Epidemiology

Accidents are the fourth leading cause of death in the United States, after heart disease, cancer, and stroke, and account for approximately 50 deaths per 100,000 population annually.⁵ Early deaths tend to result from exsanguination, whereas later posttraumatic deaths (those occurring after the first hour of hospitalization) tend to result from severe neurological injury.⁶

The prevalence of spinal cord injury varies for different geographic regions, as well as for different groups according to age, gender, and race.^7–9 Spinal cord injuries, like most traumatic injuries, tend to occur in a young, predominantly male population, although a second peak is observed in the elderly.⁷ Young males are affected 3 to 20 times more often than females.^7,10,11 In the elderly, there does not appear to be a difference in the relative number of men versus women affected, although this is in part explained by the much smaller number of men making up an elderly population.⁷

Estimates of the number of patients living with a spinal cord injury in the United States alone range from 185,000 to 400,000. Approximately 2000 U.S. hospital beds are required each year for the care of these patients.¹² According to Kraus and colleagues, of the approximately 14,000 people who sustain spinal cord injuries each year, 4200 die before reaching the hospital and an additional 1500 patients die during the initial hospitalization.¹³

Although cervical spine fractures account for 20% to 30% of all spine fractures, cervical spinal cord injuries make up more than half of all spinal cord injuries. Fortunately, only 10% to 20% of cervical fractures result in spinal cord injuries.¹⁴ Cervical cord injuries result in profound physical disability and have a considerable societal impact. In 1990, the direct cost of spinal cord injury was estimated to be $4 billion, with lost wages being estimated at $3.4 billion.¹⁵

Reliable estimates of the prevalence of cervical spine injury after trauma are difficult to make because the inclusion criteria for various studies differ markedly. In addition, the proportion of cervical fractures that are found to be unstable is not clearly known. Most authors suggest that cervical injuries occur in 2% to 6.6% of patients after blunt trauma.^16–19

A recent meta-analysis of 65 studies published between 1985 and 2008 attempted to determine the prevalence of cervical spine fracture and also to define the rate of instability.²⁰ These authors found an overall 3.7% incidence of traumatic cervical spine injury. However, there was a significant difference observed according to the level of consciousness. In alert patients, the prevalence of cervical spine injury was 2.8%, whereas patients who could not be evaluated clinically (intoxicated, altered mentation) were found to have a prevalence of 7.7%. In addition, for all detected cervical spine injuries, 41.9% were subsequently determined to be unstable.

The likelihood of a concomitant cervical spine injury in a patient with a head injury has also been well known since the 1920s²¹ and is reported to range between 4% and 8%.²² The severity of the head injury tends to positively correlate with the likelihood of a spine injury,^22–25 as does the mechanism of the head injury. For example, although vehicle-related head injuries may be associated with an approximately 10% rate of concomitant spine fracture, severe penetrating head injuries such as gunshot wounds are rarely accompanied by spine fractures.²² The spine injuries associated with moderate or severe head injury also more frequently involve the upper cervical spine.

Motor vehicle accidents cause between 35% and 45% of all spinal cord injuries.^7,26 The cervical region is the segment of the spine most frequently injured in vehicular crashes, especially when shoulder and lap belt restraints are not worn.^27,28 The National Crash Severity Study found that in accidents in which the vehicle was damaged severely enough to be towed from the scene, 1 in 300 occupants sustained a severe neck injury.²⁸ A recent study found that for drivers and front seat passengers hospitalized after a crash, 12.5% sustained a spine fracture, the majority of which were cervical.²⁹ This same study found that in these patients severe fractures accounted for only 8% and there appeared to be a protective effect of concomitant seat belt and air bag use. Along similar lines, the overall incidence of severe neck injury increased to 1 in 14 for passengers ejected from the vehicle.²⁸

Falls are the most common cause of cervical spine and spinal cord injuries in the elderly, with more than 70% of injuries in this age group resulting from this mechanism.^30,31 In addition, cervical injuries in young children and toddlers are frequently the result of falls.³² For both extremes of the age spectrum, the injuries sustained in this manner more frequently involve the upper cervical spine and are often of lesser severity.

Age-specific differences in injury patterns and outcomes must be considered during the initial evaluation, as well as during subsequent management. Although younger adult men are the most frequently represented group, injuries in the elderly are becoming more common. Even though the frequency of severe injuries in the elderly is lower, mortality rates are much higher. Coexisting spondylosis or spinal stenosis is often a complicating factor that leads to spinal cord injuries without unstable bony or ligamentous injury. Osteopenia, diffuse idiopathic skeletal hyperostosis, ankylosing spondylitis, congenital or iatrogenic fusions, spinal deformities, and other comorbid conditions may also predispose to certain injury types and greater risk for injury.

Pediatric spinal trauma occurs at an incidence of 1.8 cases per 100,000 population, with 80% of incidents occurring in patients older than 10 years.³³ Pediatric cervical spine injuries occur at different levels according to age group. Although three fourths of injuries in patients younger than 18 years occur below C4, between 70% and 87% of injuries affecting patients younger than 8 years occur at C3 or higher.³³ Upper cervical spine injuries are more likely to be fatal, with atlanto-occipital dislocation (AOD) being associated with mortality rates of 70% to 100%.^33–36

Differences in the anatomy of the pediatric and adult cervical spine are the primary reason for the differences in injury patterns. Young children have a relatively larger head in relation to the cervical spine and supporting structures, which results in a higher center of gravity of the craniocervical region and greater strain on the upper cervical ligaments with trauma. High-speed impacts result in a disproportionate incidence of AOD and other ligamentous injury.

Occipitocervical injuries as a result of air bag deployment have been identified as a specific risk to small children.^37–39 Standard three-point restraints have also been implicated in upper cervical spine injuries in young children.⁴⁰ Greater public awareness of these dangers, coupled with improved pediatric restraint systems and wider use of pediatric safety seats, should reduce the incidence of these life-threatening injuries.

Children older than 11 years appear to have injury patterns more similar to those in adult patients, with injuries more frequently involving C4 or below. Older children are also less likely than younger children to suffer severe cervical spine injury. Although vehicular trauma is the most common mechanism in all pediatric age groups, in older children, sports-related injuries replace falls as the next most common mechanism.⁴¹

Acute Care of Cervical Spine Injuries

Acute Evaluation and Management in the Emergency Department

The initial management of a trauma patient in the emergency department should involve the same assumptions made in the field. A period of stable vital signs after trauma does not imply the absence of serious injury, regardless of the time that has elapsed since the accident. One should not focus exclusively on the spine or spinal cord injury until other injuries have been diagnosed or ruled out. Although the potential for spinal injury must be kept in mind, the strict rules of immobilization must not prevent lifesaving maneuvers from being performed expeditiously.

Respiratory complications are common after cervical spinal cord injuries, and the incidence increases markedly in the presence of other bodily injuries. Furthermore, all cervical spinal cord lesions have the potential for the development of ascending levels of dysfunction because of increasing spinal cord hemorrhage or edema. Therefore, respiratory decompensation can occur at any time during the early stages of resuscitation. Because relative hypoxia can further damage an injured cord, all patients, regardless of the level of their injury, should receive supplemental oxygen. Respiratory function should be reassessed frequently and intubation performed as necessary.

As in the field, maintenance of blood pressure within normal limits is critical. If blood pressure remains low despite resuscitation with intravenous fluids, administration of a pressor such as dopamine (which is advantageous in terms of renal perfusion, has a significant incidence of tachyphylaxis when given with phenytoin [Dilantin], and should be avoided in patients with concomitant significant head injury) should be initiated and titrated to effect. A Foley catheter should be inserted to monitor urinary output and prevent bladder distention in the event that the patient has neurogenic urinary retention from a spinal cord injury.

A full skeletal x-ray series, including the chest and pelvis, should be performed as indicated (also see the section on imaging). This is especially important in a neurologically impaired patient because 11% of fractures associated with head or spinal cord injury are missed in the initial assessment and an unconscious, confused, or neurologically impaired patient may have abdominal pathology that is obscured by the neurological injury.⁵⁹ In addition, cervical spine fractures are often associated with fractures elsewhere in the spinal axis.

Disruption of sympathetic nerve function at T8 or above is frequently associated with hypothermia. Euthermia should be restored by external warming, administration of warmed intravenous fluids, and heated inspired air if the patient is intubated. Although theoretical considerations have supported the concept of controlled hypothermia in spinal cord injury, the limited clinical data available to date do not support widespread application of this strategy in clinical practice.⁶⁰

If the patient must be transported rapidly to the operating room for lifesaving surgery, lateral and anteroposterior radiographs of the cervical spine must be obtained. If possible, the thoracolumbar area should also be imaged in the emergency department, before the patient is moved to the operating room. If there is any question about a cervical or thoracolumbar injury, the patient should remain immobilized in the operating room if possible. Prolonged positioning of a patient on a spine board can result in decubitus ulcers, especially in the context of concomitant hypotension or hypothermia. For this reason, if the spinal axis can be cleared, it should be and the spine board removed. Further studies such as computed tomography (CT), oblique films, or magnetic resonance imaging (MRI) can be performed after the patient is medically stabilized.

If the patient is stable on arrival at the emergency department and emergency surgical intervention is not required, the patient can be assessed from a multisystem point of view, and the vertebral column and spinal cord can be investigated in an orderly fashion. In awake and alert patients, a full neurological examination can be carried out, and the presence or absence of spinal cord injury can be determined definitively. In combative or unconscious patients, a spinal injury must be assumed to be present until specifically ruled out. These patients present special difficulties, especially during transportation and positioning for diagnostic procedures such as CT, MRI, or angiography. All such studies should be carried out with the patient secured in the initial immobilization device if possible.

Injury to the spinal cord occurs because of stretching, crushing, vascular compromise, or compression. Certain types of injury mechanisms are more likely to be associated with specific neurological findings on clinical examination (Fig. 312-1). Spinal cord hemisection leading to Brown-Séquard syndrome usually results from penetrating trauma but may also be seen after trauma with epidural cord compression.⁵⁹ On clinical examination, one finds contralateral dissociated sensory loss (i.e., loss of pain and temperature sensation caudal to the lesion) with preserved light touch because of redundant ipsilateral and contralateral axonal pathways (anterior spinothalamic tract). Ipsilaterally, one finds proprioceptive loss and motor paralysis below the lesion. Among the incomplete spinal cord syndromes, Brown-Séquard syndrome has the best prognosis, with approximately 90% of patients regaining the ability to ambulate independently and control sphincter function.⁶¹

FIGURE 312-1 Spinal cord injury syndromes. A, Hemicord syndrome (Brown-Sequard) is manifested as loss of contralateral pain and temperature sensation with preserved light touch (anterior spinothalamic tract) and ipsilateral loss of motor function and proprioception caudal to the lesion. B, Central cord syndrome is caused by compression of the cord dorsoventrally with central hemorrhage and venous infarction. Clinical manifestations include motor weakness more pronounced in the upper extremities (central gray matter) and variable sensory loss below the lesion combined with sphincter dysfunction. C, Anterior cord syndrome is caused by injury to or compression of the anterior spinal artery with loss of motor function and pain and temperature sensation caudal to the lesion and preservation of joint position, vibratory sensation, and two-point discrimination.

After acute hyperextension injury, frequently in patients with preexisting congenital spinal stenosis, central cord syndrome may be evident.⁶² Patients with this syndrome have greater weakness in the upper extremities than in the lower extremities. Various degrees of sensory disturbance occur below the level of the lesion, and sphincter disturbance is commonly present. Only about half of these patients eventually recover enough neurological function in the lower extremities to ambulate independently.^61,63–65 Recovery of upper extremity function is also poor, and fine motor control is usually absent. Bowel and bladder control is frequently recovered.

In patients who experience vertical compression or hyperflexion injuries, an anterior cord syndrome, also known as anterior spinal artery syndrome, may occur.⁶⁶ Cord infarction in the vascular territory supplied by the anterior spinal artery is the proposed mechanism. These patients exhibit motor and sensory disturbance below the level of the lesion in the presence of intact posterior column function. This leads to a dissociated sensory loss, with loss of pain and temperature sensation caudal to the lesion but preservation of joint position sense and two-point discrimination. Anterior cord syndrome has the poorest prognosis of the incomplete cord syndromes. Only 10% to 20% of patients recover functional motor control and the ability to ambulate.⁶¹

Many potential treatment strategies for acute spinal cord injury have been examined experimentally, including hypothermia, hyperbaric oxygen, electromagnetic fields, immobilization, and various pharmacologic agents given shortly after injury, such as intravenous lidocaine, melatonin, steroids (e.g., dexamethasone, methylprednisolone, 21-aminosteroids), and opiate antagonists such as naloxone.^67–75 Although several earlier studies suggested that naloxone and glucocorticoids were ineffective in the treatment of acute spinal cord injury, other studies showed beneficial effects.^68,76–78 The Second National Acute Spinal Cord Injury Study (NASCIS 2) revealed in a prospective, randomized, double-blind study that high-dose methylprednisolone was associated with improved neurological outcome in spinal cord–injured patients when compared with placebo or naloxone.⁷⁹ This was followed by NASCIS 3, which compared 24- and 48-hour treatment with methylprednisolone with 24-hour treatment with tirilazad, a 21-aminosteroid antioxidant.⁸⁰ The results were stratified by interval between injury and initiation of treatment. The study concluded that if treatment could be initiated within 3 hours after injury, a 24-hour period of treatment with methylprednisolone should be instituted. If the treatment could not be started within 8 hours of injury, steroids were of no benefit. Although there continue to be methodologic questions about the study (e.g., there was no placebo control group), it remains the most complete and definitive study on the subject of pharmacologic treatment of spinal cord injury to date.

If during assessment in the emergency department an acute spinal cord injury is documented, treatment with methylprednisolone sodium succinate (MPSS) should be initiated without delay. To be effective, MPSS must be started within 8 hours of injury and should be given as an initial intravenous bolus of 30 mg/kg administered over a period of 15 minutes. This is followed 45 minutes later by a 5.4-mg/kg per hour continuous infusion of MPSS. If treatment is initiated within 3 hours of injury, the infusion is continued for 23 hours; if treatment is begun between 3 and 8 hours after injury, the infusion is continued for 47 hours (for a total of 48 hours).

A number of other agents have shown promise in the treatment of spinal cord injury, including calcium channel blockers such as nimodipine, modulators of excitotoxicity such as phencyclidine or dextrorphan, and blockers of lipid peroxidation and membrane disruption such as 21-aminosteroids and GM₁ ganglioside.^81–87 Unfortunately at this time, only MPSS has been shown to benefit patients, and even the long-term benefits in patients treated with MPSS remain questionable.^88,89

Imaging

After the primary survey, neurological examination, and external assessment of the spine, the next step in identifying specific spinal injuries is an imaging evaluation. The diagnostic studies performed should be chosen so that they provide maximal information in a relatively short time. Imaging modalities include plain radiographs, fluoroscopy, CT with multiplanar reconstruction, MRI, and myelography. Specific choices for imaging of trauma patients may vary depending on the specific logistics involved at each center.

Plain Radiography

Plain radiography is the foundation of spinal imaging for trauma patients suspected of having a cervical spine injury. Given the potentially devastating consequences of misdiagnosis, a low threshold for obtaining cervical spine films and a high index of suspicion for injury must exist. Indications for a cervical spine series include localized pain, deformity, crepitus or edema, altered mental status, neurological dysfunction, or head injury. In addition, patients with multiple trauma, those whose mechanism of injury suggests the potential for cervical spine injury, and those who have the potential for distracting pain from other injuries or are intoxicated should undergo cervical spine radiography.

A complete cervical spine series consists of a lateral cervical projection, an anteroposterior view, an open-mouth view of the odontoid, and oblique films.^90,91 A pillar view, a swimmer’s view, and dynamic studies are supplemental and may be considered to more fully evaluate the extent of injury.^91,92 The optimal plain film evaluation of the cervical spine depends on the patient’s clinical condition and neurological status and the circumstances and magnitude of the injury.

A cross-table lateral view should be the first film obtained in the cervical spine series, and in patients with multiple trauma, this film should precede all others. This projection is accurate in revealing posttraumatic abnormalities approximately 70% to 83% of the time.^{90,91,93–98} Completion of the series, however, markedly increases its sensitivity.^{90,93,94,99,100}

The initial cross-table film should be performed without traction because of the potential for atlanto-occipital or atlantoaxial dissociation or other major ligamentous disruption.¹⁰¹ However, this initial film is frequently inadequate to assess the lower cervical spine. Optimal visualization on the lateral projection should include the C7-T1 disk space. Depression of the shoulders by pulling down on the arms will frequently allow visualization when not precluded by other injuries. In some patients, a swimmer’s view may be required to visualize the cervicothoracic junction.

The lateral films should be evaluated for alignment, bony abnormalities, disk space abnormalities, and soft tissue abnormalities. Although careful evaluation of the bony anatomy is of primary importance, close attention should also be paid to soft tissue details. Subtle findings such as prevertebral swelling may be the only radiologic sign of an acute injury on plain radiography.^102,103

The anteroposterior view, although useful for evaluating the lower five cervical vertebrae and the upper thoracic vertebrae, is limited superiorly by superimposition of the mandible and the occiput. For this reason, the upper cervical spine is not well visualized. The superior and inferior end plates, uncinate processes, joints of Luschka, and lateral cortical margins can easily be evaluated. Superimposition of the lateral masses makes evaluation of the bases of the facet joints difficult. The spinous processes can easily be seen as a vertical row in the midline. Widening between any two processes or rotation of spinous processes with respect to the others may indicate a hyperflexion injury or a facet dislocation. The trachea is also well seen as a midline air shadow on this view. Lateral displacement of this shadow may indicate hematoma or edema caused by trauma.

The open-mouth view provides an anteroposterior projection of the upper cervical spine. Because of the opening of the mouth, the mandible is no longer superimposed on C1 and C2, which can now be well visualized. From this view, one can evaluate the coronal alignment of the atlas and the axis, and the dens should be centered between the lateral masses of the atlas. In addition, fractures of the atlas and axis, notably Jefferson’s fracture and fracture of the dens, can be evaluated. The open-mouth view does have limitations, however, such as when jaw opening is limited by facial injuries or when intubation is required. In some individuals, the anatomy is also obscured by the occipital bone or the teeth.

Oblique cervical spine films are useful for visualizing the uncinate processes of the vertebral bodies, laminae, pedicles, intervertebral foramina, articular masses, and interfacetal joints. Because the contralateral facets are obscured by the overlying vertebral bodies, bilateral oblique films are necessary for a complete evaluation.

The pillar view allows direct visualization of the individual lateral masses. In addition, the dens can be assessed if the open-mouth view is difficult or inadequate. Miller and colleagues recommended inclusion of the pillar view in all radiographic assessments of the cervical spine after trauma.¹⁰⁴ Because significant head rotation is required for this view, it has largely been supplanted by evaluation with CT.

The swimmer’ projection is another means of evaluating the cervicothoracic junction when the patient’s shoulders obscure the lower cervical spine despite arm traction. For this view, the patient is rotated slightly off true lateral and one arm is abducted 180 degrees and extended cranially while the other is extended caudally. Although these images can be helpful, they have also largely been replaced by CT.

Flexion-extension films are frequently advocated to assess ligamentous integrity in intact patients after trauma. They are clearly contraindicated in a patient with a neurological deficit, obvious fracture, or instability or in a patient with a history of a transient, resolved deficit after trauma. Acute intoxication, disorientation, and heavy analgesic administration are also contraindications. The confounding aspects of pain or muscle spasm limiting full mobility are also problematic in the acute setting. Because of the aforementioned considerations, a number of authors have found flexion-extension radiographs to be of no benefit acutely.^105–108 As MRI is increasingly becoming available, ligamentous integrity is frequently being assessed by this means.

Asymptomatic Patients

It has long been recommended that all trauma patients undergo radiographic evaluation of the cervical spine. Conversely, a policy of imaging all trauma patients has been challenged because of the issues of unnecessary radiation exposure, overuse of resources, and increased cost.^109–113 It is estimated that more than 1 million patients with blunt trauma and some potential for cervical spine injuries are seen in U.S. emergency departments annually.¹¹⁴ Several authors have found, however, that for neurologically intact patients, the incidence of spinal injury or acute fracture is less than 1%.^115–117 Consequently, there have been a number of efforts to identify clinical decision rules that would be highly sensitive for the detection of cervical spine injuries in patients who are alert and stable, thus providing both greater consistency and selectivity in the use of radiography.^113,118,119 Hoffman and coworkers proposed five criteria that classified patients as having a low probability of injury (Table 312-1). When applied to 34,069 patients undergoing cervical spine radiography, these criteria identified all but 8 of the 818 patients who had cervical spine injuries (sensitivity of 99%).¹¹⁸ Of these 8 patients falsely identified as being unlikely to have an injury, only 2 had what was previously defined by the authors as a “clinically significant” injury. According to the authors, use of the criteria would have avoided imaging in 12.6% of the overall 34,069 patients studied. In another similar effort, the Canadian C-Spine Rule (CCR) investigators developed an algorithm based on three determinations: a high-risk factor necessitating radiography; low-risk factors, one or more of which allow assessment of range of motion; and active assessment of range of motion (Fig. 312-2). In a subsequent study of 8924 patients in which the incidence of cervical spine injury was 1.7%, the CCR was found to be 100% sensitive and 42.5% specific for “significant”injuries.¹¹⁹

TABLE 312-1 The NEXUS Low-Risk Criteria

Cervical spine imaging is recommended for patients with trauma unless they meet all of the following criteria: Absence of posterior midline cervical spine tenderness No evidence of intoxication A normal level of alertness and consciousness (baseline mental status) Absence of focal neurological deficit Absence of any distracting injuries

From Hoffman JR, Wolfson AB, Todd K, et al. Selective cervical spine radiography in blunt trauma: methodology of the National Emergency X-Radiography Utilization Study (NEXUS). Ann Emerg Med. 1998;32:461-469.

FIGURE 312-2 The Canadian C-Spine Rule. It is to be used on alert (Glasgow Coma Scale score of 15), stable patients without neurological symptoms.

(Adapted from Stiell IG, Wells GA, Vandeheem K, et al. The Canadian C-Spine rule study for alert and stable trauma patients. JAMA. 286:1841-1848, 2001.)

In 2002, recommendations were published in a supplement to Neurosurgery regarding radiographic assessment of asymptomatic trauma patients.¹²⁰ In the discussion, asymptomatic patients were defined as those who

1 Are neurologically normal. These patients must have a Glasgow Coma Scale score of 15 and must not have any of the following: (a) disorientation to person, place, or time; (b) inability to remember three objects at 5 minutes; (c) delayed or inappropriate response to external stimuli; or (d) any focal motor or sensory deficit.

2 Are not intoxicated. Patients should be considered to be intoxicated if they have (a) a recent history of intoxication or intoxicating ingestion; (b) evidence of intoxication on clinical examination; or (c) laboratory evidence of the presence of drugs that alter the level of alertness, including blood alcohol levels higher than 0.08 mg/dL.

3 Do not have neck pain or midline tenderness. Midline tenderness is present if the patient complains of pain on palpation of the posterior midline of the neck from the nuchal ridge to the first thoracic vertebra.

4 Do not have an associated injury that is distracting to the patient. Significant distracting injuries have been defined as (a) long-bone fractures; (b) visceral injuries requiring surgical consultation; (c) large lacerations, degloving, or crush injuries; (d) large burns; and (e) any other injury that might impair the patient’s ability to participate in a general physical, mental, and neurological examination.

It has been estimated that approximately a third of patients evaluated in emergency departments will be asymptomatic according to these criteria.^118,121,122 With this definition in mind, the literature was reviewed and found to contain nine class I studies and numerous reports of class II and class III evidence. The resulting conclusion of this review is that asymptomatic patients “do not require radiographic assessment of the cervical spine after trauma.” Nonetheless, the incidence of cervical spine injuries in asymptomatic patients from the various study cohorts ranged from 1.9% to 6.2%.

Despite the aforementioned studies, considerable variability remains in practice. Comparison of the National Emergency X-Radiography Utilization Study (NEXUS) and CCR rules suggests that the latter may have greater sensitivity, yet many physicians are reluctant to perform an adequate range-of-motion assessment.¹²³ Both methods, when consistently and accurately applied, would appear to perform better than unstructured physician judgment and have the potential to reduce cervical spine radiographs in nearly a third of patients with blunt injuries.¹²⁴

Computed Tomography

At the present time, CT is the tomographic method of choice for the evaluation of acute spinal trauma.¹²⁵ Thin-section CT should be used to further evaluate areas of obvious or suspected cervical spine injury detected on plain radiography.^43,125–128 CT is also indicated if the plain film study is inconsistent with the patient’s clinical condition, for injuries resulting in neurological deficit, for fractures involving the posterior arch of the cervical canal, and for every fracture with suspected retropulsion of bone fragments into the canal.^129,130 CT should usually precede other supplemental studies, including MRI, dynamic studies, and digital subtraction angiography (DSA).

A potential exception to the rule of proceeding directly to CT after demonstration of an injury on initial cervical spine films may be patients with a fracture-dislocation or other subluxation and an acute neurological deficit. In these patients, early decompression of the cord is paramount, and every effort should be made to reduce the malalignment as rapidly as possible.^3,130 Application of Gardner-Wells tongs or a similar device followed by the application of traction in a controlled fashion with frequent monitoring via fluoroscopy or lateral plain films should be considered if feasible. Once alignment has been restored or an inability to effect reduction has been established, CT or in some cases MRI is then performed.

With CT, bone is imaged in exquisite detail, with clear demonstration of even small cortical disruptions, and encroachment of bone on the spinal canal can easily be seen. This is particularly useful for C1 and C2 fractures because the precise fracture subtype is often difficult to discern on plain films.^131–133 Combination fractures involving both the atlas and axis are difficult to assess without CT, and axial views are particularly useful for evaluating injuries to the vertebral body and posterior elements.^131,133 Reformatted images in the sagittal and coronal planes are now routinely performed at most centers. Images reformatted in oblique planes may also be obtained.¹⁰² Three-dimensional reformatted CT images are also occasionally of use in understanding complex fractures, although the processing time and the technical aspect required to produce these images may limit their use in the acute setting.⁹⁸

When the sensitivity of CT for the detection of cervical spine injuries has been compared with that of plain radiographs, CT is significantly better (e.g., 98% versus 52%), which has caused some to advocate it as the initial screening test for the cervical spine in high-risk patients.¹³⁴

Magnetic Resonance Imaging

MRI is increasingly being used for the acute evaluation of injuries to the cervical spine and spinal cord. Technical improvements in spinal imaging, reductions in scanning time, and increased availability of life support equipment and traction devices compatible with high magnetic fields have increased the utility and safety of these examinations in trauma patients. Because the spinal cord and surrounding structures can readily be visualized in noninvasive fashion, MRI has generally replaced contrast-enhanced myelography and postmyelography CT for the evaluation of cord compression and other intraspinal traumatic lesions.

In addition, MRI provides imaging of the ligaments, muscles, and other surrounding soft tissues. Spinal epidural hematomas, intramedullary hematomas, spinal cord contusions, myelomalacia, and spinal cord edema are usually, but not always well visualized with MRI.^135–142

MRI can directly demonstrate disruption of some ligamentous structures of the cervical spine that cannot be visualized with other radiologic techniques, such as the transverse ligament at C1-2.^137,143,144

Cervical imaging with MRI can also permit delineation of the vertebral arteries and can detect injury, although CT angiography (CTA) and DSA remain the primary means of diagnosing vascular abnormalities. Some centers use two-dimensional time-of-flight MR angiography (MRA) sequences to increase sensitivity for vascular injury. Using this methodology, Friedman and colleagues identified vertebral artery injuries in 24% of patients with severe, nonpenetrating cervical spine trauma.¹⁴⁵

Because of the ability to visualize injury to soft tissues such as ligaments, muscles, and joint capsules, there is considerable interest in the use of MRI to “clear” the spine in patients with inconclusive or negative plain films or CT who cannot be evaluated or nonetheless are suspected of having a serious injury. Benzel and associates performed MRI on a series of 174 patients with clinical features worrisome for an occult injury but with normal findings on plain radiography. Soft tissue abnormalities, including disk disruptions and ligamentous injuries, were found in 36%.¹⁴⁶

A meta-analysis of five studies investigating the use of MRI for evaluating patients with suspected cervical spine trauma (level I data) found a negative predictive value of 100% and therefore concluded that MRI could be considered a “gold standard” for clearance of the cervical spine; however, the false-positive rate could not be fully determined in this review.¹⁴⁷

The specific indications for MRI in trauma patients and the optimal timing of the study continue to be somewhat controversial. As discussed later in this chapter, some authors have argued for early MRI before closed reduction of cervical fractures and dislocations. Other indications for early imaging include patients with spinal cord injury without radiographic abnormality (SCIWORA) on plain films and CT, suspected cases of traumatic disk herniation or epidural hematoma, and patients with acute central cord syndrome and spinal stenosis. In most other circumstances, MRI is performed subacutely and is an aid to surgical planning and estimation of neurological prognosis.

Myelography

Intrathecal administration of water-soluble contrast medium, followed by plain radiography or CT, provides visualization of the spinal cord silhouette, subarachnoid space, and nerve roots. It demonstrates intramedullary and extramedullary mass lesions, obstruction to flow of cerebrospinal fluid (CSF), root avulsions, dural tears, and with delayed CT images, posttraumatic syringomyelia.^148,149 However, very little direct information can be obtained about the intrinsic pathology of the cord in the setting of acute injury, especially when compared with MRI. In the context of trauma, CT after the intrathecal administration of contrast material has largely supplanted the plain film myelography examination because less patient movement is required. If CT myelography is performed in patients with cervical injuries, the contrast agent may be introduced via the lateral C1-2 approach, thereby further minimizing movement of the patient.

These studies can usually be performed rapidly and with low morbidity; patient access is better in the CT scanner than in the MRI scanner, and scanning times are shorter. However, CT myelography is an invasive procedure with specific complications, including a risk for direct spinal cord injury with lateral C1-2 puncture, intraspinal hemorrhage, and adverse reactions to the contrast agent. Moreover, the value of the additional information obtained as compared with plain CT in guiding acute management decisions has been questioned. Thus, the role of plain film myelography or postmyelographic CT in the acute evaluation of traumatic cervical spine injuries remains controversial, and it is often reserved for institutions in which acute MRI capabilities are limited.

Other Imaging Modalities

CTA and, less frequently, MRA have been advocated to detect vertebral artery injuries when cervical fractures or dislocations are thought to be associated with high suspicion for vertebral artery injury.¹⁵⁰ Radionuclide studies have been used historically to detect occult fractures of the spine but have little application in acute trauma.

Classification of Cervical Spine Injuries

Universally accepted classifications of acute cervical spine injuries do not exist. Some of the classifications focus on the neurological aspect without analysis of the bony or soft tissue injury.^151,152 Others subdivide injuries in terms of the specific bony or soft tissue pathology without considering the biomechanics or mechanism of injury.^3,153 Still others focus on the mechanism without addressing the neurological aspects. When the reasons for classifying cervical spine injuries are considered, it seems apparent that the mechanism of injury, pattern of bony or soft tissue disruption, and type and degree of neurological injury are all relevant to such issues as assessment of stability, overall prognosis, selection of treatment, and collection of meaningful outcome data. A number of authors have suggested systems based primarily on injury mechanism.^154,155 Recently, the Spine Trauma Study Group proposed a novel classification system termed the Subaxial Injury Classification and Severity Score (SLIC).¹⁵⁶ This classification scores three major characteristics of the injury: injury morphology, status of the diskoligamentous complex, and neurological status (Table 312-2).

TABLE 312-2 The Subaxial Injury Classification and Severity Score System

Biomechanical studies and autopsy or cadaver experiments have established the fundamental relationships among injury mechanism, force vectors, and the resulting osseous and ligamentous injuries of the spine.^157–163 In such controlled laboratory experiments, pure force vectors such as flexion, extension, vertical compression (axial load), lateral flexion, rotation, or a combination of forces (e.g., simultaneous flexion and rotation) have been shown to produce specific injury patterns. Clinically, however, the causative (vector) force of injury must be inferred from historical, physical, or radiologic evidence because the mechanisms of injury are certainly not controlled. Furthermore, in all probability, the injury is a result of multiple simultaneous forces with one predominant force vector rather than a single pure force. Nonetheless, the similarities observed between the injuries produced in the laboratory with relatively pure force vectors and the patterns seen clinically support the concept that most clinical examples are the result of a predominant injury vector.¹⁶⁴

Two- and Three-Column Concepts

Holdsworth’s two-column concept of the spine is an aid to defining stability in the thoracolumbar spine.^52,165–167 The anterior column is made up of the anterior longitudinal ligament, vertebral body, intervertebral disk, and posterior longitudinal ligament; the posterior column consists of all the skeletal and ligamentous structures posterior to the posterior longitudinal ligament. This concept had been invaluable in understanding the pathophysiology of injuries occurring as a result of flexion, extension, and other forces on the cervical spine. More recently, Denis’ redefinition of this column concept to include a third, middle spinal column has added substantially to our understanding of the biomechanics of injury and to the definitions of instability after cervical spine trauma.¹⁶⁸ The middle column consists of the posterior third of the vertebral body, the anulus fibrosus, and the posterior longitudinal ligament; the posterior column is formed by the posterior neural arch, spinous process, and articular processes and corresponding articular capsules. Although the three-column concept was designed specifically for thoracolumbar fractures, both the two- and three-column models are helpful in further redefining the biomechanics of cervical spine injury as well.

Hyperflexion is caused by forceful forward rotation of the head, which is usually limited by the chin striking the chest wall. Such movement applies distraction forces to the posterior elements and compression forces to the vertebral body and disk (anterior column). Depending on the degree of force, there can be ligamentous damage and bony involvement, including subluxations, bilateral facet dislocations, and compression or avulsion fractures.

Simultaneous flexion plus rotation involves flexion with the head slightly rotated at the outset. Such forces tend to produce partial disruption of the annulus, posterior ligaments, and capsule of the facet joint and result in unilateral dislocation of the facet on the side opposite the direction of rotation.¹⁶⁹ Unilateral facet dislocation may be associated with an impaction fracture of the articular masses on the dislocated facet joint, but such a fracture is not usually a major component of the injury.

Hyperextension injuries involve a force vector applied to the face or forehead with the head rotated backward. Simultaneous distraction of the anterior column and compression of the posterior elements can occur, exactly the reciprocal of a hyperflexion injury. Hyperextension mechanisms can produce injuries such as avulsion of the anterior arch of the atlas, teardrop fractures, hyperextension fracture-dislocations, and hangman’s fractures (traumatic spondylolisthesis).

In extension-rotation injuries, the principal force is either pure hyperextension, with the head already having rotated, or simultaneous rotation and extension caused by an eccentric force vector. This mechanism often results in a pillar fracture.

Vertical compression (axial loading) occurs with forces applied to the top of the head and the cervical spine in a neutral position. Such a force is transmitted through the skull and occipital condyle to the cervical spine and results in burst-type fractures. In the atlas it results in the classic Jefferson burst fracture; in the subaxial spine a burst fracture results, with failure in compression of the anterior and middle columns.

In clinical practice, pure single-vector injuries are uncommon in the cervical spine and combined forces produce the variety of patterns seen. Force patterns producing injuries such as atlantoaxial or atlanto-occipital dissociation, odontoid fractures, and rotary subluxation at C1-2 are often complex and not readily inferred from accounts of the injury mechanism.

Because of the complexity of injury forces, classifications that attempt to infer the primary force vector are subject to interpretation. The SLIC system, alluded to earlier, instead focuses on morphology. In addition, it accounts for ligamentous injury, which factors greatly into management decisions, as well as neurological status, which is important in terms of both acute management and prognosis. A study evaluating clinical use of the classification demonstrated high degrees of interrater reliability.¹⁷⁰ Further work to assess the applicability and validity of the SLIC system are ongoing.

Cervical Spine Stability

The abstract concept of spinal stability can often be difficult to understand and apply to actual clinical situations. To define stability of the spine, several factors must be considered, including the mechanism of injury, the magnitude and direction of forces, the radiologic appearance of the lesion, the anatomic structures involved, and the neurological status of the patient. Clinically, stability of the cervical spine implies three assumptions: (1) that there will not be excessive displacement or deformity under physiologic loading; (2) that deformity or abnormal displacement will not develop during the healing process; and (3) that compression of or injury to neurological elements is not present and will not occur over time under physiologic loading.

The principal goals in the management of potential spinal instability are prevention of secondary neurological injury and provision of an optimal environment for recovery of any existing neurological injury along with the restitution of stability to the osteoligamentous structures. Achievement of these goals requires an understanding of bony and ligamentous pathology, the nature of the neural tissue injury, and the capacity for healing that can be expected. In one early review, which largely antedated modern immobilization techniques, new signs or symptoms of cervical spinal cord compression developed in 10% of patients during emergency department evaluation or during the acute phase of hospitalization.¹⁷¹ These findings underscore the importance of recognizing spinal instability and taking appropriate measures to immobilize the spine and protect the spinal cord and nerve roots. If stability cannot be established, it is always safer to assume that the spine is unstable until it can be proved otherwise.

The unique anatomy and the wide range of motion of the occipitoatlantoaxial region differentiate this area from the rest of the cervical spine. Instability of the craniocervical junction is determined by the integrity of the interrelated bony and ligamentous structures. The latter can be subdivided into outer and inner ligament groups. The outer ligaments include the articular capsules, the anterior and posterior atlanto-occipital membranes, and the nuchal ligament.¹⁷² The inner ligaments include the paired alar ligaments, the apical ligament, the transverse atlantal ligament, the vertically oriented cruciform ligament, and the tectorial membrane. Werne, in a detailed analysis of the ligamentous stability of this region, concluded that hyperflexion is limited by bony contact between the anterior rim of the foramen magnum and the tip of the dens whereas hyperextension and vertical distraction are primarily limited by the tectorial membrane.¹⁷³ Lateral bending was thought to be controlled primarily by the alar ligaments. The relative importance of these various structures was determined by sequential sectioning of the ligamentous elements.

Various anatomic structures have been implicated in the stability of the lower cervical spine. Both Bailey and Bedbrook believed that the disk and the anterior and posterior longitudinal ligaments were the most important structures for stability in the lower cervical spine.^174–177 Experimental work done by both Roaf and Munro supports these observations.^161,178

More recently, work by White and Panjabi provided additional information on the ligaments’ role in maintaining cervical spine stability.⁵² From observations on cadavers, they concluded that the loss of function of either all of the anterior or all of the posterior bony or ligamentous structures could render the lower cervical spine unstable. Furthermore, they determined that horizontal and angular displacement between cervical vertebrae did not exceed 2.7 mm or 10.7 degrees, respectively, before complete failure of the motion segment occurred. Based on these data and in conjunction with other concepts of stability, they constructed a graded checklist system for determining instability of the lower cervical spine.¹⁴⁷ Points are assigned if anterior or posterior column destruction is noted, sagittal angulation is greater than 11 degrees, sagittal plane translation is greater than 3.5 mm, there is spinal cord injury or a positive stretch test, nerve root damage or disk narrowing is present, or it is anticipated that the patient will place great stress on the cervical spine. A patient with more than 5 points is considered to have an unstable lower cervical spine. However, it is possible for patients with lower scores to have spinal instability and for patients with higher scores to be clinically asymptomatic. For this reason there is no substitute for repeat examinations to identify potential spinal instability. These authors also noted that flexion-extension radiographs may be hazardous in patients with occult ligamentous instability and recommended the so-called stretch test as a safer alternative.¹⁶²

Closed Reduction

Frequently, patients will be seen who have an acute neurological deficit referable to the spinal cord and who have obvious subluxation on imaging with resultant cord compression. Common examples include patients with unilateral or bilateral locked facets, cervical burst fractures, displaced type II odontoid fractures, and the like. Early closed reduction of these injuries with the use of tong or halo traction devices has been advocated for decades.^179–182 The rationale for this approach is to achieve rapid cord decompression along with the modicum of stability and immobilization afforded by the traction device. This practice of early closed reduction has been questioned by a number of authors who cite the potential for neurological deterioration as a result of displacement of disrupted disk material into the canal during reduction.^183–185 These authors recommend early evaluation with MRI followed by anterior diskectomy and subsequent reduction if a herniated disk is observed. The frequency of disk disruption/herniation on prereduction MRI is relatively high, 42% in the series reported by Rizzolo and coworkers,¹⁸⁶ yet the clinical significance of the finding is debated. Advocates of rapid cord decompression cite the delay incurred by screening MRI.

In 1999, Grant and coauthors reported a retrospective review of 82 examinable patients treated by rapid, fluoroscopically controlled, closed reduction of unstable cervical spine fractures. Traumatic disk disruption or herniation was noted in 46% of the patients (usually observed on postreduction MRI), and partial or complete spinal cord injury was found in 56%. Significant improvements were seen in mean American Spinal Injury Association (ASIA) motor scores 24 hours after injury in patients with both complete and incomplete injuries, with only 1 patient exhibiting deterioration (1.2%).¹⁸⁷

A recent review that attempted to define the role of closed reduction and the utility of prereduction MRI was unable to find conclusive (class I or II) evidence supporting either practice.¹⁸⁸ Nonetheless, on the basis of considerable class III data, the authors concluded that reduction of the cervical spine in awake patients by traction is possible in approximately 80% of patients, with transient neurological deficits occurring in 2% to 4% and permanent deterioration in only approximately 1%. Prereduction MRI was not considered necessary for most patients, although those with altered consciousness impeding accurate neurological assessment could be evaluated with this modality as an option. It would also be advisable to evaluate patients with normal neurological function or minor deficits before closed reduction, assuming that adequate immobilization can be ensured during transport and performance of the scan.

The cause of neurological deterioration after closed reduction by traction or manipulation is often unclear, although disk displacement as cited earlier is by no means the only mechanism. Overdistraction, concomitant hypotension, loss of reduction, and inadequate stabilization after reduction are a few of the potential mechanisms. Close observation is thus critical to minimize the risk for neurological worsening. Once reduction has been achieved, stabilization of the spine can be planned in more deliberate fashion, with consideration of associated injuries. Inability to achieve closed reduction should prompt consideration of open reduction via an anterior, posterior, or combined approach.

Restoration of Spinal Stability

Restoration of spinal stability is critical to minimize the risk for secondary injury and to allow early mobilization of the patient and thereby minimize the risks associated with prolonged bed rest. During the early stages of evaluation of a patient with cervical spine injury, the surgeon should be considering the probable course of treatment, that is, whether there is a stable injury or whether spinal instability is present and requires treatment by means of external orthoses or by internal stabilization techniques.

Specific Lesions and Their Management

Axis Fractures

The axis vertebra has unique osseous anatomy, as well as unique ligamentous, muscular, and vascular relationships, which can produce a number of distinct injury patterns. Fractures of C2 are usually classified as odontoid fractures, lateral mass fractures, fractures of the pars (traumatic spondylolisthesis or hangman’s fracture), and miscellaneous combination fractures. Approximately 20% of acute cervical spine fractures affect the axis vertebra,²¹⁰ with a type II odontoid fracture being the most common.

Odontoid Fractures

Fractures of the odontoid process, or dens, (Fig. 312-3) account for approximately 7% to 14% of cervical spine fractures and almost 60% of axis fractures.¹³²

FIGURE 312-3 Type III odontoid fracture. Because reduction was difficult to maintain, screw fixation was necessary.

Odontoid fractures are generally subdivided according to the classification of Anderson and D’Alonzo.²¹⁰ Type I fractures involve avulsion of the apical aspect of the dens by the apical or alar ligaments, or by both.

Type II fractures, which are the most common, involve an axially or obliquely oriented fracture across the base of the dens without involvement of the C2 body. These fractures are noteworthy because of their high rate of nonunion. Occasionally, there is significant comminution at the fracture line, which further complicates management and predisposes to nonunion. Hadley and colleagues termed these type IIA fractures.²¹¹

Treatment with a halo orthosis has frequently been advocated for type II fractures, although rates of nonunion ranging from 25% to 63% have been reported.²¹² Surgical stabilization with an anterior odontoid screw is thought to offer greater rates of healing while preserving atlantoaxial rotation.²¹³ Such treatment requires an intact transverse atlantal ligament and is problematic in patients with oblique fractures, a barrel chest, and severe osteopenia. Posterior atlantoaxial fusion by a variety of techniques can be considered in such cases.

Clinical factors that correlate with higher rates of nonunion for type II fractures remain controversial.^{132,211–214} Some factors that have been implicated include increasing age (especially >65 years), greater degrees of dens displacement (especially >6 mm), and posterior displacement of the dens.

Type III fractures are those in which the fracture line extends into the body of the axis. Because of the greater blood supply, these fractures generally heal when treated with a halo orthosis. Most surgeons recommend a treatment duration of 12 weeks.

Lateral Mass Fractures

Lateral mass fractures are generally the result of an axial loading mechanism. These injuries may be seen in conjunction with an adjacent C1 lateral mass fracture. Treatment is usually accomplished with a halo orthosis.

Traumatic Spondylolisthesis

Traumatic spondylolisthesis of C2, also termed a hangman’s fracture, involves bilateral fractures through the pars interarticularis or pedicles. In some cases, the fracture may extend onto the posterior axis body. Concomitant ligamentous injury and the associated instability largely dictate the subsequent management. Levine and Edwards proposed a four-level classification.²¹⁵ Type I fractures demonstrate no angulation or translation of C2 relative to C3 and can be managed with a rigid collar. Type II fractures demonstrate significant angulation (>11 degrees) and translation (>3.5 mm). Type IIA injuries in the Levine and Edwards classification exhibit no translation but high degrees of angulation. Type III injuries are rare; they consist of high degrees of angulation and translation in which there is concomitant unilateral or bilateral facet dislocation at C2-3.

Most cases of traumatic spondylolisthesis are not associated with neurological injury. Type I injuries are typically treated with a rigid collar. Type II, IIA, and III hangman’s fractures are frequently treated with a halo orthosis. Vaccaro and coworkers demonstrated that early immobilization in a halo was a viable treatment option for type II and IIA hangman’s fractures.²¹⁶ Some type III injuries are reduced with traction before placement in a vest. Some cases of significant angulation of C2 on C3 that cannot be reduced with a halo orthosis can be treated by anterior interbody fusion and plate fixation.^217,218

Combined Atlantoaxial Fractures

Concomitant fractures of the atlas and axis are not uncommon and occur in 5% to 53% of patients, depending on the exact fracture patterns.¹³¹ Because these combined injuries present unique management challenges, they have been the subject of several publications.^219–221 Many authors have noted that patients who have sustained such injuries are at greater risk for neurological injury or death than are patients with atlas or axis fractures alone.^{131,219,221–223}

Typical patterns include C1 type II odontoid, C1 type III odontoid, C1 miscellaneous, C2 (includes the lateral mass, lamina, and spinous process), and C1 hangman’s fractures. Fracture patterns of C1 fall into the four patterns described earlier: posterior arch fractures, anterior arch fractures, multiple fractures of the C1 ring (Jefferson type), and lateral mass fractures.

Treatment of combined C1-2 fractures is predicated on involvement of both vertebrae and the potential for ligamentous instability created by the injury. Surgical stabilization is more frequently used than for isolated C1 or C2 fractures, which is appropriate given the greater degree of bony and soft tissue injury incurred. Treatment options include cervical orthoses (collar, halo, Minerva, SOMI) alone, an odontoid screw combined with an orthosis, transarticular screw fixation, occipitocervical fusion, and posterior C1-2 fusion with screw fixation. Although no firm guidelines exist for this heterogeneous group of fractures, a recent review attempted to categorize the literature in this regard.²²¹ Not surprisingly, there were no class I or class II studies on the subject, with most information coming from retrospective case series or case reports. The authors of this report concluded that the nature of the axis fracture was the primary consideration dictating the treatment approach; however, the competence of the transverse ligament and atlas ring was also significant. Recently, screw fixation into the lateral masses of the atlas has emerged as a common means of dealing with a number of these fractures when the C1 arch is incompetent with or without compromise of the transverse atlantal ligament.

Subaxial Fractures

Fractures of the cervical spine below C2 tend to follow similar patterns regardless of level. The most common injury patterns include compression fractures, burst fractures, teardrop fractures, unilateral and bilateral locked facets, hyperflexion injuries, and clay shoveler’s fracture. Although any level can be affected, C5 and C6 are the most commonly injured subaxial levels.

Compression

Compression fractures are common injuries that result from a mechanism involving flexion and axial loading. There is failure of the anterior column, but the middle column is intact and there is no canal compromise or neural injury. Most of these lesions can be treated with a cervical collar. Significant kyphosis may be a consideration for surgical treatment to restore anterior column height and lordosis, although the specific indications remain controversial. Compression fractures tend to be associated with osteopenia or osteoporosis, loss of normal cervical lordosis, and pathologic fracture.

Burst Fractures

Burst fractures in the cervical spine are largely the result of axial compression forces, occasionally with a flexion component. These injuries involve two columns and are associated with retropulsion of bone into the canal (Fig. 312-4).

FIGURE 312-4 C5 burst fracture. A, Lateral radiograph. B, Reformatted computed tomographic scan.

Spinal cord injury is common with this mechanism. There may also be an angular deformity at the level of injury, and the posterior column can be involved.

Surgical treatment is usually conducted from an anterior approach, with corpectomy, strut or cage placement, and anterior plate fixation being the usual method. When posterior ligamentous injury or facet disruption is present, a posterior tension band may also be required. Patients with complete quadriplegia and insignificant deformity may also be considered for treatment with a halo. Persistent canal compromise with impairment of CSF circulation, however, may predispose patients to the later development of posttraumatic syringomyelia and ascending deficits.

Teardrop Fractures

So-called teardrop fractures involve an anterior-inferior chip off the vertebral body. The predominant mechanism is thought to be hyperflexion. Patients may have neurological injury with these fractures. With increasing degrees of axial loading, this fracture pattern transitions to a burst fracture. Management may include surgical stabilization and fusion or immobilization in a halo orthosis.

Unilateral Facet Dislocation

Unilateral facet dislocation is generally the result of a flexion-rotation mechanism. The joint capsule of the facet opposite the rotation is disrupted, and the upper vertebra rotates forward and displaces and locks the facet. Lateral radiographs demonstrate anterior subluxation of the upper vertebral body on the lower of less than 25% of the anteroposterior dimension of the body. There is evidence of rotation between the spinal segment above the injury and that below such that on a lateral radiograph, one segment appears in a true lateral projection and the other is oblique. On anteroposterior radiographs there is an abrupt shift in alignment of the spinous process shadows at the involved level. The facet dislocation or “locking” is usually readily appreciated on a plain radiograph and is even better seen on sagittal reformatted CT or MRI. Patients with these injuries may or may not have a spinal cord injury. Radicular injury producing focal weakness, numbness, or radicular pain may be observed.

Treatment usually involves closed reduction, if possible, followed by surgical stabilization or in some cases halo immobilization. Closed reduction may not be possible in some patients, particularly those with comminution of the articular processes. In these cases, open reduction followed by stabilization is generally performed.

In recent years several authors have advocated prereduction MRI in patients with unilateral facet dislocation and intact neurological findings on examination. As noted previously, there are no conclusive data regarding this practice, however.

Bilateral Facet Dislocation

Bilateral locked facets occur as a result of a hyperflexion mechanism with sufficient disruption of the posterior ligamentous complex to allow both facet complexes to be subluxed. These injuries are most frequently associated with spinal cord injury. Plain radiographs or reconstructed CT scans demonstrate an angular deformity with subluxation of the superior vertebral body of greater than 25%. This is a highly unstable injury. Because of the marked ligamentous injury, reduction can frequently be accomplished with closed techniques, although internal fixation will be required for long-term stability. Because overdistraction is a distinct possibility in this setting, frequent radiographic monitoring is critical, as is avoidance of excessive traction weight.

Hyperextension Injuries

Hyperextension injuries often occur as a result of falls or vehicular injuries. A common clinical scenario is a patient initially seen with a central cord syndrome after a fall or rear-end collision.⁶² In many of these cases, the patient has no gross spinal instability and no major fracture. There is evidence of preexisting spondylosis and stenosis. MRI will often demonstrate a signal abnormality in the cord.

Higher degrees of angular acceleration may result in disruption of the anterior longitudinal ligament and disk with a “fish mouth” anterior deformity on plain film or sagittal imaging (Fig. 312-5). Fractures of the spinous processes or laminae may also occur with this mechanism. In some cases of unstable hyperextension injury, the spine will have returned to a normal position and the bony anatomy on plain radiographs will appear normal. Prevertebral soft tissue swelling may initially be the only x-ray finding. MRI will demonstrate the ligamentous injury to best advantage.

FIGURE 312-5 Hyperextension injury in a patient with ankylosing spondylitis and complete quadriplegia.

Decompression of the cord in patients with acute trauma associated with a central cord syndrome is controversial, especially in terms of the appropriate timing. Some advocate for early decompression, whereas others advise waiting for variable periods to allow the patient’s neurological condition to stabilize and the typical improvement to plateau. Nonetheless, a patient who demonstrates documented neurological deterioration after the initial injury should undergo appropriate decompression and stabilization acutely.

Clay Shoveler’s Fracture

Clay shoveler’s fracture is an avulsion of the spinous process. This fracture typically affects the C6-T1 levels, where there are large muscular attachments to longer spinous processes. Although fracture of the spinous processes may occur most commonly after direct impact to the area, it is classically the result of muscular avulsion during brisk flexion. These fractures are typically stable and require only symptomatic treatment. When these injuries are noted, however, the physician must be diligent in screening for associated fractures or ligamentous injuries that may render the spine unstable, especially if the fracture is above C6. The finding of multiple spinous process fractures is of greater concern in terms of the potential for instability.

Conclusion

The early management of patients with cervical spine and spinal cord injuries continues to evolve. Recognition of injury and prevention of secondary or iatrogenic neurological injury are paramount considerations. A thorough understanding of injury patterns and clinical and radiographic manifestations is indispensable for accurate diagnosis and appropriate early management. The role of the neurological/spine surgeon is critical in directing the care of these patients, especially in the context of multiple trauma.

Many areas of controversy remain. The specific role of imaging modalities, optimal timing of surgery, indications for surgery with some injury patterns, and the role of corticosteroids in the management of spinal cord injury are just a few areas that remain unresolved. Research into acute interventions to mitigate primary or secondary spinal cord injury continues, but without the prospect of a “silver bullet” emerging in the near future. As always, prevention of neurological injury before, during, and after the traumatic event is paramount for optimum outcomes.