Rockwood & Green’s Fractures in Adults
6th Edition

Chapter 39
Fractures and Dislocations of the Lower Cervical Spine
Christopher M. Bono
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Lower cervical spine fractures and dislocations are common injuries following major trauma. Fractures of C6 and C7 account for nearly 40 percent of cervical spine injuries after blunt trauma (1). Because of differences in spinal canal dimensions and the mechanisms of injury, spinal cord damage is more frequently associated with lower rather than upper cervical spine fractures and dislocations. A bimodal peak in age distribution has been noted, with injuries most common in adolescents and young adults (15 to 24 years old) and middle-aged individuals (over 55 years old) (2). Advances in prehospital emergent management and critical care in specialized trauma centers have improved survival from these injuries over the past few decades.
INITIAL EVALUATION AND EMERGENCY CARE
Prehospital Care
Care for a patient with a potential cervical spine injury begins in the field. Manual immobilization of the head and neck should be maintained until a hard cervical collar can be applied. Various types of cervical orthoses are available, all of which contain an anterior window to accommodate a tracheostomy tube or facilitate an emergency cricothyroidotomy. Though a clinical difference has not been demonstrated, less motion is allowed by the NecLoc collar compared to the Miami J, Philadelphia, Aspen, and Stifneck devices (3). One group found in-field application of Gardner-Wells tongs and traction to be an effective means of immobilizing the cervical spine (4). However, this can potentially distract an underlying and unrecognized occipitocervical dissociation.
Airway security and hemodynamic resuscitation are crucial to the overall survival of the patient. Tracheal intubation and central line placement are often performed in the emergency setting. With intubation, manipulation of the neck can potentially displace unstable cervical fractures or dislocations. Manual inline stabilization should be maintained throughout the intubation process. Alternatively, mask ventilation (5) can be continued until fiberoptic (6) or nasotracheal (7) intubation can be safely performed in a hospital. If an unstable spine is highly suspected, a cricothyroidotomy might be the safest alternative for airway control (7).
Helmets, as used for sports or motorcycling, should be kept in place during initial evaluation and medical stabilization (8). Optimally it should be maintained until x-ray evaluation of the cervical spine has been performed (8). The facemask or visor can be removed to access the eyes, nose, and mouth.
In-Hospital Resuscitation
Once the patient has arrived at the emergency room, initial assessment of the ABCs (airway, breathing, and circulation) should be performed and life-saving procedures initiated. The neck should be immobilized by manual inline stabilization during transfers and when the cervical collar has been temporarily removed. The patient can be moved between the stretcher and bed using a rigid transfer board. Log-roll technique and spinal precautions should be observed at all times. Alternatively, a lift-and-slide maneuver can be used with equivalent motion prevention of a potentially unstable cervical injury (9).
Maintaining a patent airway and hemodynamic stability are crucial to patient survival. They may also be important in minimizing further ischemia to a compromised spinal cord (10). It has been recommended to maintain an arterial oxygen partial pressure of at least 100 Torr (10). Overly aggressive manipulation of the neck in order to perform intubation should be avoided because the resultant displacement of a cervical fracture or dislocation can obviate the benefits of improved oxygenation.
Patients with spinal cord injury often present with neurogenic shock. In distinction from hemorrhagic shock, in which compensatory tachycardia is usually present, neurogenic shock results in hypotension accompanied by bradycardia. This results from loss of the normal sympathetic response to low blood pressure. Pressure should be restored by a combination of postural maneuvers (Trendelenburg position), judicious fluid infusion, and vasopressor administration. If neurogenic shock is treated as purely hypovolemic shock, fluid overload can quickly ensue, leading to pulmonary edema or other systemic medical complications.
History and Physical Examination
An in depth examination can be executed in the awake and alert patient. The patient should be questioned about previous injuries, the nature of the current injury, and where he or she is feeling pain. Concomitant distracting injuries, such as extremity or pelvic fractures, can decrease a patient’s awareness of pain associated with a spinal injury. This highlights the importance of performing both an initial and delayed secondary examination.
The direction of impact, such as in a motor vehicle collision, can yield clues about the possible mechanism of spinal injury. In gunshot victims the caliber of the bullet and the direction of firing should be noted, because they have implications about the energy of the wound and the sequence of concomitant viscus injuries (for example, transpharyngeal gunshot wounds, which have a higher infection rate) (11). In the unconscious, nonalert patient, questions about the injury mechanism may be directed toward eyewitness or emergency medical technicians that were present at the scene.
Next, the spine should be examined in a systematic manner. The spinous processes should be palpated individually, noting tenderness, crepitus, or step-off. Bruising or laceration, as well as penetrating wounds, should be noted and marked. Swelling and fullness in the anterior neck can suggest prevertebral hematoma, which may be a clue to significant trauma to the spine. Rotation of the head and neck should be noted, because patients with unilateral facet dislocations can present with their heads turned toward the nondislocated side. Areas of ecchymosis on the face or scalp might be the result of a direct impact and thus suggest the direction of traumatic force delivery.
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TABLE 39-1 Myotome (Motor) and Dermatome (Sensory) Testing*
  Motor Sensory Reflex
C5 Deltoid Lateral shoulder/lateral arm Biceps
C6 Biceps/wrist extension Lateral forearm/thumb and index finger Brachioradialis
C7 Triceps/wrist flexion Middle finger Triceps
C8 Hand intrinsics/finger flexors Rings and little finger/medial forearm
T1 Hand intrinsics/finger abduction Medial arm/axilla
S5 Rectal tone PerianalBiceps BC
Myotomes (motor) and dermatomes (sensory) should be serially tested by a single-examiner in uniform fashion.
A detailed neurologic examination is performed in the awake, alert patient. This should include motor, sensory, and reflex testing in all myotomal and dermatomal regions (Table 39-1). Muscle strength should be graded from 0 to 5 and accurately documented in the chart (Table 39-2). True progression of a neurologic deficit can be an indication for emergent or urgent surgical decompression; however, this is best detected by serial examinations performed by a single practitioner. Perianal sensation is a sign of sacral nerve root sparing and can be a positive prognostic sign for neurologic recovery for patients with what otherwise would be classified as a complete spinal cord injury (no other motor or sensory function below the level of injury). If the patient has a spinal cord injury, it should be graded according to the American Spinal Injury Association (ASIA) scale (Table 39-3).
TABLE 39-2 Muscle Grade Criteria*
Motor Grade Examination Criteria
5 Able to resist full force resistance
4 Examiner able to overcome strength
3 Can overcome gravity, no resistance
2 Can move without gravity
1 Visible contraction
0 No contraction
Muscle group strength should be graded from 0 (absent) to 5 (normal).
In the nonalert patient, the neurologic examination is limited. Key components can still be performed, however. If the patient has not been pharmacologically paralyzed, rectal tone should be evaluated and graded. The presence or absence of a bulbocavernosus reflex should also be noted and documented. The return of the bulbocavernosus reflex marks the end of spinal shock, which is usually resolved within 48 hours from injury.
Initial Imaging Protocol
A lateral cervical x-ray is a standard component of the general trauma series (which also includes a chest and pelvis film). This view is useful in detecting up to 85% of cervical spine injuries (12,13). Although plain films are traditionally considered the
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standard initial imaging technique for the cervical spine, computerized tomography (CT) appears to be gaining popularity (14,15). This has been fueled by reports that only 57% of lateral cervical x-rays obtained in the emergency department enable visualization of the C7–T1 junction (16).
TABLE 39-3 American Spinal Injury Association Scale: Classification of Spinal Cord Injuries According to the Level of Impairment
Grade Motor Scorea Sensory Deficita
A 0/5 Complete
B 0/5 Incomplete
C <3/5 Incomplete
D >3/5 Incomplete
E 5/5 None
aCaudal to the level of Injury.
From Standards for Neurological and Functional Classification of Spinal Cord Injury, rev ed. Chicago: American Spinal Injury Association, 1992.
The proposed advantages of CT scan over a plain lateral cervical film as an initial screening tool are that it is more sensitive for detecting fractures and more consistently enables assessment of the occipitocervical and cervicothoracic junctions (14,17). The speed of obtaining a CT of the cervical spine has exponentially increased with the advent of helical scanners (18). Because head and body CT are becoming more routine in high-energy trauma victims, acquisition of a cervical scan adds little to the overall time in the scanner (19). A potential disadvantage of CT as an initial radiographic assessment is that subtle malalignment, facet joint gapping, or intervertebral distraction are difficult to assess using axial images alone (20). This has become less of an issue as the quality of reformatted sagittal and coronal reconstructions has improved.
Although originally described using plain x-rays, a number of anatomic landmarks and relationships can be assessed using a lateral cervical x-ray or a sagittal CT reconstruction. These include the spinolaminar line, the posterior vertebral body line, interspinous process distances, intervertebral body distances, facet alignment, and anterior vertebral body line (Fig. 39-1). A break or abnormality in one of more of these lines or relationships can suggest the presence of a subaxial cervical fracture or dislocation.
IMAGING AND INJURY DESCRIPTION
Several imaging modalities can be used to definitively assess and describe lower cervical injuries. These include plain x-rays, CT, and magnetic resonance images (MRI). Each has its role, advantages, and disadvantages.
Plain X-Rays
Injury Detection
There remains considerable disagreement concerning the optimal method to rule out lower cervical spine injury (21). The rate of missed injuries has varied from 10% to 48% (22,23,24). Infrequently, this results in neurologic deterioration (22,25). Plain x-rays are useful in detecting and describing lower cervical injuries. They clearly demonstrate the majority of injuries. A standard cervical series includes lateral, anteroposterior (AP), and open-mouth views. Between 83% and 99% of injuries can be detected using these three views (26). Oblique views are frequently obtained; however, their utility in the traumatic setting is limited. They may be somewhat helpful in visualizing fractures of the laminae or articular processes.
An x-ray series that does not allow visualization of the entire cervicothoracic junction should be considered inadequate (27). Pulling traction on the patient’s arms can facilitate imaging this region. However, this may be not feasible with concomitant injuries such a shoulder dislocation or scapulothoracic dislocation. A swimmer’s view entails placing one arm in a fully abducted position, while leaving the other arm at the patient’s side. This somewhat diminishes the obstructing shadows of the deltoid and shoulder joint to allow clearer imaging of the lower cervical and upper thoracic vertebrae.
FIGURE 39-1 X-ray lines, landmarks, and measurements using a lateral cervical spine film. The spinolaminar line (A), posterior vertebral body line (B), and anterior vertebral body line (C) are normally unbroken. On a perfect lateral view, the facet joints should appear as stacked parallelograms (D). The prevertebral soft tissue shadow is measured at the C2–3 and C6–7 disc spaces. More than 7 mm at the C2–3 or 21 mm at the C6–7 disc is strongly suggestive of an underlying spinal injury.
Various features of the lateral cervical x-ray should be noted. Prevertebral swelling can be detected by assessing the soft tissue shadow thickness anterior to the vertebral bodies (see Fig. 39-1). If this measures more than 7 mm in front of the C2–3 disc space or more than 21 mm at the C6–7 disc space, there is a high
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likelihood of a cervical spinal injury (28,29). Of importance, the absence of prevertebral (retropharyngeal) soft tissue swelling does not reliably rule out an occult cervical spine injury, as its reported sensitivity is only 65% (30).
In the awake, cooperative, and alert patient with negative static plain films and no other distracting injuries, lateral flexion-extension views of the cervical spine can be obtained. They can demonstrate instability in up to 8% of patients with negative plain films (31); however, false negatives can occur (21). In a patient with neck pain, they are best delayed until spasm has subsided, which usually takes about 2 weeks. Spasm can mask subtle instability, yielding a false negative study if performed too early after injury (31,32). Flexion-extension views may be of limited utility in detecting instability at the cervicothoracic junction in patients with high-riding shoulders. Additional advanced imaging techniques may be warranted. In the author’s practice, flexion-extension views are obtained by having the patient actively flex and extend the neck while in the seated or standing position. Thirty degrees of excursion is the minimum acceptable amount to be considered an adequate method of ruling out ligamentous injury.
The practitioner must be familiar with the normal anatomic relationships and landmarks of the cervical spine. On a good-quality AP view with the patient looking forward, the spinous processes should be aligned. Displacement of a spinous process to one side can suggest a rotational injury such as a unilateral facet dislocation, facet fracture, or displaced pedicle fracture (33). The distance between each spinous process should also be gauged on the AP view, because widening can suggest posterior ligamentous injury.
The lateral view is the so-called workhorse of injury detection and description (34). Normally unbroken lines include the spinolaminar line, posterior vertebral body line, and anterior vertebral body line (see Fig. 39-1). The spinolaminar line is perhaps the most useful, because it is not usually affected by spondylotic changes such as osteophytes, which may be present along the posterior vertebral body and, to a greater extent, the anterior vertebral body. In older patients with substantial degenerative changes, the morphology of the anterior vertebral body can be quite abnormal, making this landmark/line difficult to assess. The lateral view is useful in judging the interspinous process distances. These can be measured at each level and compared. Substantial widening at one level suggests disruption of the posterior ligamentous complex. The facet joints normally appear as stacked parallelograms on the lateral cervical x-ray. In a perfect lateral view, the joints on either side should overlie each other, facilitating assessment of joint apposition.
FIGURE 39-2 The Cobb method of measuring cervical kyphosis. A line is drawn along the superior end plate of the superior adjacent uninjured vertebrae; a second line is drawn along the inferior end plate of the inferior adjacent uninjured vertebrae. The angle subtended between the two is then measured.
Injury Description
Plain cervical x-rays are crucial to the overall description of detected injuries. A number of x-ray injury characteristics can be assessed and measured on a lateral cervical film. Segmental kyphosis can be measured by an end plate (Cobb) method or posterior vertebral body tangent method (Figs. 39-2 and 39-3). The latter may have lower interobserver variability. Kyphosis more than 11 degrees as measured by the end plate method is strongly suggestive of posterior ligamentous injury and potential instability (35). Kyphosis can be the result of posterior widening of the interspinous processes and facet joints about an injury axis of rotation near the anterior longitudinal ligament. Vertebral body fracture with height loss and interspinous gapping suggests an injury axis of rotation about the facet joints.
Anteroposterior translational deformity can be assessed and measured on the lateral view. The distance between the posterior
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vertebral body tangent lines at the level of the disc space can be used to measure the absolute distance in millimeters (Fig. 39-4). Lateral translation, though much less common, can be measured on the AP view by drawing longitudinal (vertical) lines along the lateral masses.
FIGURE 39-3 The posterior vertebral body tangent method of measuring cervical kyphosis. A line is drawn along the posterior aspect of the adjacent vertebral bodies. The angle subtended between the two is then measured.
FIGURE 39-4 Sagittal translation is measured at the level of the inferior aspect of the superior vertebral body.
Vertebral body height loss is another useful measurement that can be performed on the lateral view. Although it might reflect the axial stability of the anterior column, there are no specific criteria on a critical percentage of vertebral body height loss. The anterior and posterior vertebral body heights should be measured at the injured and adjacent uninjured levels. The distances of the uninjured levels should be averaged, and the percentage height loss for the anterior and posterior vertebral bodies calculated (Fig. 39-5B). The relative amount of comminution should be noted, although this has been more clearly categorized in the thoracolumbar spine. Primary fracture lines, as are present with so-called tear-drop fractures, should be outlined.
Computerized Tomography
Computerized tomography is more sensitive than plain x-rays in detecting and delineating fractures. Helical CT scans, which can be obtained much quicker than nonhelical CT, has facilitated acquisition of these highly detailed studies. Cervical CT has replaced the standard three-view plain x-ray trauma series as the initial imaging modality of choice in many centers (18). High-quality sagittal and coronal image reconstructions have made this transition easier, because alignment is more easily assessed in the reformatted images. Motion artifact can often feign translational deformity; evaluation by another imaging modality should be performed before drawing treatment-influencing conclusions.
Axial CT images should be studied systematically in each case. First, the vertebral bodies and pedicle should be labeled according to level so that fractures or dislocations can be accurately located. The vertebral body should be inspected for fracture
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lines. CT is particularly useful for detecting sagittal fracture lines that are usually less obvious on plain films. Fracture fragment retropulsion is readily appreciated on axial CT slices, as well as the degree of comminution of vertebral body fragments. Pedicle fractures are often undetectable with plain films, but easily detected on axial CT images. Facet and lamina fractures are also easily detected on CT images.
FIGURE 39-5 Vertebral body height loss can be expressed as a percentage. This is best assessed by measuring both anterior and posterior height of the injured and adjacent uninjured vertebral bodies.
Obvious signs of translation or dislocation can be appreciated on axial CT images (Fig. 39-6). The so-called double lumen sign (36) can occur with substantial amounts of translation, as can occur with bilateral facet dislocations. Less obvious signs can be detected by carefully examining the facet joints themselves. Unapposed articular surfaces may result in a so-called empty facet sign. Knowledge of normal anatomic relationships is crucial to detecting facet dislocations. Importantly, the inferior articular processes of the superior vertebra are normally posterior to the superior articular processes of the inferior vertebra. With completely dislocated, locked facet joints, this relationship is reversed.
Sagittal and coronal reconstructions can aid understanding the three-dimensional nature of spinal injuries. Parasagittal slices through the facet joints can help visualize dislocations, subluxations, or fracture fragment size (Fig. 39-7). Canal occlusion is best appreciated on mid-sagittal CT reconstructions.
Magnetic Resonance Imaging
The role of MRI continues to be defined in spinal trauma (37,38). Its superiority in visualizing the spinal cord, intervertebral disc, and spinal ligaments gives it some advantages over CT. MRI can detect subtle bone edema that is associated with vertebral body fractures. However, image clarity of bony architecture is inferior to CT, making it unsuitable as a stand-alone modality for fracture description. The most useful applications of MRI are in detecting traumatic disc herniations, epidural hematomata, spinal cord edema or compression, and posterior ligamentous disruption (37,38).
FIGURE 39-6 Frank dislocation is usually obvious on axial CT images, as in this case of a C6-7 fracture dislocation. More subtle amounts of translation, however, can be easily missed using axial CT images alone.
FIGURE 39-7 Paramedian CT reconstructions are useful for assessing the facet joints. In this case, a C4-5 unilateral facet perch can be appreciated.
In the author’s institution, an MRI is obtained in the following situations: (a) patients with neurologic deficits, barring a contraindication to MRI, and (b) injuries in which the integrity
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of the posterior ligamentous complex is unclear and would directly influence the treatment plan. Of concern is that MRI tends to be overly sensitize in detecting fluid or increased signal within the posterior tissues, which can lead to a false-positive reading for posterior ligamentous injury.
T2-weighted images have a so-called myelography effect in which the cerebrospinal fluid (CSF) is bright and tissues such as disc herniations are relatively dark or isointense. T2-weighted images can also demonstrate increased signals within the disc, facet capsules, or posterior interspinous process region that may be a sign of edema and disruption. The anatomic outlines of the anterior longitudinal ligament, posterior longitudinal ligament, and ligamentum flavum can also be detailed on T2-weighted MRI (Fig. 39-8). Of note, discontinuity of the anterior longitudinal ligament may not necessarily imply disruption, because this is a frequent finding on nontraumatized cervical spines (39). Short inversion time inversion-recovery (STIR) images are more sensitive than T2-weighted images in detected soft tissue or bony edema. (They are like an exaggerated T2). This is, however, at the sacrifice of image detail.
An additional application of MRI is the ability to visualize vascular structures. MR arteriograms can be used to assess the patency of the vertebral arteries. This may be indicated in cases of suspected arterial injury, such as severe dislocations or fractures that extend into the transverse foramen.
FIGURE 39-8 An MRI can be used to assess a number of important soft tissue structures. In this sagittal T2-weighted image of an uninjured cervical spine, the small arrow is pointing to the posterior longitudinal ligament. The large solid arrow is pointing to the ligamentum flavum.
CLASSIFICATION
Overview of Classification Systems
Classification of a spinal injury should ideally be based on a system that is comprehensive, is clinically prognostic, aids in treatment decision-making, and is user friendly, reliable, and reproducible. Fulfilling all, or even some of these qualities, is a difficult task that, at the time of this writing, has yet to be achieved by any available classification system for any orthopaedic injury. Regardless, there have been classification systems proposed for description of subaxial cervical spinal injuries that are worth reviewing. Although there is lack of agreement on which is the most useful, the Allen et al (40) mechanistic classification is among the most well-known, and as such, will be discussed in greatest detail (Fig. 39-9).
Mechanistic Classification of Subaxial Cervical Injuries
Allen et al (40) reviewed 165 cases of subaxial cervical spine fractures and dislocations in order to develop a classification system based on deducing the mechanism of injury. Injuries were organized into one of the following groups: compressive flexion, vertical compression, distractive flexion, compressive extension, distractive extension, and lateral flexion. Within each group, injuries were divided into grades of severity. In this retrospectively developed system, the likelihood and extent of neurologic injury was related to the group and severity of injury; however, this has not been validated prospectively since its development.
The authors hypothesized that: (a) both major and minor forces produce injury, (b) the vectors (or direction) of these forces can be deduced from x-rays, (c) the amount of energy relates to the severity of injury, (d) injuries can be organized into groups based on the force vectors, and (e) they can be further subdivided based on the energy of trauma.
Compressive Flexion
Compressive flexion (CF) injuries are divided into five stages (Fig. 39-9). The injury is speculated to occur first by flexion of the spine through the facet joints. The anterior column (vertebral body) becomes increasingly compressed and shortened. Eventually, the posterior ligamentous complex fails, noted by interspinous gapping and local kyphosis. With further energy, the facet joints will fail, leading to translational deformity. The distinguishing x-ray features of each stage should be understood. It should be noted that the stages build upon one another, so that, for example, stage 3 lesions also demonstrate the features described for compressive flexion stages 1 and 2.
CF Stage 1: Blunting of the anterosuperior vertebral body margin.
CF Stage 2: Beak appearance of the anterosuperior vertebral body margin, a sagittal vertebral body split may also be present.
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FIGURE 39-9 The five stages of compression flexion injuries.
CF Stage 3: Oblique primary fracture line that extends from the anterior vertebral body to the inferior end plate This has been subsequently described by other authors as a so-called tear-drop fracture (41).
CF Stage 4: In addition to stage 3 features, posterior translation of the upper vertebra measuring less than 3 mm.
CF Stage 5: Posterior translation of the upper vertebral measuring 3 mm or greater, facet gapping, indicating anterior and posterior ligamentous injury.
Vertical Compression Vertical compressive (VC) lesions are thought to arise from primarily axial loads to the cervical spine. Although this is the author’s description, the final stage of the injury may result from flexion or extension vectors, which ultimately produce posterior or anterior ligamentous injury, respectively (Fig. 39-10).
VC Stage 1: Central superior or inferior endplate fracture.
VC Stage 2: Superior and inferior end plate fractures, sometimes with vertebral body fracture lines that give the appearance of a quadrangular fracture fragment.
VC Stage 3: Vertebral body comminution, with or without retropulsion of fragments (this has been described by others as a burst-type cervical fracture), with or without kyphotic (late flexion type) or translational (late extension type) deformity.
Distractive Flexion
Distractive flexion (DF) injuries are thought to occur from primarily flexion injury vectors that rotate about an axis anterior to the vertebral body. Thus, distraction and failure of the posterior ligaments can occur without significant vertebral body fracture. In this injury group, increasingly higher stages do not always correspond to increasing amount of instability (Fig. 39-11).
DF Stage 1: Facet subluxation, gapping of the spinous process ligaments, indicating failure of the posterior ligamentous complex, with or without some blunting of anterosuperior vertebral body (like compressive flexion stage 1).
DF Stage 2: Unilateral facet dislocation, usually posterior ligamentous complex is intact, rotational deformity.
DF Stage 3: Bilateral facet dislocations, 50% translation of upper vertebral body on lower one.
DF Stage 4: Close to 100% translation of upper vertebral body on lower one, appearance of a so-called floating vertebra.
Compressive Extension
Compressive Extension (CE) injuries are divided into five stages (Fig. 39-12). They are postulated to start with compression of the posterior elements without failure of the anterior ligaments. Further injury leads to failure of the anterior/posterior ligaments.
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CF Stage 1: Posterior arch fracture that may be facet, pedicle, or lamina fracture, with or without rotation that can result in mild anterior translation (these are more commonly referred to as lateral mass fractures).
FIGURE 39-10 The three stages of vertical compression injuries.
CF Stage 2: Bilateral lamina fractures, can be multiple levels.
CF Stage 3: Bilateral lamina, facet, pedicle fractures without vertebral body displacement. Though admittedly “hypothetical…having not been encountered” in their review, the injury may be described as a floating lateral mass fracture.
CF Stage 4: as for CF stage 3, with partial anterior vertebral body displacement.
CF Stage 5: as for CF stage 3, with 100% anterior vertebral body displacement.
Distractive Extension
Distractive extension (DE) injuries, like DF injuries, demonstrate substantial ligamentous injury in lower stages. Initial failure is through the anterior ligaments (Fig. 39-13).
DF Stage 1: Abnormal widening of the disc space, may or may not be avulsion fractures of the anterior vertebral body margin, no posterior translation.
DF Stage 2: DF stage 1 plus posterior translation.
FIGURE 39-11 The four stages of distraction flexion injuries.
Lateral Flexion
Lateral flexion (LF) injuries occur by compression on one side of the spine. With further energy, the contralateral side can fail under tension.
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LF Stage 1: Unilateral uncovertebral vertebral fracture or asymmetric vertebral body compression.
LF Stage 2: Vertebral body or posterior arch fractures with lateral translation or unilateral facet gapping, coronal angular deformity is noted on an AP x-ray.
FIGURE 39-12 The five stages of compression extension injuries.
The system of Allen et al (40) is the most frequently cited and used classification for subaxial cervical spine injuries. Despite this, it has not been validated, retrospectively or prospectively, since its publication in 1982. Intraobserver and interobserver reliability has not been tested, to the author’s knowledge, and the significance of the injury groups on treatment decision making is not yet clear.
FIGURE 39-13 The two stages of distraction extension injuries.
Subsequent studies have demonstrated that a wide spectrum of injury patterns can occur from a single mechanism. Torg et al (42,43) found facet dislocations, tear-drop vertebral body fractures, and anterior translational injuries at the C3–4 segment in football players injured during a witnessed axial loading mechanism to the head and cervical spine. According to Allen et al (40), these would have had to occur from distractive flexion, compressive flexion, and either compressive extension or vertical compressive mechanisms, respectively. The disparity between these findings underscores the very complex three-dimensional biomechanical response of the cervical spine to even simple, unidirectional force vectors. Postulating the direction or mechanism of injury, though a common academic exercise,
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may not result in accurate or useful information. Perhaps what is more important is determination of the integrity of the ligamentous structures. This is a major, if not the primary, determinant of cervical spine stability (35).
Descriptive Classification of Subaxial Cervical Injuries
In lieu of postulating the mechanism of injury, cervical fractures and dislocations can be described based on identifiable injury characteristics that are thought to influence mechanical stability and method of treatment. Despite disagreement on a unified description system, a number of injury patterns are somewhat consistently reported in the literature. It must be kept in mind, however, that these injuries often represent different stages along a continuum, with many of them sharing characteristics.
For the purposes of this chapter’s discussion, lower cervical spine injuries can usually be described as vertebral body fractures, facet fractures, pedicle and lamina fractures, or anterior tension band disruption.
Vertebral Body Fractures
Regardless of the mechanism of injury, vertebral body fractures are readily detected by plain films and CT. Fractures may be simple wedge types, also known as compression fractures, in which there is primarily anterior height loss and no posterior vertebral involvement. Teardrop fractures, as described by Allen and Ferguson as CF stage 3 injuries, demonstrate a characteristic primary fracture that extends obliquely from the anterosuperior vertebral body to the inferior end plate. These can involve varying percentages of the end plate, which may influence the decision to perform a discectomy or corpectomy if surgical treatment is planned. Burst fractures, much like their thoracic and lumbar counterparts, demonstrate extensive vertebral body comminution, varying degrees of height loss, but, most importantly, posterior vertebral body involvement with fragment retropulsion. One area of confusion is the term teardrop burst fractures. Teardrop fractures often have a midsagittal split in addition to posterior translation, which many describe as a burst fracture. Quadrangular burst fractures, similar to that described as VC stage 2 injury by Allen and Ferguson, are sometimes distinguished in the literature from other vertebral body fractures. The clinical significance of this distinction is unknown, because the treatments are often similar. With any of these vertebral body fractures, the posterior ligamentous complex can be disrupted, either by translational, flexion, or rotational forces.
Facet Injuries
Facet injuries are extremely common. Although Allen and Ferguson have suggested that they occur primarily through distractive flexion mechanisms, it is clear that rotational forces, axial compressive forces, and various other vectors can be involved. Facet fractures can be associated with dislocations or other posterior arch fractures. Reports of facet fractures in the literature generally refer to isolated, unilateral, minimally displaced fractures of varying sizes. Often thought to be benign fractures, they can be associated with ligamentous injury, leading to subluxation and instability. Because of this potential, there is significant controversy regarding their initial treatment. Facet subluxations are the result of facet capsule and posterior ligament disruption. By definition, some portion of the articular surfaces of the involved levels is still in apposition. Facet dislocations can be unilateral or bilateral. These can be described in a number ways, such as perched or locked. By definition, the articular surfaces are no longer in opposition. Cadaveric sectioning studies, as well as intraoperative observations, have indicated that unilateral dislocations can be present without complete posterior ligamentous complex disruption and in many cases may be mechanically stable injuries. There may be some utility in distinguishing facet dislocations from facet fracture-dislocations, in which the facet joint is dislocated, unilaterally or bilaterally, and fractured. With large facet fracture fragments, reduction can be difficult to achieve or maintain by closed methods. In addition, extensive articular process fractures can preclude lateral mass screw placement.
Pedicle and Lamina Fractures
Isolated, unilateral pedicle fractures can suggest rotational instability, which can present late as in the case of isolated facet fractures. For this reason, pedicle and facet fractures are often referred to in the literature as lateral mass fractures. A concomitant lamina fracture and pedicle fracture effectively negates the contribution of the adjacent facet joint to overall cervical stability. This can be described as a floating lateral mass fracture. Such fractures can potentially destabilize two motion segments.
Anterior Tension Band Disruption
The anterior longitudinal ligament and intervertebral disc can fail in tension (see Fig. 39-41). Without speculating about the mechanism of injury, widening of the intervertebral disc space is a highly suggestive sign that the anterior tension band has been disrupted and that significant spinal instability is present. Small avulsion injuries of the vertebral body can also result in teardrop-shaped fragments and are commonly referred to as extension-type teardrop fractures. The mechanism of injury is most likely extension, with failure of the anterior ligaments being more likely than posterior ligamentous complex disruption. This fracture is typically more common in elderly patients, and should be considered more likely in this age-group, in particular if there is no kyphotic deformity at the level of injury.
APPLIED ANATOMY OF THE LOWER CERVICAL SPINE
The lower cervical spine, also known as the subaxial cervical spine, includes the C3 to C7 vertebral segments. In contrast to the anatomically and functionally unique upper cervical segments (C1 and C2, or atlas and axis, respectively), the subaxial cervical vertebrae have a relatively uniform anatomic configuration.
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Anterior Elements
The vertebral body is roughly cylindrical. It is, in fact, oblong, as its coronal diameter (left to right) is larger than its sagittal diameter (anterior to posterior). In distinction from the normally flat end plates of the thoracic and lumbar vertebrae, cervical end plates have a cup-in-saucer configuration. Viewed from the front (Fig. 39-14), bilateral prominences called uncinate processes are present along the lateral aspects of the superior end plates. The uncinate processes articulate with rounded inferolateral borders of the superior vertebral body. This articulation, called the uncovertebral joint, is a useful surgical anatomic landmark that signals proximity to the lateral extent of the vertebral body. Mechanically, it is believed to limit posterior translation of the upper vertebra (35).
The intervertebral disc is interposed between the end plates of adjacent vertebral bodies. The annulus fibrosis is intimately related to the anterior and posterior longitudinal ligaments. The longus colli muscles lie directly over and insert onto the anterolateral aspects of each cervical vertebra. The sympathetic plexus lies on top of the lateral muscle belly, placing it at risk with overly aggressive dissection or retraction, which may lead to Horner’s syndrome. The prevertebral (deep) and alar (superficial) fascial layers separate the spine from the overlying esophagus.
Transverse processes project from the lateral aspects of the vertebral body. In contrast to their flat, solid counterparts in the thoracic and lumbar spine, cervical transverse processes have a more complex anatomic shape. This is the result of distinct developmental formation. The anterior portion (Fig. 39-15) of the transverse process is actually the remnant of a rudimentary costal process. While these form ribs in the thoracic spine, in the cervical spine it partially fuses with the posterior portion (the true transverse process analogue) to form a vertebral artery foramen. The vertebral artery, a longitudinal coalescence of cervical segmental vessels, ascends to the head through the C6 to C1 transverse foramina. It enters the C7 transverse foramen in only 5% of the population (44). Fractures that enter or displace the transverse processes suggest possible traumatic injury or occlusion of the vertebral artery.
FIGURE 39-14 Diagram of the subaxial cervical spine viewed from the front. The bilateral uprisings, known as the uncinate processes, create a cup-in-saucer formation of the intervertebral disc space.
FIGURE 39-15 The transverse process is made of two components. The anterior portion is actually the remnant of a costal process (that is, rudimentary rib). The posterior portion is the true developmental transverse process. Together, they form the transverse foramen, the conduit for the vertebral artery.
In addition to its intimate relationship with the vertebral artery, the transverse process guides the cervical spinal nerves as they exit from the spinal canal. The spinal nerves lie posterior to the vertebral artery. Viewing the spine from the side, the spinal nerve appears to be cradled by the half-pipe configuration of the transverse process (Fig. 39-16) that projects slightly inferior and anterior.
Posterior Elements
Cervical pedicles project from the vertebral body in a posterolateral to anteromedial orientation. They form the posteromedial border of the vertebral artery foramina. The internal morphology of cervical pedicles, including the medial and lateral cortical thickness, can vary substantially between vertebral levels and between men and women (45,46). These characteristics make transpedicular screw insertion technically demanding.
The facet joints, also known as the zygapophyseal articulations, are highly mobile diarthrodial joints formed by the interaction of superior and inferior articular processes. They arise from the posterior aspect of the pedicles and transverse processes (see Fig. 39-16). The articular surfaces are angled approximately 45 degrees in relation to the transverse axis of each segment. There is minimal, if any, coronal angulation. The pillar of bone between the superior and inferior articular processes is commonly referred to as the lateral mass. It is a useful site for posterior screw or wire stabilization of the cervical spine.
The laminae arise from the posteromedial border of the lateral masses. The laminae project posterior and toward the midline
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to form bifid spinous processes (C2–C6). An elastic yellow ligament, called the ligamentum flavum, spans the interlaminar spaces. Strong interspinous and supraspinous ligaments (ligamentum nuchae), together form a posterior ligamentous complex. Disruption of this complex results in mechanical instability.
FIGURE 39-16 The transverse process forms a half-pipe configuration that cradles the exiting spinal nerve.
Spinal Canal and Canal Compromise
The spinal cord is contained within the spinal canal. The borders of the spinal canal are as follows:
  • Anterior: vertebral body, intervertebral disc, posterior longitudinal ligament
  • Posterior: laminae, ligamentum flavum
  • Lateral: pedicles, medial aspect of the facet joints
The spinal canal can be compromised after traumatic injury in a number of ways. Bony fragments, most often retropulsed vertebral body fragments, can intrude upon the canal and spinal cord. Perhaps the most common reason for canal compromise after cervical trauma is translational displacement, as occurs with facet joint dislocations (Fig. 39-17). In these cases, the bony canal/neural arch itself can be intact; however, their relative position causes overall canal compromise. This kind of canal compromise can be underestimated by axial CT images. Disc herniations and epidural hematoma can also cause canal compromise and spinal cord compression.
FIGURE 39-17 Spinal canal compromise in the cervical spine most commonly occurs from translational deformity, as depicted in the sagittal CT reconstruction of a patient with bilateral facet dislocations. This injury was associated with a complete spinal cord injury.
Cervical Spinal Cord Anatomy
Injury to the cervical spinal cord can be caused by ischemia, compression, distraction, penetration, or various combinations thereof. Knowledge of spinal cord and nerve root anatomy is useful in determining the level and type of spinal cord injury.
The externally visible portion of the spinal cord is made up of white matter covered by dura mater. The white appearance is from myelin that sheaths the axons that transmit between the brain and peripheral tissues. There are a number of afferent and efferent tracts that are embedded within the substance of the white matter (Fig. 39-18). The lateral spinothalamic tract is an afferent (ascending) tract located within the anterolateral aspect of the cord that transmits pain and temperature sensation. It is somatopically arranged; representation of more cephalad levels is within its anteromedial aspect and that for more caudal levels within its posterolateral aspect. Pain and temperature nerve fibers decussate at the level they exit the spinal cord. Therefore, injury to the lateral spinal thalamic tract results in pain and temperature loss of the contralateral side of the body.
The dorsal columns are composed of the fasciculi gracilis and fasciculi cuneatus (see Fig. 39-18). They transmit nonnoxious (not pain and temperature) sensory input to the brain. This includes proprioception, vibratory sense, pressure, and tactile discrimination (touch). The dorsal columns are also arranged somatopically. However, more cephalad innervation is located within the lateral regions of the tract. Tract fibers decussate
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above the foramen magnum before the spinal cord is formed. Injury therefore causes ipsilateral deficits.
FIGURE 39-18 Cross section through the spinal cord. There are distinct somatotopic patterns of innervation, which help explain the clinical presentation of various types of incomplete spinal cord injury.
Gray matter is the collection of nerve cell bodies. In a cross section of the spinal cord, it has as a butterfly or H-shaped appearance and has been divided into dorsal and anterior horns (see Fig. 39-18). The dorsal horns contain sensory nerve cell bodies that transmit pain, temperature, and touch. The anterior horns contain motor nerve cell bodies. Gray matter is topographically arranged so that more cephalad innervation is located within its central aspects. This topography explains why patients with central cord syndrome have upper extremity greater than lower extremity involvement.
BIOMECHANICS AND INJURY PATHOMECHANICS
Normal Mechanics
The biomechanics of cervical spine trauma can be considered in terms of two key phenomena: force/load transmission and injury kinematics (motion). Although injuries arise from interplay and relative proportions of both, understanding each in their simplest forms is a useful exercise.
One can consider an axial compressive load applied to a single cervical vertebra as a fundamentally pure example of load transmission. Force, or load, is resisted primarily by the vertebral body. Its trabecular makeup is well designed for this function. A smaller percentage is sustained by the facet joints. Force can be applied in different directions (for example, shear, torsion, tension), with subsequent changes in the location and structures that are maximally loaded. Theoretically, load can be applied without relative movement of vertebrae.
In a theoretically pure sense, kinematics refers to cervical vertebral motion without consideration of the forces applied. The lower cervical spine is a series of three-joint complexes that permit motion through intervertebral discs and facet joints. Kinematically, the remaining soft tissue structures, such as the anterior longitudinal ligament and posterior ligamentous complex, place limits on and influence the patterns of vertebral motion. Like other joints, motion between two vertebrae occurs about instantaneous axes of rotation (IAR). Hinge-type joints, like the elbow, have a relatively fixed IAR that allows motion in only one plane. In contrast, motion between two cervical vertebrae and their associated ligaments (referred to as a functional spinal unit) is multiplanar and occurs about a collection of IARs (Fig. 39-19). For example, sagittal motion occurs about an IAR within the subjacent vertebral body that changes with flexion and extension (35). Motion coupling is a kinematic phenomenon that describes an obligatory amount of axial rotation with lateral flexion of the cervical spine. This further complicates exact characterization of cervical IAR.
The amount of normal cervical motion at each level has been extensively described (35). Knowledge of these figures can be important in assessing spinal stability after treatment. Flexion-extension motion is greatest at the C4–5 and C5–6 segments, averaging about 20 degrees. Axial rotation ranges from 2 to 7 degrees at each of the subaxial motion segments; the majority (45% to 50%) of rotation occurs at the C1–C2 articulation. Lateral flexion is 10 to 11 degrees per level in the upper segments (C2-5). Lateral motion decreases caudally with only 2 degrees observed at the cervicothoracic junction.
Structural Injury and Cervical Pathomechanics
Traumatic injury to the bony and ligamentous structures alters both load transmission and the kinematics of the cervical spine. Under compressive flexion loads, simulated unilateral and bilateral facet injuries result in anterior displacement of the sagittal IAR and increased load transmission to the vertebral bodies (47). Anterior translation increases by 33% with sectioning of the intervertebral disc, anterior longitudinal ligament, and posterior longitudinal ligament with flexion moments applied (48). The addition of facet resection increases translation to 140%, which anatomically results in complete occlusion of the spinal canal (48).
Failure of Spinal Structures
Spinal trauma can lead to disruption of bone, ligament, or both. Bone can fail under compression, tension, or shear loads. In contrast, ligaments can fail only in tension; this can be likened to a rope that snaps. Perhaps the only exception to this rule is so-called shear failure of the intervertebral disc–end plate interaction, though this more accurately reflects tensile failure of the annular collagen fibers at the bony interface.
Flexion of the cervical spine incurs compressive loads upon
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the vertebral body/disc and tensile loads upon the posterior ligamentous complex, which is composed of the supraspinous and interspinous ligaments and facet capsules. Trauma causing hyperflexion can cause compressive failure of the vertebral body and/or tensile failure of the posterior ligamentous complex. Varying combinations of anterior and posterior failure have been demonstrated experimentally and clinically (49,50).
FIGURE 39-19 The instantaneous axes of rotation (IAR) are varied in the cervical spine. With flexion-extension (left), the IAR is located somewhere along the anterior aspect of the lower vertebral body. With lateral bending (middle), the IAR is still unknown. With axial rotation (right), the IAR is within a collection of points within the disc space.
Extension of the cervical spine leads to tensioning of the anterior longitudinal ligament and compression across the facet joints. Hyperextension trauma can lead to tensile failure of the anterior longitudinal ligament. However, this may not occur before posterior element compressive fractures, as demonstrated in cadaveric experiments (49,51). Additional distraction, shear, or rotation appears to be necessary before anterior longitudinal ligament and intervertebral disc failure (49,51,52).
Cervical teardrop fragments are created by shear failure of the anteroinferior vertebral body. Thought to occur most commonly from a compressive-flexion moment (40), the displacement of the fragment (superior and anterior) supports this proposed injury mechanism (Fig. 39-20). Teardrop fractures are often associated with wedging or blunting of the vertebral body. Sometimes there is an associated sagittal split. These additional fracture features highlight that the exact manner in which the spinal structures fail is a complex sequence of events that cannot be reliably deduced from examination of static x-ray studies. Secondary injury mechanisms from recoil of the head in response to the primary force vector can lead to circumferential ligamentous and bony disruption. To further obfuscate matters, the same or similar fracture patterns have been clinically observed with witnessed axial loading, flexion, and extension injuries mechanisms (40,43,53).
FIGURE 39-20 The proposed mechanism of failure of the teardrop fragment is shear. With forced flexion, parallel, but opposite, forces (arrows), are placed on the anteroinferior aspect of the vertebral body.
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TREATMENT METHODS AND SURGICAL TECHNIQUES
Nonoperative Management
Cervical Orthoses
The majority of cervical spine fractures can be treated nonoperatively. The most common method of nonoperative treatment is immobilization in a cervical orthosis. In reality, orthoses decrease motion rather than effect true immobilization. Orthoses work through padded contact areas strategically located over subcutaneous bony prominences. Specifically, these are the occiput, spinous processes, scapular spines, acromion processes, clavicles, sternum, and mandible. Interestingly, motion at the occipital-cervical junction is slightly increased by most cervical collars (54).
Soft cervical orthoses do little to decrease spinal motion (54). They are most commonly used after cervical strains or sprains, otherwise known whiplash-type injuries. Soft collars are worn for comfort.
Rigid cervical orthoses can provide varying degrees of immobilization depending on the construct material and the overall design. They are commonly used for emergent in-field cervical spine immobilization. An important design feature of all cervical orthoses is inclusion of a window or cutout over the anterior neck to allow access to a tracheostomy, if present. The most effective means of in-field cervical spine immobilization is strapping the chin and forehead to a rigid spine board (55). With this, addition of a cervical collar offers little additional stability.
There are many manufactured brands of rigid cervical collars. An x-ray study demonstrated that the NecLoc restricted more sagittal (flexion-extension), axial rotation, and lateral bending motion than the Miami J, Philadelphia, Aspen, or Stiffneck devices (3). The Miami J restricted extension better than the Philadelphia and Apsen collars (3). Despite these detected x-ray differences, the clinical superiority of one device over another has yet to be demonstrated.
There are a number of complications associated with use of cervical collars. Skin breakdown at bony prominences, in particular the occiput, mandible, and sternum, can occur. Up to 38% of patients with severe closed head injuries can develop skin complications with prolonged use (56). This places a priority on early injury exclusion (“clearing’’) of the cervical spine so that unnecessarily protracted collar wear can be avoided.
Cervicothoracic Orthoses
Cervicothoracic orthoses (CTO) include components that extend to the upper thorax. In this way, the braces provide more effective immobilization than simple cervical collars in all planes (54,57). Types include the sterno-occipito-mandibular immobilizer (SOMI), Minerva brace, and the Yale device. Mechanical studies have demonstrated that between 79% to 87% of sagittal motion, 75% to 77% of axial rotation, and 51% to 61% of lateral bending motion is restricted in these orthoses (58,59,60). The disadvantages of CTO braces are that they are more difficult to apply/remove and produce high resting pressures on the chin and occiput (61). Like simple cervical collars, CTOs have demonstrated increased motion at the occipitocervical junction. CTOs alone are not an effective means of immobilizing the spine below the C7–T1 junction.
Skull-Based Traction and Closed Reduction
Cervical traction can be applied to achieve a number of different goals. Traction can be used to help provide temporary immobilization of unstable cervical spine injuries (62). This may be of particular benefit when transferring patients to and from institutions or for patients awaiting operative stabilization.
Traction is most commonly used to realign or reduce cervical spine fractures or dislocations. This is achieved by application of gradually increasing amounts of weight in conjunction with frequent x-ray examination. Traction should not be used in cases in which occipitocervical instability or dissociation is present or suspected. Furthermore, traction should not be used to realign a subaxial spine injury if there is a concomitant type IIA traumatic spondylolisthesis of the axis. As such concomitant injuries may not always be initially recognized, light traction (5 to 10 lb) should be applied first, followed by a lateral x-ray to look specifically for signs of abnormal distraction between the cervical spinal segments or occipitocervical junction (63).
Two of the more common devices used to apply traction to the cervical spine are Gardner-Wells tongs and the halo-ring. In general, Gardner-Wells (G-W) tongs can be applied more quickly and easily than a halo-ring. However, G-W tongs are temporary devices that are usually removed after surgical stabilization. Traction is applied using a halo-ring if the planned definitive treatment includes halo immobilization.
Traction can be used to realign and reduce a variety of subaxial spinal injuries. Realignment of an injury can provide some, if not complete, spinal canal decompression. An example is reduction of bilateral facet dislocations. Fracture fragment retropulsion, such as that produced with burst-type injuries, is usually associated with vertebral body height loss and comminution. With application of cervical traction, ligamentotaxis can partially reduce these fragments and produce some degree of canal decompression. This maneuver, however, relies on sufficient continuity of the posterior longitudinal ligament. Segmental, traumatic kyphotic angulation can also be improved with application of traction.
Some authors advocate use of large amounts of weight (up to 140 lb) to reduce facet dislocations (64,65), however overdistraction should be avoided as it can lead to neurological decline (66,67). The biomechanical strength of the traction device is of particular significance if such practices are employed. Steel tongs are stronger than titanium-alloy or carbon-fiber tongs, though the latter two are MRI-compatible (68). Because pullout strength is diminished with repeat usage, it has been suggested that steel cranial tongs should be recalibrated after frequent usage (69). According to their manufacturers’ recommendations, carbon-fiber tongs should only be used once.
Application and Technique
Gardner-Wells tongs are fixed to the skull through two slightly cranially angulated fixation pins.
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Before application of cranial-based traction, plain x-rays or a cranial CT should be carefully inspected to rule out skull fractures. The optimal site of insertion is approximately 1 cm above the helix of the ear. Neutral pin position is aligned with the external auditory meatus, which best achieves longitudinal traction. By placing the pins slightly anterior or posterior to this point, extension or flexion moments can be delivered to help reduce kyphotic or hyperlordotic deformities, respectively (Fig. 39-21). The skin over the proposed pin site should be marked and prepped sterile with povidone-iodine (Betadine) solution. It is not necessary to shave the site, as is routinely performed when inserting halo pins. The area is then anesthetized with a local infiltration of lidocaine, raising a skin wheal, as well as delivering the medication to the underlying periosteum.
Next, the tongs are held in position and the pins are advanced to and through the skin until they engage the outer cortex of the cranium. Most tongs have an indicator on the pin ends that signal when appropriate force has been applied. It is important not to overtighten the pins, because they can penetrate the inner dipole of the skull, which might lead to intracranial injury. In contrast, pins that are insufficiently secured can loosen and pull out from the skull, leading to substantial bleeding from scalp laceration or, rarely, temporary artery injury (70). Brain abscess has also been described as a complication of cranial tongs (71).
Reduction Technique for Bilateral Facet Dislocation
A towel roll can be placed between the patient’s scapulae to raise the head slightly off the bed. The G-W tongs are applied as described above. Because the facet reduction requires some flexion in addition to distraction, the pins should be placed slightly (1 cm) posterior. The location of the so-called equator of the skull should be noted. If pins are located above (cranial) the equator, they can slide along the slope of the cranium and dislodge.
FIGURE 39-21 Application of Gardner-Wells tongs can be useful in reducing fractures and dislocations. Neutral position is just proximal to the external auditory meatus, about 1 cm above the ear. By placing the pin slightly anterior, an extension moment can be applied. Similarly, by placing the pin slightly posterior, a flexion moment can be applied.
By positioning the pulley anterior to the patient, the traction vector can be used to apply a flexion moment to the cervical spine. Rolled towels can also aid in producing neck flexion, which can help unlock the articular processes. It is important that the traction setup will allow subsequent adjustments, because it should be changed to a neutral or slightly extended vector once the facets have been reduced. Likewise, the rolled towels are removed after reduction to allow neck extension, which will help hold the facet joints reduced.
An initial weight of 5 to 10 lb should be applied, followed by a lateral x-ray to rule out occipitocervical instability or gross overdistraction of the injured segment, both of which should prompt slow and careful release of traction. Serial neurologic examinations should be performed by the same practitioner throughout the entire process. Weight can then be added in 10-lb increments every 10 to 15 minutes, followed by a lateral cervical x-ray, until reduction is achieved. Although some have proposed that no more than 55 or 60 lb should be used, weights as high as 140 lb have been safely used to obtain cervical reductions (64). If such maneuvers are used, it is paramount that the patient be awake, alert, and examinable. After reduction is confirmed by x-ray, the weight is reduced to 10 to 15 lb and the traction vector adjusted to produce slight neck extension.
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If an MRI is to be obtained following reduction, the patient is placed in a rigid cervical collar and the cranial tongs temporarily removed.
Reduction Technique for Unilateral Dislocations
Unilateral facet dislocations are typically lower-energy injuries than bilateral dislocations. Because of this, they are often quite stable in the dislocated position and can require greater amounts of weight to reduce. Although some authors have treated these injuries nonoperatively, provided the patient is neurologically intact, most recommend reduction and stabilization (72,73).
Tongs are applied in the same manner as for bilateral dislocations, with a flexion moment to facilitate unlocking of the dislocated joints. In some cases, a closed reduction maneuver can be performed to achieve an earlier reduction with possibly lighter weights. The practitioner should grasp the cervical tongs like a steering wheel, with his or her hand placed just above the pins sites (in the 4 and 8 o’clock positions). Axial compression is applied to the nondislocated side while longitudinal distraction is applied to the dislocated side. The dislocated facet should now be unlocked (Fig. 39-22). Final reduction entails reversing the rotational deformity by rotating the head toward to the dislocated side. A subtle click or thump can be heard or felt. Manual traction should then be slowly released and a lateral x-ray obtained to confirm the reduction. Once reduced, traction should be decreased to 10 or 15 lb and the neck slightly extended. Neurologic status must be serially assessed through the process.
FIGURE 39-22 Reduction maneuver for a unilateral right-sided facet dislocation. With the tongs in place and weight applied, distractive force is applied to the dislocated side, while compressive force is applied to the nondislocated side. The head is then rotated toward the dislocated side. A satisfying “clunk” signifies that the dislocation has been reduced.
The Role of Prereduction Magnetic Resonance Imaging
The role of prereduction MRI for facet dislocations remains controversial. There exists the potential for neurologic decline with closed reduction, either by open or closed methods (74,75). It is believed that intervertebral disc herniations, pulled back into the spinal cord during reduction, are a major contributing factor. Because of this, some have strongly advocated obtaining an MRI scan before reduction to rule out a disc herniation (75). This recommendation is poised, however, on a decision to perform an anterior cervical discectomy or corpectomy to remove the herniated disc before open or closed reduction.
In the unexaminable (unconscious, head-injured, intoxicated) patient with an unknown or unmonitorable neurologic
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status, a prereduction MRI appears to be prudent. However, in the awake, alert, and examinable patient, a prereduction MRI may not be necessary. Two recent clinical reports have demonstrated that closed reduction of facet dislocation can be performed safely, provided that serial neurologic examination can be adequately performed (76,77). In one study (77), five of nine patients who underwent a successful closed reduction without neurologic compromise had a new herniated disc on postreduction MRI that was not present on prereduction MRI. In addition, some patients also had increased signal within the spinal cord, but again, without associated neurologic compromise. Grant et al (76) retrospectively reviewed their results with early closed reduction in 121 patients with cervical spine dislocations. Of the 80 patients who underwent a postreduction MRI, 22% demonstrated a frank disc herniation, though this did not affect the degree or progression of neurologic deficit. Ultimately, the relative advantages and disadvantages of early reduction and anatomic alignment versus the increased complexity of performing anterior decompression and reduction on a dislocated spine are still not clearly established and will likely remain controversial in the near future.
Halo Vest
With improved techniques of rigid internal fixation of the cervical spine, halo immobilization has become a less popular form of treatment for subaxial cervical spine injuries. As discussed above, halo-based traction can be used, in particular when definitive treatment with a halo vest is planned. Halo fixation may also be a useful method of temporary stabilization of highly unstable cervical spine injuries in multiply injured patients who must undergo diagnostic and nonspine surgical procedures (78). The use of halo fixation for cervical facet dislocations has demonstrated a high rate of persistent instability and poor anatomic alignment (79,80,81). Varying rates of success have been documented for other types of subaxial cervical injuries (82,83,84,85). Despite this, halo vest immobilization remains a viable, minimally invasive method of stabilization of unstable cervical spine injuries for patients who might otherwise have contraindications to open surgical methods. Halo fixators are the best nonoperative method of resisting rotational and translational forces (86), while they are relatively ineffective at resisting axial compressive loads.
Application and Technique
If the spine has been reduced or realigned using the halo ring, the traction can remain in place until final securing of the construct. The posterior part of the vest can be placed first by log-rolling the patient from side to side, keeping in line cervical traction at all times. The anterior part of the vest can be applied and secured using the shoulder straps and side buckles. An appropriately fitted vest should extend down to the level of the xiphoid process, keeping the abdomen free, and be secured enough to maintain its position while still allowing access to the underlying skin. Proper vest fit has been demonstrated to be the most important factor in maintaining reduction (86).
Next, a small roll of towels is placed behind the occiput. The proposed pin sites should then be prepped in sterile fashion. The hair should be shaved from the posterior pin sites before sterile preparation. The optimal position of the anterior pins is 1 cm above the lateral third of the orbital rim (to avoid injury to the supraorbital nerve), while the posterior pins should be placed 1 cm above the helix of the ear (87). The pins or ring should not contact the ear, because even gentle pressure can lead to skin necrosis over time. Opposing pins should be tightened at the same time to avoid displacement of the ring, that is, the anterior right pin and the posterior left pin are tightened together. Optimal pin fixation is achieved if placed perpendicular to the bone. Tightening should be gradual, switching between the two pairs of opposing pins until the final torque of 8 inch-pounds is achieved. The lock nuts are then tightened to prevent pin loosening. Pins should be retightened 24 to 48 hours later. If a pin becomes loose with time, it can be retightened once to 8 inch-pounds if resistance is met. If not, then another pin should be placed in a new site and the loosened one removed. Even with meticulous pin site care, complications occur in about 6% of cases (88). Once the ring has been secured, the longitudinal struts are attached and secured. Cervical x-rays can then be obtained and careful adjustments made to the device to optimize reduction and alignment.
Various complications have been reported with use of the halo device. Pin site infection can occur in 6% to 20% of cases (88,89). Patients can report swallowing difficulty, which may be associated with the head and neck being overly extended. Returning the neck to a neutral or slightly flexed position can relieve this in most cases. Pressure sores can develop in 4% to 11% of patients (89) and are usually associated with improper vest fit. Meticulous skin care and frequent inspection can help avoid this complication.
Surgical Management
Surgical Timing
The optimal time to perform surgery, particularly in patients with neurologic deficits, still remains unclear. The two most commonly proposed benefits of earlier versus later surgery are improved rates of neurologic recovery and improved ability to mobilize the patient without concern of spinal displacement.
A number of animal studies have suggested a significant benefit to earlier decompression after acute spinal cord injury. In perhaps the most clinically representative spinal cord injury model reported, Dimar et al (90) found a nearly linear relationship between rate and extent of neurologic recovery and time to decompression in rats with experimentally induced incomplete spinal cord injuries with 35% canal compromise. Other animal studies using less clinically representative models, such as inflatable intracanal bladder compression, spinal cord cinching with cables, and cauda equina level injuries, have demonstrated similar time-dependent recovery rates.
To date, there is little human clinical evidence to support that early surgical decompression and stabilization improves
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neurologic recovery rates. This may largely be the result of disagreement upon what is considered early versus late surgery. In the only randomized, prospective, controlled trial found in the literature, surgery performed for cervical spinal cord injuries less than 72 hours versus more than 5 days from the injury demonstrated no significant difference in motor scores at final follow-up (91). Notwithstanding the possibility of beta error, it is also possible that surgery within a critical time period within the first 72 hours to 5 days might have made a difference. Supportively, other nonrandomized prospective studies have demonstrated that surgery performed within 8 hours or within 24 hours from injury did not result in a better neurologic outcomes (92,93). In one interesting report, performing surgery within 8 hours from the time of injury was feasible in only 10% of cases (94).
FIGURE 39-23 Anterior approach to the subaxial cervical spine. The superficial interval is between the sternocleidomastoid muscle (lateral) and strap muscles (medial). Deep dissection is between the carotid sheath (lateral, which contains the carotid artery, internal jugular, and recurrent laryngeal nerve) and the trachea and esophagus. The alar and prevertebral fascia (deepest) are swept away to access the anterior longitudinal ligament, vertebral bodies, and disc spaces.
One retrospective study found surgery performed within 72 hours had significantly better neurologic outcomes than surgery performed after 10 days from the injury. Many practitioners believe surgery should be delayed to allow for optimal medical stabilization of the patient and resolution of initial spinal cord swelling, hypothesizing that early surgery may be potentially detrimental. A number of clinical series have demonstrated that, in the least, surgery performed as soon as 8 hours does not appear to increase the rate of complications or lead to neurologic decline (94,95).
FIGURE 39-24 Open reduction of dislocated facets using an anterior approach. A laminar spreader can be used to distract and unlock the injured articular processes.
Surgical Techniques
Anterior Surgery
Anterior Approach
The anterior approach to the subaxial spine utilizes the interval plane between the sternocleidomastoid (lateral) and anterior strap (medial) muscles. The location of the incision can be determined by palpable landmarks: the cricoid cartilage is at the level of the C6 vertebral body, the thyroid cartilage is at the level of the C4-5 disc space, and the hyoid bone is at the level of the C3 vertebral body. Deeper, the interval of dissection is between the carotid sheath laterally and the trachea and esophagus medially (Fig. 39-23). The alar and deeper prevertebral fascia are then swept away to reveal the anterior surface of the cervical spine. The longitudinal fibers of the anterior longitudinal ligament can be visualized spanning the vertebral bodies and disc spaces. In the traumatized spine, there is often hematoma and edematous tissue overlying the injured segment. Disruption of the anterior ligamentous ligament or anterior disc space can also be readily visualized during the exposure. A left-sided approach is the author’s preference, because the recurrent laryngeal nerve is more consistently located within the carotid sheath and therefore at lower risk of injury than with right-sided approaches.
Decompression
Anterior decompression can be effected via discectomy or corpectomy (vertebrectomy). The decision to perform one or the other procedure is usually decided before surgery and is based on (a) the extent of bony injury and vertebral body comminution and (b) the location of compressive pathology based on imaging studies. Vertebral body fractures that involve a large portion of the end plate or are substantially comminuted are not optimal fixation points for strut grafts or fixation points for screws.
A discectomy can be performed to remove a herniated cervical disc that is compressing the neural elements. In some cases, however, the herniation can be displaced rostral or caudad behind the vertebral body. This can necessitate partial or full corpectomy of the vertebral body to adequately and safely remove the disc fragment.
If the vertebral body is fractured, the loose bony fragments can be removed piecemeal with a rongeur. The bone can potentially be reused if a titanium mesh is implanted. Alternatively, a high-speed burr can be used to remove the injured vertebral body. The width of the corpectomy should be approximately 15 to 16 mm; however, this should be determined by preoperative imaging because vertebral dimensions and anatomy can vary. In cases of high-energy injuries, the posterior longitudinal ligament
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can be disrupted. Thus, with removal of the bony fragments, the underlying spinal cord is readily visible and should be protected at all times.
Anterior Reduction of Dislocated Facets
In the presence of a herniated cervical disc associated with dislocated facet joints, one may elect to perform an anterior discectomy and decompression before reduction. This can be performed by several methods. A lamina spreader can be placed between the end plates to distract the injured segments and unlock the dislocation (Fig. 39-24). Care must be taken to avoid overdistraction, which may caused further damage to the spinal cord. Alternatively, Caspar pins can be placed into the vertebral bodies and used to lever the upper segment on the lower segment without additional distraction. A lateral intraoperative x-ray should be obtained to confirm reduction. Unreducible dislocations may necessitate additional posterior surgery to achieve reduction.
Reconstruction
After completion of the decompression, the superior and inferior end plates of the defect should be flattened and lightly burred until punctate bleeding is achieved. The corpectomy or discectomy site is then measured for strut selection and contouring. Autograft or allograft bone can be used to reconstruct the anterior column. Structural autograft can be harvested from the anterior iliac crest. The graft should be cut to match the length, width, and height of the defect. The graft is then gently impacted into place between the vertebral bodies. There should be an intimate fit between the graft and host bone. Because many injuries are highly unstable and easily overdistracted, axial compression, produced by pressing on the top of the head, can help.
Another alternative is insertion of a titanium mesh cage. A potential advantage of a cage is that the corpectomy bone can be recycled and packed inside, which may decrease the amount of iliac crest autograft required. An additional, still theoretical, advantage is possibly better incorporation and fusion because the cage can be packed with primarily cancellous rather than cortical bone (96). The disadvantage of the cage is that it has minimal end-plate contact area, which may be a risk factor for subsidence into soft bone.
Anterior Plates
Following graft insertion, anterior stabilization should be performed. Anterior cervical plates can be used to span discectomy or corpectomy defects. Screw positioning and purchase is of critical importance. With the plate well centered along the anterior vertebral bodies, holes are drilled through the plate. The drill should always be angled approximately 10 to 15 degrees toward the midline to avoid violation of the vertebral artery. In the sagittal plane, the holes should be parallel to or angled slightly away from the fused end-plate. Screw length should be determined by preoperative imaging studies and confirmed by direct measurement of the end plate and vertebral body intraoperatively before strut insertion. In total, four screws should be inserted, two into the cranial vertebra and two into the caudal vertebra.
In the earliest reports of anterior plate fixation for cervical traumatic instability, bicortical screws, which penetrated the posterior vertebral body, were recommended. However, with more recent advancements in screw and plate design, this is no longer routinely performed by most surgeons. Fixed-angle screws, which lock into the plate, offer equivalent, if not superior, biomechanical stability than nonfixed bicortical screw-plate systems (97). Locking screws also prevent anterior screw migration. One disadvantage of the first locking plate designs was that the angle that the screw could be inserted into the plate was also fixed. Newer plate designs enable variable-angle screw placement with the choice of being rigidly fixed to the plate or allowing a small degree settling.
There are several different anterior cervical plate designs available today (Fig. 39-25). For fixation of traumatic injuries, so-called dynamic plates are usually not preferred. Such designs allow axial or vertical settling during the postoperative period, either by slotted screw holes or a piston-type mechanism within the plate itself. Although these plates may offer some advantages
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in degenerative cases, such as earlier graft incorporation from increased stress-sharing, reconstruction after fracture or dislocation is focused on achieving and maintaining maximal stability. Rigid, nondynamic plates best achieve this goal. So-called low-profile plates are thin, which is thought to lessen postoperative swallowing complaints. Although such devices are acceptable to augment an anterior cervical disectomy for a degenerative process (such as a herniated disc), thicker plates are preferred in the traumatic setting.
FIGURE 39-25 Diagram depicting different plate types, including those with dynamic slotted holes (A), nondynamic (B), piston-type dynamic plates (C), and fixed- or variable-angle screws (D).
Published Results
Moerman et al (98) reviewed their results with one- or two-level fusions stabilized with an anterior Senagas plate in 22 patients with lower cervical fractures or dislocations. At 1-year follow-up, solid fusion was documented in all cases with acceptable alignment. Garvey et al (99) found equally good results in 14 patients treated with anterior Caspar plate fixation and fusion for subaxial cervical fractures and dislocations. At an average follow-up of 30 months, no cases of fixation failure had been observed. Goffin et al (100) reported 5- to 9-year follow-up results in 25 patients treated with anterior fusion and plating for cervical fractures and dislocations. Fusion was demonstrated in all cases by 1 year; plate fracture occurred in one case. Paralleling the nontrauma literature, 15 of 25 (60%) patients had evidence of adjacent segment degeneration, although this did not correlate with clinical complaints. Laus et al (101) treated 32 lower cervical fractures or dislocations with anterior surgery. Fusion was achieved in all patients by an average of 4.5 months. Neurologic recovery of one to three Frankel grades was observed in the 14 patients with an incomplete spinal cord injury and no change in those with complete spinal cord injury or no neurologic deficit. Randle et al (102) also documented their results with the Caspar plate with traumatic cervical injuries; all patients achieved solid fusion by 6 months follow-up. Brodke et al (103) compared anterior and posterior surgery for unstable cervical spine fractures with spinal cord injury. Neurologic recovery was comparable in both groups. A 90% fusion rate was achieved with anterior surgery, and 100% percent with posterior fusion; there were no differences in complaints of pain or maintenance of alignment.
Posterior Surgery
Posterior Approach
The posterior approach to the cervical spine is a midline extensile approach that can be used to access as many spinal levels as necessary. The dissection can be relatively bloodless if maintained between within the avascular plane of the ligamentum nuchae, which separates the right and left paraspinal muscles. Intramuscular hemorrhage and posterior interspinous and supraspinous process ligament damage is often apparent at the level of injury. It is important to maintain continuity of any uninjured ligaments until the correct surgical level is identified as to avoid unnecessary destabilization of other segments. Subperiosteal dissection is started on either side of the bulbous, bifid spinous process, continues down to the spinolaminar junction, and extends laterally over the laminae. Lateral dissection should be taken only at the levels to be fused. Accordingly, only the facet joints that will be fused should be exposed, along with their corresponding lateral masses.
Decompression
In the majority of acute, traumatic, subaxial spinal injuries, posterior decompression via laminectomy is not necessary. Canal compromise is most frequently caused by dislocation, translation, or retropulsed vertebral body fragments. In rare cases of anteriorly displaced posterior arch fragments, a laminectomy would be indicated to directly remove the offending compressive elements. This is not true, however, in cases of acute spinal cord injury associated with multilevel spondylotic stenosis or ossification of the posterior longitudinal ligament, in which a posterior decompressive procedure might be considered the procedure of choice if cervical lordosis has been maintained.
Reduction Maneuvers
Usually, the primarily goal of posterior surgery for subaxial cervical injuries is reduction or stabilization.
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Open reduction of dislocated facet joints can be performed using a posterior approach. Cervical traction can facilitate intraoperative maneuvers by providing distraction across the dislocated segments. If the spinous processes are intact, they can be grasped with towel clips near their base to flex and distract the injured joint. If the spinous processes are fractured, a Penfield 4 elevator or other small, flat instrument can be placed over the top of the superior articular process of the lower level. Then, angling it caudally, the inferior tip of the inferior articular process of the upper level can be levered up and posterior back into position (Fig. 39-26). If these maneuvers fail, the tip of the superior articular process of the lower vertebra can be resected using a burr or small Kerrison rongeur (Fig. 39-27).
Posterior Instrumentation
The first forms of posterior cervical stabilization were wire-based constructs, which are still commonly used today. The simplest form of wire stabilization is interspinous process wiring. Using a drill bit or a small (2- or 3-mm burr), a hole is created on either side of the superior third of the spinolaminar junction of the upper vertebra. Next, the hole is completed from side to side by puncturing the bone with a towel or sharp bone clamp. One or more wires or, optimally, a braided-cable is passed through the hole and then passed beneath the spinous process of the lower vertebra. The wire or cable is then tensioned. Alternatively, the wire can be passed through a hole in the inferior third of the spinolaminar junction of the lower level (104). A triple-wiring technique has also been described, which incorporates fixation of corticocancellous struts on either side of the spinous processes. The advantage of wiring techniques is that they are a relatively inexpensive method of posterior stabilization with nearly equivalent restoration of stability as some lateral mass plating systems (105). The disadvantages are that it cannot be used if a laminectomy has been performed or in the presence of posterior element fractures.
FIGURE 39-26 Open reduction of dislocated facets using a posterior approach. A Penfield 4 elevator (or other small, smooth elevator) is inserted over the superior articular process. It is walked inferiorly to hook the inferior (dislocated) articular process. The elevator is then levered caudally to reduce the joint.
FIGURE 39-27 A Kerrison rongeur can be used to resect the superior aspect of the articular process if open reduction maneuvers are not successful.
Published Results
Lee et al (106) treated 162 patients with flexion injuries by posterior interspinous process wiring and fusion. At 12 weeks follow-up using flexion-extension views, fusion was achieved in 100% of cases. Of note, residual kyphosis was present in 54 (34%) patients, translational deformity in 14 (9%), and hyperlordotic deformity in 7 (4%) of cases. These data suggest that although a high fusion rate can be achieved, x-ray maintenance of alignment is not as reliable.
Facet wiring has also been advocated to stabilize cervical spine injuries. In this technique, a small hole is drilled within the lateral mass at 90 degrees to the articular surface. The wire is then passed through the lateral mass hole and subsequently through a hole in a piece of corticancellous strut graft. The
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advantage of this technique is that it can be performed with laminectomy or posterior arch fractures. A disadvantage is that stability is still partially reliant on the bone graft. In addition, passage of the most inferior wire is across a joint that is not fused or included in the construct. Improved stability may be achieved by wiring the facets to a longitudinal rod or Luque rectangle (107).
Lateral mass screw fixation has become more popular in recent years. Lateral mass screws can be inserted using a number of different techniques (Fig. 39-28). With the Roy-Camille technique, orientation of the screw is more perpendicular to the long axis of the spine. This can make fixation to a rod or plate more facile, however, with the sacrifice of a shorter screw length and potentially greater risk of injury to the vertebral artery. The Magerl technique offers the advantage of greater screw length with potentially higher pull-out strength. Although the vertebral artery may be less in danger, the nerve might be more at risk as the screw tip is directed toward the level of the disc space.
Both plate and rod systems are currently available. The newest systems include variable angle titanium screws that are connected to longitudinal rods (Fig. 39-29). The advantages of these systems over lateral mass plates are that (a) they are more forgiving of minor differences in medial-lateral and proximal-distal variation of screw position and (b) they enable optimal screw placement to be determined by the patient’s anatomy or injury rather than the location of the holes in the plate.
Roy-Camille et al (108) used posterior lateral mass screws and plates to treat 197 patients with lower cervical spine injuries. Final x-ray follow-up demonstrated that initial reduction and alignment was maintained in 85% of cases. Nazarian and Louis (109) used posterior screws and lateral mass plates in 23 cases of cervical fractures, with excellent maintenance of alignment and fusion rates.
Posterior Fusion
The articular surfaces of the facets should be decorticated using a small microcurette before lateral mass plate or rod placement. A 3-mm burr is then used to lightly decorticate the lateral masses. If screws have been placed, it is important to not remove too much bone, because this may weaken the region surrounding the screw and lead to cutout. If the laminae and spinous processes are intact, their posterior surfaces should also be decorticated down to a bleeding surface. Cancellous bone harvested from the posterior iliac crest is then packed inside the facet joints. The lateral mass rods may then be placed. Additional bone is laid over the posterior elements and lateral masses.
Postoperative Care
The advantage of rigid internal fixation for cervical spinal injuries is that the need for postoperative external immobilization is usually lessened or may be eliminated. However, this should be evaluated on a case-by-case basis and determined by the quality of fixation achieved. In the author’s practice, a rigid cervical collar is prescribed for 6 weeks for awake, alert patients who will be ambulatory following surgery. In multiply injured, ventilator-dependent patients, an orthosis is avoided to facilitate nursing and respiratory care. With rigid internal fixation, the patient can be seated in a cardiac chair as tolerated in order to enhance pulmonary toilet and clearance of secretions. If indicated, postoperative antiembolic chemoprophylaxis can be started on postoperative day 4 or 5 so as to avoid an epidural hematoma. Prophylactic antibiotics are continued for 48 hours.
TREATMENT OF SPECIFIC INJURIES
Treatment should be directed toward achieving several important goals. Preservation or restoration of neurologic function is the most important. It entails decompression of the neural elements, which can be effected by realignment or direct removal of bone or disc material from the spinal canal. Mechanical spinal instability may be the result of the initial injury or decompressive surgery. Protection of the neural elements also requires that mechanical stability be restored to unstable segments. This is usually achieved by open surgical methods, although closed methods such as halo fixation can sometimes be effective.
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The definition of stability is somewhat subjective. Some make the academic distinction between neurologic stability and mechanical stability. In theory, as long as a patient with a mechanically unstable cervical injury remains flat and strict spinal precautions are maintained, neurologic stability can be maintained. In other words, the stresses that the spine would endure under these specific circumstances would pose little additional danger to the spinal cord. With more aggressive movement, neurologic stability would depend on restoration of mechanical stability.
FIGURE 39-28 Magerl (left) and Roy-Camille (right) techniques of inserting lateral mass screws.
FIGURE 39-29 Side view (A) and posterior view (B) of a diagram depicting a variable-angle posterior screw-rod construct for stabilization of lower cervical spine injuries.
Compression Fractures
Simple compression fractures of the cervical spine on x-ray examination demonstrate wedging of the anterior vertebral body without posterior vertebral body involvement. They can be considered stable if the facet joints are not subluxed or gapped, there is no vertebral body translation, and there is minimal interspinous process gapping (Fig. 39-31). There is often some degree of kyphosis, which should be carefully measured on a plain lateral x-ray using the Cobb method. Normally, there is 2 to 4 degrees of lordosis between adjacent vertebrae. More than 11 degrees of relative kyphosis is strongly suggestive of posterior ligamentous complex disruption. Importantly, absolute kyphosis at the injured segment should be considered in relation to the measured “normal” lordosis of the adjacent uninjured segments. If the posterior ligamentous complex is disrupted, the injury should be considered unstable and operative treatment is recommended.
Before MRI, implications about the integrity of the posterior ligamentous complex were based primarily on plain x-rays. In cases in which the integrity of the posterior ligamentous complex is indeterminate using plain x-rays or CT, an MRI can be obtained. Although MRI has been criticized for being overly sensitive, it can demonstrate discontinuity of the ligamentum flavum and interspinous and supraspinous ligaments and reveal soft tissue edema between the spinous processes. Patients with simple compression fractures are usually neurologically intact; thus, determination of the stability of the injury can have profound consequences.
Nonoperative Treatment
Patients with cervical compression fractures without posterior ligamentous injury can be treated nonoperatively. For injuries at C3 to C6, a rigid cervical collar usually suffices. For injuries of C7 or T1, a cervicothoracic brace may offer better control. Ultimately, if the injury is stable, the orthosis minimizes motion at the fracture site, which can decrease pain and facilitate resolution of muscular spasm. Attempts to correct minor kyphotic deformities are usually fruitless and are in reality unnecessary. A lateral x-ray should be obtained with patient sitting up or standing before discharge from the hospital, because this mechanical “litmus” test can sometimes demonstrate instability. The fracture is usually healed by 3 months, at which time flexion-extension views under the patient’s own control should be obtained to rule occult instability, either at the level of the injury or at a distant site, such as C1–C2, which may have been undetected at the time of initial presentation.
Operative Treatment
Surgical stabilization should be considered for patients with evidence of posterior ligamentous injury. This is suggested by segmental kyphosis greater than 11 degrees or substantial amounts of vertebral body wedging. Correlative numbers for the percentage of height loss and posterior ligamentous complex injury in the cervical have not yet been established. MRI evidence for ligamentous injury should also be considered. Before surgery, cervical traction with a slight extension vector can be used to realign the fracture. This is best performed in the awake patient. Though described in more detail for patients with facet
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dislocations, a herniated disc may be rule out based on the MRI as well. If the spinal canal is clear, a single level posterior fusion with instrumentation can be performed.
FIGURE 39-30 The author’s preferred technique is a modified Magerl method. A starting hole is created with a 2-mm burr bit. Dividing the lateral mass into quadrants, it is located at the superolateral aspect of the inferomedial quadrant (top). The screw is then angled laterally about 20 to 25 degrees (middle). In the sagittal plane, the screw path is kept perpendicular to the plane of the adjacent facet joint. This method allows placement of the screw within the midaspect of the lateral mass. Unicortical purchase is preferred.
FIGURE 39-31 Lateral cervical x-rays of a stable compression fracture. There is minimal appreciable kyphosis, no translation, no facet joint gapping, and minimal evidence of interspinous process widening.
Burst Fractures
Cervical burst fractures are usually high-energy injuries. X-ray hallmarks are vertebral body comminutions that involve the posterior vertebral body, usually with retropulsed fragments that result in spinal canal compromise (Fig. 39-32). Spinal cord injury is common. Immediate realignment with cranial traction can help clear the canal to some degree, provided the posterior longitudinal ligament is intact (111), and provide temporary stabilization until surgery. MRI and CT can be useful in detecting spinal cord edema and the location of retropulsed bony fragments.
Nonoperative Treatment
Nonoperative treatment might be considered in neurologically intact patients with little vertebral body comminution and only
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the mildest degree of canal compromise. There should be minimal kyphotic deformity (neutral or <5 degrees of relative kyphosis) and no indication of posterior ligamentous injury. Because of the potential for vertebral body collapse, it is the author’s preference to treat patients in a halo vest or rigid CTO. X-rays should be obtained with the patient standing or sitting, before discharge, and rigorous comparisons made to supine films. High-quality films are crucial. Patients should be followed weekly for the first month.
FIGURE 39-32 Lateral cervical x-ray (A) of a C4 burst fracture. There is relative kyphosis at the injured segment, in addition to disruption of the posterior vertebral body line. CT (B) confirms the presence of posterior vertebral body fragment retropulsion into the spinal canal.
Operative Treatment
Patients with neurologic deficit, regardless of the integrity of the posterior ligamentous complex, should be surgically decompressed and stabilized. Retropulsed vertebral body fragments are most easily accessed through a direct anterior approach. The injured vertebral body should be removed, and the spinal canal fully decompressed. Intraoperative traction can help realign the spine if significant deformity exists (Table 39-4). The anterior column should be reconstructed with a bone graft or strut. It is the author’s preference to insert a rigid titanium mesh cage filled with salvaged bone in addition to cancellous iliac crest autograft. Bone should be tightly packed into the cage, which may also enhance the surface area contact with the end
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plates. An anterior cervical plate is then applied to restore anterior stability. If the posterior ligamentous complex appears to be disrupted, it is the author’s preference to perform a posterior instrumented fusion, either during the same operation or delayed until the patient can better tolerate it.
TABLE 39-4 Pearls and Piftalls: Burst Fractures
Pearls Pitfalls
Preoperative traction for realignment and partial decompression (ligamentotaxis). Avoid posterior compression as a stand-alone construct.
Combined anterior/posterior surgery usually required. Ensure PLC is intact if nonoperative care is elected.
Corpectomized bone can be salvaged for fusion with titanium mesh cage. Stand-alone anterior or posterior constructs may be prone to failure.
Flexion-Type Tear-Drop Fractures
Tear-drop fractures are recognized by their characteristic fracture pattern, which has been described in detail above. They often have a sagittal split within the posterior vertebral body, leading many authors to refer to them as burst fractures. Flexion-type tear-drop fractures typically occur in younger patients with high-energy trauma. Posterior ligament disruption is suggested by more than 11 degrees of kyphosis or posterior vertebral body translation (Fig. 39-33). An MRI can be confirmatory. Patients often present with a neurologic deficit.
Nonoperative Treatment
There is a definite role for nonoperative treatment of cervical tear-drop fractures. Minimally displaced fractures with little kyphosis and no posterior ligamentous complex injury are stable. They can be treated in a rigid cervical collar or CTO, depending on the level of injury. Halo treatment can be used to treat unstable fractures. The apparatus can help realign fractures, which can effect canal clearance in patients with spinal cord injury. Importantly, halo treatment for unstable tear-drop fractures results in inferior x-ray results than anterior surgery, though neurologic and clinical outcome scores appear to be comparable (41). The halo should be kept in place for 3 months, provided acceptable alignment has been maintained. After the fixator has been removed, a flexion-extension x-ray should be obtained to confirm that stability has been achieved.
FIGURE 39-33 Lateral x-ray of a cervical teardrop fracture. This would be considered a stage 5 compressive flexion injury. The classic teardrop fragment can be appreciated, in addition to substantial posterior translation (retrolisthesis) of the upper vertebra on the lower vertebra. The facet joints are also widely gapped.
Operative Treatment
In patients with neurologic deficit, anterior corpectomy is usually performed to remove the offending retrolisthesed vertebral body (Table 39-5). This is followed by anterior strut grafting and rigid plating (Fig. 39-34). In some cases, an unstable tear-drop fracture can occur in a neurologically intact patient. In these cases, anterior surgery can include a nondecompressive corpectomy, which entails resection of the majority of the vertebral body back to, but not through, the posterior wall. This is best reserved for injuries without retrolisthesis. Some surgeons prefer to perform a single-level discectomy or partial corpectomy. However, extensive end-plate fracture appears to be a risk factor for failure of anterior alone constructs (112). If the initial injury demonstrated a large amount of translational deformity (>3 to 3.5 mm) and the facet joints appear to be gapped or widened, posterior surgery can be performed to provide additional stability.
In rare cases, posterior surgery alone can be elected (Fig. 39-35). This should be reserved for patients who are neurologically intact, have minimal vertebral body height loss, and have less than 30% inferior end plate involvement. A potential advantage
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of this approach is that the fusion can potentially be limited to a single motion segment.
TABLE 39-5 Pearls and Pitfalls: Flexion-Type Teardrop Fractures
Pearls Pitfalls
Anterior corpectomy most useful surgical treatment. Recognize subtle degrees of retrolisthesis (indicates posterior ligamentous complex disruption).
Preoperative reduction with tongs can be helpful. Avoid single-level anterior fusions in the presence of end plate involvement.
Stand alone posterior fixation can save a motion segment (neurologically intact patient). Consider additional posterior fixation with severe preoperative kyphosis.
FIGURE 39-34 Most teardrop fractures are treated with anterior surgery. In this case, an incomplete spinal cord injury was associated with a C5 fracture (A). A sagittal MRI (B) demonstrates enhanced bone edema within the C5 vertebral body, but it is difficult to appreciate the fracture pattern on these images. An anterior C5 corpectomy followed by strut fusion with a cage and anterior plate stabilization was performed (C).
Facet Fractures without Dislocation
There remains wide disagreement concerning the management of facet fractures without dislocation. The majority of fractures initially present as minimally displaced fractures (Fig. 39-36). Most can be treated nonoperatively with a rigid cervical collar without substantial late displacement (Table 39-6). However, in some cases the fracture itself is not the essential lesion. Occult ligamentous disruption can be present. Thus, MRI has an increasingly important role in differentiating so-called stable and unstable facet fractures and may be an important tool in treatment decision making (Fig. 39-37).
Nonoperative Treatment
Most facet fractures are minimally displaced and can be considered mechanically stable. Such patients can be treated in a rigid
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cervical collar for a period of 6 to 12 weeks, monitored by frequent x-ray examination. It is important to recognize, however, that they can be associated with occult unstable ligamentous injury (demonstrating little if any translational deformity at initial presentation). Many authors recommend routine MRI examination to rule out significant ligamentous damage. Disruption of the anterior longitudinal ligament and intervertebral disc are thought to play in important role in late displacement, although posterior ligamentous complex injury can also occur. Neurologic injury associated with the fracture is rare and, if present, is usually limited to a mild single root radiculopathy that often resolves without formal decompression. Flexionextension views should be obtained after the completion of collar immobilization to ensure stability. Although late displacement is considered to be an indicator of instability by most, it has been observed that this can autostabilize with time. It is unclear what the long-term consequences of fixed deformity on the overall clinical outcome.
TABLE 39-6 Pearls and Pitfalls: Facet Fractures
Pearls Pitfalls
Can usually be treated in a collar. Late displacement, requires frequent x-ray follow-up.
MRI useful in detecting concomitant ligamentous injuries. Posterior stabilization leads to inferior x-ray results (kyphosis).
Recognize as a rotational injury. Unrecognized ligamentous injury can lead to late displacement/dislocation and neurologic decline.
FIGURE 39-35 Rarely, unstable teardrop fractures in a neurologically intact patient can be treated with posterior surgery alone (A). The theoretical advantage is the ability to fuse only one motion segment (B).
FIGURE 39-36 Lateral cervical x-ray of a minimally displaced articular process fracture. In the author’s experience, the majority of these injuries can be treated successfully in a hard cervical collar. Frequent follow-up x-rays should be obtained to detect late instability.
Operative Treatment
Because of the inconsistent prevalence of ligamentous instability, some have aggressively recommended operative treatment for nearly all facet fractures. Others have focused the indications by employing judicious use of flexion-extension views or MRI. A validation study of the predictive value of MRI on displacement of facet fractures has yet to be published.
Either anterior or posterior surgery can be performed to treat facet fractures. Anterior surgery usually consists of a single-level interbody fusion with a plate (Fig. 39-38). The advantages of this approach are that the fusion rates are consistently high, a perceived lower infection rate than posterior approaches, and the ability to fuse only one motion segment. It is important to choose the correct level to fuse, which should be based on the facet joint involved, as opposed to the numerical level of the articular process fracture.
Posterior surgery entails stabilization and fusion and can be performed in a variety of manners. The most mechanically stable constructs are achieved with the use of bilateral lateral mass screws connected by rods or plates. However, bilateral screw placement can be precluded with large articular process fractures, which may necessitate instrumentation of the next adjacent nonfractured lateral mass. Although these issues are avoided by using interspinous process wiring, the stability of the construct is inferior and is precluded with lamina fractures. A combination construct, using an interspinous process wire and a unilateral lateral mass plate is another option (Fig. 39-39).
Published Results
There is sparse literature concerning the operative outcomes of unilateral facet fractures. Because they are considered to be rotational injuries, they are often reported along with unilateral pedicle fractures and facet dislocations. In a combined retrospective review of posterior surgery and prospective analysis of anterior surgery, anterior surgery resulted in a superior x-ray outcomes (113).
Facet Subluxation and Dislocations
The treatment of facet subluxations and dislocations are not differentiated in the literature, likely because they represent stages along a continuum from facet capsule disruption to complete, bilateral locked facets. What is inconsistent in the continuum, as highlighted by Allen et al (40), is that unilateral dislocations can occur without catastrophic posterior ligamentous complex disruption, while bilateral facet subluxations (without frank dislocation) usually occur with posterior ligamentous complex disruption.
Nonoperative Treatment
The role of nonoperative treatment for facet dislocations is minimal. If it is elected, it should be reserved for unilateral facet dislocations in patients without any signs of neurologic injury or for those who are too sick to undergo surgery. Even in these cases, cervical orthoses are not usually considered adequate treatment. The inability of halo-fixation to treat facet dislocations has been demonstrated by Sears and Fazl (80), with more than 50% of patients exhibiting persistent instability after treatment.
Frequent x-ray examination is important. Evidence of autofusion
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of the dislocated facet joint or, less frequently the disc space, is a sign of healing. After a course of about 3 months of halo immobilization, the device should be removed and the flexion-extension views should be obtained to confirm stability. Surgical fusion should be considered if instability is present.
FIGURE 39-37 Initially nondisplaced, isolated facet fractures can develop subsequent translational instability. This occurrence is probably most influenced by the concomitant soft tissue injuries. In this case, the initial fracture involved nearly all of the apposed articulating surfaces of the joint (A). An MRI demonstrated some minor disruption of the posterior annulus fibrosis (B). Although initial x-rays of the patient supine (because of a severe head injury) demonstrated no subluxation (C), x-rays taken at 2 months postinjury demonstrated about 10% to 15% subluxation (D). (continues)
Operative Treatment
The optimal treatment of unilateral or bilateral facet dislocations remains unclear. A number of different methods can be successful. It is important to recognize the limitations, advantages, and disadvantages of each. In a number of circumstances, one treatment method may be preferred over another.
The safety of closed reduction as well as the role of MRI have been discussed in previous sections. In summary, closed reduction appears to be a safe practice in the awake, cooperative patient who can be serially examined. If the patient does not fulfill these criteria, particularly in the incomplete spinal cord–injured patient, prereduction MRI is highly advised to detect a herniated disc (Table 39-7).
In the patient who has undergone successful closed reduction before operation, anterior or posterior surgery can be performed. There is no clear evidence of the superiority of one approach over another. Conceptually, posterior stabilization more directly addressed the instability caused by posterior ligamentous complex disruption. A postreduction MRI is usually performed before surgery (Fig. 39-40). Most surgeons feel uncomfortable
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performing posterior surgery alone in the presence of a herniated disc after reduction in a neurologically intact patient. Anterior surgery can be performed to carefully remove the herniated disc.
FIGURE 39-38 If surgery is elected to stabilize a facet fracture, it is the author’s preference to perform an anterior cervical discectomy and fusion.
FIGURE 39-39 If posterior surgery is elected, placement of lateral mass screws may not be technically possible on the injured side. In such cases, unilateral plate fixation combined with interspinous wiring can be performed. (Courtesy John Sledge, MD.)
TABLE 39-7 Pearls and Pitfalls: Facet Dislocations
Pearls Pitfalls
Prereduction MRI in unexaminable patients. Overcompression of posterior construct (may lead to disc extrusion).
If herniated disc present on postreduction MRI, anterior approach is advised. Anterior stabilization alone prone to failure if end plates are fractured or facet joints overdistracted.
Anterior approach may save motion segments if facet fracture(s) present. Avoid overdistraction when placing an anterior interbody graft.
There are pitfalls to both approaches. Anterior discectomy and fusion involves resection of one of the major remaining stabilizing structures—the anterior longitudinal ligament. In these approaches, one can easily overdistract the disc space while sizing and placing grafts. This can leave the facet joints gapped posteriorly, which can obviate posterior column load
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sharing. Improper fit of the interbody device can place greater demands on the anterior plate and screws, which can lead to early hardware failure.
FIGURE 39-40 Lateral cervical x-ray of a patient with bilateral facet subluxations (A). A postreduction MRI should be performed before surgery to detect the presence of a postreduction herniated disc (B). If a herniated disc is present, most surgeons would elect to perform an anterior discectomy and fusion.
During posterior surgery, in particular lateral mass screw placement, injury to the adjacent intact facet joints should be avoided. Although posterior compression can aid in articular apposition, overcompression can increase intradiscal pressure. This can cause intraoperative disc herniations that have the potential to cause additional neurologic injury. Intraoperative spinal cord monitoring is useful in such situations.
Combined anterior and posterior surgery may also be performed. This is usually reserved for patients with more severe or missed injuries with fixed deformities. It is the author’s preference to perform anterior surgery followed by posterior stabilization for patients with highly unstable bilateral facet dislocations. If the facets are gapped or kyphosis remains after anterior surgery, posterior instrumentation is performed to avoid catastrophic construct failure. Anterior and posterior surgery are rarely necessary for unilateral dislocations.
Published Results
Feldborg Nielson et al (114) found anterior fusion to result in better pain relief than posterior wiring without fusion for facet dislocations. The authors attributed this to persistent residual motion in the unfused cases. Razack et al (115) performed single-level anterior fusion with a titanium locking plate in 22 patients with bilateral facet fracture-dislocations. At an average follow-up of 32 months, only one case of instrumentation failure was reported, though all patients eventually had solid fusion and achieved stability. Vital et al (116) found that 91 bilateral facet dislocations could be successfully reduced using traction in 43%, manipulation under general anesthesia in 30%, and anterior surgical reduction in 27% of cases. Anterior discectomy and plate fixation was performed in all patients as definitive treatment. Shapiro (117) reported results of a series of 24 patients with unilateral facet dislocations. Although halo treatment was attempted in two patients who had undergone successful closed reduction, they had recurrent dislocations and eventually underwent surgery. Thus, all 24 patients underwent posterior interspinous process wiring. Fusion was successful in 23 (96%) of cases. In a later study by the same group (117), comparable clinical results were reported with interspinous wiring with lateral mass plate versus facet wiring with iliac crest for unilateral facet dislocations. Greater maintenance of kyphotic correction was observed in the plate group compared to the facet wire and iliac crest graft group. In a review of their cases, Beyer and Cabenela (72) and Beyer et al (73) found that unilateral facet dislocations or fracture-dislocations were better treated with operative
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intervention, because nonoperative management led to an unacceptably high rate of late pain and instability. In a series of 36 patients, 36% of patients treated with a halo-fixator demonstrated anatomic alignment compared to 60% in the operative group.
Pedicle and Lamina Fractures
Unilateral pedicle fractures are usually considered rotational injuries. For this reason, their evaluation and treatment is similar to that for unilateral facet fractures. Bilateral pedicle fractures may be a sign of higher-energy injury. A high index of suspicion for unstable ligamentous discontinuity should be maintained.
Lamina fractures, by themselves, are usually benign. They are frequently associated with other more significant fractures or dislocations. Multilevel lamina fractures can suggest a hyperextension mechanism of injury. Careful inspection of the uniformity of the disc spaces and the integrity of the anterior longitudinal ligament on an MRI scan help detect occult anterior tension band disruption.
Anterior Tension Band Injuries
Disruption of the anterior longitudinal ligament can be associated with vertebral body fractures that are not extensive, usually avulsion fractures near the anterior end plate (118). Abnormal widening the disc space is the clue to diagnosis (Fig. 39-41). They can be associated with posterior fractures or gross posterior ligamentous complex disruption, in which case sagittal and coronal malalignment is present. Anterior tension band injuries should be considered unstable.
Nonoperative Treatment
These injuries are usually highly unstable. Thus, nonoperative treatment is rarely considered a definitive treatment. In cases in which the patient is too sick to undergo surgery, and is intact, a flexion moment can reapproximate the vertebral bodies. If reduction can be maintained, bony ankylosis of the disc space can occur. Flexion-extension views must be obtained to confirm adequate stability.
Operative Treatment
Anterior tension band disruption, consisting of discontinuity of the anterior longitudinal ligament, intervertebral disc, and possibly the posterior longitudinal ligament, is an ideal indication for anterior surgery. An anterior discectomy and plating with fusion can restore the tension band in its mechanical sense, just as posterior fixation addresses posterior ligamentous complex disruption with bilateral facet dislocations. To the author’s knowledge, there are no dedicated series of surgical fixation of anterior tension band injuries. Because the proposed mechanism is similar, extension-type cervical teardrop fractures can be successfully treated with anterior or posterior surgery.
FIGURE 39-41 Disruption of the anterior tension bend is evidenced by widening of the disc space at the injured level, as demonstrated in this lateral x-ray. This should be considered an unstable injury.
MISCELLANEOUS INJURIES
Cervical Injuries of the Ankylosed and Spondylotic Spine
Patients who present with neck pain or neurologic deficit after major or minor trauma should be considered to have a cervical spine injury until proven otherwise. Degenerative spondylotic changes, such as vertebral body osteophytes, fixed subluxations, and facet hypertrophy can make plain films difficult to interpret. Unless a frank dislocation, translational, or intervertebral widening deformity is present, plain x-rays may not be helpful in detecting a level of injury. In these situations, CT and MRI are invaluable in demonstrating areas of preexisting stenosis, with MRI having obvious advantages in demonstrating areas of spinal cord contusion, edema, and constriction.
There are a number of specific areas that warrant particular discussion. Two of the more problematic are (a) fractures in patients with ankylosing spondylitis and diffuse idiopathic skeletal
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hyperostosis and (b) spinal cord injuries in patients with cervical spondylosis without ligamentous or bony instability.
Fractures with Ankylosing Spondylitis and Diffuse Idiopathic Skeletal Hyperostosis
The ankylosed spine should be considered as a long bone rather than the normal spinal column of articulating vertebrae. Bridging osteophytes, whether marginal as in ankylosing spondylitis (Fig. 39-42A) or nonmarginal and flowing as in diffuse idiopathic skeletal hyperostosis are the x-ray hallmarks of these diseases. They effectively fuse the spine into a solid, continuous piece of bone. As is true for an adult long bone (for example, femur) fracture, if there is a break in one region, it is likely to have propagated through both the anterior and posterior elements (Fig. 39-42B,C). Thus, fractures in patients with diffuse idiopathic skeletal hyperostosis or ankylosing spondylitis are almost universally unstable and should be treated as such.
The key to caring for patients with diffuse idiopathic skeletal hyperostosis or ankylosing spondylitis cervical fractures is early recognition in order to avoid catastrophic neurologic decline. Diagnosis is often missed, resulting in a very high rate of neurologic deficits in previously intact patients (119). Among all cervical fractures, ankylosing spondylitis has been demonstrated to be a significant risk factor for neurologic worsening (120,121). Patients should be immobilized as soon as the diagnosis is made, admitted to the hospital, and placed on strict log-roll precautions until definitive management has been decided. Patients with ankylosing spondylitis, with or without fracture, are predisposed to developing neurologic decline from epidural hematomata.
There are very little data available concerning the optimal treatment. There are advocates of nonoperative treatment. Halo fixation has been used to successfully maintain alignment and prevent displacement in patients with and without neurologic deficit (122); however, skin breakdown remains a concern, particular in patients who will remain recumbent for an extended period. Both anterior and posterior surgery have been advocated as well (123,124). Key principles in management should be kept in mind, regardless of the approach taken.
When placing patients in traction, the preexisting kyphotic deformity that is often present must be considered. Thus, inline traction, as is effectively used for most other cases, can lead to gross displacement and neural impingement. The awake patient should help guide the position of comfort when applying traction vectors. In cases of ankylosing spondylosis, kyphotic deformities usually necessitate a flexion vector.
This same concept is important when considering operative fixation. Both anterior and posterior implants should be contoured to fix the patients specific anatomy. Unless a concomitant osteotomy is being planned at the same time, internal fixation of the fracture should maintain or approximate the preinjury posture of the neck. This can often necessitate unusual implant contouring (Fig. 39-42D).
Spinal Cord Injury without Instability in the Spondylotic Spine
Patients often present with complete or incomplete spinal cord injury without x-ray signs of a frank injury, fracture, or ligamentous instability. Underlying cervical stenosis is often present, which can arise from degenerative changes or congenitally narrow canal (Fig. 39-43). This apparently increases the risk for neural injury with abrupt movements of the neck that otherwise are not severe enough to cause a mechanically destabilizing fracture or ligament injury.
There are few data concerning the best treatment. Nonoperative treatment can include a period of observation, in particular for patients with central cord lesions, in which a high percentage will have nearly complete resolution of their neural deficits. Long-term treatment is influenced by the presence of persistent signs or symptoms or myelopathy. Immobilization in a rigid cervical collar can be useful to avoid the extremes of motion, although patients usually will not voluntarily move their neck beyond these limits.
FIGURE 39-42 Lateral cervical x-ray of a patient with ankylosing spondylitis who was complaining of neck pain after a fall 2 days before presentation (A). Note the hallmarks of marginal bridging osteophytes. Also, note that this single lateral x-ray is inadequate because it does not allow visualization of the cervicothoracic junction. This is best seen on CT (B), which demonstrates a fracture through the ossified disc space. An MRI (C) confirms the presence of posterior soft tissue injury. Staged posterior and anterior surgery was performed. Note the reverse contouring of the anterior plate (D).
FIGURE 39-43 MRI of a patient who presented with central cord syndrome (A). Note the high signal intensity within the spinal cord at the level of the injury. His acute spinal cord injury quickly resolved over a few days following the injury. An anterior decompression was performed on an elective basis 6 weeks after injury for persistent imbalance, diminished upper extremity dexterity, and other myelopathic signs (B).
The role and timing of surgery is controversial. In a retrospective study, early surgery for patients with incomplete spinal cord injuries resulted in earlier neurologic recovery, with better motor scores at 1 month and 6 months (125). However, at 2 years, there was no statistically significant difference between the operative and nonoperative groups (125).
In the author’s practice, operative treatment is delayed. Following resolution of spinal shock, patients are observed for signs of neurologic recovery over a period of 2 to 3 days. If there are no signs of neurologic return, surgical decompression is performed with the hopes of improving the rate of recovery. Provided that neurologic examination demonstrates improvements in motor strength, surgery is postponed. Many patients will have complete motor and sensory recovery but demonstrate residual signs and symptoms of myelopathy (such as walking imbalance, diminished finger dexterity). In such cases, a decompressive procedure is performed electively weeks after the injury.
Gunshot Wounds to the Lower Cervical Spine
There is little information regarding cervical gunshot wounds. Kupcha et al (126) reviewed the records of 28 patients. Laminectomy was performed in 4 patients and anterior corpectomy in 1 patient, with no neurologic improvement compared to nondecompressed cases. Neck exploration was undertaken for vascular damage in 4 cases, expanding hematoma in 2 cases, and airway difficulty in 3 cases. Long-term complications were primarily thromboembolism, pulmonary congestion, and urinary tract infection. Post-traumatic syrinx developed in 2 patients. Fistulae occurred in 2 operatively and 2 nonoperatively treated patients. Despite a lack of description of the antibiotic regimen, only 1 case of spinal infection (meningitis) was reported. From these limited data, it seems that care of cervical gunshot wounds should be guided by similar general principles of other regions.
Decompression or bullet removal at the cervical cord level
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is probably not useful in improving static neural deficit, although it may be beneficial in cases of neurologic progression. Laminectomy can be useful, but should be accompanied by appropriate instrumentation and fusion (11). Extended antibiotic prophylaxis is prudent after pharyngeal, hypopharyngeal, or airway violations. The decision to surgically explore neck wounds should be dictated by the severity of extraspinal pathology.
The role of antibiotic prophylaxis after esophageal and upper airway perforation is less clear. Pooled secretions in the hypopharynx are thought to increase the propensity for infection with gunshots involving this structure. The decision to explore such wounds is usually based on the size of the lesion, because small rents can effectively be treated nonoperatively. To the authors’ knowledge, there are no controlled studies of the effects of antibiotic prophylaxis duration after upper airway injuries associated with gunshot wounds to the spine. Notwithstanding evidence of frank infection or meningitis, it is prudent to extend prophylaxis for at least 48 to 72 hours. Delayed exploration for developing neck infections is recommended, though the role of cervical gunshot wound debridement remains to be defined.
Vertebral Artery (Transverse) Foramen Fractures
The vertebral artery within the subaxial spine can be injured after cervical trauma. The mechanism of injury can be occlusion, laceration, or distractive avulsion. Vertebral artery injury can occur with fractures of the transverse processes, through which the vertebral artery passes. MR arteriograms are an effective means of noninvasive diagnosis of vertebral artery occlusion or narrowing following cervical trauma. Formal dye-injection arteriography is another option.
The incidence of vertebral artery injury following lower cervical spine trauma has been reported to be as high as 25% to 46% (127,128,129). They have been associated with facet dislocations, facet fractures with translation, and transverse foramen fractures (129). The vast majority of injuries are unilateral, which fortunately have a very low rate of clinical sequelae (130). In most cases, no specific treatment is necessary. However, the
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detection of the injury can have important influences on overall treatment decision making. The surgeon must consider the consequences of surgical techniques that can incur some risk to the vertebral artery, such as lateral mass screw placement or C1–C2 transarticular screw insertion. It may be prudent to avoid such procedures on the unaffected side, which can potentially lead to bilateral vertebral artery occlusion.
Bilateral vertebral artery injuries can be devastating, leading to cerebellar infarction. This has been reported in patients with severe dislocations of the subaxial cervical spine (131). This may prompt recanalizing pharmacologic or angiographic therapies.
C7 Spinous Process (Clay Shoveler’s Fractures)
By themselves, lower spinous process fractures are usually benign injuries. The so-called clay shoveler’s fracture is thought to occur from powerful contraction of the muscles that insert onto the spinous process. However, spinous process fractures can be present with lamina fractures, facet dislocations, and various other more significant injuries. An early report described spinous process fractures that are associated with bilateral lamina fractures as a sentinel sign to possible neurologic deterioration (132). It is thought that the floating posterior arch can be pushed forward into the spinal canal.
COMPLICATIONS OF SURGERY
Complications Specific to the Anterior Approach
The most common complication of anterior cervical surgery is swallowing difficulty or dysphagia, which may occur in up to 50% of cases. Recurrent laryngeal nerve palsy, which presents with dysphonia, occurs in approximately 4% to 5% of the time. Risk factors include exposure below C5 and revision surgery. Horner’s syndrome is an infrequent complication of the anterior cervical approach. It can occur from damage to the sympathetic plexus that may occur from overzealous retraction of the longus colli. It presents with ptosis, meiosis, and anhydrosis. Before closure of an anterior neck wound, the esophagus should be inspected for tears. Unrecognized tears, whether caused by the initial trauma or iatrogenic, should be repaired primarily to avoid deep infection. Large traumatic tears may sometimes require a rotational muscle flap from the sternocleidomastoid for coverage.
General Perioperative Complications
In the immediate postoperative period, the most devastating thing that can occur is worsened neurologic deficit. Outside of a recognized intraoperative event such as a direct spinal cord injury or posterior strut or graft displacement, a careful and detailed examination should be performed by the same practitioner who had been serially examining the patient preoperatively. It should be determined if the new deficit is above, at, or below the level at which surgery was performed and whether or not it represents a root or spinal cord injury. Plain x-rays of the operated region should be obtained first to see if catastrophic failure of the construct has occurred. If a second, missed, noncontiguous spinal lesion is suspected, a full series of cervical, thoracic, and lumbar spine films should be obtained immediately. There should be little hesitation to obtain a postoperative CT or MRI. It is for this reason that the author prefers to use titanium instrumentation, which is MRI-compatible. Screw, strut, and graft placement should be assessed to detect any impingement on the spinal canal, nerve roots, or vertebral arteries. Hardware that appears to be a likely cause of neural deficit should be removed in the operating as soon as possible.
Dural tears, whether traumatic or iatrogenic, should be repaired primarily. It is the author’s preference to use 6-0 Prolene in a running locking pattern to achieve watertight closure. In cases of large, irreparable injuries, as is common with burst fractures, a fascial graft should be sewn into place. A wound drain should not be placed in presence of a dural tear, and the patient should be covered with an antibiotic that crosses the blood–brain barrier, such as ceftriaxone, until all wound drainage stops. If a persistent leak develops, a subarachnoid lumbar drain can be placed. If the leak does not stop, the tear should be re-explored and repaired to avoid formation of a spinal-cutaneous fistula.
Early Postoperative Complications
Wound infections are among the more common early postoperative complications. The rate does not appear to be significantly higher in patients undergoing anterior cervical surgery who have a preexisting tracheostomy (133). In general, posterior surgery appears to have a slightly higher rate of infection than anterior cervical surgery.
Superficial infections usually occur within the first 10 days after surgery and may be adequately treated with oral antibiotics and local wound care. Wounds should be closely monitored, however. If they do not appear to be responding to treatment, as evidenced by increasing rubor, drainage, and pain, then early intraoperative irrigation and debridement should be performed. Intraoperative cultures are important in determining the most appropriate antibiotic regimen. Well-fixed instrumentation and bone graft should be left in place to maintain stability and promote eventual fusion. Aggressive, early surgical debridement of deep infections can help avoid late-onset osteomyelitis, epidural abscess, meningitis, and catastrophic instrumentation failure.
Late Postoperative Complications
Pseudarthrosis and hardware failure are among the more common late surgical complications. Symptomatic anterior pseudarthrosis can be treated with repeat anterior surgery, or, preferably, posterior instrumentation and fusion. Early hardware failure can be associated with insufficiently stable constructs. Multilevel (three or more) corpectomies stabilized with anterior fixation alone have a high rate of failure and should be routinely stabilized with posterior instrumentation and fusion. Anterior graft or plate extrusion can lead to swallowing difficulty or,
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more seriously, airway compromise. Late hardware failure, such as screw breakage, is often associated with nonunion, which may or may not be symptomatic or require treatement
CONTROVERSIES AND FUTURE DIRECTIONS
As with most of spine surgery, controversy remains about various aspects of treatment of lower cervical spine injuries. The benefits of early decompression of spinal cord injuries has also been, and will continue to be, a focus of heated discussion. Debate will no doubt continue concerning the safety of awake, immediate reductions for patients with facet dislocations and the role of a prereduction MRI. Likewise, controversy about the optimal surgical treatment of these injuries will continue, because many still feel that anterior surgery alone is doomed to fail.
With a genuine lack of scientific data, the optimal treatment of facet fractures is likely to remain controversial. Although some feel strongly that nearly all can be treated by nonoperative means, regardless of the development of small amounts of displacement, others remain firm that the injury should not be underestimated and requires surgical stabilization in most cases. This controversy represents, in the author’s opinion, a glaring example of the lack of understanding of the natural history of such a seemingly benign injury. It underscores the need to look further into the injury patterns and perhaps rely more heavily on MRI to stratify concomitant ligamentous injuries.
Although advances in better stabilization methods, whether they be minimally invasive or motion sparing, are on the horizon, their utility and role will depend on a better understanding of spinal injuries. In anticipation of these times, future efforts should be focused on developing a usable, reproducible, and reliable injury description system, upon which a prognostic and treatment-influencing classification system can be built.
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