Practical Orthopaedic Sports Medicine & Arthroscopy
1st Edition

Hip fractures, and fracture-dislocations are extremely uncommon in sports. When they do occur, they are associated with direct trauma encountered during contact and high-speed sports such as football, rugby, snow/cross-country skiing, cycling, and all forms of motor sports/racing (3). The injury is more common in the mature athlete, and the incidence may be directly related to increased age, and osteopenic bones. These high-energy and often violent injuries have the potential to damage the blood supply to the proximal femur and femoral head, and even when treated appropriately have a possible higher risk for a compromised long-term prognosis and poor outcome (24,25). Stress and avulsion hip fractures are fortunately the most common type encountered in sports, and occur in a younger age group, and carry a much better prognosis (14).

The hip fractures may be divided into the following categories, based on the anatomical configuration of the joint: femoral head fractures, femoral neck fractures, intertrochanteric hip fractures, subtrochanteric fractures, and acetabular fractures. The majority of reported cases refer only to fractures of the femoral neck or proximal portion of the femoral shaft (26). Regardless of the configuration and etiology, traumatic displaced and nondisplaced fractures of the hip are best treated surgically with open reduction and internal fixation (27). In athletes, these are season-ending injuries, with the potential to be career ending and disabling.

Stress fractures are most common in the lower extremities in the athletes and are seen at all levels of training and competition. There is a predilection for females, which may be mediated by hormonal mechanisms (11,40). These types of fractures are typically overuse and overload injuries sustained during endurance running, jumping, and dance (41). The mechanism involves microfractures sustained during repetitive and cyclical impact loading that overwhelm the body and bone’s ability to remodel and heal. Once a certain threshold is past, the fractures become symptomatic. Structural and chemical metabolic imbalances can alter this threshold. These fractures can occur in normal bone exposed to persistent abnormal stress, or in abnormal bone exposed to normal stress (12,31). Anything that interferes with bone remodeling, i.e., medications, nutritional deficiencies, and hormonal disturbances, can predispose an athlete to stress fractures under normal conditions. Altered bony anatomy and pathology can also be responsible and should not be overlooked (42,43).

In the hip, stress fractures can occur on both the femoral and pelvic sides of the joint. On the pelvic side, fractures occur in the medial wall and roof of the acetabulum, and in the pubic rami. These types of stress fractures should alert the physician to metabolic or structural abnormalities, as most occur due to bone insufficiency. These fractures are uncommon in young athletes, and can usually be treated symptomatically, when identified. On the femoral side, stress fractures can occur in the femoral head and neck, and depending on the configuration may have much more significant consequences, when diagnosis and treatment is delayed (5,44).

The history and clinical presentation for all stress fractures in the hip region involve the vague onset of groin and anterior thigh pain that is initially bothersome and later becomes unremitting and activity limiting. There is usually no history of trauma. Important antecedent events that should raise the level of suspicion for stress fracture include a recent increase or change in a training or practice program, footwear or training surface, and episodes of extreme muscle fatigue (14,45). When the pubic rami are affected, patients are tender to direct palpation. The physical examination is relatively nonspecific when the proximal femur and acetabulum are involved, and the only finding may be slight limitation of internal rotation in flexion. These findings can occur in numerous less consequential injuries, so frequent consecutive exams should be performed if a stress fracture is suspected. Single leg hopping is a provocative maneuver that can also help identify the problem, but it is should be done cautiously. Further diagnostic testing should be considered if the pain pattern persists after a 3 to 4 week period of relative rest.

Plain radiographs should be obtained in all patients with unremitting hip pain, despite the fact that they will likely be normal in patients with stress fractures two to four weeks after the onset of symptoms (7). The plain radiographs should be evaluated for unsuspected abnormalities, and are also useful later in the treatment process to assess healing. When plain radiographs are normal and the index of suspicion remains high for pathology because of continued or increased symptoms, advanced imaging is indicated. There is controversy as to the best modality for evaluation bone scintigraphy or MRI. Both tests have a sensitivity approaching 100% for stress fracture, but bone-scan lacks specificity and when positive is typically followed by an MRI. MRI including the proximal femur and pelvis has become our initial preference after plain films in the athlete, because the scans are readily available, identify stress fractures, localize and quantify the lesions, define the peri-articular soft-tissue, and can identify other pathology.

Femoral neck stress fractures carry the most significant consequences when diagnosis and treatment are delayed. They are more common in the skeletally mature athlete, but do occur in younger patients (7). The significance of the fracture depends on its location and extent, and if it is associated with any cortical irregularity or displacement. If displacement is present, treatment is expedient surgical reduction and fixation with cannulated titanium screws. Nondisplaced femoral neck stress fractures are assessed and treated based on a classification that combines location and biomechanical stability, lateral “tension-side” or medial “compression-side” fractures. Lateral tension-side fractures are inherently unstable, and are best treated with operative fixation (44). Compression-side fractures are biomechanically stable (Fig 32-1), and have been treated successfully with rest, limited weight bearing, and activity restriction in dependable patients (44). Unfortunately, these stable
fractures can go on to nonunion, and additional classification, based on radiographic/MRI findings, is recommended. Compression-side fractures with a visible fatigue line ≥50% of the width of the femoral neck should be treated operatively with screws. Those being treated nonoperatively should be followed with bi-weekly serial radiographs, and if delayed healing or fracture progression is noted, internal fixation is recommended (44).

Fatigue fractures of the subchondral femoral head have also been reported, and are important to consider and recognize because it can be misdiagnosed as AVN, and treated inappropriately (12). This is a rare condition in athletes, and is more likely to occur in individuals with poor bone quality. In the healthy athlete with no risk factors for AVN, the hip MRI should be evaluated closely by a musculoskeletal radiologist alerted to the possible diagnosis. In a hip with a subchondral fatigue fracture, the signal changes and bone marrow edema patterns differ. In cases without evidence for collapse, successful treatment involves limited weight-bearing and rest. When collapse is evident, bone grafting has been successful (12).

The complications associated with delayed diagnosis of hip joint related stress fractures can be devastating and extremely disabling for a healthy, athletic individual. Elite athletes seldom return to their prior level of function or sport (5). When these lesions displace, the outcome has been globally dismal, and reported complications associated with surgical fixation include infection, malalignment, leg-length discrepancy, nonunion, and AVN (44). It is therefore imperative that the physician caring for the athlete develops a high index of suspicion for hip stress fractures, understands the natural history of the process, and becomes comfortable either fully assessing and treating the problem or expediently referring the patient. In all cases, treatment should include careful evaluation and modification of the anatomic, metabolic, and environmental factors that contributed to the injury.

Avulsion fractures are the most common type of fracture encountered by the sports practitioner, especially in young male athletes (3). This type of fractures is seen more often in football and soccer players, sprinters, and jumpers (14). When the skeletal system is immature, a sudden violent muscular contraction or an excessive amount of sustained muscle action across an open apophysis may cause an avulsion fracture. Separation occurs in the cartilaginous area between the apophysis and the bone. Occasionally, they may be the result of chronic overuse apophysitis, similar to the Osgood-Schlatter’s syndrome in the knee. Different types of avulsion fractures around the hip joint have been described, and the most common are avulsion of the lesser trochanter, avulsion of the anterior superior iliac spine (ASIS), anterior inferior iliac spine (AIIS), and ischial apophysis.

AVN or osteonecrosis of the femoral head as a direct result of sports participation or training without significant prior
injury has not been described. Often the diagnosis is made incidentally, when an athlete is being evaluated for another problem, because more than one-third of the cases are idiopathic. AVN is more common in males, typically affects patients in their 30s and 40s, and is bilateral in 50% of the cases (52). It usually presents with pain in the groin region, exacerbated with activity and ambulation, but may also be asymptomatic in early stages. It should be suspected in athletes with recurrent groin pain, especially in individuals with risk factors such as steroid use, smoking, alcohol abuse, and hypercoagulable states. Special attention should be taken in the athlete with recurrent groin pain after trauma, as the reported incidence of traumatic AVN is 10% (53). Femoral head osteonecrosis is the result of altered blood supply, which causes bone necrosis, subcortical fractures, and finally collapse of the hip joint. It has been reported after hip subluxation, dislocation, and femoral neck fractures, which can all cause traumatic disruption of the vasculature (29). In the young athlete under age 12 experiencing continued groin pain and limping, Legg-Cálve-Perthes Syndrome is a variant of AVN that should be considered. In this condition, the growing femoral head loses its blood supply and a portion of the femoral head dies, causing a flattening of the weight-bearing surface of the femoral head that has a characteristic radiographic appearance.

Hip dislocation is a high-energy traumatic injury, and is an absolute orthopaedic emergency. The injury is most commonly seen in motor vehicle accidents and motor sports. In nonvehicle based sports the incidence of hip dislocation is rare, but the injury has been reported in football, rugby, hockey, gymnastics, skiing, and snowboarding (8,10,59,60,61). Although hip dislocation in contact sports is usually isolated and not associated with other visceral injuries, a screening trauma evaluation should always be performed. The age of the patient is an important consideration when dislocation is suspected because the injury may occur in lower energy situations, but has the same consequences (62). Traumatic hip subluxation follows the same injury pattern as dislocation, and is essentially the same injury with the same implications, but occurs in lower energy circumstances. The transient nature of these injuries and lack of deformity may result in under-diagnosis, and for this reason subluxation may ultimately be more significant than dislocation, because they are not evaluated and treated with the same level of urgency (8). The hip subluxation/dislocation continuum is associated with a very high incidence of long-term complications and disability, when the diagnosis and treatment are delayed (25,63,64).

Hip dislocation and subluxation can occur in anterior and posterior directions. Classification systems reference this directionality, which is based on the underlying biomechanics
of the joint and capsule. The patient’s bony morphology and capsular compliance also influence susceptibility; dysplastic hips with shallow acetabuli, patients with connective tissue disorders, and young patients with cartilaginous pliability and ligamentous laxity are at increased risk for dislocation or subluxation. The hip is in its most stable configuration in full extension, with the capsule and ligaments twisted tight and the articular surfaces compressed. In flexion the ligaments are lax and stability depends on articular congruence, which is optimized in abduction and external rotation, and least congruent in adduction. These biomechanical concepts are supported clinically by the fact that posterior dislocations are by far the most common, and account for up to 90% of all hip dislocations (25). The extent of bony damage is also dependent on the position of the leg when axial force is transmitted. When the leg is neutral or adducted, a simple dislocation without fracture occurs, but when the leg is abducted, a posterior wall acetabular and femoral head fracture is likely because increased force is required to overcome the congruence of the articular surfaces. Conversely, anterior dislocations are rare, accounting for 10% to 18% of hip dislocations, as would be predicted by the biomechanics (25). In sports, anterior dislocations have only been reported in snowboarding (60). Anterior dislocations occur in superior and inferior directions, the later being more common because the hip is in a relaxed capsule position of flexion.

Dislocations and subluxations typically present acutely during sports competition, and are caused by falls on a flexed knee with the hip adducted and flexed, but also can occur with direct blows to the hip region and knee in the same position (8). Dislocations are obvious and extremely painful, the affected leg is typically in a flexed and internally or externally rotated position, and a leg length discrepancy may be evident. Subluxations occur from the same mechanism, but spontaneous relocation can occur and the leg length discrepancy is not present. In both situations joint movement is actively and passively limited by pain. The athlete is not capable of standing when a dislocation has occurred, and should not be encouraged to stand if a subluxation is suspected. There are advocates for attempting gentle closed reduction immediately when these injuries are witnessed on the field, while the trauma literature supports reduction under anesthesia or sedation to avoid further damage to the femoral head or acetabular rim caused by muscle spasm and involuntary resistance (10,65).

When a hip dislocation or subluxation is suspected, plain radiographs with oblique views should be obtained emergently. In the case of dislocation, the patient should be taken to the operating room within 6 to 12 hours of the injury for attempted reduction under anesthesia, with the orthopaedic surgeon prepared to open the hip if a stable reduction cannot be achieved (63,65). The need for repeated attempts at relocation increases the complication rate (65). After a closed reduction and in cases of suspected subluxation with joint asymmetry on plain films and/or evidence of a posterior rim fracture, an MRI and/or CT scan should be obtained to assess congruency, hemarthrosis, and to exclude associated femoral head or acetabular fractures (Fig 32-3). When fractures are found, open concentric reduction of the joint and fixation of substantial bony rim or head fragments should be performed. In cases of subluxation, aspiration of a hemarthrosis has been shown to effectively decompress the joint and decrease the likelihood of AVN and chondrolysis (8). Postreduction stability should be assessed, as it will determine the postoperative treatment. After definitive reduction and decompression have been confirmed, post-operative motion and weight-bearing are based on the postreduction stability of the joint. Unstable joints are treated in skeletal traction for 4 to 6 weeks, and then progressed like stable joints and subluxations that are treated with touch down weight-bearing, crutches, and progressive motion for 6 weeks before the joint is loaded. MRI is repeated at 6 weeks to evaluate for signs of osteonecrosis with further surveillance based on the results (66).

Complications and the prognosis for a hip joint that has dislocated are related to the severity of the dislocation, the presence of associated fracture, and the timing of the reduction in relation to the injury (25,63,64). Femoral artery and nerve injury can occur, but are not common; in contrast sciatic nerve injuries are relatively common, with an incidence approaching 10% in posterior dislocations (67). Osteonecrosis of the femoral head is the most serious and disabling consequence. In simple dislocations, the rate of osteonecrosis is about 10%, which is similar in adults and children. In fracture dislocations, the rate of osteonecrosis can approach 50%. In cases of subluxation, the true rate of
osteonecrosis cannot be determined. In the series reported by Mooreman et al. (8), 2 out of 8 patients developed osteonecrosis, suggesting a rate of 25%. Posttraumatic hip degeneration is the most significant and common complication that occurs after hip dislocation, and has been shown to increase in situations where concentric reduction is not achieved, the time delay to reduction is greater than 12 hours, hemarthrosis are not evacuated, and in patients that develop osteonecrosis (8,25,63,64).

Injuries and lesions of the axial skeleton in the hip joint region, especially those encountered in the athletic population, are all activity limiting and also have the potential for devastating outcomes. Most bony injuries have an extended recovery and rehabilitation. Frustration from all involved— athlete, parents, and coaches—will likely be directed at the medical team. Understanding the bony pathology responsible for these hip injuries, the mechanisms, and clinical presentation is critical for the physician to appropriately care for the athlete and safely return them to their sport. When any bony injury to the hip is suspected, every athlete should be placed on crutches nonweight bearing, plain radiographs should be obtained without delay, and advanced radiography should be considered if the symptoms and exam do not correlate. The most important aspect to understand is that the majority of these bony injuries require prompt diagnosis and treatment to avoid lifelong pain and disability, a consequence that will always be significantly greater than missing any sporting event, season, scholarship, or career.