Metacarpal Sign
  • = relative shortening of 4th + 5th metacarpals
  • tangential line along heads of 5th + 4th metacarpals intersects 3rd metacarpal
    • Idiopathic
    • Pseudo- and pseudopseudohypoparathyroidism
    • Basal cell nevus syndrome
    • Multiple epiphyseal dysplasia
    • Beckwith-Wiedemann syndrome
    • Sickle cell anemia
    • Juvenile chronic arthritis
    • Gonadal dysgenesis: Turner syndrome, Klinefelter syndrome
    • Ectodermal dysplasia = Cornelia de Lange syndrome
    • Hereditary multiple exostoses
    • Peripheral dysostosis
    • Melorheostosis
    mnemonic: Ping Pong Is Tough To Teach
    • Pseudohypoparathyroidism
    • Pseudopseudohypoparathyroidism
    • Idiopathic
    • Trauma
    • Turner syndrome
    • Trisomy 13–18
Lucent Lesion in Finger
    • Enchondroma
    • Epidermoid inclusion cyst
    • Giant cell tumor
    • Reparative granuloma
    • Sarcoidosis
    • Glomus tumor (rare)
      others: aneurysmal bone cyst, brown tumor, hemophilic pseudotumor, solitary bone cyst, osteoblastoma
    • Osteosarcoma
    • Fibrosarcoma
    • Metastasis from lung, breast, malignant melanoma
mnemonic: GAMES PAGES
  • Glomus tumor
  • Arthritis (gout, rheumatoid)
  • Metastasis (lung, breast)
  • Enchondroma
  • Simple cyst (inclusion)
  • Pancreatitis
  • Aneurysmal bone cyst
  • Giant cell tumor
  • Epidermoid
  • Sarcoid
= expansion of bone with cystic changes
  • Tuberculous dactylitis (= spina ventosa)
  • Pyogenic / fungal infection
  • Syphilitic dactylitis
  • Sarcoidosis
  • Hemoglobinopathies
  • Hyperparathyroidism
  • Leukemia
Resorption of Terminal Tufts
    • Amputation
    • Burns, electric injury
    • Frostbite
    • Vinyl chloride poisoning
    • Congenital indifference to pain
    • Syringomyelia
    • Myelomeningocele
    • Diabetes mellitus
    • Leprosy
    • Scleroderma
    • Dermatomyositis
    • Raynaud disease
    • Hyperparathyroidism
    • Familial acroosteolysis
    • Pyknodysostosis
    • Progeria = Werner syndrome
    • Pachydermoperiostosis
    • Sarcoidosis
    • Psoriatic arthropathy
    • Epidermolysis bullosa
  • Acroosteolysis: (a) acquired, (b) familial
  • Massive osteolysis
  • Essential osteolysis
  • Ainhum disease
Acquired Acroosteolysis
  • Psoriasis, Porphyria
  • Ehlers-Danlos syndrome
  • Thrombangitis obliterans
  • Ergot therapy
  • Raynaud disease
  • Diabetes, Dermatomyositis, Dilantin therapy
  • Injury (thermal + electrical burns, frostbite)
  • Arteriosclerosis obliterans
  • PVC (polyvinylchloride) worker
  • Epidermolysis bullosa
  • Rheumatoid arthritis, Reiter syndrome
  • Scleroderma, Sarcoidosis
  • Progeria, Pyknodysostosis
  • Leprosy, Lesch-Nyhan syndrome
  • Absence of pain
  • Syringomyelia
  • Hyperparathyroidism
    also in: yaws; Kaposi sarcoma; pachydermoperiostosis
    • lytic destructive process involving distal + middle phalanges
    • NO periosteal reaction
    • epiphyses resist osteolysis until late

= focal opaque areas + endosteal thickening
  • Incidental in middle-aged women
  • Rheumatoid arthritis
  • Sarcoidosis
  • Scleroderma
  • Systemic lupus erythematosus
  • Hodgkin disease
  • Hematologic disorders
Fingertip Calcifications
  • Scleroderma / CREST syndrome
  • Raynaud disease
  • Systemic lupus erythematosus
  • Dermatomyositis
  • Calcinosis circumscripta universalis
  • Hyperparathyroidism
= shortening / broadening of metacarpals ± phalanges
  • Idiopathic
  • Trauma
  • Osteomyelitis
  • Arthritis
  • Turner syndrome
  • Osteochondrodysplasia
  • Pseudohypoparathyroidism, Pseudopseudohypoparathyroidism
  • Mucopolysaccharidoses
  • Cornelia de Lange syndrome
  • Basal cell nevus syndrome
  • Hereditary multiple exostoses
= curvature of finger in mediolateral plane
  • Normal variant
  • Down syndrome
  • Multiple dysplasia
  • Trauma, arthritis, contractures
  • Frequently associated with:
    • Carpenter syndrome
    • Ellis-van Creveld syndrome
    • Meckel-Gruber syndrome
    • Polysyndactyly syndrome
    • Short rib-polydactyly syndrome
    • Trisomy 13
= osseous ± cutaneous fusion of digits
  • Apert syndrome
  • Carpenter syndrome
  • Down syndrome
  • Neurofibromatosis
  • Poland syndrome
  • Others
Shoulder Instability
= recurrent subluxation / dislocation of humeral head out of the glenoid socket during activities causing symptoms
Stabilizer: inferior glenohumeral ligament-labrum complex (most important); anterior labrum-ligament complex
Lesions after first anterior dislocation:
  • traumatic, unidrectional, Bankart, surgical (TUBS)
    Age: <40 years
    • • fall on outstretched hand (FOOSH)
    • capsulolabral avulsion (Bankart lesion / its variant)
    • anterior-inferior instability
  • atraumatic, multidirectional, bilateral inferior (AMBRI)
    Age: >40 years
    • tear of supraspinatus tendon (33%)
    • fracture of greater tuberosity (33%)
    • subscapularis avulsion from humerus (33%)
Snapping Hip Syndrome
    • Osteocartilaginous bodies
  • EXTRAARTICULAR = tendon slippage
    • fascia lata / gluteus maximus over greater trochanter
    • iliopsoas tendon over iliopectineal eminence
    • long head of biceps femoris over ischial tuberosity
    • iliofemoral ligament over anterior portion of hip capsule
Increase in Teardrop Width
  • increase in distance between teardrop + femoral head
    Cause: hip joint effusion
  • increase in mediolateral size of teardrop
    Cause: hip dysplasia, chronic hip joint effusion during skeletal maturation
Protrusio Acetabuli
  • = acetabular floor bulging into pelvis
  • medial wall of acetabulum projecting medially to ilioischial line by >3 mm (in males) / >6 mm (in females)
  • crossing of medial + lateral components of pelvic “teardrop” (U-shaped radiodense area medial to hip joint with
    • lateral aspect = acetabular articular surface
    • medial aspect = anteroinferior margin of quadrilateral surface of ilium)
    • Tuberculous arthritis
    • Trauma
    • Fibrous dysplasia
    • Rheumatoid arthritis
    • Paget disease
    • Osteomalacia

mnemonic: PROT
  • Paget disease
  • Rheumatoid arthritis
  • Osteomalacia (HPT)
  • Trauma
Pain with Hip Prosthesis
Approximately 120,000 hip arthroplasties per year in USA
  • Heterotopic ossification
  • Trochanteric bursitis
  • Prosthetic fracture / periprosthetic fracture / cement fracture
  • Dislocation (due to capsular laxity / incorrect component placement)
  • Aseptic loosening
    Incidence: 50% of prostheses after 10 years/utable.
    • mechanical wear + tear
    • small-particle disease (= inflammatory-immune reaction to methylmethacrylate / metallic fragments activates phagocytes with secretion of cytokines + proteolytic enzymes leading to osteolysis)
      Rx: 30% require single-stage revision arthroplasty
  • Infection (= septic loosening)
    Incidence: 1–9%
    Organisms: Staphylococcus epidermidis (31%), Staphylococcus aureus (20%), Streptococcus viridans (11%), Escherichia coli (11%), Enterococcus faecalis (8%), group B streptococcus (5%)
    Time of onset: 33% within 3 months, 33% within 1 year, 33% >1 year after surgery
    Rx: excisional arthroplasty + protracted course of antimicrobial therapy + revision arthroplasty
Plain film:
  • migration of prosthetic components compared to previous film:
    • subsidence of prosthesis (up to 5 mm is normal for noncemented femoral component in first few months)
  • cement / prosthesis fracture
  • motion of components on stress views / fluoroscopy
  • widening of prosthesis-cement interface
  • lucency at cement-bone interface >2 mm
  • progressive widening of cement-bone lucency after 12 postoperative months
  • focal lytic area (due to particulate debris with foreign body granuloma / abscess)
  • extensive periostitis (in infection, but rare)
NUC (83% sensitive, 88% specific):
  • increased uptake of bone agent, Gallium-67, Indium-111–labeled leukocytes, complementary technetium-labeled sulfur colloid + combinations
Bone Scintigraphy:
  • normal = strong evidence against a prosthetic abnormality (= high NPV)
  • diffuse intense uptake around femoral component (= generalized osteolysis associated with aseptic loosening or infection)
  • focal uptake at distal tip of femoral component in >1 year old prosthesis = aseptic loosening
Sequential bone-gallium scintigraphy:
  • congruent spatial distribution of both tracers with gallium intensity less than bone tracer = no infection
  • spatially incongruent / intensity of gallium exceeds that of bone agent = infection
  • spatially congruent + similar intensity of both tracers = inconclusive
Combined labeled leukocyte–marrow scintigraphy:
Accuracy: >90%
Concept: Tc-99m sulfur colloid maps aberrantly located normal bone marrow as a point of reference for leukocyte tracer
  • spatially congruent distribution of both radiotracers = no infection
  • labeled leukocyte activity without corresponding sulfur colloid activity = infection
  • irregularity of joint pseudocapsule
  • filling of nonbursal spaces / sinus tracts / abscess cavities
Aspiration of fluid under fluoroscopy (12–93% sensitive, 83–92% specific for infection):
  • injection of contrast material to confirm intraarticular location
Evaluation of total hip arthroplasty
Reference line: transischial tuberosity line (R)
  • Leg length = vertical position of acetabular component = comparing level of greater / lesser tuberosity (T) with respect to line R
    High placement: shorter leg, less effective muscles crossing the hip joint
    Low placement: longer leg, muscles stretched to point of spasm with risk of dislocation
  • Vertical center of rotation
    = distance from center of femoral head (C) to line R
  • Horizontal center of rotation
    = distance from center of femoral head (C) to teardrop / other medial landmark
    Lateral position: iliopsoas tendon crosses medial to femoral head center of rotation increasing risk of dislocation
  • Lateral acetabular inclination = horizontal version
    • = angle of cup in reference to line R (40° ± 10° desirable)
      Less angulation: stable hip, limited abduction
      Greater angulation:   risk of hip dislocation
    • Varus / neutral / valgus stem position
      Varus position: tip of stem rests against lateral endosteum, increased risk for loosening
      Valgus position: tip of stem rests against medial endosteum, not a significant problem

      Initial Evaluation of Total Hip Arthroplasty
    • Acetabular anteversion (15° ± 10° desirable)
      = lateral radiograph of groin
      Retroversion: risk of hip dislocation
    • Femoral neck anteversionworks synergistically with acetabular anteversion, true angle assessed by CT
Radiographic Findings in Total Hip Arthroplasty
    • irregular cement-bone interface
      • = normal interdigitation of PMMA (polymethyl-methacrylate) with adjacent bone remodeling providing a mechanical interlock
      • PMMA is not a glue!
    • thin lucent line along cement-bone interface
      • = 0.1–1.5-mm thin connective tissue membrane (“demarcation”) along cement-bone interface accompanied by thin line of bone sclerosis
    • wide lucent zone at cement-bone interface
      = ≥2-mm lucent line along bone-cement interface due to granulomatous membrane
      Cause: component loosening ± reaction to particulate debris (eg, PMMA, polyethylene)
    • lucent zone at metal-cement interface along proximal lateral aspect of femoral stem
      = suboptimal metal-cement contact at time of surgery / loosening
    • well-defined area of bone destruction(= histiocytic response, aggressive granulomatous disease)
      Cause: granulomatous reaction as response to particulate debris / infection / tumor
    • asymmetric positioning of femoral head within acetabular component
      Cause: acetabular wear / dislocation of femoral head / acetabular disruption / liner displacement / deformity
    • cement fracture
      Cause: loosening
Bone Contusion Pattern
  • edema of midportion of lateral femoral condyle
    Cause: pivot shift injury = valgus load + external rotation of tibia / external rotation of femurapplied to various states of flexion (noncontact injury)
    Predisposed: skier, football player
    Associated with injury of:
    • anterior cruciate lig. (midsubstance > femoral attachment > tibial attachment site)
    • posterior joint capsule + arcuate ligament
    • posterior horn of lateral / medial meniscus
    • medial collateral ligament
  • ± edema of posterior patellar surface
    Cause: dashboard injury = force upon anterior proximal tibia with knee in flexed position
    Associated with:
    • rupture of posterior cruciate lig. (midsubstance > femoral attachment > tibial attachment site)
    • tear of posterior joint capsule
    • fracture / osteochondral injury of patella
    • injury of hip
  • “kissing” bone contusion pattern = anterior aspect of tibial plateau + anterior aspect of femoral condyle
    Cause: hyperextension injury = direct force upon anterior tibia while foot is planted / indirect force of forceful kicking motion
    Associated with:
    • injury to posterior / anterior cruciate lig.
    • meniscal injury
    • dislocation of knee
    • popliteal neurovascular injury
    • complete disruption of posterolateral complex
  • P.24

  • edema in lateral aspect of femoral condyle (secondary to direct blow)
  • small area of edema in medial femoral condyle (due to avulsive stress to medial collateral ligament)
    Predisposed: football player
    Cause: clip injury = pure valgus stress with knee in mild flexion
    Associated with injury of:
    • medial collateral ligament (at femoral attachment site
    • anterior cruciate ligament
    • medial meniscus
    • combination of all three = O’Donoghue triad
  • anterolateral aspect of lateral femoral condyle
  • inferomedial aspect of patella
    Predisposed: teenaged / young adult athletes with shallow trochlear groove
    Cause: lateral patellar dislocation = twisting motionwith knee in flexion + quadriceps contraction
    Associated with injury of:
    • medial retinaculum
    • medial patellofemoral ligament (near femoral attachment site) most important stabilizing structure)
    • medial patellotibial ligament
Double PCL sign on MRI
  • Bucket-handle tear of medial / lateral meniscus
  • Ligament of Humphrey
  • Torn ACL
  • Fracture fragments
  • Osteophyte
  • Loose body
Absent bow-tie sign
  • Bucket-handle tear of medial meniscus
  • Congenitally hypoplastic / ring-shaped meniscus
  • Small meniscus in child / petite adult
  • Partial meniscectomy
  • Arthritic degeneration
Unique Tibial Lesions
  • Fibrous dysplasia
  • Ossifying fibroma
  • Adamantinoma
Tibiotalar Slanting
= downward slanting of medial tibial plafond
  • Hemophilia
  • Still disease
  • Sickle cell disease
  • Epiphyseal dysplasia
  • Trauma
Abnormal Foot Positions
    • Varus = adduction
      = axis of 1st metatarsal deviated medially relative to axis of talus
    • Valgus = abduction
      = axis of 1st metatarsal deviated laterally relative to axis of talus
    • Inversion = supination
      = inward turning of sole of foot
    • Eversion = pronation
      = outward turning of sole of foot
    talipes (talus, pes) = any deformity of the ankle and hindfoot
    • Equinus
      = hindfoot abnormality with reversal of calcaneal pitch so that the heel cannot touch the ground
    • Calcaneal foot
      = very high calcaneal pitch so that forefoot cannot touch the ground
    • Pes planus = flatfoot
      = low calcaneal pitch + (usually) heel valgus + forefoot eversion
    • Pes cavus
      = high calcaneal pitch (fixed high arch)
Clubfoot = Talipes Equinovarus
Common severe congenital deformity characterized by
  • equinus of heel (reversed calcaneal pitch)
  • heel varus (talocalcaneal angle of almost zero on AP view with both bones parallel to each other)
  • metatarsus adductus (axis of 1st metatarsal deviated medially relative to axis of talus)
  • Arthrogryposis multiplex congenita
  • Chondrodysplasia punctata
  • Neurofibromatosis
  • Spina bifida
  • Myelomeningocele
Rocker-bottom Foot = Vertical Talus
  • vertically oriented talus with increased talocalcaneal angle on lateral view
  • dorsal navicular dislocation at talonavicular joint
  • heel equinus
  • rigid deformity
Associated with: Arthrogryposis multiplex congenita; spina bifida; trisomy 13–18
Talar Beak = Hypertrophied Talar Ridge
  • Talocalcaneal type of tarsal coalition
  • Diffuse idiopathic skeletal hyperostosis (DISH)
  • Acromegaly
  • Rheumatoid arthritis
Heel Pad Thickening
= heel pad thickening >25 mm (normal <21 mm)
mnemonic: MAD COP
  • Myxedema
  • Acromegaly
  • Dilantin therapy
  • Callus
  • Obesity
  • Peripheral edema

Soft-tissue Masses of Foot + Ankle
    • synovial proliferations
      • Pigmented villonodular synovitis (PVNS)
      • Giant cell tumor (GCT) of tendon sheath
    • posttraumatic
      • Plantar fasciitis
    • inflammatory
    • uncertain origin
      • Ganglion cyst
      • Epidermoid cyst
      • Morton neuroma
      • Florid reactive periostitis
      • Rheumatoid nodules
    • Plantar fibromatosis
    • Deep fibromatosis
    • Infantile digital fibromatosis
    • Hemangioma
    • Nerve sheath tumor
    • Lipoma, angiolipoma
Soft tissues
Categories of Soft-tissue Masses
    Incidence: 300:100,000 annually; benign:malignant = 100:1
    • benign (most frequent)
      • Lipoma
      • Hemangioma
      • Desmoid tumor
      • Ganglion cyst
      • Pigmented villonodular synovitis
      • Neurofibroma (5%)
    • malignant (most frequent)
      Frequency: 1% of all cancers in adults, increasing with age
      • Malignant fibrous histiocytoma
      • Liposarcoma
Value of Conventional Radiographs
  • Identification of osseous abnormalities:callus related to fractures, osteocartilaginous mass, myositis ossificans
  • Identification of a primary bone lesion:osteomyelitis, Ewing sarcoma, osteosarcoma
Histologic Classification of Soft-tissue Lesions
    • Lipoma
    • Angiolipoma
    • Liposarcoma
    • Fibroma
    • Nodular fasciitis
    • Aggressive fibromatosis / desmoid
    • Fibrosarcoma
    • Rhabdomyoma
    • Leiomyoma
    • Rhabdomyosarcoma
    • Leiomyosarcoma
    • Hemangioma
    • Hemangiopericytoma
    • Hemangiosarcoma
    • Lymphangioma
    • Lymphangiosarcoma
    • Lymphadenopathy in lymphoma / metastasis
    • Nodular synovitis
    • Pigmented villonodular synovitis
    • Synovial sarcoma
    • Neurofibroma
    • Neurilemoma
    • Ganglioneuroma
    • Malignant neuroblastoma
    • Neurofibrosarcoma
    • Myositis ossificans
    • Extraskeletal osteoma
    • Extraskeletal chondroma
    • Extraskeletal chondrosarcoma
    • Extraskeletal osteosarcoma
Fat-containing Soft-tissue Masses
    • Lipoma
    • Intra- / intermuscular lipoma
    • Synovial lipoma
    • Lipoma arborescens = diffuse synovial lipoma
    • Neural fibrolipoma = fibrolipomatous tumor of nerve
    • Macrodystrophia lipomatosa
    • Lipoblastoma (only in infancy + early childhood)
    • Lipomatosis = diffuse overgrowth of mature adipose tissue infiltrating through the soft tissues of affected extremity / trunk
    • Hibernoma = rare benign tumor of brown fat; often in peri- / interscapular region, axilla, thigh, chest wall
      • marked hypervascularity
    • Liposarcoma
    • Hemangioma
    • Elastofibroma
    • Myxoid tumors: intramuscular myxoma, extraskeletal myxoid chondrosarcoma, myxoid malignant fibrous histiocytoma
    • Neural tumors: neurofibroma, neurilemoma, malignant schwannoma
      • 73% have tissue attenuation less than muscle
    • Hemorrhage

Extraskeletal Osseous + Cartilaginous Tumors
    • cloudlike “cumulus” type of calcification
    • Myositis ossificans
    • Fibrodysplasia ossificans progressiva
    • Soft-tissue osteoma
    • Extraskeletal osteosarcoma
    • Myositis ossificans variants
      • Panniculitis ossificans
      • Fasciitis ossificans
      • Fibroosseous pseudotumor of digits
    • arcs and rings, spicules and floccules of calcification
    • Synovial osteochondromatosis
    • Soft-tissue chondroma
    • Extraskeletal chondrosarcoma
  • Synovial sarcoma
  • Benign mesenchymoma
    = lipoma with chondroid / osseous metaplasia
  • Malignant mesenchymoma
    = 2 or more unrelated sarcomatous components
  • Calcified / ossified tophus of gout
  • Ossified soft-tissue masses of melorheostosis
  • Tumoral calcinosis
  • Pilomatricoma = calcifying epithelioma of Malherbe
    • • lesion arises from hair matrix cells with slow growth confined to the subcutaneous tissue of the face, neck, upper extremities
    • central sandlike calcifications (84%)
    • peripheral ossification (20%)
Soft-tissue Calcification
Metastatic / Metabolic Calcification
= deposit of calcium salts in previously normal tissue
  • as a result of elevation of Ca × P product above 60–70
  • with normal Ca × P product after renal transplant
Location: lung (alveolar septa, bronchial wall, vessel wall), kidney, gastric mucosa, heart, peripheral vessels
  • Skeletal deossification
    • 1° HPT
    • Ectopic HPT production (lung / kidney tumor)
    • Renal osteodystrophy + 2° HPT
    • Hypoparathyroidism
    • Prolonged immobilization
  • Massive bone destruction
    • Widespread bone metastases
    • Plasma cell myeloma
    • Leukemia
  • Hypercalcemia
    • Primary hyperparathyroidism
    • Hypervitaminosis D
    • Milk-alkali syndrome
    • Sarcoidosis
    • Hydroxyapatite deposition disease
    • IV administration of calcium salts
  • Idiopathic hypercalcemia
  • Hyperuricemia
    • Tophaceous gout
Dystrophic Calcification
= in presence of normal serum Ca + P levels secondary to local electrolyte / enzyme alterations in areas of tissue injury / inflammation
  • Metabolic disorder without hypercalcemia
    • Renal osteodystrophy with 2° HPT
    • Hypoparathyroidism
    • Pseudohypoparathyroidism
    • Pseudopseudohypoparathyroidism
    • Gout
    • Pseudogout = chondrocalcinosis
    • Ochronosis = alkaptonuria
    • Diabetes mellitus
  • Connective tissue disorder
    • Scleroderma = progressive systemic sclerosis
    • Dermato- and polymyositis
    • Systemic lupus erythematosus
    • Mixed connective tissue disorders
  • Trauma
    • Neuropathic calcifications
    • Frostbite
    • Myositis ossificans progressiva
  • Infestation
    • Cysticercosis
    • Dracunculosis (guinea worm)
    • Loiasis
    • Bancroft filariasis
    • Hydatid disease
    • Leprosy
  • Vascular disease
    • Atherosclerosis
    • Media sclerosis (Mönckeberg)
    • Venous calcifications
    • Tissue infarction (eg, myocardial infarction)
  • Miscellaneous
    • Ehlers-Danlos syndrome
    • Pseudoxanthoma elasticum
    • Werner syndrome = progeria
    • Calcinosis (circumscripta, universalis, tumoral calcinosis)
  • Neoplastic disease
    • Synovial sarcoma
    • Osteosarcoma
    • Chondrosarcoma
    • Necrotic tumor
  • Degenerative disease
    • Calcium pyrophosphate deposition disease
    • Calcific tendonitis (in 3% of adults)
      Location: shoulder > hip > elbow > wrist > knee
    • Calcific bursitis
  • Metaplasia
    • Synovial osteochondromatosis
Generalized Calcinosis
  • Collagen vascular disorders
    • Scleroderma
    • P.27

    • Dermatomyositis
  • Idiopathic calcinosis universalis
Idiopathic Calcification
  • Tumoral calcinosis
    • normal calcium + elevated phosphate levels
Interstitial Calcinosis
Calcinosis Circumscripta
  • firm white commonly ulcerating dermal papules / plaques / subcutaneous nodules extruding a chalky white material of hydroxyapatite
  • Acrosclerosis: granular deposits around joints of fingers + toes, fingertips
  • Scleroderma + CREST syndrome: acrosclerosis + absorption of ends of distal phalanges
  • Dermatomyositis: extensive subcutaneous deposits
  • Varicosities: particularly in calf
  • 1° Hyperparathyroidism: infrequently periarticular calcinosis
  • Renal osteodystrophy with 2° hyperparathyroidism: extensive vascular deposits even in young individuals
  • Hypoparathyroidism: occasionally around joints; symmetrical in basal ganglia
  • Vitamin D intoxication: periarticular in rheumatoid arthritis (puttylike); calcium deposit in tophi
Calcinosis Universalis
  • Progressive disease of unknown origin
    Age: children + young adults
    Associated with: poly- and dermatomyositis
  • plaque- / sheetlike calcium deposits in skin + subcutis; sometimes in tendons + muscles + fascia
  • NO true bone formation
Soft-tissue Ossification
= formation of trabecular bone
  • Myositis ossificans progressiva / circumscripta
  • Paraosteoarthropathy
  • Soft-tissue osteosarcoma
  • Parosteal osteosarcoma
  • Posttraumatic periostitis = periosteoma
  • Surgical scar
  • Severely burned patient
Connective Tissue Disease
  • = group of disorders that share a number of clinical + laboratory features
  • • Features:
    • relatively specific: arthritis, myositis, Raynaud phenomenon with digital ulceration, tethered skin in extremities + trunk, malar rash sparing nasolabial folds, morning stiffness
    • relatively nonspecific: polyarthralgias (most common initial symptom), myalgias, mottling of extremities, muscle weakness + tenderness
  • • Laboratory findings:
    • relatively specific: ANA in peripheral rim / nucleolar pattern, anti-DNA, elevated muscle enzyme
    • relatively nonspecific: ANA in homogeneous pattern, anti-single-stranded DNA, positive rheumatoid factor
Types and most distinctive features:
  • Rheumatoid arthritispositive rheumatoid factor, prominent morning stiffness, symmetric erosive arthritis
  • Systemic lupus erythematosusmalar rash, photosensitivity, serositis, renal disorders with hemolytic anemia, leukopenia, lymphopenia, thrombocytopenia, positive ANA
  • Sjögren syndromedry eyes + mouth, abnormal Schirmer test
  • SclerodermaRaynaud phenomenon, skin thickening of distal extremities proceeding to include proximal extremities + chest + abdomen, positive ANA in a nucleolar pattern
  • Polymyositis, dermatomyositisheliotrope rash over eyes, proximal muscle weakness, elevated muscle enzymes, inflammation at muscle biopsy
Mixed Connective Tissue Disease
  • = disorder that shares distinctive features of ≥2 different connective tissue diseases in same patient (eg, overlapping features of SLE, PSS, polymyositis)
  • • pulmonary hypertension (due to interstitial pulmonary fibrosis / intimal proliferation of pulmonary arterioles)
MR signal intensity of normal muscle:
  • higher than water + lower than fat on T1WI
  • much lower than water + fat on T2WI
Intramuscular Mass
    • Intramuscular abscess
    • Focal myositis = benign inflammatory pseudotumor
    • Necrotizing fasciitis
    • Sarcoidosis
      • nodules with central star-shaped area of fibrosis surrounded by granuloma
    • Sickle cell crisis
    • Poorly controlled diabetes
    • Compartment syndrome
    • Crush injury
    • Severe ischemia
    • Intraarterial chemotherapy
    • Rhabdomyolysis = severe muscle injury with loss of integrity of muscle cell membranes
      Cause: trauma, severe exercise, ischemia, burn, toxin, IV heparin therapy, autoimmune inflammation
      Cx: renal damage from myoglobulinemia, tetany, compartment syndrome
    • Intramuscular hematoma (eg, severe muscle strain, laceration, contusion, spontaneous)
    • Myositis ossificans traumatica

Muscle Edema
muscle hyperintensity on STIR images
    • Dermatomyositis
    • Polymyositis
    • Radiation therapy: straight sharp margins, involves muscle + subcutaneous fat
    • Early stage of myositis ossificans
    • Lymphoma
    • Bacterial / infectious myositis
      • direct extension from adjacent infection (eg, osteomyelitis, subcutaneous abscess)
      • hematogenous
    • Inclusion body myositis (probably due to para-myxovirus infection) resembling polymyositis
    • Sport / electric injury
    • Diabetic muscular infarction
    • Focal nodular myositis
    • Metabolic myopathy: eg, phosphofructokinase deficiency, hypokalemia, alcohol overdose
    • Viral myositis
    • Subacute muscle denervation
      Time of onset: 2–4 weeks after denervation
      • spinal cord injury, poliomyelitis, peripheral nerve injury / compression (ganglion cyst, bone spur), Graves disease, neuritis
    • Muscle contusion (from direct blow)
    • Muscle strain (= injury at musculotendinous junction from overly forceful muscle contraction)
      Predilection for: hamstring, gastrocnemius m., biceps brachii m.)
    • Delayed-onset muscle soreness
      = overuse injury becoming symptomatic hours / days after overuse episode)
    • Compartment syndrome
      = increased pressure within indistensible space of confining fascia leading to venous occlusion, muscle + nerve ischemia, arterial occlusion, tissue necrosis
      Cause: trauma, burns, heavy exercise, extrinsic pressure, intramuscular hemorrhage
      • severe pain
      • dysfunction of sensory + motor nerves passing through affected compartment
    • Sickle cell crisis
Fatty Infiltration of Muscle
  • Chronic stage of muscle denervation (eg, poliomyelitis, stroke, peripheral nerve injury)
  • Chronic disuse (eg, chronic tendon tear, severe osteoarthritis)
  • Late stage of severe muscle injury
  • Long-term high-dose corticosteroid medication affecting truncal muscles
Fixation devices
Internal Fixation Devices
  • Screws
    • Cortical screw = shallow finely threaded over entire length, blunt tip
      Use: fixation of plates
    • Cancellous screw = wide thread diameter with varying length of smooth shank between head + threads
      Use: compression across fracture site
    • Malleolar screw = partially threaded
    • Interference screw = short, fully threaded, cancellous thread pattern, self-tapping tip, recessed head
      Use: within tunnel holding bone graft of ACL and PCL reconstruction
    • Cannulated screw = hollow screw inserted over guide pin
      Use: fracture of femoral neck
    • Herbert screw = cannulated screw threaded on both ends with different pitches, no screw head
      Use: scaphoid fracture
    • Dynamic hip screw = screw free to slide within barrel of side plate allowing impaction of fracture during healing without perforation of subarticular cortex
      Use: subcapital, intertrochanteric, subtrochanteric fracture
  • Washer
    • Flat washer = increase surface area over which force is distributed
    • Serrated washer = spiked edges used for affixing avulsed ligaments
  • Plates
    • compression plate
      Use: compression of stable fractures
    • — neutralization plate = protects fracture from bending, rotation + axial-loading forces
    • buttress plate = support of unstable fractures in compression / axial loading
      • Straight plate
        • straight plate with round holes
        • dynamic compression plate = oval holes
        • tubular plate = thin pliable plate with concave inner surface
        • reconstruction plate = thin pliable plate to allow bending, twisting, contouring
      • Special plates
        T-shaped, L-shaped, Y-shaped, cloverleaf, spoon, cobra, condylar blade plate, dynamic compression screw system
  • Staples
    Fixation = bone = epiphyseal = fracture staples with smooth / barbed surface
    • Coventry = stepped osteotomy staple
    • stone = table staple
  • Wires
    • K wire = unthreaded segments of extruded wire of variable thickness
      Use: temporary fixation
    • Cerclage wiring = wire placed around bone

      No Caption Available.

      Use: fixation of comminuted patellar fracture, holding bone grafts in position
    • Tension band wiring = figure-of-eight wire placed on tension side of bone
      Use: olecranon / patellar fractures
External Fixation Devices
= smooth / threaded pins / wires attached to an external frame
  • unilateral pin = enters bone only from one side
    • Steinmann pin = large-caliber wire with pointed tip
    • Rush pin = smooth intramedullary pin
    • Schanz screw = pin threaded at one end to engage cortex, smooth at other end to connect to external fixation device
    • Knowles pin (for femoral neck fracture)
  • transfixing pin = passes through extremity supported by external fixation device on both ends
Intramedullary Fixation Devices
Use: diaphyseal long bone fractures
  • (a) nail = driven into bone without reaming
  • (b) rod = solid / hollow device with blunted tip driven into reamed channel (reaming disrupts blood supply and may decrease the rate of fracture healing)
  • (c) interlocking nail = accessory pins / screws / deployable fins placed to prevent rotation
  • 1. Rush pin = beveled end + hooked end
  • 2. Ender nail = oval in cross section
  • 3. Sampson rod = slightly curved rigid rod with fluted surface
  • 4. Küntscher nail = cloverleaf in cross section with rounded tip

Anatomy and Metabolism of Bone
Bone minerals
  • 99% in bone
  • serum calcium
    • protein-bound fraction (albumin)
    • ionic (pH-dependent) 3% as calcium citrate / phosphate in serum
Absorption: facilitated by vitamin D
Excretion: related to dietary intake; >500 mg/24 hours = hypercalciuria
Absorption: requires sodium; decreased by aluminum hydroxide gel in gut
Excretion: increased by estrogen, parathormone decreased by vitamin D, growth hormone, glucocorticoids
Bone marrow
  • Red marrow
    = hematopoietically active with a rich + extensive vascular supply, composed of erythrocyte + leukocyte + platelet precursors
    –in adolescence: 40% fat, 40% water, 20% protein
    –at age 70: 60% fat, 30% water, 10% protein
  • Yellow / fatty marrow
    with a sparse vascular network; composed of 80% fat, 15% water, 5% protein
    • Distribution changes throughout life with conversion from red to fatty marrow
      @ birth: marrow contains primarily hematopoietically active cells
      @ 1 year: phalanges of feet
      @ puberty: diaphysis of long bones
      @ 1st 2 decades: conversion begins in appendicular skeleton progressing to the axial skeleton; conversion in long bones begins in diaphysis > distal metaphysis > proximal metaphysis
      @ 3rd decade: residual red marrow remains in skull, spine, sternum, flat bones, proximal ends of humerus + femur; acetabulum superiorly + medially > ilium > around sacroiliac joints
Anatomic sites for MRI marrow screening:
  • –spine (SAG images)
  • –pelvis + femora (COR images)
      PTH Action Net Effect
    Principal: (1) phosphate diuresis (1) Serum: increase in Ca
      (2) resorption of Ca + P from bone decrease in P
    Secondary: (3) resorption of Ca from gut (2) Urine: increase in Ca
      (4) reabsorption of Ca from renal tubule increase in P
  • Differences in signal intensity are maximized on T1WI but diminished on T2WI
  • red marrow:
    • iso- / slightly hyperintense compared with muscle on T1WI + T2WI (longer T1 relaxation time)
    • hypointense compared with fatty marrow (shorter T2 relaxation time)
  • yellow marrow:
    • isointense compared with subcutaneous fat on T1WI (relatively short T1 relaxation time compared with water)
    • iso- / hypointense compared with subcutaneous fat on T2WI
    • hyperintense compared with muscle on T2WI (long T2 relaxation time compared with water)
Major stimulus: low levels of serum calcium ions (action requires vitamin D presence)
Target organs:
(a) BONE: increase in osteocytic + osteoclastic activity mobilizes calcium + phosphate = bone resorption
(b) KIDNEY: (1) increase in tubular reabsorption of Ca2+
(2) decrease in tubular reabsorption of phosphate (+ amino acids) = phosphate diuresis
(c) GUT: increased absorption of calcium + phosphorus
Major function:
  • increase of serum calcium levels
  • increase in serum alkaline phosphatase (50%)
Vitamin D Metabolism
required for
  • adequate calcium absorption from gut
  • synthesis of calcium-binding protein in intestinal mucosa
  • parathormone effects (stimulation of osteoclastic + osteocytic resorption of bone)
  • inactive form of vitamin D3 present through diet / exposure to sunlight (photoconversion of 7-dehydrocholesterol in skin to cholecalciferol); vitamin D3 is converted into 25-OH-vitamin D3 by liver and then converted into 1,25-OH vitamin D3 (biologically most active form = hormone) by kidney

    Stimulus for conversion: (1) hypophosphatemia
    (2) PTH elevation
(a) BOWEL: (1) increased absorption of calcium from bowel
(2) increased absorption of phosphate from distal small bowel
(b) BONE: (1) proper mineralization of osteoid
(2) mobilization of calcium + phosphate (potentiates parathormone action)
(c) KIDNEY: (1) increased absorption of calcium from renal tubule
(2) increased absorption of phosphate from renal tubule
(d) CELL: binds to receptor on nucleus which leads to activation of genes involved in calcium homeostasis
secreted by parafollicular cells of thyroid
Major stimulus: increase in serum calcium
Target organs:
(a) BONE: (1) inhibits parathormone-induced osteoclasis by reducing number of osteoclasts
(2) enhances deposition of calcium phosphate; responsible for sclerosis in renal osteodystrophy
(b) KIDNEY: inhibits phosphate reabsorption in renal tubule
(c) GUT: increases excretion of sodium + water into gut
Major function: decreases serum calcium + phosphate
Physis = Growth Plate
Four distinct zones of cartilage in longitudinal layers
  • Germinal zone = small cells
    adjacent to epiphyseal ossification center
  • Zone of proliferation = flattened cells
    arranged in columns
  • Zone of hypertrophy = swollen vacuolated cells
    • zone of maturation
    • zone of degeneration
    • zone of provisional calcification
  • Zone of primary and secondary spongiosa
Normal shoulder joint anatomy
Glenoid Labrum
  • = 4-mm–wide fibrocartilaginous ring with considerable variation in shape attached to glenoid rim
  • variations in attachment above epiphyseal line (= junction of upper + middle thirds of glenoid body fossa)
  • labrum continuous with glenoid articular cartilage inferior to epiphyseal line
  • triangular / rounded shape on cross-sectional image
  • blends superiorly with biceps tendon
Superior Sublabral Sulcus / Recess
= variations in depth of sulcus between glenoid rim + labrum
Types of Attachment of the Biceps-Labral Complex
Location: 12 o’clock position at the site of biceps tendon attachment (in sagittal plane)
Types of attachment of biceps-labral complex (BLC):
  • BLC firmly adherent to superior pole of glenoid without a sulcus / sublabral foramen
  • small sulcus = BLC attached several mm medially; hyaline cartilage beneath labrum; may be continuous with sublabral foramen which is anterior to BLC
  • deep probe-patent sulcus = meniscoid labrum with large sulcus between labrum and hyaline cartilage
  • may be continuous with sublabral foramen
  • best visualized on coronal CT / MR
    DDx: type II SLAP lesion
Biceps Tendon
  • = long head of biceps muscle
  • attached to anterosuperior aspect of glenoid rim with fibers to
    • anterosuperior labrum (biceps-labral complex)
    • posterosuperior labrum (biceps-labral complex)
    • supraglenoid tubercle
    • base of coracoid process
  • exits joint through intertubercular groove
  • secured to intertubercular groove by transverse lig.
Glenohumeral Ligaments
= thickened bands of joint capsule functioning as shoulder stabilizers
Superior Glenohumeral Ligament
  • = most consistently identified
  • arises from upper pole of glenoid cavity and base of coracoid process
  • attaches to middle glenohumeral ligament + anterosuperior labrum + biceps tendon
  • inserts just superior to lesser tuberosity in region of bicipital groove
  • courses in plane perpendicular to middle glenohumeral ligament + parallel to coracoid process
  • best visualized on transverse CT / MR
Middle Glenohumeral Ligament (MGL)
  • = varies most in size + attachment; may be absent
  • • ligament stretched when arm externally rotated
  • courses obliquely from superomedial to inferolateral
  • attaches medially on scapular neck / superior portion of anterior glenoid rim
  • attaches to anterior aspect of anatomic neck of humerus medial to lesser tuberosity
  • may be thick + cordlike
  • best visualized on sagittal / transverse CT / MR
    Normal Anatomy of Right Shoulder En Face (arrow in sublabral foramen)

Inferior Glenohumeral Ligament (IGL)
  • = important stabilizer of anterior shoulder joint, ie, it tightens during abduction + external rotation + prevents glenohumeral dislocation at the end range of motion
  • • ligament + labrum function as single unit = glenohumeral labral-ligamentous complex
  • attaches to inferior 2/3 of the circumference of the entire labrum over a variable distance
  • attaches to humerus laterally
  • Anterior band of IGL = thickened anterior-superior extent of ligament
  • Axillary pouch
  • Posterior band of IGL (usually thinner)
Normal Anatomic Variants of Shoulder
Sublabral Foramen = Sublabral Hole
= sublabral hole between labrum + glenoid
Incidence: 11% of individuals
Location: 2 o’clock position anterior to biceps tendon attachment
may coexist with sublabral recess
DDx: labral tear
Buford Complex
  • = cordlike thickening of middle glenohumeral ligament directly attaching to anterosuperior glenoid + absence of anterosuperior labrum
    Incidence: 1.5% of individuals
    Location: 2 o’clock position anterior to biceps tendon attachment
  • course of middle glenohumeral ligament can be followed on serial images from origin to insertion
  • may coexist with sublabral recess
    DDx: displaced anterosuperior labral fragment
    Buford Complex
    Rotator Cuff (dorsal aspect)
    Coracoacromial Arch (lateral aspect)

Foramen of Weitbrecht
= opening between SGL and MGL
Foramen of Rouviere
= opening between MGL and IGL
Rotator cuff muscles
mnemonic: SITS
  • Supraspinatus
  • Infraspinatus
  • Teres minor
  • Subscapularis
Occurrence of bone centers at elbow
mnemonic: CRITOE
Capitellum 1 year (3–6 months)
Radial head 4 years (3–6 years)
Internal humeral epicondyle 7 years (5–7 years, last to fuse)
Trochlea 10 years (9–10 years)
Olecranon 10 years (6–10 years)
External humeral epicondyle 11 years (9–13 years)
mnemonic: Nelson’s X: 1, 7, 10, 11 years
Carpal bones
mnemonic: Some Lovers Try Positions That They Can’t Handle
proximal row distal row
Scaphoid Trapezium
Lunate Trapezoid
Triquetrum Capitate
Pisiform Hamate
  • Remember that trapezium comes before trapezoid in the dictionary as well!
Ulnar Variance
  • = relative lengths of distal articular surfaces of radius and ulna
  • neutral = both surfaces at same level = equal length of ulna + radius
  • positive = ulnar surface distal to radial surface = long ulna
  • negative = ulnar surface proximal to radial surface = short ulna
    Occurrence of Bone Centers (numbers in years)
    Carpal Tunnel (radiograph)
    Wrist Cross Section of Distal Radioulnar Joint with the 6 Extensor Compartments (dorsal aspect)
    Carpal Bones and Ligaments (volar aspect)

    Central Segments of Scapholunate and Lunotriquetral Ligaments (coronal)
    Palmar and Dorsal Segments of Scapholunate and Lunotriquetral Ligaments (transverse)
Effect of wrist position:
  • increase of ulnar variance
    • maximum forearm pronation
    • firm grip
  • decrease of ulnar variance
    • maximum forearm supination
    • cessation of grip
Radiographic standard view of unloaded wrist:
  • posteroanterior, neutral forearm rotation, elbow flexed 90°, shoulder abducted 90°
Lower extremity
Pes Anserinus
  • = [pes, Latin = foot; anser, Latin = goose]
  • = tendinous configuration of 3 flexors + medial rotators of knee joint attaching inferomedially to tibial tuberosity
    mnemonic: Say GraceSe before eating goose
    • Sartorius tendon (anterior)
    • Gracilis tendon (middle)
    • Semitendinosus tendon (posterior)
Iliotibial Tract
= strong stabilizing band of deep fascia composed of the fusion of aponeurotic coverings of:
  • Tensor fascia lata
  • Gluteus maximus m.
  • Gluteus medius m.
  • supracondylar tubercle of lateral femoral condyle
  • lateral tubercle of tibia = Gerdy tubercle (main site)
  • patella + patellar ligament
  • medial hamstring
    • Semimembranosus m.
    • Semitendinosus m.
      Function: flexion + medial rotation of knee joint
  • lateral hamstring
    = long + short head of biceps femoris m.
    Function: flexion + lateral rotation of knee joint
Cruciate Ligaments
Both cruciate ligaments are intracapsular but extrasynovial!
Anterior Cruciate Ligament (ACL)
Function: limits anterior tibial translation
Origin: inner face of lateral femoral condyle
Insertion: noncartilaginous region of anterior aspect of intercondylar eminence of tibia
Anatomy: several distinct bundles of fibers
(1) large posterior bulk = spiraling together at femoral origin
(2) small anteromedial bundle diverging at tibial insertion
  • thin solid taut dark band (sagittal MR with knee in extension) almost parallel to intercondylar roof (= Blumensaat line):
    • with knee extension posterolateral band taut
    • with increasing flexion:
      anteromedial band becomes more taut + posterolateral band more lax
  • thin hypointense band parallel to inner aspect of lateral femoral condyle + fanlike configuration toward tibial spine (coronal MR)
  • thin ovoid hypointense band proximally, elliptical configuration distally with higher intensity (axial MR)
  • greater signal intensity than posterior cruciate ligament (due to anatomy)
Posterior Cruciate Ligament (PCL)
Function: limits posterior tibial translation
Origin: in a depression posterior to intercondylar region of tibia below joint surface
Insertion: most distal + anterior aspect of inner face of medial femoral condyle
  • thick dark band slightly posteriorly convex (arclike course on sagittal MR with knee in extension)
  • medial to ACL (coronal MR)
Collateral Ligaments of Knee Joint
Medial (Tibial) Collateral Ligament
Origin: just distal to adductor tubercle of femur
Insertion: anteromedial face of tibia distal to level of tibial tubercle about 5 cm below joint line

Name of Muscle Origin Insertion
Deltoid lateral third of clavicle deltoid tuberosity of humerus
  lateral border of acromion deltoid tuberosity of humerus
  lower part of spinous process of scapula deltoid tuberosity of humerus
Subscapularis medial 2/3 of costal surface of scapula superior aspect of lesser tubercle of humerus
Pectoralis major    
   –clavicular portion medial half of clavicle crest of greater tubercle of humerus
   –sternocostal portion manubrium + corpus of sternum crest of greater tubercle of humerus
   –abdominal portion anterior sheath of rectus abdominis crest of greater tubercle of humerus
Pectoralis minor 2nd / 3rd–5th ribs superomedial aspect of coracoid process
Biceps brachii    
   –long head supraglenoid tubercle of scapula tuberosity of radius
   –short head tip of coracoid process tuberosity of radius
Coracobrachialis tip of coracoid process medial surface of middle third of humerus
Supraspinatus supraspinatus fossa of scapula greater tubercle of humerus, highest facet
Infraspinatus infraspinatus fossa of scapula greater tubercle of humerus, middle facet
Teres minor upper 2/3 of lateral border of scapula greater tubercle of humerus, lower facet
Teres major dorsum of inferior angle of scapula inferior crest of lesser tubercle of humerus
Hip Flexors
Name of Muscle Origin Insertion
Gracilis inferior pubic ramus pes anserinus
Semimembranosus ischial tuberosity medial tibial condyle
Semitendinosus ischial tuberosity pes anserinus
Biceps femoris    
   –long head ischial tuberosity fibular head
   –short head lateral linea aspera fibular head
   –longus superior pubic ramus medial linea aspera
   –magnus inferior pubic ramus medial linea aspera
Sartorius anterior superior iliac spine pes anserinus
   –rectus anterior inferior iliac spine patellar tendon
   –vastus lateralis greater trochanter patellar tendon
   –vastus medialis medial intertrochanteric line patellar tendon
   –iliacus ilium lesser trochanter
   –psoas lumbar spine lesser trochanter
Tensor fasciae latae anterior superior iliac spine anterolateral tibia

Cross Section through L4-5
Cross Section through S1-2
Cross Section through Acetabular Roof
Cross Section through L5-S1
Cross Section through S4
Cross Section through Greater Trochanter

Cross Section through Obturator Foramen
Cross Section through Mid Thigh
Fat Pads of the Right Hip in Perfect AP Position
Cross Section through Minor Trochanter
Cross Section through Mid Thigh
Bony Landmarks of the Right Hip in Perfect AP Position

  • deep portion:
    • meniscofemoral ligament
    • meniscotibial ligaments
  • superficial portion
    • vertical band from femoral epicondyle to pes anserinus
    • posterior oblique ligament = posterior oblique band from femoral epicondyle to semimembranosus tendon
deep and superficial dark bands separated by a thin bursa + fatty tissue (on coronal MR)
Lateral (Fibular) Collateral Ligament
Origin: lateral aspect of lateral femoral condyle
Insertion: styloid process of fibular head
  • bicipital tendon + iliotibial band join lateral collateral ligament
Posterior Ankle Tendons
Achilles Tendon
Size: 7 mm in AP thickness (largest tendon of the body)
Origin: gastrocnemius + soleus muscle
  • surrounded by loose paratenon without tendon sheath
Plantaris Tendon
parallels Achilles tendon anteromedially
Insertion: Achilles tendon. calcaneus, plantar fascia
Medial Flexor Tendons
Posterior Tibialis Tendon
Size: twice the size of flexor digitorum longus tendon
Course: beneath medial malleolus (used as pulley)
Insertion: navicular, all cuneiforms, base of first four metatarsals, os naviculare
Flexor Digitorum Longus
Flexor Hallucis Longus
Course: groove beneath posterior process of talus, beneath sustentaculum tali
Insertion: base of distal phalanx of hallux
Cross Section through Distal Right Leg mnemonic for medial tendons: Tom, Dick and Harry from medial to lateral
  • Tibialis posterior
  • Digitorum longus (flexor)
  • Hallucis longus (flexor)

Plantar Compartments of the Midfoot
Plantar Compartments of the Forefoot
Medial compartment = bordered by medial septum (extending from plantar aponeurosis to navicular bone, medial cuneiform bone, and lateral border of plantar surface of 1st metatarsal bone); contains abductor hallucis m. + flexor hallucis brevis m. + flexor hallucis longus tendon
Lateral compartment = bordered by lateral septum (extending from plantar aponeurosis to medial surface of 5th metatarsal bone); contains abductor m. + short flexor m. + opponens m. of 5th toe
Central compartment = bordered by medial + lateral septa; communicates directly with posterior compartment of calf; subdivided by horizontal septa: adductor hallucis m. separated from quadratus plantae m.; contains flexor digitorum brevis m. + flexor digitorum longus tendon + quadratus plantae m. + lumbricales mm. + adductor hallucis m.
Deep subcompartment = bordered by transverse fascia of forefoot; separated from quadratus plantae m.; contains adductor hallucis m.

Accessory Ossicles of the Foot
  • Os talotibiale
  • Os supratalare
  • Os supranaviculare
  • Os infranaviculare
  • Os intercuneiforme
  • Os cuneometatarsale II dorsale
  • Os intermetatarsale
  • Secondary cuboid
  • Calcaneus secundarius
  • Os tibiale externum
  • Trigonum
  • Os accessorium supracalcaneum
  • Os subcalcis
  • Os peroneum
  • Os vesalianum
  • Talus accessorius
  • Os cuneonaviculare mediale
  • Sesamum tibiale anterius
  • Os cuneometatarsale I plantare
  • Cuboides secundarium
  • Os trochleare calcanei
  • Sesamoid talus - int. malleolus
  • Os subtibiale
  • Os sustentaculi
  • Os retinaculi
  • Os subfibulare
  • Talus secundarius
Calcaneal Pitch = Calcaneal Inclination Angle = determines longitudinal arch of foot; angle between line drawn along the inferior border of calcaneus connecting the anterior and posterior prominences + line representing the horizontal surface
Boehler Angle = angle between first line drawn from posterosuperior prominence of calcaneus anteriorly to sustentaculum tali + second line drawn from anterosuperior prominence posteriorly to sustentaculum tali; measures integrity of calcaneus
Talocalcaneal Angle on LAT View = angle between lines drawn through mid-transverse planes of talus + calcaneus; the midtalar line parallels the longitudinal axis of the first metatarsal
Intermetatarsal Angle = amount that 1st + 2nd metatarsals diverge from each other
Heel Valgus cannot be measured directly on radiographs but inferred from the talocalcaneal angle and estimated on coronal CT sections
Talocalcaneal Angle on AP View = KITE ANGLE = the midtalar and midcalcaneal lines parallel the 1st + 4th metatarsals; angle is greater in infants
Angle of Metatarsal Heads = obtuse angle formed by lines tangential to metatarsal heads

Bone and Soft-Tissue Disorders
= autosomal recessive lethal chondrodystrophy characterized by extreme micromelia, short trunk, large cranium
TRIAD: (1) severe short-limb dwarfism
(2) lack of vertebral calcification
(3) large head with normal / decreased calvarial ossification
Birth prevalence: 2.3:100,000
Path: disorganization of cartilage
  • TYPE I = Parenti-Fraccaro disease
    • = defective enchondral + membranous ossification
    • complete lack of ossification of calvarium + spine + pelvis
    • absent sacrum + pubic bone
    • extremely short long bones without bowing, especially femur, radius, ulna
    • thin ribs with multiple fractures (frequent)
  • TYPE II = Langer-Saldino disease
    • = defective enchondral ossification only
    • good ossification of skull vault
    • nonossification of lower lumbar vertebrae + sacrum
    • short + stubby horizontal ribs without fractures
  • • often subcutaneous edema
  • irregular flared metaphyses (esp. humerus)
  • short trunk with narrow chest + protruding abdomen
  • redundant soft tissues
  • polyhydramnios (common)
  • increase in HC:AC ratio
Prognosis: lethal often in utero / within few hours or days after birth (respiratory failure)
DDx: often confused with thanatophoric dwarfism
Heterozygous Achondroplasia
  • Prototype of rhizomelic dwarfism!
  • = autosomal dominant / sporadic (80%) disease with quantitatively defective endochondral bone formation; related to advanced paternal age; epiphyseal maturation + ossification unaffected
Incidence: 1:26,000–66,000 births, most common of lethal bone dysplasias; M < F
  • • normal intelligence + motor function
  • • neurologic defects
  • • classically circus dwarfs
  • @ Skull
    • • flat nasal bridge (hypoplastic base of skull)
    • • macrocephaly + brachycephaly with enlarged bulging forehead (nonprogressive hydrocephalus)
    • • relative prognathism
    • large calvarium with frontal bossing
    • depression of nasion
    • broad mandible
    • constricted basicranium + small foramen magnum:
      • communicating hydrocephalus caused by obstruction of basal cisterns + aqueduct
Cx: apnea + sudden death (due to compression of spinal cord + lower brain stem)
  • @ Chest
    • anteroposterior narrowing of chest
    • short anteriorly flared concave ribs
    • squaring of inferior scapular margin
  • @ Spine
    • hypoplastic bullet- / wedge-shaped vertebra:
      • rounded anterior beaking of vertebra in upper lumbar spine (DDx: Hurler disease)
      • decreased vertebral height
    • scalloped posteriorly concave vertebral margin
    • scoliosis:
      • thoracolumbar angular kyphosis (gibbus)
      • exaggerated sacral lordosis
    • stenosis of lumbar spine:
      • narrowing of interpedicular space due to laminar thickening
      • ventrodorsal narrowing of spine due to short pedicles
      • bulging / herniation of intervertebral disks
    • wide intervertebral foramina
  • @ Pelvis
    • • protuberant abdomen
    • • prominent buttocks
    • • rolling gait from backward tilt of pelvis and hip joints
    • square flattened iliac bones = tombstone configuration
    • “champagne glass”-shaped pelvic inlet
    • lack of flaring of iliac wings
    • horizontal acetabula (= flat acetabular angle)
    • small sacrosciatic notch
  • @ Extremities
    • • short stubby limbs + fingers
    • • trident hand = separation of 2nd + 3rd digit and inability to approximate 3rd + 4th finger
    • • limited range of motion of elbow
    • predominantly rhizomelic micromelia of long bones (femur, humerus):
      • “trumpet” appearance of long bones = shortening with disproportionate metaphyseal flaring (actually normal width of metaphysis)
      • short femoral necks
      • limb bowing
    • “ball-in-socket” epiphysis = broad V-shaped distal femoral metaphysis in which epiphysis is incorporated
    • high position of fibular head (= disproportionately long fibula)
    • short ulna with thick proximal + slender distal end
    • brachydactyly (short tubular bones of hand + feet), especially short proximal + middle phalanges
OB-US (diagnosable >21–27th week GA):
  • shortening of proximal long bones: femur length <99th percentile between 21 and 27 weeks MA
  • increased BPD, HC, HC:AC ratio
  • decreased FL:BPD ratio
  • normal mineralization, no fractures
  • normal thorax + normal cardiothoracic ratio
  • three-pronged (= trident) hand = 2nd + 3rd + 4th finger of similarly short length without completely approximating each other (= PATHOGNOMONIC)

Cx: (1) Hydrocephalus + syringomyelia (small foramen magnum)
(2) Recurrent ear infection (poorly developed facial bones)
(3) Neurologic complications (compression of spinal cord, lower brainstem, cauda equina, nerve roots): apnea and sudden death
4) Crowded dentition + malocclusion
Prognosis: long life
DDx: various mucopolysaccharidoses
Homozygous Achondroplasia
= hereditary autosomal dominant disease with severe features of achondroplasia (disproportionate limb shortening, more marked proximally than distally)
Risk: marriage of two achondroplasts to each other
  • large cranium with short base + small face
  • flattened nose bridge
  • short ribs with flared ends
  • hypoplastic vertebral bodies
  • decreased interpedicular distance
  • short squared innominate bones
  • flattened acetabular roof
  • small sciatic notch
  • short limb bones with flared metaphyses
  • short, broad, widely spaced tubular bones of hand
Prognosis: often stillborn; lethal in neonatal period (from respiratory failure)
DDx: thanatophoric dysplasia
= part of osteochondroplasias
Prevalence: 4:1,000,000
Etiology: mutation of genes encoding for cartilage oligomeric matrix protein (COMP) on chromosome 19 (closely related to multiple epiphyseal dysplasia)
Age at presentation: 2–4 years
  • • normal facial features and intelligence
  • • adult height 82–130 (mean, 118) cm
  • • disturbance of gait
  • • joint laxity
  • @ Skull: normal
  • @ Spine
    • persistent oval-shaped vertebral bodies
    • anterior beaking, platyspondyly
    • odontoid dysplasia
    • disk space widening
  • @ Extremities
    • short long bones with flared metaphyses
    • small irregular flared epiphyses with delayed development
    • medial beaking of proximal femoral neck (CHARACTERISTIC)
    • genu valgum, genu varum, genu recurvatum
    • shortening + widening of phalanges and metacarpals + metatarsals
  • @ Pelvis
    • widened triradiate cartilage
Cx: premature osteoarthritis
DDx: (1) Achondroplasia (large head with prominent frontal region + depressed bridge of nose, normal epiphyses, trident hands)
(2) Multiple epiphyseal dysplasia (near normal pelvis)
(3) Spondyloepiphyseal dysplasia congenita (hip joints more affected + near normal extremities)
(4) Diastrophic dwarfism (joint contractures and scoliosis at birth / in early infancy)
(5) Metatrophic dwarfism (dumbbell-shaped long bones + flattened vertebrae in infancy, less epiphyseal involvement)
= syndrome characterized by
  • increased height of skull vault due to generalized craniosynostosis (= acrocephaly, oxycephaly)
  • syndactyly of fingers / toes
Type I : Apert syndrome = acrocephalosyndactyly
Type II : Vogt cephalosyndactyly
Type III : Acrocephalosyndactyly with asymmetry of skull + mild syndactyly
Type IV : Wardenburg type
Type V : Pfeiffer type
Acroosteolysis, Familial
dominant inheritance
Age: onset in 2nd decade; M:F = 3:1
  • • sensory changes in hands + feet
  • • destruction of nails
  • • joint hypermobility
  • • swelling of plantar of foot with deep wide ulcer + ejection of bone fragments
  • @ Skull
    • wormian bones
    • craniosynostosis
    • basilar impression
    • protuberant occiput
    • resorption of alveolar processes + loss of teeth
  • @ Spine
    • spinal osteoporosis ± fracture
    • kyphoscoliosis + progressive decrease in height
Etiology: excess growth hormone due to eosinophilic adenoma / hyperplasia in anterior pituitary
  • • gigantism in children: advanced bone age + excessive height (DDx: Soto syndrome of cerebral gigantism = large skull, mental retardation, cerebral atrophy, advanced bone age)
  • osseous enlargement (phalangeal tufts, vertebrae)
  • flared ends of long bone
  • cystic changes in carpals, femoral trochanters
  • osteoporosis
  • @ Hand
    • • spadelike hand
    • widening of terminal tufts
  • @ Skull
    • prognathism (= elongation of mandible) in few cases
    • sellar enlargement + erosion
    • enlargement of paranasal sinuses: large frontal sinuses (75%)
    • P.44

    • calvarial hyperostosis (especially inner table)
    • enlarged occipital protuberance
  • @ Vertebrae
    • posterior scalloping in 30% (secondary to pressure of enlarged soft tissue)
    • anterior new bone
    • loss of disk space (weakening of cartilage)
  • @ Soft tissue
    • heel pad >25 mm
  • @ Joints
    • premature osteoarthritis (commonly knees)
= chronic suppurative infection characterized by formation of multiple abscesses, draining sinuses, abundant granulation tissue secondary to mucosal disruption + low tissue oxygen tension
Organism: Actinomyces israelii / naeslundii / viscosus / eriksonii, gram-positive non–acid-fast anaerobic pleomorphic small filamentous bacterium with proteolytic activity, superficially resembling the morphology of a hyphal fungus (Gomori methenamine silver stain-positive filaments); closely related to mycobacteria
  • contiguous: production of proteolytic enzymes allows crossing of normal anatomic barriers
  • hematogenous
Histo: mycelial form in tissue; as opportunistic pathogens rod-shaped bacterial form normally inhabits oropharynx (dental caries, gingival margins, tonsillar crypts) + GI tract
Predisposed: individuals with very poor dental hygiene, immunosuppressed patients
Location: mandibulofacial > intestinal > lung
Clinical types:
  • Mandibulo- / cervicofacial actinomycosis (55%)
    Cause: poor oral hygiene
    • • draining cutaneous sinuses
    • • “sulfur granules” in sputum / exudate = colonies of organisms arranged in circular fashion = mycelial clumps with thin hyphae 1–2 mm in diameter
    • osteomyelitis of mandible (most frequent bone involved) with destruction of mandible around tooth socket
    • no new-bone formation
    • spread to soft tissues at angle of jaw + into neck
  • Abdominopelvic / ileocecal / abdominal actinomycosis (20%)
    Cause: rupture / surgery of appendix; IUD use (25% of IUDs become eventually colonized with serious infections in 2–4%)
    Location: initially localized to cecum / appendix
    • •fever, leukocytosis, mild anemia
    • • weight loss, nausea, vomiting
    • • lower abdominal pain
    • • chronic sinus in groin, vaginal discharge
    • • yellow / brown sulfur granules on cervical Papanicolaou smear
    • fold thickening + ulcerations (resembling Crohn disease)
    • rupture of abdominal viscus (usually appendix)
    • fistula formation
    • abscess in liver (15%), retroperitoneum, psoas muscle, pelvis, tubo-ovarian abscess (containing yellow “sulfur granules” = 1–2-mm colony of gram-positive bacilli)
    • hydronephrosis (due to ureteral compression by pelvic abscess)
  • Pleuropulmonary / thoracic actinomycosis (15%)
    Cause: aspiration of infected material from oropharynx / hematogenous spread
    Predisposed: alcoholics
    Histo: masses of PMN leukocytes containing round actinomycotic / sulfur granules surrounded by a rim of granulation tissue
    • @ Lung
      • • draining chest wall sinuses (spread through fascial planes)
      • enhancing extensive transfissural chronic segmental consolidation (acute airspace pneumonia rare); usually unilateral + upper lobe predominance
      • cavitary lesion (abscess) with ringlike enhancement
      • fibrotic pleuritis
      • chronic pleural effusion / empyema
        • central areas of low attenuation within consolidation
        • adjacent pleural thickening
        DDx: carcinoma, tuberculosis, bacterial / fungal pneumonia
    • @ Vertebra + ribs
      • destruction of vertebra with preservation of disk + small paravertebral abscess without calcification (DDx to tuberculosis: disk destroyed, large abscess with calcium)
      • thickening of cervical vertebrae around margins
      • destruction / thickening of ribs
  • Mixed organs (10%)
    • @ Tubular bones of hands
      • destructive lesion of mottled permeating type
      • cartilage destruction + subarticular erosive defects in joints (simulating TB)
    • @ Skin, brain, pericardium
Dx: anaerobic culture; species-specific antibodies
Rx: surgical débridement + high doses of penicillin
  • = locally aggressive / malignant lesion
    Histo: pseudoepithelial cell masses with peripheral columnar cells in a palisade pattern with varying amounts of fibrous stroma; areas of squamous / tubular / alveolar / vessel transformation; prominent vascularity; resembles ameloblastoma of the jaw
    Age: 25–50 years, commonest in 3rd–4th decade
  • • frequently history of trauma
  • • local swelling ± pain
    Location: middle 1/3 of tibia (90%), fibula, ulna, carpals, metacarpals, humerus, shaft of femur
  • eccentric round osteolytic lesion with sclerotic margin, may have additional foci in continuity with major lesion (CHARACTERISTIC)
  • P.45

  • may show mottled density
  • bone expansion frequent
  • often multiple
    Prognosis: tendency to recur after local excision; after several recurrences pulmonary metastases may develop
    DDx: fibrous dysplasia (possibly related)
Ainhum Disease
  • [ainhum, Brazilian tribal language = fissure, saw, sword]
    Etiology: unknown
    Histo: hyperkeratotic epidermis with fibrotic thickening of collagen bundles below; chronic lymphocytic inflammatory reaction may be present; arterial walls may be thickened with narrowed vessel lumina
    Incidence: up to 2%
    Age: usually in males in 4th + 5th decades; Blacks (West Africa) + their American descendants; M > F
  • • deep soft-tissue groove forming on medial aspect of plantar surface of proximal phalanx with edema distally
  • • painful ulceration may develop
    Location: mostly 5th / 4th toe (rarely finger); near interphalangeal joint; mostly bilateral
  • sharply demarcated progressive bone resorption of distal / middle phalanx with tapering of proximal phalanx to complete autoamputation (after an average of 5 years)
  • osteoporosis
Rx: early surgical resection of groove with Z-plasty
DDx: (1) Neuropathic disorders (diabetes, leprosy, syphilis)
(2) Trauma (burns, frostbite)
(3) Acroosteolysis from inflammatory arthritis, infection, polyvinyl chloride exposure
(4) Congenitally constricting bands in amniotic band syndrome
= extracellular deposition of a chemically diverse group of protein polysaccharides in body tissues (β2-microglobulin); tends to form around capillaries + endothelial cells of larger blood vessels causing ultimately vascular obliteration with infarction
β2-microglobulin = low-molecular-weight serum protein not filtered by standard dialysis membranes
Path: stains with Congo red
At risk: patients on long-term hemodialysis
  • bone pain (eg, shoulder pain)
  • periarticular rubbery soft-tissue swelling + stiffness (shoulders, hips, fingers):
    • carpal-tunnel syndrome (commonly bilateral)
  • Bence Jones protein (without myeloma)
Amyloid Arthropathy
= synovial-articular pattern of amyloidosis
Location: cervical spine, hip, shoulder, elbow
  • juxtaarticular soft-tissue swelling (amyloid deposited in synovium, joint capsule, tendons, ligaments) ± extrinsic osseous erosion
  • mild periarticular osteoporosis
  • subchondral cysts + well-defined sclerotic margin
  • joint space preserved until late in course of disease
  • subluxation of proximal humerus + femoral neck
  • MR:
    • extensive deposition of abnormal soft tissue of low to intermediate signal intensity on T1WI + T2WI covering synovial membrane, filling subchondral defects, extending into periarticular tissue
    • joint effusion
DDx: inflammatory arthritis
Diffuse Amyloid Marrow Deposition
  • generalized osteoporosis
  • coarse trabecular pattern (DDx: sarcoidosis)
  • pathologic collapse of vertebral body may occur
  • = localized destructive lesion of amyloidosis (rarest form)
    Location: appendicular > axial skeleton
  • focal medullary lytic lesion with endosteal scalloping (± secondary invasion + erosion of articular bone)
    Cx: pathologic fracture
Aneurysmal Bone Cyst
= expansile pathologically benign lytic lesion of bone containing thin-walled cystic cavities filled with chronic blood products; name derived from roentgen appearance
  • primary ABC (65–99%)
    local circulatory disturbance as a result of trauma
  • secondary ABC (1–35%)
    arising in preexisting bone tumor causing venous obstruction / arteriovenous fistula: giant cell tumor (39%), osteoblastoma, chondroblastoma, angioma, telangiectatic osteosarcoma, solitary bone cyst, fibrous dysplasia, xanthoma, chondromyxoid fibroma, nonossifying fibroma, metastatic carcinoma
Histo: “intraosseous arteriovenous malformation” with honeycombed spaces filled with blood + lined by granulation tissue / osteoid; areas of free hemorrhage; sometimes multinucleated giant cells; solid component predominates in 5–7%
    • = primary cystic / telangiectatic tumor of giant cell family, originating in bone marrow cavity, slow expansion of cortex; rarely related to history of trauma
    • = posttraumatic hemorrhagic cyst; originating on surface of bones, erosion through cortex into marrow
Age: peak age 16 years (range 10–30 years); in 75% <20 years; F > M
  • pain of relatively acute onset with rapid increase of severity over 6–12 weeks
  • ± history of trauma
  • neurologic signs (radiculopathy to quadriplegia) if in spine
Location: (a) spine (12–30%) with slight predilection for posterior elements; thoracic > lumbar > cervical spine (22%); involvement of vertebral body (40–90%); may involve two contiguous vertebrae (25%)
(b) long bones: eccentric in metaphysis of femur, tibia, humerus, fibula; pelvis

  • purely lytic eccentric radiolucency
  • aggressive expansile ballooning lesion of “soap-bubble” pattern + thin internal trabeculations
  • rapid progression within 6 weeks to 3 months
  • sclerotic inner portion
  • almost invisible thin cortex (CT shows integrity)
  • tumor respects epiphyseal plate
  • no periosteal reaction (except when fractured)
  • “blood-filled sponge” = fluid-fluid / hematocrit levels due to blood sedimentation (in 10–35%)
  • multiple cysts of different signal intensity representing different stages of blood by-products:
    • heterogeneous fluid-fluid levels within loculations reflecting hemorrhage with sedimentation
    low-signal intensity rim = intact thickened periosteal membrane
  • heterogeneous enhancement
  • “doughnut sign” = peripheral increased uptake (64%)
  • hypervascularity in lesion periphery (in 75%)
Prognosis: 20–30% recurrence rate
Rx: preoperative embolotherapy; complete resection; radiation therapy (subsequent sarcoma possible)
Cx: (1) pathologic fracture (frequent)
(2) extradural block with paraplegia
DDx: (1) Giant cell tumor (particularly in spine)
(2) Hemorrhagic cyst (end of bone / epiphysis, not expansile)
(3) Enchondroma
(4) Metastasis (renal cell + thyroid carcinoma)
(5) Plasmacytoma
(6) Chondro- and fibrosarcoma
(7) Fibrous dysplasia
(8) Hemophilic pseudotumor
(9) Hydatid cyst
= diffuse infiltration of bone / soft tissue by hemangiomatous / lymphangiomatous lesions
Age: first 3 decades of life
May be associated with:
  • chylothorax, chyloperitoneum, lymphedema, hepatosplenomegaly, cystic hygroma
    • indolent course
      Location: femur > ribs > spine > pelvis > humerus > scapula > other long bones > clavicle
    • osteolysis with honeycomb / latticework (“hole-within-hole”) appearance
    • may occur on both sides of joint
      DDx: solitary osseous hemangioma
    • = extensive involvement of bone
      Histo: endothelium-lined cysts in bone
      Age: peak 10–15 years; range of 3 months to 55 years
      Location: long bones, skull, flat bones
    • multiple osteolytic metaphyseal lesions of 1–2 mm to several cm with fine sclerotic margins + relative sparing of medullary cavity
    • may show overgrowth of long bone
    • endosteal thickening
    • sometimes associated with soft-tissue mass ± phleboliths
    • chylous pleural effusion suggests fatal prognosis
      DDx: (other polyostotic diseases such as) histiocytosis X, fibrous dysplasia, metastases, Gaucher disease, congenital fibromatosis, Maffucci syndrome, neurofibromatosis, enchondromatosis
    • • poor prognosis
    • Maffucci syndrome
    • Osler-Weber-Rendu syndrome
    • Klippel-Trenaunay-Weber disease
    • Kasabach-Merritt syndrome
    • Gorham disease
= aggressive vascular malignancy with frequent local recurrence + distant metastasis
Histo: vascular channels surrounded by hemangiomatous / lymphomatous cellular elements with high degree of anaplasia
Age: M:F = 2:1
Associated with: Stewart-Treves syndrome
= angiosarcoma with chronic lymphedema developing in postmastectomy patients
Location: skin (33%); soft tissue (24%); bone (6%): tibia (23%), femur (18%), humerus (13%), pelvis (7%)
DDx: hemangioendothelioma, hemangiopericytoma
Ankylosing Spondylitis
= autoimmune disease of unknown etiology primarily affecting axial skeleton
Age: 15–35 years; M:F = 3:1–10:1; Caucasians:Blacks = 3:1
Associated with: (1) ulcerative colitis, regional enteritis
(2) iritis in 25%
(3) aortic insufficiency + atrioventricular conduction defect
  • HLA-B 27 positive in 96%
  • insidious onset of low back pain + stiffness
    Path: involves synovial + cartilaginous joints and sites of ligamentous attachment
    • axial skeleton: sacroiliac joints, thoracolumbar + lumbosacral junctions
      • HALLMARK is sacroiliac joint involvement!
    • peripheral skeleton (10–20%): sternal joint, symphysis pubis, hip, glenohumeral joint
    • tendinous insertions in pelvis + proximal femur
    Temporal course: initial abnormalities of sacroiliac joints + thoracolumbar junction with gradual involvement of remainder of spine

  • @ Skull
    • temporomandibular joint space narrowing, erosions, osteophytosis
  • @ Hand (30%)
    Target area: MCP, PIP, DIP
    • exuberant osseous proliferation
    • osteoporosis, joint space narrowing, osseous erosions (deformities less striking than in rheumatoid arthritis)
  • @ Sacroiliac joint / symphysis pubis
    • initially sclerosis of joint margins primarily on iliac side (bilateral + symmetric late in disease, may be unilateral + asymmetric early in disease)
    • later irregularities + widening of joint (cartilage destruction)
    • bony fusion
  • @ Pelvis
    • periostitic “whiskering”: ischial tuberosity, iliac crest, ischiopubic rami, greater femoral trochanter, external occipital protuberance, calcaneus
  • @ Spine
    • squaring = straightened / convex anterior vertebral margins = erosive osteitis of anterior corners
    • “shiny corner” = reactive sclerosis of corners of vertebral bodies
    • diskitis = erosive abnormalities of diskovertebral junction
    • “diskal ballooning” = biconvex shape of intervertebral disk related to osteoporotic deformity ± diskal calcification
    • marginal syndesmophyte formation = thin vertical radiodense spicules bridging the vertebral bodies = ossification of outer fibers of annulus fibrosus (NOT anterior longitudinal ligament):
      • “bamboo spine” on AP view = undulating contour due to syndesmophytosis
        Cx: prone to fracture resulting in pseudarthrosis
    • asymmetric erosions of laminar + spinous processes of lumbar spine
    • ossification of supraspinous + interspinous ligaments:
      • “dagger sign” = single radiodense line on AP view
      • “trolley-track” sign on AP view = central line of ossification with two lateral lines of ossification (apophyseal joint capsules)
    • apophyseal + costovertebral joint ankylosis (on oblique views)
    • dorsal arachnoid diverticula in lumbar spine with erosion of posterior elements (Cx: cauda equina syndrome)
    • atlantoaxial subluxation
  • @ Chest
    Incidence: 1% of patients with ankylosing spondylitis
    Histo: interstitial + pleural fibrosis with foci of dense collagen deposition, NO granulomas
    • bone manifestations obvious + severe
      Location: apices / upper lung fields
    • sternomanubrial joint irregularities + sclerosis
    • uni- / bilateral coarse upper lobe pulmonary fibrosis with upward retraction of hila (DDx: tuberculosis)
    • reticulonodular progressively confluent opacities in lung apices
    • apical bullae + cavitation (mimicking TB)
    • HRCT:
      • peripheral interstitial lung disease
      • bronchiectasis
      • paraseptal emphysema
      • apical fibrosis
      Cx: superinfection, especially with aspergillosis (mycetoma formation) / atypical mycobacteria
      DDx: other causes of pulmonary apical fibrosis (primary infection by fungi / mycobacteria; cancer)
  • @ Cardiovascular
    • Aortitis (5%) of ascending aorta ± aortic valve insufficiency
    Prognosis: 20% progress to significant disability; occasionally death from cervical spine fracture / aortitis
    DDx: (1) Reiter syndrome (unilateral asymmetric SI joint involvement, paravertebral ossifications)
    (2) Psoriatic arthritis (unilateral asymmetric SI joint involvement, paravertebral ossifications)
    (3) Inflammatory bowel disease
    (4) Sternocostoclavicular hyperostosis (pustulosis palmaris et plantaris)
Anterior Tibial Bowing
  • = congenital painless nonprogressive bilateral anterior leg bowing
    Age: beginning in early childhood
  • • may be accompanied by mental retardation, goiter, anemia
  • anterior bowing of tibia + fibula, bilaterally, symmetrically at middiaphysis
  • thickening of posterior tibial + fibular cortices
  • minor radioulnar bowing
  • kyphoscoliosis
  • extensive dural calcification
    DDx: Luetic saber shin (bowing at lower end of tibia + anterior cortical thickening)
Apert Syndrome
Frequency: 5.5:1,000,000 neonates
Etiology: autosomal dominant with incomplete penetrance; sporadic (in majority)
Associated with CNS anomalies:
  • megalocephaly, gyral abnormalities, hypoplastic white matter, heterotopic gray matter, frontal encephalocele, corpus callosal agenesis, Kleeblattschädel, cleft palate, ventriculomegaly (? related to skull base hypoplasia, rarely progressive)
  • IQ varies depending on CNS anomalies (in 50% normal)
  • otitis media (high prevalence)
  • bifid uvula
  • conductive hearing loss (common due to external + middle ear malformations)
  • @ Skull
    • • downturned mouth
    • brachycephalic skull (due to coronal craniosynostosis) + flat occiput
    • widened metopic + sagittal sutures extending from glabella to posterior fontanel (closing between 2 to 4 years)
    • hypoplastic / retruded midface:
      • hypertelorism
      • shallow orbits with proptosis
      • P.48

      • underdeveloped paranasal sinuses
      • underdeveloped maxilla with prognathism
    • high pointed arch of palate
    • prominent vertical crest in middle of forehead (increased intracranial pressure)
    • V-shaped anterior fossa due to elevation of lateral margins of lesser sphenoid
    • sella may be enlarged
    • stylohyoid ligament calcification (38–88%)
    • cervical spine fusion (in up to 71%), commonly of 5th and 6th vertebrae
    • choanal stenosis
  • @ Hand & feet
    • severe symmetric syndactyly = fusion of distal portions of phalanges, metacarpals / carpals (most often of 2nd, 3rd + 4th digit)
    • absence of middle phalanges
    • missing / supernumerary carpal / tarsal bones
    • pseudarthroses
  • @ GU (10%)
    • • cryptorchidism
    • hydronephrosis
    • polycystic kidneys (rare)
    • bicornuate uterus (rare)
Arteriovenous Fistula of Bone
Etiology: (a) acquired (usually gunshot wound)
(b) congenital
Location: lower extremity most frequent
  • soft-tissue mass
  • presence of large vessels
  • phleboliths (DDx: long-standing varicosity)
  • accelerated bone growth
  • cortical osteolytic defect (= pathway for large vessels into medulla)
  • increased bone density
  • = nonprogressive congenital syndrome complex characterized by poorly developed + contracted muscles, deformed joints with thickened periarticular capsule and intact sensory system
Pathophysiology: congenital / acquired defect of motor unit (anterior horn cells, nerve roots, peripheral nerves, motor end plates, muscle) early in fetal life with immobilization of joints at various stages in their development
Cause: ? neurotropic agents, toxic chemicals, hard drugs, hyperthermia, neuromuscular blocking agents, mytotic abnormalities, mechanical immobilization
Incidence: 0.03% of newborn infants; 5% risk of recurrence in sibling
Path: diminution in size of muscle fibers + fat deposits in fibrous tissue
Associated with: (1) neurogenic disorders (90%)
(2) myopathic disorders
(3) skeletal dysplasias
(4) intrauterine limitation of movement (myomata, amniotic band, twin, oligohydramnios)
(5) connective tissue disorders
Distribution: all extremities (46%), lower extremities only (43%), upper extremities only (11%); peripheral joints >> proximal joints; symmetrical
  • • clubfoot
  • • congenital dislocation of hip
  • • claw hand
  • • diminished muscle mass
  • • skin webs
  • flexion + extension contractures
  • osteopenia ± pathologic fractures
  • congenital dislocation of hip
  • carpal coalition
  • vertical talus
  • calcaneal valgus deformity
Asphyxiating Thoracic Dysplasia
  • = autosomal recessive dysplasia
    Incidence: 100 cases
    Associated with: renal anomalies (hydroureter), PDA
  • • respiratory distress due to reduced thoracic mobility (abdominal breathing) + frequent pulmonary infections
  • • progressive renal failure + hypertension
  • @ Chest
    • markedly narrow + elongated bell-shaped chest:
      • chest diameter significantly decreased compared with that of the abdomen
    • normal size of heart leaving little room for lungs
    • horizontal clavicles at level of 6th cervical vertebra
    • short horizontal ribs + irregular bulbous costochondral junction
  • @ Pelvis
    • trident pelvis (retardation of ossification of triradiate cartilage)
    • small iliac wings flared + shortened in cephalocaudal diameter (“wineglass” pelvis)
    • short ischial + pubic bones
    • reduced acetabular angle + acetabular spurs
    • premature ossification of capital femoral epiphysis
  • @ Extremities
    • rhizomelic brachymelia (humerus, femur) = long bones shorter + wider than normal
    • metaphyseal irregularity
    • postaxial hexadactyly (occasionally)
    • shortening of distal phalanges + cone-shaped epiphyses in hands + feet
    • proximal humeral + femoral epiphyses ossified at birth (frequently)
  • @ Kidneys
    • medullary cystic renal disease = enlarged kidneys with linear streaking on nephrogram (in adulthood)
    • OB-US:
      • proportionate shortening of long bones
      • small thorax with decreased circumference
      • increased cardiothoracic ratio
      • occasionally polydactyly
      • polyhydramnios
      Prognosis: neonatal death in 80% (respiratory failure + infections)
      DDx: Ellis-van Creveld syndrome
Avascular Necrosis
  • = consequence of interrupted blood supply to bone with death of cellular elements
Terminology (now often used interchangeably):
  • Osteonecrosis = ischemic bone death due to sepsis
  • Avascular necrosis = avascular and aseptic bone necrosis
  • Ischemic necrosis = necrosis of epiphyseal + subarticular bone
  • Bone infarction = necrosis of metaphyseal + diaphyseal bone
  • cellular ischemia leading to death of hematopoietic cells (in 6–12 hours), osteocytes (in 12–48 hours) and lipocytes (in 2–5 days)
  • necrotic debris in intertrabecular spaces + proliferation and infiltration by mesenchymal cells + capillaries
  • mesenchymal cells differentiate to osteoblasts on the surface of dead trabeculae synthesizing new bone layers + resulting in trabecular thickening
  • obstruction of extra- and intraosseous vessels by arterial embolism, venous thrombosis, traumatic disruption, external compression (increased marrow space pressure)
  • cumulative stress from cytotoxic factors
  • NO predisposing factors in 25%!
  • Traumatic interruption of arteries
    • @ femoral head:
      • Femoral neck fracture (60–75%)
      • Dislocation of hip joint (25%)
      • Slipped capital femoral epiphysis (15–40%)
    • @ carpal scaphoid:
      • 4–6 months after fracture (in 10–15%), in 30–40% of nonunion of scaphoid fracture
        Site: proximal fragment (most common)
    • @ humeral head (infrequent)
    • @ talus (after talar neck fracture)
  • Embolization of arteries
    • Hemoglobinopathy: sickle-cell disease
    • Nitrogen bubbles: Caisson disease
    • Fat: ethanol abuse with pancreatitis
  • Vasculitis
    • Collagen-vascular disease: SLE
    • Radiation exposure
  • Abnormal accumulation of cells
    • Lipid-containing histiocytes: Gaucher disease
    • Fat cells: steroid therapy
  • Idiopathic
    • Spontaneous osteonecrosis of knee
    • Legg-Calvé-Perthes disease
    • Freiberg disease (repetitive microtrauma)
mnemonic: PLASTIC RAGS
  • Pancreatitis, Pregnancy
  • Legg-Perthes disease, Lupus erythematosus
  • Alcoholism, Atherosclerosis
  • Steroids
  • Trauma (femoral neck fracture, hip dislocation)
  • Idiopathic (Legg-Perthes disease), Infection
  • Caisson disease, Collagen disease (SLE)
  • Rheumatoid arthritis, Radiation treatment
  • Amyloid
  • Gaucher disease
  • Sickle cell disease
  • Gaucher disease
  • Idiopathic (Legg-Calvé-Perthes, Köhler, Chandler)
  • Vasculitis (SLE, polyarteritis nodosa, rheumatoid arthritis)
  • Environmental (frostbite, thermal injury)
  • Irradiation
  • Neoplasia (-associated coagulopathy)
  • Fat (prolonged corticosteroid use increases marrow)
  • Alcoholism
  • Renal failure + dialysis
  • Caisson disease
  • Trauma (femoral neck fracture, hip dislocation)
  • Sickle cell disease
Location: femoral head (most common), humeral head, femoral condyles
  • dense osteonecrotic bone (due to lack of resorption relative to healthy osteopenic bone + new bone laid down over necrotic trabeculae)
  • radiolucent rim around area of osteonecrosis (due to absorption around necrotic bone)
Avascular Necrosis of Hip
  • Involvement of one hip increases risk to contralateral hip to 70%!
    Age: 20–50 years
  • • hip / groin / thigh / knee pain
  • • limited range of motion
Plain film (positive only several months after symptoms):
  • subtle relative sclerosis of femoral head secondary to resorption of surrounding vascularized bone (earliest sign)
  • radiolucent crescent parallel to articular surface in weight-bearing portion secondary to subchondral structural collapse of necrotic segment
    Site: anterosuperior portion of femoral head (best seen on frog leg view)
  • preservation of joint space (DDx: arthritis)
  • flattening of articular surface
  • increased density of femoral head (compression of bony trabeculae following microfracture of nonviable bone, calcification of dendritic marrow, creeping substitution = deposition of new bone)
Classification (Steinberg):


Stage 0 = normal
Stage I = normal / barely detectable trabecular mottling; abnormal bone scan / MRI
Stage IIA = focal sclerosis + osteopenia
Stage IIB = distinct sclerosis + osteoporosis + early crescent sign
Stage IIIA = subchondral undermining (“crescent sign”) + cyst formation
Stage IIIB = mild alteration in femoral head contour / subchondral fracture + normal joint space
Stage IV = marked collapse of femoral head + significant acetabular involvement
Stage V = joint space narrowing + acetabular degenerative changes
NUC (80–85% sensitivity):
  • Bone marrow imaging (with radiocolloid) more sensitive than bone imaging (with diphosphonates)
  • More sensitive than plain films in early AVN (evidence of ischemia seen as much as 1 year earlier)
  • Less sensitive than MR
Technique: imaging improved with double counts, pinhole collimation
  • early: cold = photopenic defect (interrupted blood supply)
  • late: “doughnut sign” = cold spot surrounded by increased uptake secondary to
    • capillary revascularization + new-bone synthesis
    • degenerative osteoarthritis
CT (utilized for staging of known disease):
  • staging upgrades in 30% compared with plain films
MR (90–100% sensitive, 85% specific for symptomatic disease):
Prevalence of clinically occult disease: 6%
  • MR imaging changes reflect the death of marrow fat cells (not death of osteocytes with empty lacunae)!
  • Sagittal images particularly useful!
    • decreased Gd-enhancement on short-inversion-recovery (STIR) images (very early)
    • low-signal intensity band with sharp inner interface + blurred outer margin on T1WI within 12–48 hours (= mesenchymal + fibrous repair tissue, amorphous cellular debris, thickened trabecular bone) seen as
      • band extending to subchondral bone plate
      • complete ring (less frequent)
    • “double-line sign” on T2WI (in 80%) [MORE SPECIFIC] = juxtaposition of inner hyperintense band (granulation tissue) + outer hypointense band (chemical shift artifact / fibrosis + sclerosis)
    • “pseudohomogeneous edema pattern” = inhomogeneous large areas of mostly decreased signal intensity on T1WI
    • hypo- to hyperintense lesion on T2WI
    • contrast-enhancement of interface + surrounding marrow + within lesion
    • predilection for anterosuperior portion of femoral head (sagittal images!)
      Stage T1 T2 Analogous to
      A high intermediate fat
      B high high subacute blood
      C low high fluid / edema
      D low low fibrosis
    • cleft of low-signal intensity running parallel to the subchondral bone plate within areas of fatlike signal intensity on T1WI
    • hyperintense band (= fracture cleft filled with articular fluid / edema) within the intermediate- or low-signal-intensity necrotic marrow on T2WI
    • lack of enhancement within + around fracture cleft
    • focal depression of subchondral bone
      Cx: early osteoarthritis through collapse of femoral head + joint incongruity in 3–5 years if left untreated
      Rx: (1) core decompression (for grade 0–II): most successful with <25% involvement of femoral head
      (2) osteotomy (for grade 0–II)
      (3) arthroplasty / arthrodesis / total hip replacement (for grade >III)
      DDx: bone marrow edema (ill-delimited marrow changes, no reactive interface); epiphyseal fracture (speckled / linear hypointense areas, focal depression of epiphyseal contour); spondyloarthropathy
Blount Disease
  • = avascular necrosis of medial tibial condyle
    Age: >6 years
  • • limping, lateral bowing of leg
  • medial tibial condyle enlarged + deformed (DDx: Turner syndrome)
  • irregularity of metaphysis (medially + posteriorly prolonged with beak)
Calvé-Kümmel-Verneuil Disease
  • = avascular necrosis of vertebral body
    Age: 2–15 years
  • uniform collapse of vertebral body into flat thin disk
  • increased density of vertebra
  • neural arches NOT affected
  • disks are normal with normal intervertebral disk space
  • intravertebral vacuum cleft sign (PATHOGNOMONIC)
    DDx: eosinophilic granuloma, metastatic disease
Freiberg Disease
[Albert Henry Freiberg (1868–1940), orthopedic surgeon in Cincinnati, Ohio]
= osteochondrosis of head of 2nd (3rd / 4th) metatarsal
Age: 10–18 years; M:F = 1:3
  • metatarsalgia, swelling, tenderness
  • flattening, increased density, cystic lesions of metatarsal head
  • widening of metatarsophalangeal joint
  • osteochondral fragment
  • sclerosis + flattening of metatarsal head
  • increased cortical thickening
Kienböck Disease
  • [Robert Kienböck (1871–1953), radiologist in Vienna, Austria]
  • = avascular necrosis of lunate bone

    Predisposed: individuals engaged in manual labor with repeated/single episode of trauma
    Age: 20–40 years
    Associated with: ulna minus variant (short ulna) in 75%
  • • progressive pain + soft-tissue swelling of wrist
    Location: uni- > bilateral (usually right hand)
  • initially normal radiograph
  • osteonecrotic fracture of carpal lunate
  • increased density + altered shape + collapse of lunate
    Cx: scapholunate separation, ulnar deviation of triquetrum, degenerative joint disease in radiocarpal / midcarpal compartments
    Rx: ulnar lengthening / radial shortening, lunate replacement
Köhler Disease
  • = avascular necrosis of tarsal scaphoid
    Age: 3–10 years; boys
  • irregular outline
  • fragmentation
  • disklike compression in AP direction
  • increased density
  • joint space maintained
  • decreased / increased uptake on radionuclide study
Legg-Calvé-Perthes Disease
  • = idiopathic avascular necrosis of femoral head in children; one of the most common sites of AVN;
    in 5–10% bilateral
    Age: (a) 2–12 (peak, 4–8) years: M:F = 5:1
    (b) adulthood: Chandler disease
    Cause: trauma in 30% (subcapital fracture, epiphyseolysis, esp. posterior dislocation), closed reduction of congenital hip dislocation, prolonged interval between injury and reduction
    insufficient femoral head blood supply (epiphyseal plate acts as a barrier in ages 4–10; ligamentum teres vessels become nonfunctional; blood supply is from medial circumflex artery + lateral epiphyseal artery only)
    I = histologic + clinical diagnosis without radiographic findings
    II = sclerosis ± cystic changes with preservation of contour + surface of femoral head
    III = loss of structural integrity of femoral head
    IV = in addition loss of structural integrity of acetabulum
    • 1 week–6 months (mean 2.7 months) duration of symptoms prior to initial presentation: limp, pain
  • NUC (may assist in early diagnosis):
    • decreased uptake (early) in femoral head = interruption of blood supply
    • increased uptake (late) in femoral head =
      • revascularization + bone repair
      • degenerative osteoarthritis
    • increased acetabular activity with associated degenerative joint disease
    • Early signs:
      • femoral epiphysis smaller than on contralateral side (96%)
      • sclerosis of femoral head epiphysis (sequestration + compression) (82%)
      • slight widening of joint space due to thickening of cartilage, failure of epiphyseal growth, presence of joint fluid, joint laxity (60%)
      • ipsilateral bone demineralization (46%)
      • alteration of pericapsular soft-tissue outline due to atrophy of ipsilateral periarticular soft tissues (73%)
      • rarefaction of lateral + medial metaphyseal areas of neck
      • NEVER destruction of articular cortex as in bacterial arthritis
    • Late signs:
      • delayed osseous maturation of a mild degree
      • “radiolucent crescent line” of subchondral fracture = small archlike subcortical lucency (32%)
      • subcortical fracture on anterior articular surface (best seen on frog leg view)
      • femoral head fragmentation
      • femoral neck cysts (from intramedullary hemorrhage in response to stress fractures)
      • loose bodies (only found in males)
    • Regenerative signs:
      • coxa plana = flattened collection of sclerotic fragments (over 18 months)
      • coxa magna = remodeling of femoral head to become wider + flatter in mushroom configuration to match widened metaphysis + epiphyseal plate
    • loss of “asterisk” sign (= starlike pattern of crossing trabeculae in center of femoral head) with distortion of asterisk and extension to surface of femoral head
    • normal signal intensity in marrow of femoral epiphysis replaced by low signal intensity on T1WI + high signal intensity on T2WI = “asterisk” sign
    • “double-line” sign (80%) = sclerotic nonsignal rim producing line between necrotic + viable bone edged by a hyperintense rim of granulation tissue
    • fluid within fracture plane
    • hip joint incongruity: lateral femoral head uncovering, labral inversion, femoral head deformity
    Cx: severe degenerative joint disease in early adulthood
    Rx: bed rest, abduction bracing (to reduce stress on infarcted head)
Panner Disease
  • (NOT osteonecrosis)
  • = benign self-limited disorder of fragmented ossification in epiphysis of capitellum
    Age: children 7–12 years of age
Preiser Disease
  • = nontraumatic osteonecrosis of scaphoid

Spontaneous Osteonecrosis of Knee
Cause: ? meniscal tear (78%), trauma with resultant microfractures, vascular insufficiency, degenerative joint disease, severe chondromalacia, gout, rheumatoid arthritis, joint bodies, intraarticular steroid injection (45–85%)
Age: 7th decade (range 13–83 years)
  • acute onset of pain
Location: weight-bearing medial condyle more toward epicondylus (95%), lateral condyle (5%), may involve tibial plateau
  • radiographs usually normal (within 3 months after onset)
  • positive bone scan within 5 weeks (most sensitive)
  • flattening of weight-bearing segment of medial femoral epicondyle
  • radiolucent focus in subchondral bone + peripheral zone of osteosclerosis
  • horizontal subchondral fracture (within 6–9 months) + osteochondral fragment
  • periosteal reaction along medial side of femoral shaft (30–50%)
    Cx: osteoarthritis
Talar AVN
  • Fractures involving the talar body have a higher prevalence of AVN
  • Risk of AVN:
    • nondisplaced fracture
      - talar neck fracture (Hawkins type I) 0–15%
    • fracture with dislocation / subluxation of:
      - subtalar joint (Hawkins type II) 20–50%
      - ankle + subtalar joints (Hawkins type III) almost 100%
      - subtalar + tibiotalar + talonavicular joints (Hawkins type IV fracture) 100%
  • increase in talar dome opacity / sclerosis
  • deformity + articular collapse + bone fragmentation
  • absent Hawkins sign = thin subchondral radiolucent line along talar dome (due to disuse osteopenia) indicates an adequate blood supply
Basal Cell Nevus Syndrome
  • = syndrome of autosomal dominant inheritance characterized by
    • multiple cutaneous basal cell carcinomas during childhood
    • odontogenic keratocysts of mandible
    • ectopic calcifications
    • skeletal anomalies
  • • multiple nevoid basal cell carcinomas (nose, mouth, chest, back) at mean age of 19 years; after puberty aggressive, may metastasize
  • • pitlike defects in palms + soles
  • • mental retardation
Association: high incidence of medulloblastoma in children; ovarian fibroma (in 17%); cardiac fibroma (in 14%)
  • @ mandibular hypoplasia:
    • multiple mandibular + maxillary cysts (dentigerous cysts + ectopic dentition)
  • anomalies of upper 5 ribs:
    • forked = bifid rib (most commonly 4th rib)
    • agenesis / supernumerary ribs
    • fusion of adjacent ribs
    • dysplastic distorted ribs
  • bifid spinous processes, spina bifida
  • scoliosis (cervical + upper thoracic)
  • hemivertebrae + block vertebrae
  • Sprengel deformity (scapula elevated, hypoplastic, bowed)
  • deficiency of lateral clavicle
  • brachydactyly
  • extensive calcification of falx + tentorium
  • ectopic calcifications of subcutaneous tissue, ovaries, sacrotuberous ligaments, mesentery
  • bony bridging of sella turcica
  • macrocephaly
Battered Child Syndrome
  • Most common cause of serious intracranial injuries in children <1 year of age; 3rd most common cause of death in children after sudden infant death syndrome + true accidents
    Prevalence: 1.7 million cases reported + 833,000 substantiated in United States in 1990 (45% neglected children, 25% physically abused, 16% sexually abused children); resulting in 2,500–5,000 deaths/year; 5–10% of children seen in emergency rooms
    Age: usually <2 years
  • • skin burns, bruising, lacerations, hematomas (SNAT = suspected nonaccidental trauma)
  • @ Skeletal trauma (50–80%)
    Site: multiple ribs, costochondral / costovertebral separation, acromion, skull, anterior-superior wedging of vertebra, tibia, metacarpus
    Unusual sites: transverse fracture of sternum, lateral end of clavicles, scapula, vertebral compression, vertebral fracture dislocation, disk space narrowing, spinous processes
    Other clues: bilateral acute fractures, fractures of lower extremities in children not yet walking
    • multiple asymmetric fractures in different stages of healing (repeated injury = HALLMARK)
    • exuberant callus formation at fracture sites
    • avulsion fracture of ligamentous insertion; frequently seen without periosteal reaction
    • @ Epiphysis
      • separation of distal epiphysis
    • @ Metaphysis
      • marked irregularity + fragmentation of metaphyses (DDx: osteochondritis stage of congenital syphilis; infractions of scurvy)
      • “corner” fracture (11%) = “bucket-handle” fracture
        = avulsion of an arcuate metaphyseal fragment overlying the lucent epiphyseal cartilage

        Cause: sudden twisting motion of extremity (periosteum easily pulled away from diaphysis but tightly attached to metaphysis)
        Location: knee, elbow, distal tibia, fibula, radius, ulna
    • @ Diaphysis
      • isolated spiral fracture (15%) of diaphysis secondary to external rotatory force applied to femur / humerus
      • extensive periosteal reaction from large subperiosteal hematoma apparent after 7–14 days following injury (DDx: scurvy, copper deficiency)
      • cortical hyperostosis extending to epiphyseal plate (DDx: not in infantile cortical hyperostosis)
  • @ Head trauma (13–25%)
    • Most common cause of death + physical disability!
      • Impact injury with translational force: skull fracture (flexible calvaria + meninges decrease likelihood of skull fractures), subdural hematoma, brain contusion, cerebral hemorrhage, infarction, generalized edema
      • Whiplash injury with rotational force: shearing injuries + associated subarachnoid hemorrhage
    • • bulging fontanels, convulsions
    • • ocular lesions, retinal detachment
    • Skull film (associated fracture in 1%):
      • linear fracture > comminuted fracture > diastases (conspicuously absent)
    • CT:
      • subdural hemorrhage (most common): interhemispheric location most common
      • subarachnoid hemorrhage
      • epidural hemorrhage (uncommon)
      • cerebral edema (focal, multifocal, diffuse)
      • acute cerebral contusion as ovoid collection of intraparenchymal blood with surrounding edema
    • MR:
      • More sensitive in identifying hematomas of differing ages
      • white matter shearing injuries as areas of prolonged T1 + T2 at corticomedullary junction, centrum semiovale, corpus callosum
  • @ Viscera (3%)
    • Second leading cause of death in child abuse
    Cause: crushing blow to abdomen (punch, kick)
    Age: often >2 years
    • small bowel / gastric rupture
    • hematoma of duodenum / jejunum
    • contusion / laceration of lung, pancreas, liver, spleen, kidneys
    • traumatic pancreatic pseudocyst
Cx: (1) Brain atrophy (up to 100%)
(2) Infarction (50%)
(3) Subdural hygroma
(4) Encephalomalacia
(5) Porencephaly
DDx: normal periostitis of infancy, long-term ventilator therapy in prematurity, osteogenesis imperfecta, congenital insensitivity to pain, infantile cortical hyperostosis, Menkes kinky hair syndrome, Schmid-type chondrometaphyseal dysplasia, scurvy, congenital syphilitic metaphysitis
Benign Cortical Defect
= developmental intracortical bone defect
Age: usually 1st–2nd decade; uncommon in boys <2 years of age; uncommon in girls <4 years of age
  • asymptomatic
    Site: metaphysis of long bone
  • well-defined intracortical round / oval lucency
  • usually <2 cm long
  • sclerotic margins
Cx: pathologic / avulsion fracture following minor trauma (infrequent)
Prognosis: (1) Spontaneous healing resulting in sclerosis / disappearance
(2) Ballooning of endosteal surface of cortex = fibrous cortical defect
(3) Medullary extension resulting in nonossifying fibroma
Bone Infarct
  • Occlusion of vessel:
    • thrombus: thromboembolic disease, sickle cell disease (SS + SC hemoglobin), polycythemia rubra vera
    • fat: pancreatitis (intramedullary fat necrosis from circulating lipase), alcoholism
    • gas: Caisson disease, astronauts
  • Vessel wall disease:
    • Arteritis: SLE, rheumatoid arthritis, polyarteritis nodosa, sarcoidosis
    • Arteriosclerosis
  • Vascular compression by deposition of:
    • fat: corticosteroid therapy (eg, renal transplant, Cushing disease)
    • blood: trauma (fractures + dislocations)
    • inflammatory cells: osteomyelitis, infection, histiocytosis X
    • edema: radiation therapy, hypothyroidism, frostbite
    • substances: Gaucher disease (vascular compression by lipid-filled histiocytes), gout
  • Others: idiopathic, hypopituitarism, pheochromocytoma (microscopic thrombotic disease), osteochondroses
Medullary Infarction
  • Nutrient artery is the sole blood supply for diaphysis!
Location: distal femur, proximal tibia, iliac wings, ribs, humeri
  • Acute phase:
    • NO radiographic changes without cortical involvement
    • area of rarefaction
    • infarcted area hypointense on T1WI + hyperintense on T2WI
    • bone marrow scan: diminished uptake in medullary RES for long period of time
    • bone scan: photon-deficient lesion within 24–48 hours; increased uptake after collateral circulation established
  • Healing phase (complete healing / fibrosis / calcification):
    • demarcation by zone of serpiginous / linear calcification + ossification parallel to cortex
    • dense bone indicating revascularization
    • P.54

    • focal lesion with fatty marrow signal intensity centrally + surrounding hypointense rim (corresponding to reactive / sclerotic bone)
Cortical Infarction
  • Requires compromise of (a) nutrient artery and (b) periosteal vessels!
    Age: particularly in childhood where periosteum is easily elevated by edema
  • avascular necrosis = osteonecrosis
  • osteochondrosis dissecans
Cx: (1) Growth disturbances
   √cupped / triangular / coned epiphyses
   √“H-shaped” vertebral bodies
(2) Fibrosarcoma (most common), malignant fibrous histiocytoma, benign cysts
(3) Osteoarthritis
Bone Island
  • = focal lesion of densely sclerotic (compact) bone nesting within spongiosa
Age: any age (mostly 20–80 years of age); grows more rapidly in children
Histo: nest of lamellar compacted bone with haversian system embedded within medullary canal
Pathogenesis: ? misplaced cortical hamartoma,? developmental error of endochondral ossification as a coalescence of mature bone trabeculae with failure to undergo remodeling; not inherited
Location: ilium + proximal femur (88–92%), ribs, spine (1–14%), humerus, phalanges (not in skull)
  • round / oval / oblong solitary osteoblastic lesion with abrupt transition to surrounding normal trabecular bone
  • long axis of bone island parallels long axis of bone
  • usually 2–10 mm in size; lesion >2 cm in longest axis = giant bone island
  • “brush border” = “thorny radiations” = sharply demarcated margins with feathery peripheral radiations (HALLMARK) blending with trabeculae of surrounding spongiosa
  • may show activity on bone scan, esp. if large (33%)
  • may demonstrate slow growth / decrease in size (32%)
  • NO involvement of cortex / radiolucencies / periosteal reaction
Prognosis: may increase to 8–12 cm over years (40%); may decrease / disappear
DDx: (1) Osteoblastic metastasis (aggressive, break through cortex, periosteal reaction)
(2) Low-grade osteosarcoma (cortical thickening, extension beyond medullary cavity)
(3) Osteoid osteoma (pain relieved by aspirin, nidus)
(4) Benign osteoblastoma
(5) Involuted nonossifying fibroma replaced by dense bone scar
(6) Eccentric focus of monostotic fibrous dysplasia
(7) Osteoma (surface lesion)
= multisystemic zoonosis of worldwide distribution; endemic in Saudi Arabia, Arabian Peninsula, South America, Spain, Italy (secondary to ingestion of raw milk / milk products)
Organism: small gram-negative nonmotile, nonsporing, aflagellate, nonencapsulated coccobacilli: Brucella abortus, B. suis, B. canis, B. melitensis
Histo: small intracellular pathogens shed in excreta of infected animals (urine, stool, milk, products of conception) cause small noncaseating granuloma within RES
Location: commonest site of involvement is reticulo-endothelial system; musculoskeletal system
  • 1–3 weeks between initial infection + symptoms
    • Radiologic evidence of disease in 69% of symptomatic sites!
  • Brucellar spondylitis (53%)
    Age: 40 years is average age at onset
    • pain, localized tenderness, radiculopathy, myelopathy
    Location: lumbar (71%) > thoracolumbar (10%) > lumbosacral (8%) > cervical (7%) > thoracic (4%)
    • focal form
      • bone destruction at diskovertebral junction (anterior aspect of superior endplate)
      • associated with bone sclerosis + anterior osteophyte formation + small amount of gas
    • diffuse form: entire vertebral endplate / whole vertebral body affected with spread to adjacent disks + vertebral bodies
      • bone destruction associated with sclerosis
      • small amount of disk gas (25–30%)
      • obliteration of paraspinal muscle-fat planes
      • no / minimal epidural extension
        DDx: TB (paraspinal abscess, gibbus)
  • @ Extraspinal disease
    • Brucellar synovitis (81%)
      Location: knee > sacroiliac joint > shoulder > hip > sternoclavicular joint > ankle > elbow
      Site: organism localized in synovial membrane
      • serosanguinous sterile joint effusion
    • Brucellar destructive arthritis (9%)
      • indistinguishable from tuberculous / pyogenic arthritis
    • Brucellar osteomyelitis (2%)
      • pain, tenderness, swelling
    • Brucellar myositis (2%)
Dx: serologic tests (enzyme-linked immunosorbent assay, counterimmunoelectrophoresis, rose bengal plate test
Rx: combination of aminoglycosides + tetracyclines
DDx: fibrous dysplasia, benign tumor, osteoid osteoma
Caisson Disease
Etiology: during too rapid decompression = reduction of surrounding pressure (ascent from dive, exit from caisson / hyperbaric chamber, ascent to altitude) nitrogen bubbles form (nitrogen more soluble in fat of panniculus adiposus, spinal cord, brain, bones containing fatty marrow)
  • “the bends” = local pain in knee, elbow, shoulder, hip
  • neurologic symptoms (paresthesia, major cerebral / spinal involvement)
  • P.55

  • “chokes” = substernal discomfort + coughing (embolization of pulmonary vessels)
    Location: mostly in long tubular bones of lower extremity (distal end of shaft + epiphyseal portion); symmetrical lesions
  • early: area of rarefaction
  • healing phase: irregular new-bone formation with greater density
  • peripheral zone of calcification / ossification
  • ischemic necrosis of articular surface with secondary osteoarthritis
Calcium Pyrophosphate Dihydrate Crystal Deposition Disease
  • Most common crystalline arthropathy
    Types: 1. Osteoarthritic form (35–60%)
    2. Pseudogout = acute synovitis (10–20%)
    3. Rheumatoid form (2–6%)
    4. Pseudoneuropathic arthropathy (2%)
    5. Asymptomatic with tophaceous pseudogout (common)
    Associated with: hyperparathyroidism, hypothyroidism, hemochromatosis, hypomagnesemia
    Prevalence: widespread in older population; M:F = 3:2
  • • calcium pyrophosphate crystals in synovial fluid + within leukocytes (characteristic weakly positive birefringent diffraction pattern)
  • • acute / subacute / chronic joint inflammation
    Location: (a) knee (especially meniscus + cartilage of patellofemoral joint)
    (b) wrist (triangular fibrocartilage in distal radioulnar joint bilaterally)
    (c) pelvis (sacroiliac joint, symphysis)
    (d) spine (annulus fibrosis of lumbar intervertebral disk; NEVER in nucleus pulposus as in ochronosis)
    (e) shoulder (glenoid), hip (labrum), elbow, ankle, acromioclavicular joint
  • polyarticular chondrocalcinosis (in fibro- and hyaline cartilage)
  • large subchondral cyst (HALLMARK)
  • numerous intraarticular bodies (fragmentation of subchondral bone)
  • involvement of tendons, bursae, pinnae of the ear
    N.B.: pyrophosphate arthropathy resembles osteoarthritis: joint space narrowing + extensive subchondral sclerosis
  • @ Hand
    Distribution: radiocarpal compartment; trapezioscaphoid joint + 1 CMC; 2,3 MCP joints; bilateral symmetric
    • resembling degenerative joint disease (without DIP and PIP involvement)
    • small hook-like osteophytes at radial aspect of metacarpal heads 2 & 3
    • extensive narrowing / obliteration of joint space between distal radius + scaphoid:
      • incorporation of scaphoid into articular surface of radius
      • prominent cysts
    • calcification of triangular fibrocartilage
    • scapholunate separation
    • destruction of trapezioscaphoid space
  • @ Knee
    • medial femorotibial + patellofemoral compartments commonly involved simultaneously (as in osteoarthritis) but with greater osseous destruction + fragmentation
    • disproportionate narrowing of patellofemoral joint
  • @ Spine
    • chondrocalcinosis / calcifications of outer fibers of annulus fibrosus resembling syndesmophytes
    • vertical radiodense line in symphysis pubis
Camptomelic Dysplasia
= sporadic / autosomal recessive dwarfism
Incidence: 0.05:10,000 births
Associated with:
  • Hydrocephalus (23%)
  • Congenital heart disease (30%): VSD, ASD, tetralogy, AS
  • Hydronephrosis (30%)
  • • npretibial dimple
  • macrocephaly, cleft palate, micrognathia (90–99%)
  • @ Chest & spine
    • hypoplastic scapulae (92%)
    • narrow bell-shaped chest
    • hypoplastic vertebral bodies + nonmineralized pedicles (especially lower cervical spine)
  • @ Pelvis
    • vertically narrowed iliac bones
    • vertical inclination of ischii
    • wide symphysis
    • narrow iliac bones with small wings
    • shallow acetabulum
  • @ Extremities (lower extremity more severely affected)
    • dislocation of hips + knees
    • anterior bowing (= campto) of long bones: marked in tibia + moderate in femur
    • hypoplastic fibula
    • small secondary ossification center of knee
    • small primary ossification center of talus
    • clubfoot
  • OB-US:
    • bowing of tibia + femur
    • decreased thoracic circumference
    • hypoplastic scapulae
    • ± cleft palate
Prognosis: death usually <5 months of age (within first year in 97%) due to respiratory insufficiency
Carpal Tunnel Syndrome
= entrapment syndrome caused by chronic pressure on the median nerve within the carpal tunnel
Cause: repetitive wrist / finger flexion; carpal tunnel crowding by cyst / mass / flexor tendon tendinitis or tenosynovitis / anomalous origin of lumbrical muscles
Pathogenesis: probably ischemia with venous congestion (stage 1), nerve edema from anoxic damage to capillary endothelium (stage 2), impairment of venous + arterial blood supply (stage 3)

  • nocturnal hand discomfort
  • weakness, clumsiness, finger paresthesias
    • “pseudoneuroma” of median nerve = swelling of median nerve proximal to carpal tunnel
    • swelling of nerve within carpal tunnel
    • increased signal intensity of nerve on T2WI
    • volar bowing of flexor retinaculum
    • swelling of tendon sheath (due to tenosynovitis)
    • mass(es) within carpal tunnel
    • marked enhancement (nerve edema = breakdown of blood-nerve barrier)
    • no enhancement (ischemia) provoked by wrist held in an extended / flexed position
Carpenter Syndrome
  • autosomal recessive
  • • retardation
  • • hypogonadism
  • patent ductus arteriosus
  • acro(oxy)cephaly
  • preaxial polysyndactyly + soft-tissue syndactyly
Cerebrocostomandibular Syndrome
  • = rare bone disorder of uncertain transmission
  • • respiratory distress (due to flail chest + airway abnormalities)
  • 11 pairs of ribs:
    • abnormal costovertebral articulations
    • posterior ossification gaps resembling fractures
  • microcephaly
  • micrognathia
  • congenital heart disease
    DDx: multiple fractures
Incidence: 1% of primary bone neoplasms (700 cases in world literature)
Age: peak in 2nd decade (range of 8–59 years); 10–26 years (90%); M:F = 2:1; occurs before cessation of enchondral bone growth
Path: derived from primitive cartilage cells
Histo: polyhedral chondroblasts + multinucleated giant cells + nodules of pink amorphous material
(= chondroid) = epiphyseal chondromatous giant cell tumor (resembles chondromyxoid fibroma); “chicken wire” calcification = pericellular deposition of calcification is virtually PATHOGNOMONIC
  • symptomatic for months to years prior to treatment
  • mild joint pain, tenderness, swelling (joint effusion)
  • limitation of motion
  • long bones (80%): proximal femur + greater trochanter (23%), distal femur (20%), proximal tibia (17%), proximal humerus (17%)
    • 2/3 in lower extremity, 50% about knee
    • may occur in apophyses (minor + greater trochanter, patella, greater tuberosity of humerus)
  • flat bones: near triradiate cartilage of innominate bone, rib (3%)
  • short tubular bones of hand + feet
Site: eccentric medullary, subarticular location with open growth plate (98% begin within epiphysis); tumor growth may continue to involve metaphysis (50%) + rarely diaphysis
  • oval / round eccentrically placed lytic lesion of epiphysis
  • 1–4 cm in diameter occupying < one-half of epiphysis
  • well-defined sclerotic margin, lobulated in 50%
  • stippled / irregular calcifications in 25–30–50% (cartilaginous clumps better visualized by CT)
  • intact scalloped cortical border
  • thick periosteal reaction in metaphysis (50%) / joint involvement
  • periostitis of adjacent metaphysis / diaphysis (30–50%)
  • open growth plate in majority of patients
  • MR tends to overestimate extent + aggressiveness due to large area of reactive edema!
  • intermediate to low signal intensity on T2WI relative to fat
  • extensive intramedullary signal abnormalities consistent with bone marrow edema
  • peripheral rim of very low signal intensity
  • hypointense changes on T1WI + hyperintense on T2WI in adjacent soft tissues (muscle edema) in 50%
  • ± joint effusion
Prognosis: almost always benign; may become locally aggressive; rarely metastasizes
Dx: surgical biopsy
Rx: curettage + bone chip grafting (recurrence in 25%)
DDx: (1) Ischemic necrosis of femoral head (may be indistinguishable, more irregular configuration)
(2) Giant cell tumor (usually larger + less well demarcated, not calcified, older age group with closed growth plate)
(3) Chondromyxoid fibroma
(4) Enchondroma
(5) Osteomyelitis (less well-defined, variable margins)
(6) Aneurysmal bone cyst
(7) Intraosseous ganglion
(8) Langerhans cell histiocytosis (less well-defined, variable margins)
(9) Primary bone sarcoma
Chondrodysplasia Punctata
  • = proportional / mesomelic dwarfism
    Etiology: peroxisomal disorder characterized by fibroblast plasmalogen deficiency
    Incidence: 1:110,000 births
    Associated with: CHD (common)
    • • flat face
    • • congenital cataracts
    • • ichthyotic skin thickening
    • • mental retardation
    • P.57

    • • cleft palate
    • multiple small punctate calcifications of varying size in epiphyses (knee, hip, shoulder, wrist), in base of skull, in posterior elements of vertebrae, in respiratory cartilage and soft tissues (neck, rib ends) before appearance of ossification centers
    • prominent symmetrical shortening of femur + humerus (rarely all limbs symmetrically affected)
    • congenital dislocation of hip
    • flexion contractures of extremities
    • clubfeet
    • metaphyseal splaying of proximal tubular bones (in particular about knee)
    • thickening of diaphyses
    • prominent vertebral + paravertebral calcifications
    • coronal clefts in vertebral bodies
      Prognosis: death usually <1 year of age
      DDx: Zellweger syndrome
    • more common milder nonlethal variety;
    • autosomal dominant
    • • normal intelligence
    • more widespread but milder involvement as above
      Prognosis: survival often into adulthood
Cx: respiratory failure (severe underdevelopment of ribs), tracheal stenosis, spinal cord compression
DDx: (1) Cretinism (may show epiphyseal fragmentation, much larger calcifications within epiphysis)
(2) Warfarin embryopathy
(3) Zellweger syndrome
Chondroectodermal Dysplasia
  • = autosomal recessive acromesomelic dwarfism
    Incidence: 120 cases; in inbred Amish communities
    Associated with: congenital heart disease in 50% (single atrium, ASD, VSD)
  • • ectodermal dysplasia:
    • absent / hypoplastic brittle spoon-shaped nails
    • irregular + pointed dysplastic teeth, partial anodontia, teeth may be present at birth
    • scant / fine hair
  • •obliteration of maxillary mucobuccal space (thick frenula between alveolar mucosa + upper lip)
  • •strabismus
  • •genital malformations: epispadia, hypospadia, hypoplastic external genitalia, undescended testicles
  • hepatosplenomegaly
  • accelerated skeletal maturation
  • normal spine
  • @ Skull
    • wormian bones
    • cleft lip
  • @ Chest
    • elongated narrow thorax in AP + transverse dimensions exaggerating the heart size
    • cardiomegaly (frequently ASD / single atrium)
    • short horizontal ribs + anterior osseous expansion
    • elevated clavicles
  • @ Pelvis
    • small flattened ilium
    • trident shape of acetabulum with indentation in roof + bony spur (almost pathognomonic)
    • acetabular + tibial exostoses
  • @ Extremities
    • variety of micromelia (= thickening + shortening of all long bones):
      • acromelia = hypoplasia / absence of terminal phalanges
      • mesomelia = shortening of forearms + lower legs (radius + tibia > humerus + femur)
    • cone-shaped epiphyses
    • premature ossification of proximal humeral + femoral epiphyses
    • @ Upper extremity
      • “drumstick” forearm = swelling of proximal end of ulna + distal end of radius
      • anterior dislocation of radial head (due to shortening of ulna)
      • carpal / tarsal fusion = frequent fusion of two / more carpal (hamate + capitate) + tarsal bones (after complete ossification)
      • supernumerary carpal bones
      • postaxial polydactyly common (usually finger, rarely toe) ± syndactyly of hands + feet
    • @ Lower extremity
      • genu valgum:
        • slanting of proximal tibial metaphysis (= delayed development of tibial plateau)
        • excessive shortening of fibula
      • widening of proximal tibial shaft
      • medial tibial diaphyseal exostosis
  • OB-US:
    • proportional shortening of long bones
    • small thorax with decreased circumference
    • increased cardiothoracic ratio
    • ASD
    • polydactyly
    Prognosis: death within first month of life in 33–50% (due to respiratory / cardiac complications)
    DDx: asphyxiating thoracic dysplasia (difficult distinction); rhizomelic achondroplasia
Chondromalacia Patellae
  • = pathologic softening of patellar cartilage leading to defects of surface (chondrosis) / osteoarthritis
    Cause: trauma, tracking abnormality of patella
  • • anterior knee pain
  • • asymptomatic (incidental arthroscopic diagnosis)
Chondromyxoid Fibroma
Rare benign cartilaginous tumor; initially arising in cortex
Incidence: <1% of all bone tumors
Histo: chondroid + fibrous + myxoid tissue (related to chondroblastoma); may be mistaken for chondrosarcoma
Age: peak 2nd–3rd decade (range of 5–79 years); M:F = 1:1
  • slowly progressive local pain, swelling, restriction of motion

    Grade Arthroscopic Pathology T1WI of MRI
    1 softening + swelling of articular cartilage (chondrosis) focal hypointense areas not extending to cartilage surface / subchondral bone (MR / MR arthrography unreliable)
    2 blistering of articular cartilage producing deformity of surface <1 cm in diameter focal hypointense areas extending to cartilage surface with preservation of sharp cartilage margins
    3 surface irregularity + cartilage fibrillation with minimal extension to subchondral bone >1 cm in diameter focal hypointense areas extending to articular surface but not to osseous surface; loss of sharp dark margin between articular cartilage of patella + trochlea
    4 ulceration with exposure of subchondral bone focal hypointense areas extending from subchondral bone to cartilage surface; cartilage thinned to subchondral bone
    Location: (a) long bones (60%): about knee (50%), proximal tibia (82% of tibial lesions), distal femur (71% of femoral lesions), fibula
    (b) short tubular bones of hand + feet (20%)
    (c) flat bones: pelvis, ribs (classic but uncommon)
    Site: eccentric, metaphyseal (47–53%), metadiaphyseal (20–43%), metaepiphyseal (26%), diaphyseal (1–10%), epiphyseal (3%)
  • expansile ovoid lesion with radiolucent center + oval shape at each end of lesion
  • long axis parallel to long axis of host bone (1–10 cm in length and 4–7 cm in width)
  • geographic bone destruction (100%)
  • well-defined sclerotic margin (86%)
  • expanded shell = bulged + thinned overlying cortex (68%)
  • partial cortical erosion (68%)
  • scalloped margin (58%)
  • septations (57%) may mimic trabeculations
  • stippled calcifications within tumor in advanced lesions (7%)
  • NO periosteal reaction (unless fractured)
    Prognosis: 25% recurrence rate following curettage
    Cx: malignant degeneration distinctly unusual
    DDx: (1) Aneurysmal bone cyst
    (2) Simple bone cyst
    (3) Nonossifying fibroma
    (4) Fibrous dysplasia
    (5) Enchondroma
    (6) Chondroblastoma
    (7) Eosinophilic granuloma
    (8) Fibrous cortical defect
    (9) Giant cell tumor
    • no preexisting bone lesion
    as a complication of a preexisting skeletal abnormality such as
    • Osteochondroma
    • Enchondroma
    • Parosteal chondroma
Spread: via marrow cavity / periosteum
Metastases (uncommon) to: lung, epidural space
  • chondroid matrix mineralization of “rings and arcs” (CHARACTERISTIC) in 70%
  • nonmineralized portion of tumor hypodense to muscle (high water content of hyaline cartilage)
  • extension into soft-tissues
  • low to intermediate signal intensity on T1WI
  • high signal intensity on T2WI + hypointense areas (due to mineralization / fibrous septa)
  • enhancement of fibrous septations
Central Chondrosarcoma
    Incidence: 3rd most common primary bone tumor (1st multiple myeloma, 2nd osteosarcoma); 8–17% of biopsied primary bone tumors
    Path: lobular morphology with variable amounts of calcium; presence of fibrous bands at tumor-marrow interface suggests malignancy (DDx from atypical enchondroma)
    Histo: arises from chondroblasts (tumor osteoid is never formed)
    Age: median 45 years; 50% >40 years; 10% in children (rapidly fatal); M:F = 2:1
  • hyperglycemia as paraneoplastic syndrome (85%)
    Location: neck of femur, pubic rami, proximal humerus, ribs (19%), skull (sphenoid bone, cerebellopontine angle, mandible), sternum, spine (3–12%)
    Site: central within medullary canal + meta- / diaphysis
  • expansile osteolytic lesion 1 to several cm in size
  • short transition zone ± sclerotic margin (well defined from host bone)
  • ± small irregular punctate / snowflake type of calcification; single / multiple
  • late: loss of definition + break through cortex
  • endosteal cortical thickening, sometimes at a distance from the tumor (due to invasion of haversian system)
  • presence of large soft-tissue mass
    DDx: benign enchondroma, osteochondroma, osteosarcoma, fibrosarcoma
Peripheral Chondrosarcoma
  • = malignant degeneration of hereditary multiple osteochondromatosis and rarely of a solitary exostosis (beginning in cartilaginous cap of exostosis)

    Frequency: 8% of all chondrosarcomas
    Average age: 50–55 years for solitary exostosis; 25–30 years for hereditary multiple osteochondromatosis; M:F = 1.5:1
    Histo: low histologic grade in 67–85%
  • • growth after skeletal maturity
  • • gradually increasing pain, often worse at night
  • • local swelling / palpable mass (45%)
    Location: pelvis, hip, scapula, sternum, ribs, ends of humerus / femur, skull, facial bones
  • growth of a previously unchanged osteochondroma in a skeletally mature patient
  • unusually large soft-tissue mass (= hyaline cartilage cap) containing flocculent / streaky chondroid calcifications (CHARACTERISTIC):
    • cartilage cap 1.5–12 cm (average, 5.5–6 cm) thick
      • >1.5 cm is suspect of malignant transformation
  • irregular / indistinct lesion surface:
    • dense radiopaque center with streaks radiating to periphery with loss of smooth margin
    focal regions of radiolucency in interior of lesion
  • erosion / destruction of adjacent bone
    Metastases: in 3–7%, most commonly to lung
    Rx: wide resection
    Prognosis: 70–90% long-term survival
    DDx: (1) Osteochondroma (densely calcified with multiple punctate calcifications)
    (2) Parosteal osteosarcoma (more homogeneous density of calcified osteoid)
Clear Cell Chondrosarcoma
  • Usually mistaken for chondroblastoma because of low grade malignancy (may be related)!
Histo: small lobules of tissue composed of cells with centrally filled vesicular nuclei surrounded by large clear cytoplasm
Age: 19–68 years, predominantly after epiphyseal fusion
Location: proximal femur, proximal humerus, proximal ulna, lamina vertebrae (5%); pubic ramus
Site: epiphysis
  Enchondroma Intramedullary Chondrosarcoma
Mean age and sex 40 years; M:F = 2:3 50 years; M:F = 11:9
Palpable mass 28% 82%
Pain 40% (fracture associated) 95% (longer duration + increasing severity)
Lesion location hands, feet axial skeleton (spine, pelvis)
Site diaphysis metaphysis, epiphysis
Lesion size <5 cm >5–6 cm
Endosteal scalloping    
   relative to cortical thickness 90% <2/3 of cortical thickness 90% >2/3 of cortical thickness,
   relative to lesion length 66% along <2/3 of lesion 79% along >2/3 of lesion
Cortical remodeling (radiography) 15% 47%
Cortical thickening (radiography) 17% 47%
Periosteal reaction (radiography) 3% 47%
Pathologic fracture (radiography) 5% 27%
Matrix mineralization (CT) 100% (more extensive) 94% (less extensive)
Cortical destruction (CT) 8% 88%
Soft-tissue extension (MR) 3% 76%
Small hyperintense foci (T1WI) 65% 35%
  • single lobulated oval / round sharply marginated lesion of 1–2 cm in size
  • surrounding increased bone density
  • aggressive rapid growth over 3 cm
  • may contain calcifications
  • bone often enlarged
  • indistinguishable from conventional chondrosarcoma / chondroblastoma (slow growth over years)
Extraskeletal Chondrosarcoma
Incidence: 2% of all soft-tissue sarcomas
Myxoid Extraskeletal Chondrosarcoma
(most common)
Mean age: 50 years (range 4–92 years); M > F
Histo: surrounded by fibrous capsule + divided into multiple lobules by fibrous septa; delicate strands of small elongated chondroblasts are suspended in an abundant myxoid matrix; foci of mature hyaline cartilage are rare
  • • slowly growing soft-tissue mass
  • • pain + tenderness (33%)
  • Metastatic in 40–45% at time of presentation!
    Location: extremities (thigh most common)
    Site: deep soft tissues; subcutis (25%)
  • lobulated soft-tissue mass WITHOUT calcification / ossification
  • usually between 4 and 7 cm in diameter
  • approximately equal to muscle on T1WI + equal to fat on T2WI
  • may mimic a cyst / myxoma

Prognosis: 45% 10-year survival rate; 5–15 years survival after development of metastases
Extraskeletal Mesenchymal Chondrosarcoma
  • 50% of all mesenchymal chondrosarcomas arise in soft tissues
    Histo: proliferation of small primitive mesenchymal cells with scattered islands of cartilage; hemangiopericytoma-like vascular pattern
    Bimodal age distribution: M = F
    • tumors of head + neck in 3rd decade (common): meninges, periorbital region
    • tumors of thigh + trunk in 5th decade
  • • frequently metastasized to lungs + lymph nodes
  • matrix mineralization (50–100%) characterized as rings + arcs / flocculent + stippled calcification / dense mineralization
  • approximately equal to muscle on T1WI + equal to fat on T2WI
  • signal voids from calcifications
  • homogeneous enhancement
Prognosis: 25% 10-year survival rate
Cleidocranial Dysostosis
  • = delayed ossification of midline structures (particularly of membranous bone)
  • Autosomal dominant disease
  • @ Skull
    • • large head
    • diminished / absent ossification of skull (in early infancy)
    • wormian bones
    • widened fontanels + sutures with delayed closure
    • persistent metopic suture
    • brachycephaly + prominent bossing
    • large mandible
    • high narrow palate (± cleft)
    • hypoplastic paranasal sinuses
    • delayed / defective dentition
  • @ Chest
    • hypoplasia / absence (10%) of clavicles (defective development usually of lateral portion, R > L (DDx: congenital pseudarthrosis of clavicle)
    • thorax may be narrowed + bell-shaped
    • supernumerary ribs
    • incompletely ossified sternum
    • hemivertebrae, spondylosis (frequent)
  • @ Pelvis
    • delayed ossification of bones forming symphysis pubis (DDx: bladder exstrophy)
    • hypoplastic iliac bones
  • @ Extremities
    • radius short / absent
    • elongated second metacarpals
    • pseudoepiphyses of metacarpal bases
    • short hypoplastic distal phalanges of hand
    • pointed terminal tufts
    • coned epiphyses
    • coxa vara = deformed / absent femoral necks
    • accessory epiphyses in hands + feet (common)
  • cephalopelvic disproportion (large fetal head + narrow birth canal of affected maternal pelvis) necessitates cesarean section
Histo: chronic granulomatous process in bones, joints, periarticular structures
Location: (a) bones: most frequently in metaphyses of long bones + medial end of clavicle, spine, ribs, pelvis / bony prominences of patella, tibial tuberosity, calcaneus, olecranon, acromion
(b) weight-bearing joints (33%): ankle, knee, wrist, elbow
   • “desert rheumatism” = immune-complex–mediated arthritis
(c) tenosynovitis of hand, bursitis
  • focal areas of destruction, formation of cavities (early) = bubbly bone lesion
  • bone sclerosis surrounding osteolysis (later, rare)
  • proliferation of overlying periosteum
  • destruction of vertebra with preservation of disk space
  • psoas abscess indistinguishable from tuberculosis, may calcify
  • joints rarely infected (usually monoarticular from direct extension of osteomyelitic focus): synovial effusion, osteopenia, joint space narrowing, bone destruction, ankylosis
  • soft-tissue abscesses common
    DDx: tuberculosis
Congenital Insensitivity to Pain With Anhydrosis
  • = rare autosomal recessive disorder presumably on the basis of abnormal neural crest development
    Age: presenting at birth
    Incidence: 15 reported cases
    Path: absence of dorsal + sympathetic ganglia, deficiency of neural fibers <6 μm in diameter + disproportionate number of fibers of 6–10 μm in diameter
  • • history of painless injuries + burns (DDx: familial dysautonomia, congenital sensory neuropathy, hereditary sensory radicular neuropathy, acquired sensory neuropathy, syringomyelia)
  • • abnormal pain + temperature perception
  • • burns, bruises, infections are common
  • • biting injuries of fingers, lips, tongue
  • • absence of sweating
  • • mental retardation
    CRITERIA: (1) defect must be present at birth
    (2) general insensitivity to pain
    (3) general mental / physical retardation
  • epiphyseal separation in infancy (epiphyseal injuries result in growth problems)
  • metaphyseal fractures in early childhood
  • diaphyseal fractures in late childhood
  • Charcot joints = neurotrophic joints (usually weight-bearing joints) with effusions + synovial thickening
  • ligamentous laxity
  • bizarre deformities + gross displacement + considerable hemorrhage (unnoticed fractures + dislocations)
  • P.61

  • osteomyelitis + septic arthritis may occur + progress extensively
    DDx: (1) sensory neuropathies (eg, diabetes mellitus)
    (2) hysteria
    (3) syphilis
    (4) mental deficiency,
    (5) syringomyelia
    (6) organic brain disease
Cornelia De Lange Syndrome
  • • mental retardation (IQ <50)
  • • hirsutism; hypoplastic genitalia
  • • feeble growling cry
  • • high forehead; short neck
  • • arched palate
  • • bushy eyebrows meeting in midline + long curved eyelashes
  • • small nose with depressed bridge; upward tilted nostrils; excessive distance between nose + upper lip
  • small + brachycephalic skull
  • hypoplasia of long bones (upper extremity more involved)
  • forearm bones may be absent
  • short radius + elbow dislocation
  • thumbs placed proximally (hypoplastic 1st metacarpal)
  • short phalanges + clinodactyly of 5th finger
Cortical Desmoid
  • = rare fibrous lesion of the periosteum
    Age: peak 14–16 years (range of 3–17 years); M:F = 3:1
    Histo: shallow defect filled with proliferating fibroblasts, multiple small fragments of resorbing bone (microavulsions) at tendinous insertions
  • • no localizing signs / symptoms
    Location: posteromedial aspect of medial femoral epicondyle along medial ridge of linea aspera at attachment of adductor magnus aponeurosis; 1/3 bilateral
  • area of cortical thickening
  • 1–2 cm irregular, shallow, concave saucerlike crater with sharp margin
  • lamellated periosteal reaction
  • localized cortical hyperostosis proximally (healing phase)
  • May be confused with a malignant tumor (eg, osteosarcoma) / osteomyelitis!
Cri-Du-Chat Syndrome
  • = deletion of short arm of 5th chromosome (5 p)
  • • generalized dwarfism due to marked growth retardation
  • • failure to thrive
  • • peculiar high-pitched cat cry (hypoplastic larynx)
  • • antimongoloid palpebral fissures
  • • strabismus
  • • profound mental retardation
  • • round facies
  • • low-set ears
    Associated with: congenital heart disease (obtain CXR!)
  • agenesis of corpus callosum
  • microcephaly
  • hypertelorism
  • small mandible
  • faulty long-bone development
  • short 3rd, 4th, 5th metacarpals
  • long 2nd, 3rd, 4th, 5th proximal phalanges
  • horseshoe kidney
    Dx: made clinically
Crouzon Syndrome
  • = Apert syndrome without syndactyly
  • = skull + cranial base deformities characterized by craniosynostosis, maxillary hypoplasia, shallow orbits, ocular proptosis, bifid uvula, cleft palate
    Prevalence: 1:25,000
    Etiology: autosomal dominant inheritance (in 67%)
    Associated intracranial anomalies: anomalous venous drainage, hydrocephalus (often progressive), Chiari I malformation (71%)
  • • parrot-beak nose
  • • strabismus
  • • deafness
  • • mental retardation
  • • dental abnormalities
  • • bifid uvula
  • • acanthosis nigrans (= hyperpigmented hyperkeratotic lesions on neck + near joint flexures)
  • premature craniosynostosis: acro(oxy)cephaly / brachycephaly / scaphocephaly / trigonocephaly / “cloverleaf” skull
  • hypertelorism + exophthalmos (due to shallow orbits)
  • hypoplastic maxilla (relative prominence of mandible)
  • cleft palate
  • calcification of stylohyoid ligament (in 50% of patients >4 years of age)
  • C2 to C5 spine abnormalities (in up to 40%)
  • elbow malformation (18%)
  • minor hand deformities (10%)
  • visceral anomalies (7%)
  • musculoskeletal deformities (7%)
  • cloverleaf appearance (coronal view) + bilateral frontal indentations (axial view) of skull
  • increased interorbital distance + ocular proptosis
  • mild ventriculomegaly
Cruciate Ligament Injury
    • failure to identify ligament
    • amorphous areas of high signal intensity on T1WI + T2WI with inability to define ligamentous fibers
    • focal discrete complete disruption of all visible fibers
    • abnormal signal intensity within substance of ligament with some intact + some discontinuous fibers
Anterior Cruciate Ligament Injury (ACL tear)
Frequency: in up to 69% of all patients undergoing arthroscopy; in up to 72% of acutely injured knees with hemarthrosis
Mechanism: twisting, valgus impaction + internal rotation, hyperextension of knee with foot planted (football) / lower leg forcibly externally rotated during knee flexion (backwards fall while skiing)
  • • pivot shift test (82–90% sensitive) = examiner applies valgus stress on internally rotated leg while flexing the knee; induced anterolateral rotary subluxation reduces spontaneously at 40° flexion with an audible “pop”
  • • anterior drawer sign (22–80% sensitive) = proximal tibia displaces anteriorly with the knee flexed at 60°–90°
  • • Lachman test (77–99% sensitive) = same as anterior drawer sign with knee flexed at 10°–20°
    Location: midsubstance of ligament / near femoral attachment (in adults) / avulsion of anterior intercondylar eminence or tibial spines (in children)
  • If the ACL appears intact in one of the sagittal oblique sequences discordant findings in other sequences can be disregarded!
    Site: intrasubstance tear near insertion of femoral condyle (frequently); bone avulsion (rarely)
  • loss of fiber continuity + abnormal fiber orientation on PD image
  • hyperintense signal (= focal fluid collection / soft-tissue edema) replacing the tendon substance in acute tear on T2WI
  • pseudomass (hematoma + torn fibers) in intercondylar notch near femoral attachment
  • concavity of anterior margin of ligament
  • nondisplaced avulsion fracture of tibial eminence in children (coronal T1WI)
Secondary signs (low sensitivity, high specificity):
  • anterior translation of tibia (= anterior drawer sign) by >5 mm with respect to femur measured at midsagittal plane of lateral femoral condyle
  • “uncovering” of lateral meniscus = posterior displacement of posterior horn of lateral meniscus >3.5 mm behind tibial plateau
  • bowed PCL due to increased laxity = angle between proximal + distal limbs of PCL <105°
Associated signs:
  • for anterolateral rotary instability (football, skiing):
    • bone bruise in lateral compartment (posterolateral tibia + terminal sulcus of lateral femoral condyle) in 40–90% on fat-suppressed T2WI
      • ACL intact in 28% of adolescents with bone bruise
    • low-signal–intensity line surrounded by region of high-signal–intensity marrow edema in posterior aspect of lateral tibial plateau (= occult fracture) on STIR image
  • for hyperextension injury:
    • bone contusion in anterior tibial plateau + femoral condyles
  • varus stress with external rotation:
    • avulsion of joint capsule from lateral tibial rim (Segond fracture)
  • deepening of lateral femoral sulcus >1.5 mm (due to osteochondral impaction injury)
False-positive Dx:
  • slice thickness / interslice gap too great
  • adjacent fluid / synovial proliferation
  • cruciate ganglion / synovial cyst
Associated injuries:
  • meniscal tear (lateral > medial) in 65%
Rx: (1) conservative: strengthening of quadriceps muscle + brace for activities
(2) arthroscopic reconstruction with autograft (patellar tendon / combined semitendinosus and gracilis tendon) or allograft (cadaveric patellar / Achilles tendon)
Subacute ACL Tear
Definition: few weeks after injury
  • fibers better defined as hemorrhage + edema subside
  • change in fiber contour + angle of residual fragments
Chronic ACL Tear
Definition: months to years after injury
  • bridging fibrous scar within intercondylar notch (simulating an intact ligament with its low signal intensity)
  • disorganized scar tissue instead of linear parallel fibers
  • major distal ACL fragment assumes a more horizontal orientation (= less steep than the roof of the intercondylar notch or Blumensaat line)
  • ACL may fuse to posterior cruciate ligament
  • complete absence of ligament
Partial ACL Tear (15%)
  • Extremely difficult to diagnose! 40–50% of partial tears are missed on MR!
  • • positive Lachman test (in 12–30%)
  • MR primary signs positive for injury (in 33–43%)
Posterior Cruciate Ligament Injury (PCL)
Prevalence: 2–23% of all knee injuries
  • midsubstance of PCL most frequently involved (best seen on sagittal images)
  • bone avulsion from posterior tibial insertion (<10%), best seen on lateral plain film
  • Direct blow to proximal anterior tibia with knee flexed (dashboard injury)
    • midsubstance PCL tear
    • injury to posterior joint capsule
    • bone contusion at anterior tibial plateau + femoral condyles farther posteriorly
  • Hyperextension of knee
    • avulsion of tibial attachment of PCL (with preservation of PCL substance)
    • ± ACL rupture
    • bone contusion in anterior tibial plateau + anterior aspect of femoral condyles
  • Severe ab- / adduction + rotational forces
    • + injury to collateral ligaments
    Associated with: coexistent ligamentous injury in 70%
    anterior cruciate ligament 27–38%
    medial collateral ligament 20–23%
    lateral collateral ligament 6–7%
    medial meniscal tear 32–35%
    lateral meniscal tear 28–30%
    bone marrow injury 35–36%
    effusion 64–65%
  • In 30% of cases injury of PCL is isolated!
  • • posterior tibial laxity
  • • difficult to evaluate arthroscopically unless ACL torn
Deep Fibromatosis
Aggressive Infantile Fibromatosis
  • = childhood equivalent of deep fibromatosis
    Age: first 2 years of life; rarely >5 years of age; M > F
    Histo: may mimic infantile fibrosarcoma
  • • firm nodular soft-tissue mass within skeletal muscle / fascia / periosteum
Location: head, neck (tongue, mandible, mastoid), shoulder, thigh, foot
Extraabdominal Desmoid Tumor
  • = common benign aggressively growing soft-tissue tumor arising from connective tissue of muscle, fascia, aponeurosis outside abdominal cavity
Peak age: 25–35 years
Histo: parallel halo arrays of uniform-appearing fibroblasts surrounded by highly variable amounts of collagen fibers with infiltrative growth pattern
  • • painless soft-tissue mass
    Location: extremities (70%); shoulder (20%), chest wall + back (15%), thigh (12%), mesentery (10%), neck (10%), knee (7%); solitary (majority) / synchronous multicentricity in same extremity (10–15%)
  • Most common benign soft-tissue tumor of the foot
    Site: fascia in / around muscle
  • mostly <10 cm in diameter
  • @ Bone
    • Erlenmeyer flask deformity in multicentric fibromatosis (infrequent)
  • @ Abdominal wall
    Prevalence: in 87% in females of childbearing age
    Predilection: female patients taking birth control pills / during or after pregnancy
    Location: aponeurosis of rectus abdominis, internal oblique muscle
  • poorly defined (with invasion of fat / muscle) / lobulated well-defined lesion
  • hypo- / isointense to muscle on T1WI
  • hyperintense (hypercellular) / hyperintense with areas of low intensity (intermixed with fibrous components) / hypointense (hypocellular) on T2WI
Cx: compresses / engulfs adjacent structures
Prognosis: 75% recurrence within 2 years after surgical excision (up to 87% local recurrence in <30 years of age; 20% recurrence rate in >20 years of age)
Abdominal Desmoid Tumor
  • = uncommon benign tumor of the subgroup of fibromatoses consisting of fibrous tissue with insidious growth [desmos, Greek = band / tendon]
Location: mesentery (most common mesenteric primary), musculoaponeurosis of rectus, internal oblique muscle; occasionally external oblique muscle
Age: peak age in 3rd decade, 70% between 20 and 40 years of age; M:F = 1:3
Path: poorly circumscribed coarsely trabeculated tumor resembling scar tissue, confined to musculature + overlying aponeurosis
Histo: elongated spindle-shaped cells of uniform appearance, septated by dense bands of collagen, infiltration of adjacent tissue (DDx: low-grade fibrosarcoma, reactive fibrosis)
Associated with: Gardner syndrome, multiple pregnancies, prior trauma
• firm slowly growing deep-seated mass
Size: 5–20 cm in diameter
  • hypointense to muscle on T1WI + variable intensity on T2WI
  • ill-defined / well-circumscribed mass
  • usually higher attenuation than muscle
  • ± enhancement
  • retraction, angulation, distortion of small / large bowel with mesenteric infiltration
  • sharply defined + smoothly marginated mass of low / medium / high echogenicity
Cx: compression / displacement of bowel / ureter, intestinal perforation
Prognosis: locally aggressive growth; 25–65% recurrence rate
Rx: local resection + radiotherapy, antiestrogen therapy
DDx: (1) Malignant tumor: metastasis, fibrosarcoma, rhabdomyosarcoma, synoviosarcoma, liposarcoma, fibrous histiocytoma, lymphoma
(2) Benign tumor: neurofibroma, neuroma, leiomyoma
(3) Acute hematoma
Infantile Myofibromatosis
  • = rare disorder characterized by proliferation of fibroblasts


Cause: unknown
Frequency: most common fibromatosis in childhood
Age: at birth (in 60%), <2 years (in 89%); M:F = 1.7:1
Path: well-marginated soft-tissue lesion 0.5–3 cm in diameter with scarlike consistency ± infiltration of surrounding tissues
Histo: spindle-shaped cells in short bundles and fascicles in periphery of lesion with features of both smooth muscle + fibroblasts; hemangiopericytoma-like pattern in center with necrosis, hyalinization, calcification

  • Solitary lesion (50–75%)
    Location: dermis, subcutis, muscle (86%); head, neck, trunk, bone (9%), GI tract (4%)
    Prognosis: spontaneous regression in 100%; recurrence after surgical excision in 7–10%
  • Multicentric disease (25–50%)
    Location: skin (98%), subcutis (98%), muscle (98%), bone (57%), viscera (25–37%): lung (28%), heart (16%), GI tract (14%), pancreas (9%), liver (8%)
    Prognosis: related to extent + location of visceral lesions with cardiopulmonary + GI involvement as harbingers of poor prognosis (death in 75–80%); spontaneous regression (33%)
  • • firm nodules in skin, subcutis, muscle
  • • ± overlying scarring of skin with ulceration
  • @ Skeleton
    Location: any bone may be involved; commonly in femur, tibia, rib, pelvis, vertebral bodies, calvarium; often symmetric
    Site: metaphysis of long bones
    • eccentric lobulated lytic foci with smooth margins 0.5–1.0 cm in size
    • well-defined with narrow zone of transition
    • initially no sclerosis; sclerotic margin with healing
    • osseous foci may increase in size and number
    • healing leaves little residual abnormality
    • unusual osseous findings:
      • periosteal reaction, pathologic fracture
      • vertebra plana, kyphoscoliosis with posterior scalloping of vertebral bodies
    • NUC (bone scan):
      • increased / little radiotracer uptake
      DDx: (1) Langerhans cell histiocytosis (skin lesions)
      (2) Neurofibromatosis (multiple masses)
      (3) Osseous hemangiomas / lymphangiomatosis / lipomatosis
      (4) Metastatic neuroblastoma
      (5) Multiple nonossifying fibromas
      (6) Enchondromatosis
      (7) Hematogenous osteomyelitis (unusual organism)
      (8) Fibrous dysplasia
  • @ Soft tissue
    • solid mass with central necrosis
    • central / peripheral solitary / multiple calcifications
    • prominent vascularity of skin lesions resembles hemangiomas
    • CT:
      • attenuation increased compared to muscle, before + after contrast enhancement
    • MR:
      • hypo- to hyperintense mass on T1WI + T2WI
      DDx: (1) Neurofibromatosis
      (2) Infantile fibrosarcoma, leiomyosarcoma
      (3) Angiomatosis
  • @ Lung
    • interstitial fibrosis, reticulonodular infiltrates
    • discrete mass
    • generalized bronchopneumonia
  • @ GI tract
    • diffuse narrowing / multiple small filling defects
= autoimmune inflammatory myopathy with diffuse nonsuppurative inflammation of striated muscle + skin
Cause: cell-mediated (type IV) autoimmune attack on striated muscle
Pathophysiology: damaged chondroitin sulfate no longer inhibits calcification
Path: atrophy of muscle bundles followed by edema and coagulation necrosis, fibrosis, calcification
Histo: mucoid degeneration with round cell infiltrates concentrated around blood vessels
Age: bimodal: 5–15 and 50–60 years; M:F = 1:2
  • gradual onset of muscle weakness
  • elevated muscle enzymes (creatinine kinase, aldolase)
  • myositis-specific autoantibodies: anti-Jo-1
    • anti-aminoacyl-tRNA synthetase
      • arthritis, Raynaud phenomenon, fever, fatigue
      • interstitial lung disease
        Prognosis: requires prolonged treatment
    • anti-Mi-2 antibodies:
      • V-shaped chest rash (= shawl rash)
      • cuticular overgrowth
        Prognosis: good response to medication
    • anti-signal recognition particle antibodies
      • abrupt onset myositis ± heart involvement
  • @ Skeletal musculature
    Location: thigh (vastus lateralis + intermedius m. with relative sparing of rectus + biceps femoris m.) > pelvic girdle > upper extremity > neck flexors > pharyngeal muscles
    • bilateral symmetric edema in pelvic + thigh muscles
    • fatty infiltration + muscle atrophy (over months to years)
    • sheetlike confluent calcifications in soft tissues of extremities (quadriceps, deltoid, calf muscles), elbows, knees, hands, abdominal wall, chest wall, axilla, inguinal region) in 75%
  • @ Skeleton
    • pointing + resorption of terminal tufts
    • rheumatoid-like arthritis (rare)
    • “floppy-thumb” sign
      Cx: flexion contractures; soft-tissue ulceration
  • @ Chest
    • • respiratory muscle weakness
    • disseminated pulmonary infiltrates (reminiscent of scleroderma)
    • diaphragmatic elevation with reduced lung volumes + basilar atelectasis
    • interstitial fibrosis (5–30%), most severely at lung bases:
      • fine reticular pattern progressing to coarse reticulonodular pattern + honeycombing
    • bronchiolitis obliterans organizing pneumonia
    • diffuse alveolar damage
    • HRCT:
      • predominantly linear abnormalities + ground-glass attenuation
      • air-space consolidation in middle + lower lung zones with peribronchial + subpleural distribution

        Cx: aspiration pneumonia (most common finding due to pharyngeal muscle weakness)
  • @ Myocardium
    • changes similar to skeletal muscle
  • @ GI tract
    • progressive weakness of proximal striated muscle:
      • dysphagia
    • atony + dilatation of esophagus
    • atony of small intestines + colon
Clinical forms:
  • ACUTE FORM = childhood-onset form
    • • fever, joint pain, lymphadenopathy, splenomegaly, subcutaneous edema
    • more severe dermatomyositis
      Prognosis: death within a few months
  • CHRONIC FORM = adult-onset form
    • = insidious onset with periods of spontaneous remission and relapse
    • • low-grade fever, muscular aches + pains, edema
    • • muscle weakness (due to active inflammation, necrosis, muscle atrophy with fatty replacement, steroid-induced myopathy)
    • first symptom in 50%
    • • skin erythema: heliotrope rash (= dusky erythema of eyelids) with periorbital edema, Gottron sign (= scaly erythematous papules of knuckles, major joints and upper body)
    • first symptom in 25%
Cx: increased prevalence of malignant neoplasms of breast, prostate, lung, ovary, GI tract, kidney
Dx: muscle biopsy (normal in up to 15%)
  • = involves skeletal muscle only
    Age: 4th decade
Desmoplastic Fibroma
  • = rare locally aggressive benign neoplasm of bone with borderline malignancy resembling soft-tissue desmoids / musculoaponeurotic fibromatosis
Incidence: 107 cases in world literature
Histo: intracellular collagenous material in fibroblasts with small nuclei
Age: mean of 21 years (range 15 months to 75 years); in 90% <30 years; M:F = 1:1
  • slowly progressive pain + local tenderness
  • palpable mass
Location: mandible (26%), ilium (14%), >50% in long bones (femur [14%], humerus [11%], radius [9%], tibia [7%], clavicle), scapula, vertebra, calcaneus
Site: central meta- / diaphyseal (if growth plate open); may extend into epiphysis with subarticular location (if growth plate closed)
  • geographic (96%) / moth-eaten (4%) bone destruction without matrix mineralization
  • narrow (96%) / poorly defined (4%) zone of transition
  • no marginal sclerosis (94%)
  • residual columns of bone with “pseudotrabeculae” are CLASSIC (91%)
  • bone expansion (89%); may grow to massive size (simulating aneurysmal bone cyst / metastatic renal cell carcinoma)
  • breach of cortex + soft-tissue mass (29%)
Cx: pathologic fracture (9%)
Prognosis: 52% rate of local recurrence
Rx: wide excision
DDx: (1) Giant cell tumor (round rather than oval, may extend into epiphysis + subchondral bone plate)
(2) Fibrous dysplasia (occupies longer bone, contains mineralized matrix, often with sclerotic rim)
(3) Aneurysmal bone cyst (eccentric blowout appearance rather than fusiform)
(4) Chondromyxoid fibroma (eccentric with delicate marginal sclerosis + scalloped border)
Developmental Dysplasia of Hip (DDH)
  • = deformity of acetabulum due to disrupted relationship between femoral head and acetabulum
  • Acetabular dysplasia (without femoral subluxation / dislocation) can be determined only by imaging!
  • Late intrauterine event (98%)
    • mechanical:
      • oligohydramnios (restricted space in utero)
      • firstborn (tight maternal musculature)
        • in 60% of patients with DDH
      • breech position (hip hyperflexion results in shortening of iliopsoas muscle; L:R = 4:1)
        • in 30–50% of patients with DDH
        • only 2–4% of deliveries are breech
    • physiologic (females are more sensitive to):
      • maternal estrogen (not inactivated by immature fetal liver) blocks cross-linkage of collagen fibrils
      • pregnancy hormone relaxin
  • Teratologic (2%) due to a neuromuscular disorder (myelodysplasia, arthrogryposis) occurring during 12th–18th week GA
  • Postnatal onset (<1%)
Incidence: 0.15% of neonates (Australia 1%, Netherlands 3.7%, Poland 3.9%, Israel 5.9%, Austria 6.6%, Norway 16.9%)
Age: most dislocations probably occur after birth; M:F = 1:4–1:8; Caucasians > Blacks
Increased risk:
  • infants born in frank breech position (25%; risk of breech:vertex = 6–8:1)
  • congenital torticollis (10–20%)
  • skull-molding deformities; scoliosis; generalized joint laxity (Larsen syndrome, Ehlers-Danlos syndrome, Down syndrome [5%]); neuromuscular disorders (eg, myelodysplasia, spina bifida, sacral agenesis, arthrogryposis multiplex)
  • family history of DDH (6–20%): 6% risk for subsequent sibling of normal parents, 36% risk for subsequent sibling of one affected parent; 12% risk for patient’s own children
  • foot deformities [metatarsus adductus, clubfoot (2%)
  • neonatal hyperextension of hips: swaddling of infants in hip extension / strapping to cradle board

Radiographic Lines of Hip Joint Position
Anatomy: acetabulum has a small bony component + a large cartilaginous component at birth; acetabulum highly susceptible for modeling within first 6 weeks of age + minimally susceptible >16 weeks of age
  • Normal hip
  • Lax = subluxable hip
    • subluxability up to 6 mm is normal in newborns (still under influence of maternal hormones); decreasing to 3 mm by 2nd day of life
  • Concentric dislocatable unstable hip
    • = joint laxity allowing nondisplaced femoral head to become subluxed / dislocated under stress
      Incidence: 0.25–0.85% of all newborn infants (2/3 are firstborns)
    • • Barlow positive
    • slight increase in femoral anteversion
    • mild marginal abnormalities in acetabular cartilage
    • early labral eversion
      Prognosis: 60% will become stable after 1 week; 88% will become stable by age of 2 months
  • Decentered subluxed hip
    • = femoral head shallow in location
    • loss of femoral head sphericity
    • increased femoral anteversion
    • early labral inversion
    • shallow acetabulum
  • Eccentric dislocated hip
    • = femoral head frankly displaced out of acetabulum
      • reducible = Ortolani positive
      • irreducible = Ortolani negative
    • accentuated flattening of femoral head
    • shallow acetabulum
    • limbus formation (= inward growth + hypertrophy of labrum)
  • “hip click” = usually result of joint capsule and tendon stretching + snapping (often confused with “hip clunk”)
    Acetabular Sector angles (in normal right hip)
  • positive examination result (up to 3 months of age):
    • positive Ortolani reduction test = reduction of proximal femur into the acetabulum by progressive abduction of flexed hips and knees ± associated with audible “clunk”
    • positive Barlow dislocation test = displacement of proximal femur by progressive adduction with downward pressure (piston maneuver) on flexed hips and knees associated with audible “clunk”
  • warning signs on physical examination:
    • limited hip abduction on affected side
    • shortening of thigh on affected side:
      • asymmetric thigh / buttock creases
      • Allis sign = Galeazzi sign = affected knee is lower with knees bent in supine position
      • Trendelenburg test = visible drooping + shortening on dislocated side with child standing on both feet, then one foot
Location: left:right:bilateral = 11:1:4
Radiologic lines:
  • Line of Hilgenreiner
    • = line connecting superolateral margins of triradiate cartilage
  • Acetabular angle / index
    • = slope of acetabular roof = angle that lies between Hilgenreiner’s line and a line drawn from most superolateral ossified edge of acetabulum to superolateral margin of triradiate cartilage
  • Perkin’s line
    • = vertical line to Hilgenreiner’s line through the lateral rim of acetabulum
  • Shenton’s curved line
    • = arc formed by inferior surface of superior pubic ramus (= top of obturator foramen) + medial surface of proximal femoral metaphysis to level of lesser trochanter
    • disruption of line (DDx: coxa valga)
  • Center-edge angle
    • = angle subtended by one line drawn from the acetabular edge to center of femoral head + second line perpendicular to line connecting centers of femoral heads
    • <25° suggests femoral head instability
AP pelvic radiograph: >6–8 weeks of age (von Rosen view = legs abducted 45° + thighs internally rotated)
  • Not reliable first 3 months of life!
  • proximal + lateral migration of femoral neck:

    • eccentric position of proximal femoral epiphysis (position estimated by a circle drawn with a diameter equivalent to width of femoral neck)
    • interrupted discontinuous arc of Shenton’s line
    • line drawn along axis of femoral shaft will not pass through upper edge of acetabulum but intersect the anterior-superior iliac spine (during Barlow maneuver)
    • apex of metaphysis lateral to edge of acetabulum
    • femoral shaft above horizontal line drawn through the Y-synchondroses
    • unilateral shortening of vertical distance from femoral ossific nucleus / femoral metaphysis to Hilgenreiner’s line
    • femoral ossific nucleus / medial beak of femoral metaphysis outside inner lower quadrant of coordinates established by Hilgenreiner’s + Perkin’s lines
    acetabular dysplasia = shallow incompletely developed acetabulum:
  • acetabular angle >30° strongly suggests dysplasia
  • development of false acetabulum
  • delayed ossification of femoral epiphysis (usually evident between 2nd and 8th month of life)
US (practical only up to 4–6 months of age):
  • Too sensitive during first 2 weeks of life!
  • (1) static evaluation (popularized in Europe by Graf)
  • (2) dynamic evaluation (popularized in USA by Harcke)
  • @ Relationship of femoral head & acetabulum
    • femoral head position at rest in neutral position
    • hip instability under motion + stress maneuvers
    • dislocated (= eccentric) hip can be reduced (Ortolani positive):
      • hypoechoic femoral head not centered over triradiate cartilage between pubis + ischium (on transverse view)
      • increased amount of soft-tissue echoes (“pulvinar”) between femoral head and acetabulum
      • cartilaginous acetabular labrum interposed between head and acetabulum (inverted labrum)
      • posterior + superior dislocation of head against ilium
    • equator sign = <50% of femoral head lies medial to line drawn along iliac bone (on coronal view): >58% coverage is normal; 58% to 33% coverage is indeterminate; <33% coverage is abnormal
  • @ Femoral head
    • disparity in size of directly visualized unossified femoral head
    • disparity in presence + size of ossific nucleus
  • @ Acetabulum
    • delayed ossification of acetabular corner
    • wavy contour of bony acetabulum with only slight curvature
    • abnormally acute alpha angle (= angle between straight lateral edge of ilium + bony acetabular margin)
      • α >60° in an infant is normal
      • α 55–60° can be normal <4 weeks of age
      • α <55° occurs in an immature acetabulum
      • 4°–6° interobserver variation!
Prognosis: alpha-angle <50° at birth / 50°–59° after 3 months indicates significant risk for dislocation without treatment; follow-up at 4-week intervals are recommended
No Caption Available.

  • sector angle = angle between line drawn from center of femoral head to acetabular rim + horizontal axis of pelvis (= reflection of acetabular support)
  • anterior acetabular sector angle <50°
  • posterior acetabular sector angle <90°
Cx: (1) Avascular necrosis of femoral head
(2) Intraarticular obstacle to reduction
   (a) pulvinar = fibrofatty tissue at apex of acetabulum
   (b) hypertrophy of ligamentum teres
   (c) labral hypertrophy / inversion
(3) Extraarticular obstacle to reduction (iliopsoas tendon impingement on anterior joint capsule with infolding of joint capsule)
Prognosis: 78% of hips become spontaneously normal by 4th week + 90% by 9th week
Rx: (1) Flexion-abduction-external rotation brace (Pavlik harness) / splint / spica cast
(2) Femoral varus osteotomy
(3) Pelvic (Salter) / acetabular rotation
(4) Increase in acetabular depth (Pemberton)
(5) Medialization of femoral head (Chiari)
Diastrophic Dysplasia
  • = autosomal recessive severe rhizomelic dwarfism secondary to generalized disorder of cartilage followed by fibrous scars + ossifications
  • • diastrophic = “twisted” habitus
  • • “cauliflower ear” = ear deformity from inflammation of pinna
  • • laryngomalacia
  • • lax + rigid joints with contractures
  • • normal intellectual development
  • @ Axial skeleton
    • cleft palate (25%)
    • cervical spina bifida occulta
    • hypoplasia of odontoid
    • severe progressive kyphoscoliosis of lumbar spine (not present at birth)
    • narrowed interpedicular space in lumbar spine
    • short + broad bony pelvis
    • posterior tilt of sacrum
  • @ Extremities
    • severe micromelia (predominantly rhizomelic = humerus + femur shorter than distal long bones
    • widened metaphysis
    • flattened epiphysis (retardation of epiphyseal ossification) with invagination of ossification centers into distal ends of femora
    • multiple joint flexion contractures (notably of major joints)
    • dislocation of one / more large joints (hip, elbow), lateral dislocation of patella
    • coxa vara (common)
    • medially bowed metatarsals
    • clubfoot = severe talipes equinovarus
    • ulnar deviation of hands
    • oval + hypoplastic 1st metacarpal bone + abducted proximally positioned thumb = “hitchhiker’s thumb” (CHARACTERISTIC)
    • bizarre carpal bones with supernumerary centers
    • widely spaced fingers
  • OB-US:
    • proportionately shortened long bones
    • hitchhiker thumb
    • clubfeet
    • joint contractures
    • abnormal spinal curvature
Prognosis: death in infancy (due to abnormal softening of tracheal cartilage)
Diffuse Idiopathic Skeletal Hyperostosis
  • = common ossifying diathesis characterized by bone proliferation at sites of tendinous + ligamentous attachment (enthesis)
  • may be caused by altered vitamin A metabolism (elevated plasma levels of unbound retinol)
  • long-term ingestion of retinoid derivatives for treatment of acne (eg, Accutane®);
? hypertrophic variant of spondylosis deformans
Age: >50 years; M:F = 3:1
  • • pain, tenderness in extraspinal locations
  • • restricted motion of vertebral column
  • • hyperglycemia
  • • positive HLA-B27 in 34%
  • increased incidence of hyperostosis frontalis interna
  • @ Spine
    Location: middle + lower thoracic > lower cervical > entire lumbar spine
    • flowing ossification of at least 4 contiguous vertebral bodies:
      • osteophytes located anteriorly + laterally on right side (not on left because of aorta)
      • osteophytes largest at level of intervertebral disk
      • radiolucency beneath deposited bone
    • disk spaces well preserved, no apophyseal ankylosis, no sacroiliitis
  • @ Pelvis
    • bridge across superior aspect of symphysis pubis
    • ossification of iliolumbar + sacrotuberous + sacroiliac ligaments (high probability for presence of spinal DISH, DDx: fluorosis)
    • “whiskering” at iliac crest, ischial tuberosity, trochanters
    • broad osteophytes at lateral acetabular edge, inferior portions of sacroiliac joints
  • @ Extremities
    • big heel spurs (on plantar + posterior surface of calcaneus)
    • spur of olecranon process of ulna
    • spur on anterior surface of patella
    • ossification of coracoclavicular ligament, patellar ligament, tibial tuberosity, interosseous membranes
Cx: postoperative heterotopic bone formation (hip)
DDx: (1) Fluorosis (increased skeletal density)
(2) Acromegaly (posterior scalloping, skull features)
(3) Hypoparathyroidism
(4) X-linked hypophosphatemic vitamin D–resistant rickets

(5) Ankylosing spondylitis (squaring of vertebral bodies, coarser syndesmophytes, sacroiliitis, apophyseal alteration)
(6) Intervertebral osteochondrosis (vacuum phenomenon, vertebral body marginal sclerosis, decreased intervertebral disk height)
Hip Dislocation
Incidence: 5% of all dislocations
    Mechanism: classical dashboard injury (= flexed knee strikes dashboard)
    Associated with: fractures of posterior rim of acetabulum, femoral head
    • adducted lower extremity flexed at hip
    Mechanism: forced abduction + external rotation
    Associated with: fractures of acetabular rim, greater trochanter, femoral neck, femoral head (characteristic depression on posterosuperior and lateral portion)
    • anterior obturator dislocation
    • superoanterior / pubic hip dislocation
    • • lower extremity in external rotation
    • prominent lesser trochanter
    • obturator position of femoral head
    Mechanism: force applied to lateral side of trochanter
Patellar Dislocation
Incidence: 2–3% of all knee injuries
Mechanism: during attempt to slow forward motion while pivoting medially on a planted foot; internal rotation of femur on fixed tibia while knee is flexed + quadriceps contraction produces a net lateral force
At risk: shallow trochlear groove
Associated with: medial meniscal tear / major ligamentous injury in 31%
Age: young physically active people
  • • hemarthrosis (most common cause of hemarthrosis in young conscripts)
  • • swelling + tenderness of medial retinaculum
  • >50% not clinically diagnosed initially!
  • increased signal intensity / thickening / disruption of medial patellar retinaculum
  • lateral patellar tilt
  • contusion / microfracture / osteochondral injury of nonarticular surface of lateral femoral condyle + medial articular surface of patella
  • hemarthrosis
  • bone contusion of anterolateral aspect of lateral femoral condyle + inferomedial aspect of patella
  • sprain / disruption / avulsion of medial retinaculum + medial patellofemoral ligament + medial patellotibial lig.
    Mr Imaging Signs of Patellar Dislocation
  • elevation of vastus medialis obliquus muscle
Rx: (1)Temporary immobilization + rehabilitation: successful in 75%
(2) Surgery: fixation of osteochondral fragments, medial capsule repair, lateral retinacular release, vastus medialis et lateralis rearrangement, medial retinaculum reefing
Shoulder Dislocation
Sternoclavicular Dislocation (3%)
Acromioclavicular Dislocation (12%)
Grade 1 = soft-tissue swelling + no joint widening
Grade 2 = subluxation with elevation of clavicle of <5 mm (weight-bearing!)
Grade 3 = dislocation with wide AC joint + increased coracoclavicular distance
Glenohumeral Dislocation (85%)
  • Glenohumeral joint dislocations make up >50% of all dislocations!
Anterior / Subcoracoid Shoulder Dislocation
(95% of all shoulder dislocations)
Types: subcoracoid, subglenoid, subclavicular, intrathoracic
Mechanism: external rotation + abduction (fall on outstretched arm / hand behind occiput); 40% recurrent
Age: in younger individuals in their teens
  • Bankart lesion = anterior capsulolabral avulsion
    • = avulsion of anterior-inferior glenoid labrum including labral insertion of inferior glenoid ligament
      [Arthur Sydney Blundell Bankart (1879–1951), British orthopedic surgeon]
May be associated with:
  • bony Bankart fracture of anterior rim of glenoid
  • fracture of greater tuberosity (15%)
  • Hill-Sachs defect (50%) = depression / impacted fracture of posterolateral surface of humeral head at / above level of coracoid process (due to impaction against anterior edge of glenoid rim in subglenoid type)
    [Harold Arthur Hill (1901–1973) and Maurice David Sachs (1909–1987), radiologists in San Francisco, CA]

MRI (arthrography improves sensitivity to 89–99%, and specificity to >90%):
  • hemorrhagic effusion (in acute injury)
  • increased signal intensity in anterior-inferior labrum + capsule (DDx: magic angle artifact)
  • labrum + capsule lifted away from glenoid
  • discrete tear / fragmentation of labrum
  • ± tear of middle glenohumeral ligament
  • ± fracture of anterior-inferior glenoid
  • tear of degenerated supraspinatus tendon (in 33% of patients >40 years of age)
  • tear of degenerated subscapularis tendon (in 33% of patients >40 years of age)
  • greater-tuberosity humeral fracture (in 33%)
  • paralabral cysts are usually associated with labral tears; may cause denervation of suprascapular nerve simulating impingement syndrome (DDx: age-related degeneration)
Cx: (1) Recurrent dislocations (in up to 90% of young active individuals)
(2) Repeated dislocations due to incomplete / inadequate healing = chronic recurrent anterior shoulder instability
(3) Arthritis (with repeated subluxations)
Rx: (1) Conservative treatment for most
(2) Surgical fixation for young athletes
Posterior Shoulder Dislocation (2–4%)
Cause: (a)traumatic: convulsive disorders /electric shock therapy
(b) nontraumatic: voluntary, involuntary, congenital, developmental
Types: subacromial, subglenoid, subspinous
  • In >50% unrecognized initially + subsequently misdiagnosed as frozen shoulder!
  • Average interval between injury and diagnosis is 1 year!
  • rim sign (66%) = distance between medial border of humeral head + anterior glenoid rim <6 mm
May be associated with:
  • trough sign (75%) = “reverse Hill-Sachs” = compression fracture of anteromedial humeral head (tangential Grashey view of glenoid!)
  • fracture of posterior glenoid rim
  • avulsion fracture of lesser tuberosity
  • tear of subscapularis tendon
  • empty bicipital groove (= dislocated bicipital tendon)
Inferior Shoulder Dislocation (1–2%)
  • = extremity held over head in fixed position with elbow flexed
Mechanism: severe hyperabduction of arm resulting in impingement of humeral head against acromion
  • humeral articular surface faces inferiorly
Cx: rotator cuff tear; fracture of acromion ± inferior glenoid fossa ± greater tuberosity; neurovascular injury
No Caption Available.
Superior Shoulder Dislocation (<1%)
= humeral head driven upward through rotator cuff
May be associated with: fracture of humerus, clavicle, acromion
DDx: drooping shoulder (transient phenomenon after fracture of surgical neck of humerus due to hemarthrosis / muscle imbalance)
Gadolinium Shoulder Arthrography
  • fluoroscopically guided needle insertion from an anterior approach
  • confirmation of needle placement with iodinated contrast material
  • injection of 12–20 mL of diluted gadolinium chelate solution:
    • 0.1 mL of gadolinium DTPA (469 mg/mL) into
    • 20 mL of bacteriostatic saline
  • patient’s arm and shoulder are moved through full range of motion
Wrist Dislocation
Mechanism: fall on outstretched hand
Incidence: 10% of all carpal injuries
Lunate Dislocation
Perilunate Dislocation
  • 2–3 times more common than lunate dislocation
    accompanied by fracture in 75% (= transscaphoid perilunate dislocation)
  • most commonly dorsal dislocation
Rotary Subluxation of Scaphoid
= tearing of interosseous ligaments of lunate, scaphoid, capitate
Mechanism: acute dorsiflexion of wrist; may be associated with rheumatoid arthritis
  • gap >4 mm between scaphoid + lunate (PA view)
  • foreshortening of scaphoid
  • ring sign of distal pole of scaphoid
Midcarpal Dislocation
Down Syndrome
Chromosomes: 95% nondisjunction, 5% translocation
Incidence: 1:870 live births, most common karyotype / chromosomal abnormality in USA

  • mental retardation
  • hypotonia in infancy
  • characteristic facies
  • Simian crease
  • @ Skull
    • hypotelorism
    • persistent metopic suture (40–79%) after age 10
    • hypoplasia of sinuses + facial bones
    • microcrania (brachycephaly)
    • delayed closure of sutures + fontanels
    • dental abnormalities (underdeveloped tooth No. 2)
    • flat-bridged nose
  • @ Axial skeleton
    • atlantoaxial subluxation (25%)
    • anterior scalloping of vertebral bodies
    • “squared vertebral bodies” = centra high and narrow = positive lateral lumbar index (ratio of horizontal to vertical diameters of L2)
  • @ Chest
    • congenital heart disease (40%): endocardial cushion defect, VSD, tetralogy of Fallot
    • hypersegmentation of manubrium = 2–3 ossification centers (90%)
    • gracile ribs; 11 pairs of ribs (25%)
  • @ Pelvis (frontal view)
    • flaring of iliac wings (= rotation of iliac wings toward coronal plane at sacroiliac joints) = “Mickey Mouse ears” / “elephant ears”:
      • decreased iliac angle + index (in 70–80%)
    • flattening of acetabular roof (small acetabular angle)
    • elongated + tapered ischia
  • @ Extremities
    • metaphyseal flaring
    • clinodactyly (50%); widened space between first two digits of hands + feet
    • hypoplastic and triangular middle + distal phalanges of 5th finger = acromicria (DDx: normal individuals, cretins, achondroplastic dwarfs)
    • pseudoepiphyses of 1st + 2nd metacarpals
  • @ Gastrointestinal
    • umbilical hernia
    • “double bubble” sign (8–10%) = duodenal atresia / stenosis / annular pancreas
    • tracheoesophageal fistula
    • anorectal anomalies
    • Hirschsprung disease
    • advanced maternal age
      • In 1:385 live births for women >35 years of age
      • HOWEVER: 80% of fetuses with Down syndrome are born to mothers <35 years of age
    • quad test (2nd trimester maternal serum screening):
      • low (0.7 MoM) maternal alpha-fetoprotein (20–30%)
      • increased (2.04 MoM) hCG (DDx: decreased in trisomy 18)
      • decreased (0.79 MoM) unconjugated estriol (uE3)
      • decreased dimeric inhibin A levels
      • optimal time for test between 15 and 16 weeks GA
      • detects 75% of cases with Down syndrome with a 5% screen-positive rate
      Disadvantage: late performance in 2nd trimester, 25% of Down syndrome cases not detected, many amniocenteses unnecessarily recommended
    • low pregnancy-associated plasma protein A (PAPP-A @ 10–14 weeks EGA
    • first-trimester ultrasound markers:
      • nuchal translucency
        • = measurement of space between spine and overlying skin on midsagittal view
          Best time: 10w3d–13w6d EGA
        • ≥5 mm during 14–18 weeks
        • ≥6 mm during 19–24 weeks
          Cause: heart failure, abnormal extracellular matrix, abnormal lymphatic development
      • absent nasal bone
        Best time: between 10 and 14 weeks EGA
      • absent / reversed Doppler flow in ductus venosus during atrial contraction
    • major structural malformations:
      Best time: 18 weeks EGA
      • VSD / complete AV canal (50%)
      • cystic hygroma, resolved by 20th week MA (DDx: Turner syndrome, trisomy 18, trisomy 13, triploidy)
      • omphalocele
      • double bubble of duodenal atresia (8–10%), not apparent before 22 weeks GA
      • hydrothorax
      • mild cerebral ventricular dilatation
      • agenesis of corpus callosum
      • imperforate anus
      minor markers:
      • elevated BPD / femur ratio (secondary to short femur)
      • ratio of measured-to-expected femur length ≥0.91 [expected femur length:–9.3105 + 0.9028 × BPD] (sensitivity 40%, specificity 95%, false-positive rate of 2–7%, 0.3% PPV for low-risk population [1:700], 1% PPV for high-risk population [1:250])
      • ratio of measured-to-expected humerus length ≥0.90 [expected humerus length:–7.9404 + 0.8492 × BPD] (1–2% PPV for low-risk population; 3% PPV for high-risk population)
      • flared iliac crest = iliac wings rotated toward coronal plane:
        • mean iliac angle at superiormost level of 95.6 ± 11.7° (compared to 76.4 ± 16.8° for euploid fetuses)
      • sandal-gap deformity = separation of great toe (45%)
      • hypoplasia of middle phalanx of 5th digit resulting in clinodactyly (= inward curve) in 60%
      • mild fetal pyelectasis (17–25%)
      • echogenic bowel at <20 weeks GA (15%, in 0.6% of normals)
      • echogenic intracardiac focus, usually in left ventricle = thickening of papillary muscle (18%, in 5% of normals)
      • frontal lobe shortening (measured from the inner table of the frontal bone to the posterior margin of the thalamus)
      • brachycephaly
      • small cerebellum
      • IUGR (in 30%)
      • polyhydramnios
    Cx: leukemia (increased frequency 3–20 x)

  • = mesomelic long-bone shortening (forearm + leg); autosomal dominant
  • M:F = 1:4
  • • limited motion of elbow + wrist
  • bilateral Madelung deformity:
    • radial shortening in relation to ulna
    • bowing of radius laterally + dorsally
    • dorsal subluxation of distal end of ulna
    • carpal wedging between radius + ulna (due to triangular shape of distal radial epiphysis + underdevelopment of ulna)
DDx: pseudo-Madelung deformity (from trauma / infection)
Dysplasia Epiphysealis Hemimelica
  • = uncommon skeletal developmental disorder representing an epiphyseal osteochondroma
Incidence: 1:1,000,000
Age: 2–4 years; M:F = 3:1
Cause: failure of normal progression of cellular cartilage breakdown (= aclasis); spontaneous occurrence
Path: lobulated mass protruding from epiphysis with a cartilaginous cap
Histo: normal bone + hyaline cartilage with abundant enchondral ossification (= abnormal cellular activity at cartilaginous ossification center)
  • Localized form = monostotic involvement: usually hindfoot and ankle
  • Classic form (>66%) = more than one area of involvement in a single extremity with characteristic hemimelic distribution: talus, distal femur, distal tibia
  • Generalized / severe form = disease involving the whole lower extremity
    • pelvic involvement: femoral head, symphysis pubis, triradiate cartilage
    • hypertrophy of ipsilateral iliac bone
  • antalgic (= pain-avoiding) gait; palpable mass
  • varus / valgus deformity; limb length discrepancy
  • limited joint mobility and function
Location: lower extremity (tarsus, knee, ankle); rare in upper extremity (humerus, ulna, scapula)
Site: restricted to medial OR lateral side of limb (= hemimelic), ie, medial:lateral = 2:1
  • @ Infant & toddler
    • premature appearance of an eccentric, lobulated, overgrown, asymmetric ossification center
    • stippled calcification of anomalous cartilage
  • @ Childhood
    • disorganized epiphyseal calcification accompanied by irregular ossification
    • osteochondroma-like growth from one side of epiphysis
    • premature closure of physis results in limb deformity and limb length discrepancy
    • irregular articular surface combined with angular deformity
    • undertubulation of bone as a consequence of secondary involvement of metaphysis
Cx: premature secondary osteoarthritis
DDx: osteochondroma
Echinococcus of Bone
Occurs occasionally in the USA; usually in foreign-born individuals; bone involvement in 1%
Histo: no connective tissue barrier; daughter cysts extend directly into bone
  • Pelvis, sacrum, rarely long tubular bones
    • round / irregular regions of rarefaction
    • multiloculated lesion (bunch of grapes)
    • no sharp demarcation (DDx: chondroma, giant cell tumor) with secondary infection:
      • thickening of trabeculae with generalized perifocal condensation
      • cortical breakthrough with soft-tissue mass
  • Vertebra
    • sclerosis without pathologic fracture
    • intervertebral disks not affected
    • vertebral lamina often involved
    • frequently involvement of adjacent ribs
Ehlers-Danlos Syndrome
= group of autosomal dominant diseases of connective tissue characterized by abnormal collagen synthesis
Types: 10 types have been described that differ clinically, biochemically, and genetically
Age: present at birth; predominantly in males
  • hyperelasticity of skin
  • fragile brittle skin with gaping wounds and poor healing
  • molluscoid pseudotumors over pressure points
  • hyperextensibility of joints
  • joint contractures with advanced age
  • bleeding tendency (fragility of blood vessels)
  • blue sclera, microcornea, myopia, keratoconus, ectopia lentis
  • @ Soft tissues
    • multiple ovoid calcifications (2–10 mm) in subcutis / in fatty cysts (“spheroids”), most frequently in periarticular areas of legs
    • ectopic bone formation
  • @ Skeleton
    • hemarthrosis (particularly in knee)
    • malalignment / subluxation / dislocation of joints on stress radiographs
    • recurrent dislocations (hip, patella, shoulder, radius, clavicle)
    • precocious osteoarthrosis (predominantly in knees)
    • ulnar synostosis
    • kyphoscoliosis
    • spondylolisthesis
    • spina bifida occulta
  • @ Chest
    • diaphragmatic hernia
    • panacinar emphysema + bulla formation
    • tracheobronchomegaly + bronchiectasis
  • @ Arteries
    • aneurysm of great vessels, aortic dissection, tortuosity of arch, ectasia of pulmonary arteries
      (Cx following arteriography: aortic rupture, hematomas)
  • GI tract
    • ectasia of gastrointestinal tract

= benign tumorlike lesion forming as a reaction to mechanical friction
Incidence: in 24% of women + 11% of men >55 years (autopsy study)
Age: elderly; M:F = 1:2
Histo: enlarged irregular serrated elastic hypereosinophilic fibers, collagen, scattered fibroblasts, occasional lobules of adipose tissue
  • • asymptomatic
  • • may remain clinically inapparent
    Location: between inferior margin of scapula + posterior chest wall; bilateral in 25%
  • inhomogeneous poorly defined lesion of soft-tissue attenuation similar to muscle
  • well-defined intermediate-signal intensity lesion with interlaced areas of fat-intensity signal on T1WI + T2WI
= benign cartilaginous growth in medullary cavity; bones preformed in cartilage are affected (NOT skull)
Incidence: 3–17% of biopsied primary bone tumors
♢Second most common cartilage-containing tumor!
Etiology: continued growth of residual benign rests of cartilage displaced from the growth plate
Age: 10–30 years; M:F = 1:1
Histo: lobules of pure hyaline cartilage
• usually asymptomatic, painless swelling
Location: (usually solitary; multiple = enchondromatosis)
(a) in 40% small tubular bones of wrists + hand (most frequent tumor here), distal + mid aspects of metacarpals, proximal / middle phalanges
(b) proximal femur, proximal humerus, tibia, radius, ulna, foot, rib (3%)
Site: central within medullary canal + metaphyseal; epiphysis only affected after closure of growth plate
  • oval / round area of geographic destruction with lobulated contour + fine marginal line
  • cortical endosteal scalloping
  • ground-glass appearance
  • dystrophic calcifications within small cartilage nodules / fragments of lamellar bone: pinhead, stippled, flocculent, “rings and arcs” pattern
  • bulbous expansion of bone with thinning of cortex in small tubular bones of phalanx, rib, fibula
  • Madelung deformity = bowing deformities of limb, discrepant length
  • NO cortical breakthrough / periosteal reaction
  • MR:
    • low- to intermediate-signal intensity on T1WI + high-signal intensity on T2WI
    • low-signal intensity matrix calcifications
    • normal fat marrow interspersed between cartilage nodules
    • peripheral enhancement pattern
Cx: (1) Pathologic fracture
(2) Malignant degeneration in long-bone enchondromas in 15–20% (gradually increasing pain in an adult patient)
DDx: (1) Epidermoid inclusion cyst (phalangeal tuft, history of trauma, more lucent)
(2) Unicameral bone cyst (rare in hands, more radiolucent)
(3) Giant cell tumor of tendon sheath (commonly erodes bone, soft-tissue mass outside bone)
(4) Fibrous dysplasia (rare in hand, mostly polyostotic)
(5) Bone infarct
(6) Chondrosarcoma (exceedingly rare in phalanges, metacarpals, metatarsals)
  • = nonhereditary failure of cartilage ossification
Cause: derangement of cartilaginous growth resulting in migration of cartilaginous rests from epiphyseal plate into metaphysis where they proliferate
Age: early childhood presentation
Association: juvenile granulosa cell tumor of ovary
  • growth disparity with leg / arm shortening
  • hand + feet deformity
Location: predominantly unilateral monomelic distribution (a) localized (b) regional (c) generalized
  • well-demarcated rounded radiolucencies / columnar streaks of decreased density from epiphyseal plate into diaphysis of long bones = cartilaginous rests
  • expansile remodeling of affected bone:
    • clublike deformity / expansion of metaphyseal region
    • predominant thinning of cortex + endosteal scalloping
    • bony spurs pointing toward the joint (DDx: exostosis points away from it)
  • cartilaginous areas show punctate calcifications with age:
    • matrix mineralization with TYPICAL arc-and-ring appearance of chondroid lesions
  • associated with dwarfing of the involved bone due to impairment of epiphyseal fusion
  • bowing deformities of limb bones
  • discrepancy in length = Madelung deformity (radius, ulna)
  • small bones of feet + hands: aggressive deforming tumors that may break through cortex secondary to tendency to continue to proliferate
  • fanlike radiation of cartilage from center to crest of ilium
Cx: sarcomatous transformation (in 25–30%): osteosarcoma (young adults); chondro- / fibrosarcoma (in older patients)
Maffucci Syndrome
  • = nonhereditary mesodermal dysplasia characterized by enchondromatosis + multiple soft-tissue cavernous hemangiomas + less commonly lymphangiomas
    Age: 25% during 1st year of life; 45% prior to 6 years; 78% before puberty; M > F
    Association: juvenile granulosa cell tumor of ovary
    • multiple blue subcutaneous nodules particularly on digits + extremities (cavernous hemangiomas)
    • • normal intelligence
    Location: unilateral involvement (50%) / marked asymmetry; distinct predilection for tubular bones of hands + feet

    • phleboliths may be present
    • striking tendency for enchondromas to be very large projecting into soft tissues
    • growth disturbance of long bones (common)
    Cx: (a) malignant transformation of
       (1) Enchondroma to chondrosarcoma / fibrosarcoma (15–20%)
       (2) Cavernous hemangioma to hemangiosarcoma / hemangioendothelioma / lymphangiosarcoma (in 3–5%)
    (b) increased prevalence of ovarian carcinoma, pancreatic carcinoma, CNS glioma, gastrointestinal adenocarcinoma
    Prevalence of malignancy: 23–100%
    DDx: Ollier disease (without hemangiomas)
Engelmann-Camurati Disease
Cause: autosomal dominant; disturbance in intramembranous bone formation + modeling (as occurs in cortex of long bones, calvaria, mandible, facial bones, midsegment of clavicle)
Age: 5–25 years (primarily in childhood); M > F
  • neuromuscular dystrophy = delayed walking (18–24 months) with wide-based waddling gait; often misdiagnosed as muscular dystrophy / poliomyelitis
  • weakness + easy fatigability in legs
  • bone pain + tenderness usually in midshaft of long bones
  • underdevelopment of muscles secondary to malnutrition
  • NORMAL laboratory values
Location: usually symmetrical; NO involvement of hands, feet, ribs, scapulae
  • @ Skull (initially affected)
    • amorphous increase in density at base of skull
    • encroachment of frontal + sphenoid sinus; sparing of maxillary sinus
  • @ Long bones (bilateral symmetrical distribution)
    Site: tibia > femur > fibula > humerus > ulna > radius
    • fusiform enlargement of diaphyses with cortical thickening (endosteal + periosteal accretion of mottled new bone) and progressive obliteration of medullary cavity
    • progression of lesions along long axis of bone toward either end
    • abrupt demarcation of lesions (metaphyses + epiphyses spared)
    • relative elongation of extremities
DDx: (1) Chronic osteomyelitis (single bone)
(2) Hyperphosphatasemia (high alkaline phosphatase levels)
(3) Paget disease (age, new-bone formation, increased alkaline phosphatase)
(4) Infantile cortical hyperostosis (fever; mandible, rib, clavicles; regresses, <1 year of age)
(5) Fibrous dysplasia (predominantly unilateral, subperiosteal new bone)
(6) Osteopetrosis (very little bony enlargement)
(7) Vitamin A poisoning
Epidermoid Cyst
  • = proliferation of surface epidermal cells within the dermis
    Histo: production of keratin within closed space lined by surface epidermis
    Associated with: nevoid basal cell syndrome (Gorlin syndrome) patients have a high prevalence of epidermoid / dermoid cysts
  • isointense / slightly hyperintense relative to muscle on T1WI
  • hyperintense with focal areas of decreased signal on T2WI
Epidermoid Inclusion Cyst
Age: 2nd–4th decade; M > F
Histo: stratified squamous epithelium, keratin, cholesterol crystals (soft white cheesy contents)
  • history of trauma (implantation of epithelium under skin with secondary bone erosion)
  • asymptomatic
Location: superficially situated bones such as calvarium (typically in frontal / parietal bone), phalanx (usually terminal tuft of middle finger), L > R hand, occasionally in foot
  • well-defined round osteolysis with sclerotic margin
  • cortex frequently expanded + thinned
  • NO calcifications / periosteal reaction / soft-tissue swelling
  • pathologic fracture often without periosteal reaction
DDx: (a) in finger: glomus tumor, enchondroma (rare in terminal phalanx)
(b) in skull: infection, metastasis (poorly defined), eosinophilic granuloma (beveled margin)
Epiphyseolysis of Femoral Head
  • = atraumatic fracture through hypertrophic zone of physeal plate
Frequency: 2:100,000 people
Etiology: growth spurt, renal osteodystrophy, rickets, childhood irradiation, growth hormone therapy, trauma (Salter-Harris type I epiphyseal injury)
Pathogenesis: widening of physeal plate during growth spurt + change in orientation of physis from horizontal to oblique increases shear forces
Age: overweight 8–17 year old boys (mean age for boys 13, for girls 11 years); M:F = 3:1; black > white
Associated with:
  • malnutrition, endocrine abnormality, developmental dysplasia of hip (during adolescence)
  • delayed skeletal maturation (after adolescence)
  • • hip pain (50%) / knee pain (25%) for 2–3 weeks
Location: usually unilateral; bilateral in 20–37% (at initial presentation in 9–18%)
  • widening of epiphyseal growth plate (preslip phase):
    • irregularity + blurring of physeal physis
    • demineralization of neck metaphysis
  • posteromedial displacement of head (acute slip):
    • decrease in neck-shaft angle with alignment change in the growth plate to a more vertical orientation
    • line of Klein (= line drawn along superior edge of femoral neck) fails to intersect the femoral head
      Line of Klein in Normal Hip
    • P.75

    • epiphysis appears smaller due to posterior slippage:
      early slips are best seen on cross-table LAT view
      CAVE: positioning into a frog leg view may cause further displacement
  • sclerosis + irregularity of widened physis (chronic slip):
    • metaphyseal blanch sign = area of increased opacity in proximal part of metaphysis (healing response)
Grading (based on femoral head position):
mild = displaced by <1/3 of metaphyseal diameter
moderate = displaced by 1/3–2/3 of diameter
severe = displaced by >2/3 of metaphyseal diameter
Cx: (1) Chondrolysis = acute cartilage necrosis (7–10%) = rapid loss of >50% of thickness of cartilage
   √joint space <3 mm
(2) Avascular necrosis of femoral head (10–15%): risk increases with advanced degree of slip, delayed surgery for acute slip, anterior pin placement, large number of fixation pins, subcapital osteotomy
(3) Pistol-grip deformity = broadening + shortening of femoral neck in varus deformity
(4) Degenerative osteoarthritis (90%)
(5) Limb-length discrepancy due to premature physeal closure
Rx: (1) limitation of activity
(2) prophylactic pinning
(3) osteotomy
♢ Attempted reductions increase risk of AVN!
Essential Osteolysis
= progressive slow bone-resorptive disease
Histo: proliferation + hyperplasia of smooth muscle cells of synovial arterioles
  • progressive osteolysis of carpal + tarsal bones
  • thinned pointed proximal ends of metacarpals + metatarsals
  • elbows show same type of destruction
  • bathyrocephalic depression of base of skull
DDx: (1) Massive osteolysis = Gorham disease (local destruction of contiguous bones, usually not affecting hands / feet)
(2) Mutilating forms of rheumatoid arthritis
(3) Tabes dorsalis
(4) Leprosy
(5) Syringomyelia
(6) Scleroderma
(7) Raynaud disease
(8) Regional posttraumatic osteolysis
(9) Ulcero-mutilating acropathy
(10) Mutilating forms of rheumatoid arthritis
(11) Acrodynia mutilante (nonhereditary)
Ewing Sarcoma
Incidence: 4–10% of all bone tumors (less common than osteo- / chondrosarcoma); most common malignant bone tumor in children; 4th most common bone tumor overall
  • Clinically, radiologically, and histologically very similar to PNET!
Histo: small round cells, uniformly sized + solidly packed (DDx: lymphoma, osteosarcoma, myeloma, neuroblastoma, carcinoma, eosinophilic granuloma) invading medullary cavity and entering subperiosteum via Haversian canals producing periostitis, soft-tissue mass, osteolysis; glycogen granules present (DDx to reticulum cell sarcoma); absence of alkaline phosphatase (DDx to osteosarcoma); MIC2 cell surface immunoreactivity (in 100%)
Age: peak 15 years (range 5 months to 54 years); in 95% 4–25 years; in 30% <10 years; in 39% 11–15 years; in 31% >15 years; in 50% <20 years;M:F = 1:2; Caucasians in 96%
  • severe localized pain
  • soft-tissue mass
  • fever, leukocytosis, anemia (in early metastases) simulating infection
  • femur (25%), pelvis-ilium (14%), tibia (11%), humerus (10%), fibula (8%), ribs (6–10%)
  • long bones in 60%: metadiaphysis (44%), middiaphysis (33%), metaphysis (15%), metaepiphyseal (6%), epiphyseal (2%); usually no involvement of epiphysis as tumor originates in medullary cavity with invasion of Haversian system
  • flat bones in 40%: pelvis, scapula, skull, vertebrae (in 3–10%; sacrum > lumbar > thoracic > cervical spine); ribs (in 7% > age 10; in 30% < age 10)
    • >20 years of age predominantly in flat bones
    • <20 years of age predominantly in cylindrical bones (tumor derived from red marrow)
  • 8–10 cm long lytic lesion in shaft of long bone (62% lytic, 23% mixed density, 15% dense)
  • mottled “moth-eaten” destructive permeative lesion (72%) (late finding)
  • penetration into soft tissue (55%) with preservation of tissue planes (DDx: osteomyelitis with diffuse soft-tissue swelling)
  • early fusiform lamellated “onionskin” periosteal reaction (53%) / spiculated = “sunburst” / “hair-on-end” (23%), Codman triangle
  • cortical thickening (16%)
  • cortical destruction (18%)
  • ± cortical sequestration
  • reactive sclerotic new bone (30%)
  • bone expansion (12%)
  • @ Ewing sarcoma of rib:
    • primarily lytic / sclerotic / mixture of lysis + sclerosis
    • disproportionately large inhomogeneous soft-tissue mass
    • large intrathoracic + minimal extrathoracic component
    • P.76

    • may spread into spinal canal via intervertebral foramen
Metastases to: lung, bones, regional lymph nodes in 11–30% at time of diagnosis, in 40–45% within 2 years of diagnosis
Cx: pathologic fracture (5–14%)
Prognosis: 60–75% 5-year survival
DDx: (1) Multiple myeloma (older age group)
(2) Osteomyelitis (duration of pain <2 weeks)
(3) Eosinophilic granuloma (solid periosteal reaction)
(4) Osteosarcoma (ossification in soft tissue, near age 20, no lamellar periosteal reaction)
(5) Reticulum cell sarcoma (clinically healthy, between 30 and 50 years, no glycogen)
(6) Neuroblastoma (< age 5)
(7) Anaplastic metastatic carcinoma (>30 years of age)
(8) Osteosarcoma
(9) Hodgkin disease
Extramedullary Hematopoiesis
  • = compensatory response to deficient bone marrow blood cell production
    Etiology: prolonged erythrocyte deficiency due to
    • destruction of RBC:
      • congenital hemolytic anemia (sickle cell anemia, thalassemia, hereditary spherocytosis), acquired hemolytic anemia, idiopathic severe anemia, erythroblastosis fetalis
    • inability of normal blood-forming organs to produce erythrocytes: iron deficiency anemia, pernicious anemia, myelofibrosis, myelosclerosis, polycythemia vera, carcinomatous / lymphomatous replacement depletion of bone marrow (chronic myelogenous leukemia, Hodgkin disease)
    • NO hematologic disease in 25%
  • • absence of pain, bone erosion, calcification
  • • chronic anemia
    Sites: in areas of fetal erythropoiesis
  • @ spleen
    • splenomegaly
    • focal isodense masses on enhanced CT
  • @ liver, lymph nodes
  • @ thorax: mediastinum, heart, thymus, lung
    • uni- / bilateral smooth lobulated paraspinal masses between T8 and T12
    • anterior rib ends expanded by masses
  • @ Spine
    • Most commonly afflicted in thalassemia
    • • back pain, symptoms of spinal cord compression
    • coarsened trabeculation
    • extramedullary hematopoiesis in epidural space
  • @ adrenal glands
  • @ renal pelvis
  • @ gastrointestinal lymphatics
  • @ dura mater (falx cerebri and over brain convexity)
  • @ cartilage, broad ligaments
  • @ thrombi, adipose tissue
  • @ Bone marrow reconversion = conversion of fatty to hematopoietic marrow
    Sequence: vertebrae > flat bones of pelvis > long bones of extremities (proximal metaphysis > distal metaphysis > diaphysis)
  • lack of calcification / bone erosion
Familial Idiopathic Acroosteolysis
  • = rare bizarre entity of unknown etiology
    Location: may be unilateral
  • fingernails remain intact
  • • sensory changes + plantar ulcers rare
  • pseudoclubbing of fingers + toes with osteolysis of terminal + more proximal phalanges
  • genu varum / valgum
  • hypoplasia of proximal end of radius
  • subluxation of radial head
  • scaphocephaly, basilar impression
  • wide sutures, persistent metopic suture, Wormian bones, poorly developed sinuses
  • kyphoscoliosis
  • severe osteoporosis + fractures at multiple sites (esp. of spine)
  • protrusio acetabuli
Fanconi Anemia
  • = autosomal recessive disease with severe hypoplastic anemia + skin pigmentation + skeletal and urogenital anomalies
  • • skin pigmentation (melanin deposits) in 74% (trunk, axilla, groin, neck)
  • • anemia onset between 17 months and 22 years of age
  • • bleeding tendency (pancytopenia)
  • • hypogonadism (40%)
  • • microphthalmia (20%)
  • anomalies of radial component of upper extremity (strongly suggestive):
    • absent / hypoplastic / supernumerary thumb
    • hypoplastic / absent radius
    • absent / hypoplastic navicular / greater multangular bone
  • slight / moderate dwarfism
  • minimal microcephaly
  • renal anomalies (30%): renal aplasia, ectopia, horseshoe kidney
Prognosis: fatal within 5 years after onset of anemia; patient’s family shows high incidence of leukemia
Farber Disease
Histo: foam cell granulomas; lipid storage of neuronal tissue (accumulation of ceramide + gangliosides)
  • • hoarse weak cry
  • • swelling of extremities; generalized joint swelling
  • • subcutaneous + periarticular granulomas
  • • intermittent fever, dyspnea
  • • lymphadenopathy
  • capsular distension of multiple joints (hand, elbow, knee)
  • juxtaarticular bone erosions from soft-tissue granulomas
  • subluxation / dislocation
  • disuse / steroid deossification
Prognosis: death from respiratory failure within 2 years
Femoroacetabular impingement
= repetitive microtrauma due to an anatomic conflict between proximal femur + acetabular rim at extreme range of motion
Age: 2nd–3rd decade; in patients with increased sports activity
Femoroacetabular Impingement

  • Cam FAI
    • = nonspherical shape of femoral head with reduced depth of femoral waist leads to abutment of femoral head-neck junction against acetabular rim
    • osseous bump deforming femoral head-neck junction (50%)
    • a-angle of >55° (measured at the anterosuperior position on radial images rotated around center line of femoral neck)
    • cartilage lesions at anterosuperior acetabulum at posterior and posteroinferior acetabulum (pincer FAI)
  • Pincer FAI
    • = acetabular overcoverage limits range of motion
      Cause: protrusio acetabuli, acetabular retroversion
    • deep acetabulum (head center >5 mm below rim)
    • osseous bump deforming femoral head-neck junction (33%)
    • cartilage lesions at posterior and posteroinferior acetabulum (countercoup damage)
  • ossification of acetabular rim
  • separate bone fragment / os acetabuli
    Cx: premature osteoarthritis initially with cartilage damage + labral tears
    Rx: surgery in patients without osteoarthritis consisting of reshaping of femoral waist / trimming of acetabular rim / periacetabular osteotomy
= autosomal recessive lethal short-limb skeletal dysplasia
Incidence: 5 cases
  • severe micromelia + broad dumbbell-shaped metaphyses
  • flat + clefted pear-shaped vertebral bodies
  • short + cupped ribs
  • frontal bossing
  • low-set abnormally formed ears
Prognosis: stillbirth / death shortly after birth
DDx: (1) Thanatophoric dysplasia
(2) Metatropic dysplasia
(3) Spondyloepiphyseal dysplasia
Fibrodysplasia Ossificans Progressiva
  • = MYOSITIS OSSIFICANS PROGRESSIVA (misnomer since primarily connective tissues are affected)
  • = rare slowly progressive sporadic / autosomal dominant disease with variable penetrance characterized by remissions + exacerbations of fibroblastic proliferation, subsequent calcification + ossification of subcutaneous fat, skeletal muscle, tendons, aponeuroses, ligaments
Histo: edema with proliferating fibroblasts in a loose myxoid matrix; subsequent collagen deposition plus calcification + ossification of collagenized fibrous tissue in the center of nodules
Age: presenting by age 2 years (50%)
  • initially subcutaneous painful masses on neck, shoulders, upper extremities
  • progressive involvement of remaining musculature of back, chest, abdomen, lower extremities
  • lesions may ulcerate and bleed
  • muscles of back + proximal extremities become rigid followed by thoracic kyphosis
  • inanition secondary to jaw trismus (masseter, temporal muscle)
  • “wry neck” = torticollis (due to restriction of sternocleidomastoid muscle)
  • respiratory failure (thoracic muscles affected)
  • conductive hearing loss (fusion of middle ear ossicles)
    • rounded / linear calcification in neck / shoulders, paravertebral region, hips, proximal extremity, trunk, palmar + plantar fascia forming ossified bars + bony bridges
    • ossification of voluntary muscles, complete by 20–25 years (sparing of sphincters + head)
    • may appear before ectopic ossification
    • • clinodactyly
    • microdactyly of big toes (90%) and thumbs (50%) = usually only one large phalanx present / synostosis of metacarpal + proximal phalanx (first sign)
    • phalangeal shortening of hand + foot (middle phalanx of 5th digit)
    • shortened 1st metatarsal + hallux valgus (75%)
    • shortened metacarpals + metatarsals
    • shallow acetabulum
    • short widened femoral neck
    • thickening of medial cortex of tibia
    • progressive fusion of posterior arches of cervical spine
    • narrowed AP diameter of cervical + lumbar vertebral bodies
    • ± bony ankylosis
CAVE: surgery is hazardous causing accelerated ossification at the surgical site
Fibroma of Soft Tissue
Histo: hypocellular highly collagenic tumor
Age: 3rd and 4th decades; M > F
Location: tendon sheath of distal upper extremity
  • slowly growing lesion 1–5 cm in size
  • MR:
    • small hypointense nodule on all pulse sequences
Incidence: 4% of all primary bone neoplasm
    • following radiotherapy of giant cell tumor / lymphoma / breast cancer
    • P.78

    • underlying benign lesion: Paget disease (common); giant cell tumor, bone infarct, osteomyelitis, desmoplastic fibroma, enchondroma, fibrous dysplasia (rare)
    • dedifferentiation of low-grade chondrosarcoma
Histo: spectrum of well to poorly differentiated fibrous tissue proliferation; will not produce osteoid / chondroid / osseous matrix
Age: predominantly in 3rd–5th decade (range of 8–88 years); M:F = 1:1
Metastases to: lung, lymph nodes
  • localized painful mass
Location: tubular bones in young, flat bones in older patients; femur (40%), tibia (16%) (about knee in 30–50%), jaw, pelvis (9%); rare in small bones of hand + feet or spinal column
Site: eccentric at diaphyseal-metaphyseal junction into metaphysis; intramedullary / periosteal
    • = intramedullary
    • well-defined lucent bone lesion
    • thin expanded cortex
    • aggressive osteolysis with geographic / ragged / permeative bone destruction + wide zone of transition
    • occasionally large osteolytic lesion with cortical destruction, periosteal reaction + soft-tissue invasion
    • sequestration of bone may be present (DDx: eosinophilic granuloma, bacterial granuloma)
    • sparse periosteal proliferation (uncommon)
    • intramedullary discontinuous spread
    • no calcification
      DDx: malignant fibrous histiocytoma, myeloma, telangiectatic osteosarcoma, lymphoma, desmoplastic fibroma, osteolytic metastasis
    • = rare tumor arising from periosteal connective tissue
      Location: long bones of lower extremity, jaw
    • contour irregularity of cortical border
    • periosteal reaction with perpendicular bone formation may be present
    • rarely extension into medullary cavity
Cx: pathologic fracture (uncommon)
Prognosis: 20% 10-year survival
DDx: (1) Osteolytic osteosarcoma (2nd–3rd decade)
(2) Chondrosarcoma (usually contains characteristic calcifications)
(3) Aneurysmal bone cyst (eccentric blown-out appearance with rapid progression)
(4) Malignant giant cell tumor (begins in metaphysis extending toward joint)
Fibrous Cortical Defect
Incidence: 30% of children; M:F = 2:1
Age: peak age of 7–8 years (range of 2–10 years); mostly before epiphyseal closure
Histo: fibrous tissue from periosteum invading underlying cortex
  • asymptomatic
Location: metaphyseal cortex of long bone; posterior medial aspect of distal femur, proximal tibia, proximal femur, proximal humerus, ribs, ilium, fibula
  • round when small, average diameter of 1–2 cm
  • oval, extending parallel to long axis of host bone
  • cortical thinning + expansion may occur
  • smooth, well-defined / scalloped margins
  • larger lesions are multilocular
  • involution over 2–4 years
  • potential to grow and encroach on the medullary cavity leading to nonossifying fibroma
  • bone islands in the adult may be residue of incompletely involuted cortical defect
Fibrous Dysplasia
  • = benign fibroosseous developmental anomaly of the mesenchymal precursor of bone, manifested as a defect in osteoblastic differentiation and maturation
Cause: probable gene mutation during embryogenesis
Age: 1st–2nd decade (highest incidence between 3 and 15 years), 75% before age 30; progresses until growth ceases; M:F = 1:1
Path: spongiosa of medullary cavity filled by abnormal fibrous tissue containing poorly calcified trabeculae
Histo: matrix of immature collagen contains small irregularly shaped trabeculae of immature, inadequately mineralized “woven” bone; trabeculae not rimmed by osteoblasts (DDx from ossifying fibroma); cartilaginous islands present in 10% (DDx: chondrosarcoma)
Clinical Types:
  • MONOSTOTIC FORM (70–80%)
    • usually asymptomatic until 2nd–3rd decade
      Location: ribs (28%), proximal femur (23%), tibia, craniofacial bones (10–25%), humerus
    Age: mean age of 8 years
    • 2/3 symptomatic by age 10
    • leg pain, limp, pathologic fracture (75%)
    • abnormal vaginal bleeding (25%)
    • coast of Maine café-au-lait spots = few yellowish to brownish dark patches of cutaneous pigmentation with irregular / serrated border, predominantly on back of trunk (30–50%), buttocks, neck, shoulders; often ipsilateral to bone lesions (DDx: more numerous and lighter “coast of California” spots of neurofibromatosis)
      Associated with: endocrinopathy (in 2–3%)
      Location: usually unilateral + asymmetric; femur (91%), tibia (81%), pelvis (78%), foot (73%), ribs, skull + facial bones (50%), upper extremities, lumbar spine (14%), clavicle (10%), cervical spine (7%)
      Site: metadiaphysis
    • leg length discrepancy (70%)
    • “shepherd’s crook” deformity (35%)
    • facial asymmetry
    • tibial bowing
    • rib deformity
    • “ray” pattern = involvement of all phalanges + metacarpal bone of a single digit
  • P.79

    Incidence: in 10–25% of monostotic form / in 50% of polyostotic form / isolated
    • cranial asymmetry
    • facial deformity
    • nasal stuffiness
    • proptosis
    • visual impairment / unilateral blindness
      Location: sphenoid, frontal, maxillary, ethmoid bones > occipital, temporal bones
    • unilateral overgrowth of facial bones + calvarium (NO extracranial lesions)
    • outward expansion of outer table maintaining convexity (DDx: Paget disease with destruction of inner + outer table)
    • prominence of external occipital protuberance
      Cx: neurologic deficit secondary to narrowed cranial foramina (eg, blindness)
  • CHERUBISM (special variant)
    • = autosomal dominant disorder of variable penetrance
      Age: childhood; more severe in males
    • • bilateral jaw fullness + slight upward turning of eyes
    • bilateral expansile multiloculated cystic masses with symmetric involvement of mandible + maxilla
      Cx: problems with dentition after perforation of cortex
      Prognosis: regression after adolescence
May be associated with:
  • endocrine disorders:
    • precocious puberty in girls
    • hyperthyroidism
    • hyperparathyroidism: renal stones, calcinosis
    • acromegaly
    • diabetes mellitus
    • Cushing syndrome: osteoporosis, acne
    • growth retardation
  • soft-tissue myxoma (rare) = Mazabraud syndrome: typically multiple intramuscular lesions in vicinity of most severely affected bone
VARIANT: McCune-Albright syndrome (10%)
Sex: almost exclusively in girls
  • polyostotic unilateral fibrous dysplasia
  • “coast of Maine” café-au-lait spots (35%)
  • endocrinopathy: peripheral sexual precocity (menarche in infancy [20%]), hyperthyroidism
    • • swelling + tenderness
    • • limp, pain (± pathologic fracture)
    • • increased alkaline phosphatase
    • • advanced skeletal + somatic maturation (early)
    Common location: rib cage (30%), craniofacial bones [calvarium, mandible] (25%), femoral neck + tibia (25%), pelvis
    Site: metaphysis is primary site with extension into diaphysis (rarely entire length)
    • normal bone architecture altered + remodeled
    • lesions in medullary cavity: radiolucent / “ground-glass” appearance / increased density
    • trabeculated appearance due to reinforced subperiosteal bone ridges in wall of lesion
    • expansion of cortices (ribs, skull, long bones) with “blown-out” appearance
    • well-defined sclerotic margin of reactive bone = rind
    • endosteal scalloping with thinned / lost cortex (ribs, long bones) and intervening normal cortex is HALLMARK
    • lesion may undergo calcification + enchondral bone formation = fibrocartilaginous dysplasia
    • increased activity on bone scan during early perfusion + on delayed images
    • Most cases of monostotic fibrous dysplasia are incidental findings on a cranial CT examination!
    • ground-glass lucencies
    • sclerotic margins + well-defined borders
    • expansion of bone
    • MRI should not be used to differentiate fibrous dysplasia from other entities due to the extreme variability in the appearance of the bone lesions!
    • homogeneous / mildly heterogeneous marrow lesions hyperintense to fat (60%) / of intermediate / of low signal intensity on T2WI
    • marrow lesions hypointense to muscle on T1WI
    • increased tracer uptake on bone scans (lesions remain metabolically active into adulthood)
    • @ Skull
      • skull deformity with cranial nerve compromise
      • proptosis
      Location: frontal bone > sphenoid bone; hemicranial involvement (DDx: Paget disease is bilateral)
      • “blistering / bubbling” cystic calvarial lesions (CHARACTERISTIC), commonly crossing sutures
      • sclerotic skull base, may narrow neural foramina (visual + hearing loss)
      • widened diploic space with displacement of outer table, inner table spared (DDx: Paget disease, inner table involved)
      • obliteration of sphenoid + frontal sinuses due to encroachment by fibrous dysplastic bone
      • inferolateral displacement of orbit
      • sclerosis of orbital plate + small orbit + hypoplasia of frontal sinuses (DDx: Paget disease, meningioma en plaque)
      • occipital thickening
      • mandibular cystic lesion (very common) = osteocementoma, ossifying fibroma
    • @ Pelvis + ribs
      • bubbly cystic lesions (extremely common)
      • fusiform enlargement of ribs + loss of normal trabecular pattern + thin preserved cortex (in up to 30%)
        • Fibrous dysplasia is the most common cause of a benign expansile lesion of a rib!
        • A rib is the most common site of monostotic fibrous dysplasia!
      • protrusio acetabuli
    • @ Extremities
      • • short stature as adult / dwarfism
      • premature fusion of ossification centers
      • epiphysis rarely affected before closure of growth plate
      • P.80

      • bowing deformities + discrepant limb length (tibia, femur) due to stress of normal weight bearing
      • “shepherd’s crook” deformity of femoral neck = coxa vara
      • pseudarthrosis in infancy = osteofibrous dysplasia (DDx: neurofibromatosis)
      • premature onset of arthritis
    Cx: (1) Dedifferentiation into osteo- / fibro- / (rarely) chondrosarcoma or malignant fibrous histiocytoma (0.5–1%, more often in polyostotic form)
    • increasing pain
    √enlarging soft-tissue mass
    √previously mineralized lesion turns lytic
    (2) Pathologic fractures: transformation of woven into lamellar bone may be seen, subperiosteal healing without endosteal healing
    • Paget disease (mosaic pattern histologically, radiographically similar to monostotic cranial lesion, outer table involved, sparing of facial bones)
    • Neurofibromatosis (rarely osseous lesions, vertebral column is primary target, ribbon ribs, cystic intraosseous neurofibroma rare, café-au-lait spots smooth, familial disease)
    • HPT (principally histologic problem, chemical changes, generalized deossification, subperiosteal resorption)
    • Osteofibrous dysplasia (almost exclusively in tibia of children <10 years + anterior bowing, monostotic, lesion begins in cortex, spontaneous regression)
    • Nonossifying fibroma
    • Simple bone cyst
    • Giant cell tumor (no sclerotic margin)
    • Enchondromatosis
    • Eosinophilic granuloma (beveled margin in skull, “black hole” on CT of lower density)
    • Osteoblastoma
    • Hemangioma
    • Meningioma
    Prognosis: bone lesions usually do not progress beyond puberty
Fibrous Histiocytoma
Benign Fibrous Histiocytoma
Incidence: 0.1% of all bone tumors
Histo: interlacing bundles of fibrous tissue in storiform pattern (whorled / woven) interspersed with mono- / multinucleated cells resembling histiocytes, benign giant cells, and lipid-laden macrophages; resembles nonossifying fibroma / fibroxanthoma
Age: 23–60 years
  • localized intermittently painful soft-tissue swelling
Location: long bone, pelvis, vertebra (rare)
Site: typically in epiphysis / epiphyseal equivalent
  • well-defined radiolucent lesion with septa / soap-bubble appearance / no definable matrix
  • may have reactive sclerotic rim
  • narrow transition zone (= nonaggressive lesion)
  • no periosteal reaction
Rx: curettage
DDx: nonossifying fibroma (childhood / adolescence, asymptomatic, eccentric metaphyseal location)
Atypical Benign Fibrous Histiocytoma
Histo: “atypical aggressive” features = mitotic figures present
  • lytic defect with irregular edges
Prognosis: may metastasize
Malignant Fibrous Histiocytoma
Histo: spindle-cell neoplasm of a mixture of fibroblasts + giant cells resembling histiocytes with nuclear atypia and pleomorphism in pinwheel arrangement; closely resembles high-grade fibrosarcoma (= fibroblastic cells arranged in uniform pattern separated by collagen fibers)
(a) pleomorphic-storiform subtype (50–60%)
(b) myxoid subtype (25%)
(c) giant cell subtype (5–10%)
(d) inflammatory subtype (5–10%)
(e) angiomatoid subtype (<5%)
Age: 10–90 (average 50) years; peak prevalence in 5th decade; more frequent in Caucasians; M:F = 3:2
Location: potential to arise in any organ (ubiquitous mesenchymal tissue); soft tissues >> bone
Soft-tissue MFH
Incidence: 20–30% of all soft-tissue sarcomas; most common primary malignant soft-tissue tumor of late adult life
  • Any deep-seated invasive intramuscular mass in a patient >50 years of age is most likely MFH!
Location: extremities (75%), [lower extremity (50%), upper extremity (25%)], retroperitoneum (15%), head + neck (5%)
Site: within large muscle groups
  • large painless soft-tissue mass with progressive enlargement over several months
  • mass usually 5–10 cm in size with increase over months / years
  • poorly defined curvilinear / punctate peripheral calcifications / ossifications (in 5–20%)
  • cortical erosion of adjacent bone (HIGHLY SUGGESTIVE FEATURE)
  • CT:
    • well-defined soft-tissue mass with central hypodense area = myxoid MFH (DDx: hemorrhage, necrosis, leiomyosarcoma with necrosis, myxoid lipo- / chondrosarcoma)
    • enhancement of solid components
  • MR:
    • inhomogeneous poorly defined lesion iso- / hyperintense to muscle on T1WI + hyperintense on T2WI
Prognosis: larger + more deeply located tumors have a worse prognosis; 2-year survival rate of 60%; 5-year survival rate of 50%; local recurrence rate of 44%; metastatic rate of 42% (lung, lymph nodes, liver, bone)
DDx: (1) Liposarcoma (younger patient, presence of fat in >40%, calcifications rare)
(2) Rhabdomyosarcoma
(3) Synovial sarcoma (cortical erosion)

Osseous MFH
Prevalence: 5% of all primary malignant bone tumors
  • painful, tender, rapidly enlarging mass
  • pathologic fracture (20%)
Associated with: prior radiation therapy, bone infarcts, Paget disease, fibrous dysplasia, osteonecrosis, fibroxanthoma (= nonossifying fibroma), enchondroma, chronic osteomyelitis
  • 20% of all osseous MFH arise in areas of abnormal bone!
Location: femur (45%), tibia (20%), 50% about knee; humerus (10%); ilium (10%); spine; sternum; clavicle; rarely small bones of hand + feet
Site: central metaphysis of long bones (90%); eccentric in diaphysis of long bones (10%)
  • radiolucent defect with ill-defined margins (2.5–10 cm in diameter)
  • extensive mineralization / small areas of focal metaplastic calcification
  • permeation + cortical destruction
  • expansion in smaller bones (ribs, sternum, fibula, clavicle)
  • occasionally lamellated periosteal reaction (especially in presence of pathologic fracture)
  • soft-tissue extension
Cx: pathologic fracture (30–50%)
DDx: (1) Metastasis
(2) Fibrosarcoma (often with sequestrum)
(3) Reticulum cell sarcoma
(4) Osteosarcoma
(5) Giant cell tumor
(6) Plasmacytoma
Pulmonary MFH (extremely rare)
  • solitary pulmonary nodule without calcification
  • diffuse infiltrate
  • NUC:
    • increased uptake of Tc-99m MDP (mechanism not understood)
    • increased uptake of Ga-67 citrate
  • US:
    • well-defined mass with hyperechoic + hypoechoic (necrotic) areas
  • CT:
    • mass of muscle density with hypodense areas (necrosis)
    • invasion of abdominal musculature, but not IVC / renal veins (DDx to renal cell carcinoma)
  • Angio:
    • hypervascularity + early venous return
Focal Fibrocartilaginous Dysplasia of Tibia
Associated with: tibia vara
Age: 9–28 months
Histo: dense hypocellular fibrous tissue resembling tendon with lacuna formation
  • • slight shortening of affected leg
Location: insertion of pes anserinus (= tendinous insertion of gracilis, sartorius, semitendinosus muscles) distal to proximal tibial physis; unilateral involvement
  • unilateral tibia vara
  • well-defined elliptic obliquely oriented lucent defect in medial tibial metadiaphyseal cortex
  • sclerosis along lateral border of lesion
  • absence of bone margin superomedially
Prognosis: resolution in 1–4 years
DDx: (1) Unilateral Blount disease (typically bilateral in infants, varus angulation of upper tibia, decreased height of medial tibial metaphysis, irregular physis)
(2) Chondromyxoid fibroma, eosinophilic granuloma, osteoid osteoma, osteoma, fibroma, chondroma (not associated with tibia vara, soft-tissue mass)
= soft-tissue injury in which there is a break in the continuity of bone or cartilage
General description:
    open Fx = communication between fractured bone + skin
    complete Fx = all cortical surfaces disrupted
    incomplete Fx = partial separation of bone
    greenstick Fx = break of one cortical margin only with intact periosteum due to tension on soft growing bone
    buckle / torus Fx = buckling of cortex due to compression
    bowing Fx = plastic deformity of thin long bone (clavicle, ulna, fibula)
    lead-pipe Fx = combination of greenstick + torus Fx
    simple Fx = noncomminuted
    comminuted Fx = >2 fragments
    segmental Fx = isolated segment of shaft
    butterfly fragment = V-shaped fragment not completely circumscribed by cortex
  • DIRECTION OF FRACTURE LINE in relation to long axis of bone: transverse, oblique, oblique-transverse, spiral
Special terminology:
avulsion Fx = fragment pulled off by tendon / ligament from parent bone
transchondral Fx = cartilaginous surface involved
chondral Fx = cartilage alone involved
osteochondral Fx = cartilage + subjacent bone involved
Description of anatomic positional changes:
  • = change in position of distal fracture fragment in relation to proximal fracture fragment
    • = longitudinal change of fragments
    • distraction = increase from original anatomic length
    • shortening = decrease from original anatomic length
    • — impacted = fragments driven into each other
    • — overriding = also includes latitudinal changes
    • — overlapping = bayonet apposition
  • P.82

    • = latitudinal change of anatomic axis:
    • undisplaced
    • anterior, posterior, medial / ulnar, lateral / radial
    • = long axes of fragments intersect at the fracture apex:
    • medial / lateral, ventral / dorsal
    • varus = angular deviation of distal fragment toward midline on frontal projection
    • — valgus = angular deviation of distal fragment away from midline on frontal projection
    • eg, “ventral angulation of fracture apex”
    • eg, “in anatomic / near anatomic alignment”
    • Difficult to detect radiographically!
    • differences in diameters of apposing fragments
    • mismatch of fracture line geometry
    • — internal / external rotation
  • Typical time course:
    • Acute phase (3–4 weeks)
      • abnormal in 80% <24 hours, in 95% <72 hours
      • Elderly patients show delayed appearance of positive scan
      • broad area of increased tracer uptake (wider than fracture line)
    • Subacute phase (2–3 months) = time of most intense tracer accumulation
      • more focal increased tracer uptake corresponding to fracture line
    • Chronic phase (1–2 years)
      • slow decline in tracer accumulation
      • in 65% normal after 1 year; >95% normal after 3 years
  • Return to normal:
    • Non–weight-bearing bone returns to normal more quickly than weight-bearing bone
    • Rib fractures return to normal most rapidly
    • Complicated fractures with orthopedic fixation devices take longest to return to normal
    • Simple fractures: 90% normal by 2 years
    • Open reduction / fixation: <50% normal by 3 years
    • Delayed union: slower than normal for type of fracture
    • Nonunion: persistent intense uptake in 80%
    • Complicated union (true pseudarthrosis, soft-tissue interposition, impaired blood supply, presence of infection)
      • intense uptake at fracture ends
      • decreased uptake at fracture site
    • Vertebral compression fractures: 60% normal by 1 year; 90% by 2 years; 97% by 3 years
Pathologic Fracture
= fracture at site of preexisting osseous abnormality
Cause: tumor, osteoporosis, infection, metabolic disorder
Stress Fracture
= fractures produced as a result of repetitive prolonged muscular action on bone that has not accommodated itself to such action
Insufficiency Stress Fracture
= normal physiologic stress applied to bone with abnormal elastic resistance / deficient mineralization
  • Osteoporosis
  • Renal osteodystrophy
  • Osteomalacia / rickets
  • Hyperparathyroidism
  • Radiation therapy
  • Rheumatoid arthritis
  • Paget disease
  • Fibrous dysplasia
  • Osteogenesis imperfecta
  • Osteopetrosis
  • Prolonged corticosteroid treatment
  • Tumor treatment with ifosfamide, methotrexate
Location: thoracic vertebra, sacrum, pubic bone, ilium, lower extremity (calcaneus, tibia, fibula)
Fracture orientation: perpendicular to long axis of bone
Plain film / CT (1–2 weeks after onset of fracture):
  • cortical lucency (due to disruption)
  • periosteal new bone formation
  • medullary sclerosis (endosteal callus formation)
  • zone of low signal intensity on T1WI + variable intensity on T2WI (= discrete fracture line)
  • surrounded by diffuse marrow edema (hypointense on T1WI + hyperintense)
  • hyperintense components of circumferential periosteal reaction + early callus + surrounding edema adjacent to bone on T2WI with enhancement after IV Gd-chelate (DDx: osteomyelitis with more eccentric involvement)
NUC (bone scan):
  • increased abnormal uptake
Pelvic Insufficiency Stress Fracture
  • severe pain in lower back + sacroiliac joints; radiates to buttocks, hips, groin, legs; worsens with weight bearing
  • walking ability impaired
Incidence: 1.8–5% of women >55 years
Predisposed: postmenopausal women
Location: sacral ala, parasymphyseal region of os pubis, pubic rami, supraacetabular region, iliac blades, superomedial portion of ilium
  • occult fracture:
    Site: sacrum > supraacetabulum, ilium
    • sclerotic band, cortical disruption, fracture line
    • Often obscured by overlying bowel gas + osteopenia!
      Type Bone Quality Load
      Traumatic normal single large
      Fatigue (stress) normal repetitive
      Insufficiency (stress) abnormal (metabolic) minimal
      Pathologic abnormal (tumor) minimal
      Fatigue (Stress) and insufficiency fracture of Hip
  • P.83

  • aggressive fracture:
    Site: parasymphysis, pubic rami
    • exuberant callus formation, osteolysis + fragments (with prolonged or delayed healing / chronic nonunion)
    CAVE: fracture may be misdiagnosed as neoplasm; interpretation also histologically difficult
  • butterfly / H-shaped (“Honda sign”) / asymmetric incomplete H-shaped pattern of sacral uptake
  • pelvic outlet view for parasymphyseal fx
CT and MR (most accurate modalities):
  • sclerotic band, linear fracture line, cortical disruption, fragmentation, displacement
  • bone marrow edema
  • Excludes bone destruction + soft-tissue masses!
Prognosis: healing in 12–30 months
Femoral Insufficiency Fracture
Site: subcapital
  • subtle femoral neck angulation
  • trabecular angulation
  • subcapital impaction line
Fatigue Stress Fracture
  • = normal bone subjected to repetitive stresses (none of which is singularly capable of producing a fracture) leading to mechanical failure over time
    Risk factors: new / different / rigorous repetitive activity; female sex; increased age; Caucasian race; low bone mineral density; low calcium intake; fluoride treatment for osteoporosis; condition resulting in altered gait
  • • activity-related pain abating with rest
  • • constant pain with continued activity
  • @ Spine
    • Clay shoveler’s fracture: spinous process of lower cervical / upper thoracic spine
    • Spondylolysis = pars interarticularis of lumbar vertebrae: ballet, lifting heavy objects, scrubbing floors
    • Ribs: carrying heavy pack, golf, coughing
  • @ Upper extremity
    • Clavicle: postoperative (radical neck dissection)
    • Coracoid process of scapula: trap shooting
    • Coronoid process of ulna: pitching ball, throwing javelin, pitchfork work, propelling wheelchairs
    • Distal shaft of humerus: throwing ball
    • Hook of hamate: swinging golf club / tennis racquet / baseball bat
  • @ Pelvis
    • Obturator ring of pelvis: stooping, bowling, gymnastics
      Site: superior / inferior pubic ramus
    • Sacrum (<2%): long-distance runner, military recruits
      Site: unilateral (? due to leg length discrepancy)
  • @ Lower extremity
    • Femoral neck: ballet, long-distance running
      Site: medial femoral neck
      • subtle lucency / sclerosis (= acute fracture)
      • lucent line surrounded by sclerosis (= subacute fracture)
    • Femoral shaft: ballet, marching, long-distance running, gymnastics
    • Patella: hurdling
    • Tibial shaft: ballet, jogging
    • Fibula: long-distance running, jumping, parachuting
  • @ Foot (in order of frequency):
    • Second metatarsal: marching, stomping on ground, prolonged standing, ballet, postoperative bunionectomy
    • Calcaneus: jumping, parachuting, prolonged standing, recent immobilization
      • vertical / oblique fracture orientation anterior to tuberosity
    • Navicular: stomping on ground, marching, prolonged standing, ballet
      • vertically oriented fracture in midbody
      • Midfoot fractures are difficult to diagnose by conventional radiography; CT + MRI are often helpful
    • Sesamoids of metatarsal: prolonged standing
X-RAY (15% sensitive in early fractures, increasing to 50% on follow-up):
  • –cancellous (trabecular) bone (notoriously difficult to detect)
    • subtle blurring of trabecular margins
    • faint sclerotic radiopaque area of peritrabecular callus (50% change in bone density needed)
    • sclerotic band (due to trabecular compression + callus formation) usually perpendicular to cortex
  • –compact (cortical) bone
    • “gray cortex sign” = subtle ill definition of cortex
    • intracortical radiolucent striations (early)
    • solid thick lamellar periosteal new bone formation
    • endosteal thickening (later)
  • Follow-up radiography after 2–3 weeks of conservative therapy
    Salter-Harris Classification of Epiphyseal Plate injury
    Rang and Ogden’s additions to Salter-Harris Classification

NUC (“gold standard” = almost 100% sensitive):
  • abnormal uptake within 6–72 hours of injury (prior to radiographic abnormality)
  • “stress reaction” = focus of subtly increased uptake
  • focal fusiform area of intense cortical uptake
  • abnormal uptake persists for months
MR (very sensitive modality; fat saturation technique most sensitive as it detects an increase in water content of medullary edema / hemorrhage):
  • diminished marrow signal intensity on T1WI of fracture line
  • increased marrow signal intensity on T2WI (edema may obscure the fracture line), resolves within 6 months in 90%
  • low-intensity band contiguous with cortex on T2WI = fracture line of more advanced lesion
CT (least sensitive modality):
helpful in: longitudinal stress fracture of tibia; in confusing pediatric stress fracture (to detect endosteal bone formation)
  • Shin splints (activity not increased in angiographic / blood-pool phase)
    • long linear uptake on posteromedial (soleus muscle) / anterolateral (tibialis anterior muscle) tibial cortex on delayed images (from stress to periosteum at muscle insertion site)
  • Osteoid osteoma (eccentric, nidus, solid periosteal reaction, night pain)
  • Chronic sclerosing osteomyelitis (dense, sclerotic, involving entire circumference, little change on serial radiographs)
  • Osteomalacia (bowed long bones, looser zones, gross fractures, demineralization)
  • Osteogenic sarcoma (metaphyseal, aggressive periosteal reaction)
  • Ewing tumor (lytic destructive appearance with soft-tissue component, little change on serial radiographs)
Epiphyseal Plate Injury
Prevalence: 6–18–30% of bone injuries in children <16 years of age
Peak age: 12 years
Location: distal radius (28%), phalanges of hand (26%), distal tibia (10%), distal phalanges of foot (7%), distal humerus (7%), distal ulna (4%), proximal radius (4%), metacarpals (4%), distal fibula (3%)
Mechanism: 80% shearing force; 20% compression
Resistance to trauma: ligament > bone > physis (hypertrophic zone most vulnerable)
Salter-Harris classification (considering probability of growth disturbance)
  • [Robert Bruce Salter (1924–) and W. Robert Harris (1922–), orthopedic surgeons in Toronto, Canada]
  • Prognosis is worse in lower extremities (ankle + knee) irrespective of Salter-Harris type!
mnemonic: SALTR
Slip of physis = type 1
Above physis = type 2
Lower than physis = type 3
Through physis = type 4
Rammed physis = type 5

Salter Type 1 (6–8.5%)
  • = slip of epiphysis due to shearing force separating epiphysis from physis
    Line of cleavage: confined to physis
    Location: most commonly in phalanges, distal radius (includes: apophyseal avulsion, slipped capital femoral epiphysis)
  • displacement of epiphyseal ossification center
    Prognosis: favorable irrespective of location
Salter Type 2 (73–75%)
= shearing force splits growth plate
Line of fracture: through physis + extending through margin of metaphysis separating a triangular metaphyseal fragment (= “corner sign”)
Location: distal radius (33–50%), distal tibia + fibula, phalanges
Prognosis: good, may result in minimal shortening
Salter Type 3 (6.5–8%)
  • = intraarticular fracture, often occurring after partial closure of physis
    Line of fracture: vertically / obliquely through epiphysis + extending horizontally to periphery of physis
    Location: distal tibia, distal phalanx, rarely distal femur
  • epiphysis split vertically
    Prognosis: fair (imprecise reduction leads to alteration in linearity of articular plane)
Salter Type 4 (10–12%)
Location: lateral condyle of humerus, distal tibia
  • fracture involves metaphysis + physis + epiphysis
    Prognosis: guarded (may result in deformity + angulation)
Salter Type 5 (<1%)
  • = crush injury with injury to vascular supply
    Location: distal femur, proximal tibia, distal tibia
    Often associated with: fracture of adjacent shaft
  • no immediate radiographic finding
  • shortening of bone + cone epiphysis / angular deformity on follow-up
    Prognosis: poor (impairment of growth in 100%)
Triplane Fracture (6%)
Location: distal tibia, lateral condyle of distal humerus
  • vertical fracture of epiphysis + horizontal cleavage plane within physis + oblique fracture of adjacent metaphysis
  • MR:
    • focal dark linear area (= line of cleavage) within bright physis on gradient echo images (GRE)
    Cx: (1) progressive angular deformity from segmental arrest of germinal zone growth with formation of a bone bridge across physis = “bone bar”
    (2) limb length discrepancy from total cessation of growth
    (3) articular incongruity from disruption of articular surface
    (4) Bone infarction in metaphysis / epiphysis
Apophyseal Injury
Mechanism: excessive avulsive force
  • Physis under secondary ossification center is weakest part!
    At risk: young athletes: hurdlers, sprinters, cheerleaders (repetitive to and fro adduction / abduction + flexion / extension)
    Age: children > adults
    √ Avulsion injury of lesser trochanter in adults suggests underlying malignant disease
  • • pain, point tenderness, swelling
  • irregularity at site of avulsion
  • displaced pieces of bone of variable size:
    • crescentic ossific opacity if viewed on tangent
    • very subtle disk-shaped opacity if seen en face
    abnormal foci of heterotopic ossification (later)
  • prominent bone formation in chronic avulsion injury from overuse with repeated microtraumas
DDx of healing acute injury: osteomyelitis, Ewing sarcoma
Hand Fracture
Bennett Fracture
  • [Edward Hallaran Bennett (1837–1907), surgeon in Dublin, Ireland]
    Mechanism: forced abduction of thumb
  • intraarticular fracture-dislocation of base of 1st metacarpal
  • small fragment of 1st metacarpal continues to articulate with trapezium
  • lateral retraction of 1st metacarpal shaft by abductor pollicis longus
Rx: anatomic reduction important, difficult to keep in anatomic alignment
Cx: pseudarthrosis
Boxer’s Fracture
Mechanism: direct blow with clenched fist
  • transverse fracture of distal metacarpal (usually 5th)
Gamekeeper’s Thumb
= SKIER’S THUMB (originally described as chronic lesion in hunters strangling rabbits)

Incidence: 6% of all skiing injuries; 50% of skiing injuries to the hand
Mechanism: violent abduction of thumb with injury to ulnar collateral ligament (UCL) in 1st MCP (faulty handling of ski pole)
Location Muscle Origin / Insertion
Anterior superior iliac spine sartorius muscle + tensor fasciae latae m.
Anterior inferior iliac spine rectus femoris muscle
Lesser trochanter iliopsoas muscle
Ischial tuberosity hamstrings
Greater trochanter gluteus medius + minimus, internal obturator, gemellus, piriformis
Iliac crest abdominal musculature
Symphysis pubis + inferior pubic ramus long + short adductors, gracilis
No Caption Available.
  • disruption of ulnar collateral ligament of 1st MCP joint, usually occurring distally near insertion on proximal phalanx
  • radial stress examination necessary to document ligamentous disruption
  • displacement of UCL superficial to aponeurosis of adductor pollicis (= Stener lesion) [torn end of UCL may be marked by avulsed bone fragment]
Navicular Fracture
  • Most frequent (90%) of all carpal bones fractures!
    Mechanism: fall on dorsiflexed outstretched hand
  • • pain + tenderness at anatomic snuff box
    Radiographic misses: 25–33–65%
    N.B.: If initial radiograph negative, reexamine in 2 + 6 weeks after treatment with short-arm spica cast!
  • MR: high sensitivity
    Bone scan: up to 100% sensitive, 93% PPV after 2–3 days
    Prognosis: dependent on following factors
    • fracture displacement = >1 mm offset / angulation / rotation of fragments (less favorable)
    • location (blood supply derived from distal part):
      • distal 1/3 (10%) = usually fragments reunite
      • middle 1/3 (70%) = failure to reunite in 30%
      • proximal 1/3 (20%) = failure to reunite in 90%
    • orientation of fracture
      • transverse / horizontal oblique = relatively stable
      • vertical oblique (less common) = unstable
    • Good prognosis with distal fracture + no displacement + no ligamentous injury!
    • Less favorable prognosis with displaced / comminuted fracture + proximal pole fracture!
    Cx: avascular necrosis of proximal fragment
Rolando Fracture
  • [Silvio Rolando (?–1931?), surgeon in Genoa, Italy]
  • comminuted Y- / T-shaped intraarticular fracture-dislocation through base of thumb metacarpal
Prognosis: worse than Bennett’s fracture (difficult to reduce)
No Caption Available.
Forearm Fracture
Barton Fracture
  • [John Rhea Barton (1794–1871), orthopedic surgeon at Pennsylvania Hospital, Philadelphia]
    Mechanism: fall on outstretched hand
  • P.87

  • intraarticular oblique fracture of ventral / dorsal lip of distal radius
  • carpus dislocates with distal fragment up and back on radius
Chauffeur Fracture
    [Jonathan Hutchinson (1828–1913), British surgeon]
  • = name derived from direct trauma to radial side of wrist sustained from recoil of crank used in era of hand cranking to start automobiles
    Mechanism: acute dorsiflexion + abduction of hand
  • triangular fracture of radial styloid process
Colles Fracture
  • [Abraham Colles (1773–1843), surgeon in Dublin, Ireland]
  • = POUTEAU FRACTURE (term used in France)
  • [Claude Pouteau (1725–1775), surgeon in Lyon, France]
  • Most common fracture of forearm!
Mechanism: fall on outstretched hand
  • nonarticular radial fracture in distal 2 cm
  • dorsal displacement of distal fragment + volar angulation of fracture apex
  • ± ulnar styloid fracture
  • “silver-fork” deformity
    Cx: posttraumatic arthritis
    Rx: anatomic reduction important
  • Significant postreduction deformity:
    • Residual positive ulnar variance >5 mm indicates unsatisfactory outcome in 40%
    • Dorsal angulation of palmar tilt >15° decreases grip strength + endurance in >50%
Essex-Lopresti Fracture
  • [Peter Gordon Essex-Lopresti (1918–1951), surgeon at Birmingham Accident Center, England]
  • comminuted displaced radial head fracture
  • dislocation of distal radioulnar joint
Galeazzi Fracture
  • [Ricardo Galeazzi (1866–1952), orthopedic surgeon in Italy]
Mechanism: fall on outstretched hand with elbow flexed
Anterior Humeral Line and Elbow fat Pads
  • radial shaft fracture (most commonly) at junction of distal to middle third with dorsal angulation
  • subluxation / dislocation of distal radioulnar joint
  • ulnar plus variance (= radial shortening) of >10 mm implies complete disruption of interosseous membrane = complete instability of radioulnar joint
    Cx: (1) High incidence of nonunion, delayed union, malunion (unstable fracture)
    (2) Limitation of pronation / supination
Monteggia-type Fracture
= fracture of ulnar shaft + dislocation of radial head
Bado Classification:
  • [Jose Luis Bado (1903–1977), orthopedic surgeon from Uruguay]
  • Type I = classic Monteggia fracture
    • [Giovanni Battista Monteggia (1762–1815), Italian surgeon]
      Mechanism: direct blow to the forearm
    • anteriorly angulated proximal ulnar fracture
    • anterior dislocation of radial head
    • may have associated wrist injury
      Cx: nonunion, limitation of motion at elbow, nerve abnormalities
  • Type II = reverse Monteggia fracture
    • radial head displaced posteriorly / posterolaterally
    • dorsally angulated proximal ulnar fracture
  • Type III
    • anterior / anterolateral dislocation of radial head
    • ulnar metaphyseal fracture
  • Type IV
    • anterior displacement of radial head
    • fracture of proximal third of radius + ulna at the same level
Smith Fracture
  • [Robert William Smith (1807–1873), succeeding Colles as professor of surgery at Trinity College in Dublin, Ireland]
Mechanism: hyperflexion with fall on back of hand
  • nonarticular distal radial fracture
  • ventral displacement of fragment
  • radial deviation of hand
  • “garden spade” deformity
    Cx: altered function of carpus
Elbow Fracture
  • common among children 2–14 years of age
  • @ Soft-tissue
    • displacement of anterior + posterior fat pads
      (= elbow joint effusion with supracondylar / lateral condylar / proximal ulnar fractures)
    • supinator fat pad (= fracture of proximal radius)
    • focal edema medially (= medial epicondyle fx) / laterally (= lateral condyle fx)
  • @ Humerus (80%)
    • Supracondylar fracture (55%)
      Mechanism: hyperextension with vertical stress
      • transverse fracture line
      • distal fragment posteriorly displaced / tilted
      • P.88

      • anterior humeral line intersecting anterior to posterior third of capitellum (on lateral x-ray)
        Fractures of the Acetabulum
    • Lateral condylar fracture (20%)
      Mechanism: hyperextension with varus stress
      • fracture line between lateral condyle + trochlea / through capitellum
    • Medial epicondylar fracture (5%)
      Mechanism: hyperextension with valgus stress
      • avulsion of medial epicondyle (by flexor muscles of forearm)
      • may become trapped in joint space (after reduction of concomitant elbow dislocation)
  • @ Radius (10%)
    Mechanism: hyperextension with valgus stress
    • Salter-Harris type II / IV fracture
    • transverse metaphyseal / radial neck fracture
    Mechanism: hyperextension with varus stress
    • dislocation as part of Monteggia fracture (from rupture of annular ligament)
  • @ Ulna (10%)
    • longitudinal linear fracture through proximal shaft
      Mechanism: hyperextension with vertical stress
    • transverse fracture through olecranon
      Mechanism: hyperextension with valgus / varus stress; blow to posterior elbow in flexed position
    • coronoid process avulsion
      Mechanism: hyperextension-rotation associated with forceful contraction of brachial m.
Rib Fracture
Associated with: pneumothorax, hemothorax, lung contusion / laceration
  • @ 1st rib
    • Indicates substantial trauma (due to protected location)
      Cause: acute trauma / fatigue fracture (from carrying a heavy back pack)
      Associated with: aortic / great vessel injury; thoracic vertebral fracture; scapular fracture
  • @ Lower ribs
    Associated with: injury to upper abdominal organs / diaphragm
Malgaigne Fracture

Flail Chest
  • = fracture of >4 contiguous ribs
  • • paradoxic motion of chest wall with respiration
  • • respiratory failure
Cough Fracture
Location: 4–9th rib in anterior axillary line
Pelvic Fracture
Unstable pelvic fractures:
  • anterior compression
    • Bilateral vertical pubic rami fractures
    • Symphysis + sacroiliac joint diastasis
  • lateral compression
    • Malgaigne (ipsilateral anterior + posterior fx)
    • Bucket-handle (contralateral anterior + posterior fx)
  • vertical shear
    • Superior displacement of pelvis
Acetabular Fracture
Anatomy & Function:
  • most important portion of acetabulum is roof / dome;
  • weight-bearing surface for entire lower limb is derived + supported by 2 columns which are oriented in an inverted “Y” and join above the acetabular roof at an angle of 60°:
    • anterior iliopubic column of acetabulum
    • posterior ilioischial column of acetabulum
Classification (Judet and Letournel):
  • Elementary fractures
    Posterior wall 27% Anterior column 5%
    Transverse 9% Posterior column 4%
    Anterior wall 2%    
  • Associated fractures
    Transverse + posterior wall 27%
    Both columns 19%
    T-shaped 6%
    Anterior wall + posterior hemitransverse 5%
    Posterior column + posterior wall 3%
Duverney Fracture
Posterior wall (lip / rim) fracture (27%)
Mechanism: indirect force transmitted through length of femur with flexed hip joint (knee strikes dashboard)
Associated with: posterior dislocation of femur
Transverse fracture (9%)
N.B.: most difficult to diagnose + comprehend
  • transects both the iliopubic + ilioischial columns with fracture line in an anteroposterior direction
Anterior column fracture (5%)
Mechanism: blow to greater trochanter with hip externally rotated
Associated with: posterior column / transverse fracture
  • fracture begins between anterior iliac spines + traverses the acetabular fossa + ends in the ischiopubic ramus
Posterior column fracture (4%)
Mechanism: indirect force transmitted through length of femur with hip abducted
Associated with: posterior dislocation of femur + sciatic nerve injury
  • fracture begins at greater sciatic notch + traverses the posterior aspect of acetabular fossa + ends in the ischiopubic ramus
Anterior wall fracture (2%)
Mechanism: force transmitted through greater trochanter
Associated with: posterior dislocation of femur + sciatic nerve injury
  • fracture begins on anterior rim of acetabulum + emerges on lateral aspect of superior pubic ramus
Malgaigne Fracture
  • [Joseph François Malgaigne (1806–1865), French surgical historian, published first comprehensive book on fractures]
  • = fracture-dislocation of one side of the pelvis with anterior + posterior disruption of pelvic ring

Tibial Plateau Fractures
Mechanism: direct trauma
  • • shortening of involved extremity
  • vertical fractures through one side of pelvic ring
    • superior to acetabulum (ilium)
    • inferior to acetabulum (pubic rami)
    • ± sacroiliac dislocation / fracture
  • lateral unstable fragment contains acetabulum
Bucket Handle Fracture
  • double vertical fracture through superior and inferior pubic rami + sacroiliac joint dislocation on contralateral side
Duverney Fracture
  • [Joseph Guichard Duverney (1648–1730), French surgeon]
  • isolated fracture of iliac wing
Knee Fracture
Segond Fracture
  • [Paul Ferdinand Segond (1851–1912), surgeon in chief at Salpêtrière in Paris, France]
    Mechanism: external rotation + varus stress causing excessive tension on the lateral capsular ligament
    Associated with: lesion of anterior cruciate ligament (75–100%), meniscal tear (67%)
  • • anterolateral instability of the knee
  • small cortical avulsion fracture of proximal lateral tibial rim just distal to lateral plateau
Tibial Plateau Fracture (Schatzker classification)
Mechanism: valgus force (“bumper / fender fracture” from lateral force of automobile against a pedestrian’s fixed knee) / compression force often in extension
Type I = wedge-shaped pure cleavage fracture 6%
Type II = combined cleavage + median compression fracture 25%
Type III = pure compression fracture 36%
Type IV = medial plateau fracture with a split /depressed comminution 10%
Type V = bicondylar fracture, often withinverted Y appearance 3%
Type VI = transverse / oblique fracture withseparation of metaphysis fromdiaphysis 20%
  • Lateral plateau fractures (type I–III) are most common!
  • Fractures of medial plateau are associated with greater violence and higher percentage of associated injuries!
Foot Fracture
Ankle Fracture
Incidence: ankle injuries account for 10% of all emergency room visits; 85% of all ankle sprains involve lateral ligaments
Ligamentous connections at ankle:
  • binding tibia + fibula
    • anterior inferior tibiofibular ligament (= tibiofibular syndesmosis)
    • posterior inferior tibiofibular ligament
    • transverse tibiofibular ligament
    • interosseous membrane
  • lateral malleolus
    85% of all ankle sprains involve these ligaments:
    • anterior talofibular ligament
    • posterior talofibular ligament
    • calcaneofibular ligament
  • medial malleolus = deltoid ligament with
    • navicular portion
    • sustentaculum portion
    • talar portion
Lateral Malleolar Fractures
Weber Type A
  • [Bernhard Georg Weber (1929–), orthopedic surgeon in St. Gall, Switzerland]
  • Mechanism:
    • avulsive forces affect lateral ankle structures
    • impactive forces secondary to talar shift stress medial structures
  • sprain / rupture of lateral collateral ligament
    • Anterior tibiofibular ligament ruptures alone in 66%
    • Injury of all 3 lateral ligaments in 20%

      Prognosis: chronic lateral ankle instability in 10–20%
    • transverse avulsion of malleolus sparing tibiofibular ligaments
    • ± oblique fracture of medial malleolus
    • ± posterior tibial lip fracture
Weber Type B
  • Mechanism:
    • avulsive forces on medial structures
    • impacting forces on lateral structures (talar impact)
  • oblique / spiral fracture of lateral malleolus starting at level of joint space extending proximally
  • lateral subluxation of talus
  • partial disruption of tibiofibular ligament
  • ± sprain / rupture / avulsion of deltoid ligament
  • ± transverse fracture of medial malleolus
  • Dupuytren Fracture
    • [Guillaume Dupuytren (1777–1835), French surgeon]
    • fracture of distal fibula above a disrupted tibiofibular ligament + disruption of deltoid ligament
  • LeFort Fracture of Ankle
    • [Leon Clement LeFort (1829–1893), French surgeon]
    • vertical fracture of anterior medial portion of distal fibula
    • avulsion of anterior tibiofibular ligament
Ankle Fractures
Maisonneuve Fracture
Weber Type C
  • fibular fracture higher than ankle joint (Maisonneuve fracture if around knee)
  • ± deltoid ligament tear
  • ± medial malleolar fracture
  • tear of tibiofibular ligament / avulsion of anterior tubercle (Tillaux-Chaput) / avulsion of posterior tubercle (Volkmann)
  • tear of interosseous membrane = lateral instability
  • Tillaux Fracture
    • [Paul Jules Tillaux (1834–1904), French surgeon and anatomist]
    • avulsion injury of anterior tibial tubercle at attachment of distal anterior tibiofibular ligament
  • Maisonneuve Fracture
    • [Jacques Gilles Maisonneuve (1809–1897), student of Dupuytren]
    • tear of distal tibiofibular syndesmosis + interosseous membrane
    • spiral fracture of upper third of fibula
    • associated fracture of medial malleolus / rupture of deep deltoid ligament
Chopart Fracture
  • [François Chopart (1743–1795), surgeon in Paris, France]
  • fracture-dislocation through midtarsal / Chopart (calcaneocuboid + talonavicular) joint
  • commonly associated with fractures of the bones abutting the joint
Jones Fracture
  • [Robert Jones (1857–1933), British orthopedic surgeon and pioneer in radiology described fracture in Ann Surg 1902]
    Mechanism: adduction of forefoot with ankle in plantar flexion
  • transverse fracture at base of 5th metatarsal bone at junction of diaphysis and metaphysis (>1.5 cm distal to proximal tip of metatarsal tuberosity)
    Cx: delayed union / nonunion (poor blood supply)

Peroneus Brevis Avulsion Fracture
  • Most common fracture of the proximal 5th metatarsal bone
    Mechanism: plantar flexion + inversion (stepping off a curb)
  • transverse avulsion fracture of base of 5th metatarsal bone
    Location: proximal to metatarsal tuberosity (insertion of peroneus brevis tendon); usually extraarticular
    DDx: Jones fracture (slightly different location)
Lisfranc Fracture
  • [Jacques Lisfranc De Saint Martin (1790–1847), surgeon in Napoleon’s army]
    Mechanism: metatarsal heads fixed and hindfoot forced plantarward and into rotation
  • fracture-dislocation / fracture-subluxation of tarsometatarsal joints (typically 2 through 5)
  • lateral displacement of metatarsals
Shepherd Fracture
  • [Francis J. Shepherd (1851–1929), demonstrator in anatomy at McGill University in Montreal, Canada]
  • fracture of lateral tubercle of posterior process of talus
    DDx: os trigonum
Calcaneal Fracture
Incidence: most commonly fractured tarsal bone; 60% of all tarsal fractures; 2% of all fractures in the body; commonly bilateral