Assessment of the Cervical Spine after Trauma

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CHAPTER 312 Assessment of the Cervical Spine after Trauma

Acute injuries of the spine and spinal cord are among the most common causes of death and disability resulting from trauma.14 Organized trauma systems, improvements in prehospital care, advances in surgical stabilization techniques, and specialized centers for rehabilitation have all contributed to improving outcomes after cervical spinal cord injury. Despite these advances, however, prevention of injuries altogether or, at a minimum, prevention of additional secondary injury will have the greatest impact on overall outcomes.

For this reason, evaluation plus treatment of trauma to the spine, spinal cord, and nerve roots requires a systematic approach integrated into the overall management of the trauma patient. Early diagnosis of injury, preservation of spinal cord and nerve root function, and restoration of spinal alignment and stability are the keys to successful management.

Although it may be a truism that all patients who have suffered significant trauma should be suspected of having a cervical spine injury, accuracy in diagnosis and management is achieved with a thorough knowledge of the epidemiology of spinal injury, injury patterns, clinical diagnosis, and the use and interpretation of imaging studies. Armed with this information, a clinician is better able to assess the likelihood of specific injuries in specific types of trauma situations.

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.79 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.1619

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,2225 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%.3336

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.3739 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

Prehospital Management

Because vehicular crashes, falls, and sports-related injuries all have the potential for cervical spine injury, all accident victims must be assumed to have an unstable cervical spine until proved otherwise.

The potential for an unstable spine must be considered at the scene of the accident even as the initial priorities of airway, breathing, and circulation are addressed and the patient is prepared for extrication and moved. Increased awareness of the potential for instability and implementation of advanced immobilization techniques during extrication and transport have been associated with a decline in complete spinal cord lesions.42 Gillingham43 and Geisler and associates44 both reported on vertebral injuries made worse by well-intentioned but faulty first aid at the accident scene.

Commonly, airway obstruction after trauma is the result of prolapse of the tongue or airway obstruction by blood, secretions, or foreign bodies. Frequently, the airway can be established by using the chin lift or jaw thrust technique to bring the tongue forward. The mouth and oropharynx should be checked for debris and cleared either manually or with suction. In a semiconscious or unconscious patient, an oropharyngeal or nasopharyngeal airway should be inserted gently if indicated. An esophageal obturator airway can be inserted in an unconscious patient who has suffered respiratory arrest, although it is contraindicated in those with an intact gag reflex. The laryngeal mask airway has been used increasingly in this setting with good results.4547

If a satisfactory airway or adequate ventilation cannot be established or maintained with the previous methods, endotracheal intubation is required. Gentle, manual in-line traction should be performed during this maneuver. Care should be taken to avoid overly vigorous traction because significant spinal distraction carries a risk for neurological injury.48 Although blind nasal intubation has been advocated in this setting, it is contraindicated in those with a basilar skull fracture. The latter is suspected in individuals with raccoon eyes, significant craniofacial trauma, Battle’s sign, or clear fluid in the nose or nasal secretions.

Respiratory insufficiency should be suspected in all patients with cervical cord injuries. Hypoventilation can result from paralysis of the intracostal muscles, which leaves the patient breathing by use of the diaphragm alone. High cervical cord injury, as in a patient with no arm function (i.e., above the outflow to the phrenic nerves at C3-5), may be associated with paralysis of one or both diaphragms, as well as the intercostals. Inadequate ventilation in a quadriplegic or quadriparetic patient is another indication for early intubation.

Assessment of the circulation can be difficult in the setting of acute trauma. Although hypotension is usually the result of hypovolemia or cardiac dysfunction, hypotension in a spinal cord–injured patient may be the result of loss of sympathetic tone with decreased peripheral vascular resistance.49,50 This results in venous pooling and decreased cardiac preload, which is exacerbated by the lack of reflex, sympathetically mediated tachycardia. Unlike patients with hypotension as a result of acute blood loss, these patients may appear to be peripherally well perfused with pink warm extremities—so-called warm shock.

Regardless of the presumed cause of the hypotension, intravenous access should be gained rapidly. Initial therapy should follow routine protocols for intravascular volume expansion.

Extrication of a patient with a suspected spinal injury requires immobilization of the neck and maintenance of normal axial alignment of the body. Except in the presence of extreme circumstances, such as fire, no patient should be moved before rigorous spinal stabilization is achieved. Soft collars allow complete neck movement in all planes and should not be used.51,52 Instead, if a patient is seated in a vehicle or in a position that makes full access difficult, a rigid collar can be placed for some support. With the patient still in the vehicle, a half backboard can be used for removal of the victim from the vehicle. Placement of the individual in the supine position on a long backboard is accomplished as soon as possible. Immobilization is augmented with sandbags or plastic intravenous bags placed along the head and neck with tape passed from one edge of the backboard to the other across the forehead.53,54 This method allows free movement of the jaw and lower part of the face for easy airway control.

The half backboard and long backboard may not be suitable for extrication of victims in all circumstances. Other alternatives include the Kendrick extrication device, which is a close-fitting jacket with extensions behind and on both sides of the head and neck, and the scoop sledge stretcher.55 Pediatric patients also present unique problems with regard to immobilization. Because of the proportions of a young child, immobilization on a standard backboard may result in neck flexion. The use of specially designed pediatric backboards can minimize this problem.56

If the patient is found in the water with a suspected cervical spine or cord injury, all efforts should be made to keep the patient floating on the surface with support for the head and neck. The common error of carrying the injured person to dry ground usually allows the head to dangle unsupported. Instead, extrication from the water can often be accomplished relatively easily by securing the individual to a long board while still in the water.

A motorcyclist, bicyclist, or athlete may be found at an accident scene with a helmet still in place. In-line traction should be applied for removal, with a second rescuer supporting the head and neck. If the helmet cannot easily be removed, it can be left in place during transport as long as the patient’s airway is not compromised. For sports injuries in particular, it is appreciated that only the facemask of the helmet need be removed to obtain access to the airway; the rest of the helmet can be removed later, thereby preventing any manipulation before evaluation of the injury.57,58

Before transport, the patient must be secured and fastened to the transport device and be able to withstand complete inversion without loss of immobilization. During transport, the patient may be confined to a small space, thus making many medical interventions difficult. Therefore, potential difficulties should be anticipated and prevented. The immobilization must be sufficiently secure to handle unstable transportation conditions or an agitated and unruly patient. An ability to deal with regurgitation and prevent aspiration or upper airway obstruction must be present at all times during transport. If there is a question about the adequacy of the airway, intubation should be performed before the patient is loaded in the transport vehicle because urgent intubation en route can be difficult and dangerous.

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

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.61,6365 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.6775 Although several earlier studies suggested that naloxone and glucocorticoids were ineffective in the treatment of acute spinal cord injury, other studies showed beneficial effects.68,7678 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.8187 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.90,91,9398 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.105108 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.109113 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%.115117 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

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.

image

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

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.43,125128 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.131133 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.135142

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.

Classification of Cervical Spine Injuries

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