Orthopedic surgeons or neurosurgeons manage most acute fractures of the spine. Knowledge of the signs of fracture instability is the key to appropriate selection of fractures that can be managed safely by primary care providers. Cervical spine fractures are nearly always the result of significant trauma and are frequently unstable. Cervical spine injuries are common in children, and the inherent ligamentous laxity allows the child’s spine to absorb and dissipate forces, leading to fewer serious spinal injuries. Thoracolumbar spine fractures are more common than fractures of the cervical spine. Younger patients fracture their thoracolumbar spine after a high-energy force, but fractures in elderly patients may occur secondary to minimal or no trauma because of underlying osteoporosis. Osteoporotic compression fractures are probably the most common type of spine fracture encountered in the office setting.
Cervical Spine Fractures (Adult)
The cervical spine is composed of seven vertebrae ( Figure 10-1 ). The bony ring of the first cervical vertebra (C1) does not contain a vertebral body or a distinct spinous process but is composed of anterior and posterior arches and lateral masses. Its articulation with C2 is circular and flat. The odontoid process of C2 is an extension of the vertebral body and is tightly bound to C1 by the dense fibers of the transverse ligament. The transverse ligament prevents forward subluxation of C1 relative to C2 during flexion. In the lower cervical vertebrae (C3-C7), the laminae arise from the pedicles on the posterior aspect of the vertebral body and join posteriorly to form the spinous processes. With the exception of C8, the cervical nerve roots exit superior to the pedicle at each level (e.g., the C5 nerve root passes between C4 and C5; the C8 nerve root passes between C7 and T1).
The three-column model is a useful way to evaluate spine fractures ( Figure 10-2 ). The anterior column is composed of the anterior half of the vertebral body and the anterior ligamentous complex (anterior portion of the annulus fibrosus and the anterior longitudinal ligament). The middle column is composed of the posterior half of the vertebral body, the posterior portion of the annulus fibrosus, and the posterior longitudinal ligament. The posterior column is composed of the facet joints, the laminae, the spinous processes, and the posterior ligamentous complex (the facet capsules and the interspinous ligaments). Simple wedge compression fractures are caused by failure of the anterior column while the middle column remains intact. These fractures are usually stable. Burst fractures result in failure of the anterior and middle columns and are usually unstable as a result of retropulsion of bony fragments into the spinal canal. Fracture dislocations of the spine, resulting from flexion rotation forces, disrupt all three columns and are highly unstable fractures.
Mechanism of Injury
Cervical spine fractures occur in a bimodal age distribution: most injuries occur among subjects 15 to 24 years old, but a second smaller peak occurs among subjects older than 55 years old. Whereas patients younger than 30 years of age most commonly injure their cervical spine during motor vehicle accidents (MVAs) or sports (mostly diving), cervical spine fractures in patients older than 35 years are more likely caused by falls or gunshot wounds. The cause of injury is highly correlated with the anatomic site of injury. MVAs most commonly cause injuries at C1 followed by C5, C6, and C7. Falls and sports-related injuries cause fractures at C5, C6, or C7. Gunshot wounds are randomly distributed.
The first step in recognition of cervical spine fractures is to be especially alert to their possible occurrence. A significant number of patients with an acute cervical spine injury suffer from a delayed or missed diagnosis. Factors that contribute to a delayed diagnosis include head injury, altered consciousness (resulting from head injury or alcohol or other drugs), multiple traumatic injuries, and poor-quality radiographs.
The conscious patient may complain of neck pain, pain with motion of the neck, or loss of motor strength to one or more extremities. Complaints of sensory loss, numbness, or tingling are variable. Pain or tenderness of the neck should be elicited by palpation only, not by movement of the neck or spine. Motor function is tested by having the patient move the extremities on command. Sensation to light touch is tested to help assess the level of injury. The unconscious patient with a head injury must be presumed to have a neck injury until proven otherwise.
After a traumatic primary injury to the spinal cord, several metabolic abnormalities can cause secondary injury to the cord. This secondary injury includes loss of local vascular control, neurogenic shock, hypoperfusion of the cord, edema, and inflammation.
Immobilization of the cervical spine should be maintained until imaging can rule out an unstable injury. Even with less severe trauma, imaging of the cervical spine must be performed in the presence of an abnormal mental status, neurologic deficit, disproportionate midline neck pain, intoxication, or painful distracting injury. Either plain radiographs or a computed tomography (CT) scan may be used to evaluate the cervical spine in low-risk patients. If CT imaging is being performed to assess for other traumatic internal injuries of the head or chest, then plain radiographs are unnecessary.
Imaging Decision Rules
Well-validated and sensitive clinical decision rules have been developed to determine the need for cervical spine imaging. The NEXUS Low-risk Criteria (NLC) was prospectively validated in a large, multicenter, observational study. The NLC has been shown to have a sensitivity of 99.6% and a specificity of 12.9%. The NLC decision rule stipulates that imaging is unnecessary if patients satisfy all five of the following low-risk criteria:
Absence of posterior midline cervical tenderness
Normal level of alertness
No evidence of intoxication
No abnormal neurologic findings
No painful distracting injuries (e.g., long bone fractures, large lacerations, burns)
Routine radiographs to assess the cervical spine include cross-table lateral, anteroposterior (AP), and open-mouth odontoid views ( Figure 10-3 ). The lateral view detects the majority of cervical spine fractures, but a technically adequate three-view series increases the diagnostic yield. The normal odontoid view shows the dens projecting from the body of C2, symmetrically flanked by the lateral masses of C1. A systematic review of plain radiographs of the cervical spine is essential if serious injuries are to be recognized. Examining the radiographs in a stepwise fashion helps ensure that cervical spine instability or fracture is not missed. Table 10-1 lists the steps to follow in reviewing cervical spine films.
|All vertebrae on the lateral||If all seven cervical vertebrae are not easily seen on the lateral view, repeat radiographs should be taken.|
|Presence of lordosis||Straightening of the cervical spine or loss of the normal cervical lordosis may be caused by simple muscle spasm or indicate a more serious injury.|
|Vertebral alignment||Anterior and posterior aspects of the vertebral bodies should form smooth continuous curves. Signs of instability include angulation of more than 11 degrees between adjacent vertebral bodies, more than 3.5 mm anterior or posterior displacement of the vertebral body, increased distance between the spinous processes, and facet joint widening.|
|Spinolaminal line||The spinolaminal line should form a smooth lordotic curve behind the posterior vertebral lines. This line connects the bases of the spinous processes and appears as a bright radiodensity posterior to the vertebral bodies.|
|Spinous processes||Examine the tips of the spinous processes for evidence of displacement or increased space between the spinous processes. The size and shape of the spinous processes vary, so a line connecting the tips is of limited use.|
|Soft tissue examination||Measure the soft tissues anterior to the upper cervical vertebrae. The soft tissue anterior to C1 through C3 should be no more than 7 mm wide.|
|Spinous processes||The spinous processes should be well aligned vertically. Any lateral displacement usually indicates a fracture.|
|C1–C2 articulation||The spaces between the lateral edges of the odontoid and the medial borders of the lateral masses should be approximately equal. The lateral masses should line up directly over the body of C2 without overlapping.|
All vertebrae on the Lateral View
All seven cervical vertebrae must be clearly visible on the lateral view, or repeat films must be taken. If the C7 vertebra is obscured by soft tissue, an attempt should be made to lower the shoulders by pulling the arms toward the feet with slow traction. If this is unsuccessful, the swimmer’s view may be necessary to demonstrate C7 adequately. For this view, one of the patient’s arms is abducted 180 degrees while traction is applied to the other arm, and the beam is directed at 15 to 20 degrees caudal. If the lower cervical vertebrae still cannot be seen on this view, CT evaluation is required.
Presence of Lordosis
The presence or absence of the normal cervical lordosis should be observed. Straightening of the cervical spine or loss of the normal cervical lordosis may be attributable to a simple muscle spasm or may be a clue to a more serious injury ( Figure 10-4 ).
The anterior and posterior aspects of the vertebral bodies should be well aligned, forming smooth continuous curves ( Figure 10-5 ). Signs of instability include angulation between adjacent vertebral bodies of more than 11 degrees, anterior or posterior displacement of the vertebral body of more than 3.5 mm, increased distance between the spinous processes, and facet joint widening. A stepoff of up to 3.5 mm may be a normal variant along the posterior vertebral bodies. In the context of trauma to the cervical spine, further radiologic testing with dynamic flexion-extension views or CT scanning is required to determine whether the stepoff is abnormal or a normal variant. If the amount of stepoff increases in flexion or extension, the spine is unstable.
The spinolaminal line is behind the posterior vertebral line (see Figure 10-5 ). On the lateral radiograph, the junction of the lamina and the base of the spinous process appears as a bright radiodensity posterior to the vertebral bodies. The line connecting these junctions should form a smooth lordotic curve.
On the lateral view, the tips of the spinous processes are examined for evidence of displacement or increased space between the spinous processes. The size and shape of the spinous processes are variable, so a line connecting the tips is of limited use. On the AP view, the spinous processes should be well aligned vertically. Any lateral displacement usually indicates a fracture.
The position of the odontoid in relation to the lateral articulating masses of C1 should be examined. The spaces between the lateral edges of the odontoid and the medial borders of the lateral masses should be approximately equal. The lateral masses should line up directly over the body of C2 without overlap.
Soft Tissue Examination
The soft tissues anterior to the upper cervical vertebrae should be measured. The soft tissue anterior to the body of C2 should be no more than 7 mm wide. More soft tissue swelling may indicate an occult cervical spine fracture. The thickness of the soft tissue anterior to C4 through C7 varies from 14 to 22 mm wide; thus, measurements are of limited diagnostic value at this level.
The utility of these views is uncertain. Dynamic flexion-extension cervical spine radiographs should only be considered in alert cooperative patients and may demonstrate previously undetected ligamentous disruption. They are indicated if initial radiographs show a stable cervical spine but a small possibility of instability remains. The patient must be able to actively flex and extend the neck at least 30 degrees in each direction and have no neurologic deficit. Neither the radiology technician nor the attending physician should manipulate the neck to obtain these radiographs. The patient should slowly flex and extend the neck actively as far as possible, stopping for pain or paresthesias. Signs of instability on these dynamic views include more than 3.5 mm of horizontal displacement between adjacent disks, displaced apophyseal joints, widened disk spaces, loss of more than 30% of disk height, or prevertebral hematoma.
CT is useful in demonstrating bony lesions, particularly when a cervical spine fracture is suspected but not confirmed on plain radiographs. Based on a systematic review, in patients with blunt trauma, CT is superior to plain radiographs in the detecting a cervical spinal injury. If a fracture or subluxation is detected on plain films, a CT scan should always be obtained to better visualize the fracture and determine whether any displacement has occurred. Plain radiographs are still adequate as the initial screen in patients at low risk for cervical spine injury.
Magnetic Resonance Imaging
Magnetic resonance imaging (MRI) is useful for visualization of soft tissues, including ligamentous structures and clear definition of canal compromise. It is useful in diagnosing nerve root avulsion, hematoma, and other vascular injury of the neck.
Fractures of C1 may be caused by axial loads or extension forces. The most common fracture is a bilateral burst fracture (Jefferson fracture) through the posterior arch and lateral masses. Fortunately, this fracture does not typically result in neurologic injury. Posterior arch fractures are usually caused by hyperextension. The transverse ligament is disrupted, and the fracture is unstable if the lateral masses extend laterally beyond those of the axis on the open-mouth odontoid view ( Figure 10-6 ). CT scanning is required in the complete evaluation of C1 fractures.
Fractures of C2 usually occur at the arch or the odontoid. Fractures of the arch are caused by hyperextension. The unstable hangman’s fracture occurs when breaks occur through both arches. In this type of C2 fracture, C2 is subluxated anteriorly relative to C3, and the posterior elements of C2 may be displaced posteriorly. CT scanning may be needed to detect a nondisplaced hangman’s fracture. Fractures of the odontoid most commonly occur at the junction of the odontoid process and the body as a result of a forced flexion or extension of the head (e.g., a fall forward onto the forehead). These fractures often require surgical treatment. Avulsion fractures of the tip of the odontoid are usually horizontal and are stable, requiring only simple collar immobilization.
Unilateral or bilateral facet dislocations cause subluxation of one vertebra relative to another. Signs of subluxation include narrowing of the intervertebral disk space, anterior angulation, and increased distance between the spinous processes ( Figure 10-7 ). Unilateral facet dislocation, caused by axial loading with flexion and rotation, results in partial anterior subluxation of less than 50% of the vertebral body width. This is usually a stable injury. Bilateral facet dislocation is caused by severe flexion forces and disrupts both the middle and posterior columns. This unstable injury results in significant subluxation with the vertebra displaced more than 50% of the width of the body relative to the adjacent vertebra ( Figure 10-8 ).
Simple wedge (compression) fractures of the cervical spine can occur with even minor flexion loading forces. On the lateral radiograph, the anterior vertebral body end plate is compressed, usually in the absence of any subluxation or displacement of the vertebra ( Figure 10-9 ). In stable simple wedge fractures, the height of the posterior vertebral cortex is maintained. These fractures must be further evaluated with dynamic flexion-extension views of the cervical spine to detect any subluxation. Fractures causing loss of more than 25% of the vertebral body height may be associated with disruption of the posterior ligamentous complex (two-column fracture).
Flexion Teardrop Fractures
This injury, caused by combined flexion and compression forces, is actually a fracture dislocation and is among the most unstable of all cervical spine fractures. A small anteroinferior teardrop fragment is present with subluxation of the vertebral body or facets or angulation of the spine ( Figure 10-10 ). The teardrop fragment typically remains aligned with the inferior vertebra, and the posterior fragment remains aligned with the vertebra superior to the level of injury. These fractures must be distinguished from a small anteroinferior avulsion fracture that has no signs of subluxation, comminution, or angulation.
These fractures, caused by compression and flexion forces (e.g., diving injury), are comminuted and disrupt both the anterior and middle columns. Severe spinal cord injury occurs if the fracture fragments displace anteriorly and posteriorly. The middle and lower cervical vertebrae are most frequently involved.
Spinous Process Fractures
Fractures of the spinous processes occur as a result of direct trauma to the process, sudden deceleration and resultant neck flexion after high velocity trauma, or avulsion forces from severe muscular contraction. An avulsed tip of the spinous process of C6 or C7 is known as the “clay shoveler’s fracture” ( Figure 10-11 ) because historically the strong pull of neck and shoulder muscles during heavy physical work could result in an avulsion fracture. On the AP radiograph, the affected spinous process may be seen displaced laterally from the midline. Fractures of the tip of the spinous process are stable and must be distinguished from fractures at the base of the process that may disrupt the posterior ligamentous complex. Dynamic flexion-extension radiographs of the cervical spine should be checked to ensure that the anterior and posterior columns remain aligned. A nonfused apophysis of a spinous process can be confused with an acute fracture.
Indications for Referral
Most cervical spine fractures are unstable and require definitive care by a specialist. Even minor fractures noted on plain radiographs may be associated with significant ligamentous injuries that render the cervical spine unstable. Although stable fractures such as a simple anterior wedge fracture or a spinous process fracture can be managed by the primary care provider, consultation with a spine orthopedist or neurosurgeon and review of the radiographs are helpful in the management of these patients.
Before transport, the patient with a suspected cervical spine fracture should be placed in the neutral supine position on a backboard. A scoop-type stretcher should be used if available. The neck should then be stabilized with a firm, preferably two-piece, cervical collar to minimize neck motion. The head and neck should then be stabilized with sandbags and the chest and extremities securely strapped to the backboard. During transport to an appropriate facility, the patient should be kept in slight Trendelenburg position to minimize the effects of neurogenic shock.
On the patient’s arrival at a well-staffed facility, Advanced Trauma Life Support (ATLS) protocols should be followed. Hemodynamically unstable patients typically are taken to the operating room rather than delaying further with any imaging because they are presumed to have an unstable cervical spine injury in this circumstance. The cervical spine and paraspinous musculature should be palpated for tenderness or deformity followed by a complete neurologic survey.
Stabilization of the cervical spine with early mobilization and rehabilitation is the key to treating cervical spine fractures and may be accomplished by either nonoperative or operative means. Stabilization in more severe and unstable cervical spine fractures is usually achieved by using a halo and vest or through operative stabilizing procedures.
Stable fractures such as nondisplaced anterior wedge fractures or isolated spinous process fractures with intact ligamentous support may be treated with a rigid cervical orthosis (e.g., Philadelphia collar) and analgesics for 4 to 8 weeks. The patient should wear this orthosis until the neck is nontender and then begin gentle range of motion (ROM) exercises under the guidance of a physical therapist. Some patients may benefit from the use of muscle relaxants during the rehabilitation period. Neck muscle strengthening exercises can be started after full painless ROM is achieved. Normal activities should be resumed gradually, and vigorous physical activity is best avoided until normal motion and strength are restored. Patients with anterior wedge fractures should have repeat radiographs taken at weekly intervals to document healing and check for any further loss of vertebral height. A follow-up radiograph of a spinous process fracture is advised after the neck is nontender to document evidence of radiographic healing.
Return to Work or Sports
Patients with simple wedge compression fractures or spinous process fractures may return to nonstrenuous occupations after the tenderness is gone and they have regained normal or near-normal ROM of the cervical spine. Decisions about returning to work must be individualized for patients who have sustained an unstable fracture, flexion teardrop fracture, fracture dislocation, or burst fracture. Close consultation with a neurosurgeon is recommended.
Cervical Spine Fractures (Pediatric)
Cervical spine injuries among children are fundamentally different from adults’ injuries because of anatomic differences and dissimilar causes of injury. Cervical spine injuries are relatively uncommon among children: fewer than 1% of all cervical spine injuries occur among children younger than 15 years of age. Typically, the child’s cervical spine does not take on an adult-like appearance until 8 years of age. In children younger than 8 years of age, anatomic differences specific to children include the greater relative mass of the head, underdeveloped neck muscles, greater ligamentous laxity, horizontally oriented posterior facets, and incomplete ossification of the vertebral bodies. Ligamentous laxity allows the child’s cervical spine to absorb and dissipate traumatic forces without injury to the vertebra or the spinal cord. However, these anatomic differences predispose children to wedge-shaped anterior vertebral fractures and anterior sliding injuries, especially in the upper cervical region (C1 to C4). The most common sites for fractures in children younger than 8 years of age are the upper cervical vertebrae C1 to C3. In children older than 8 years of age, fractures of C6 and C7 are the most common.
Mechanism of Injury
The cause of injury varies with the patient’s age. Infants may sustain neck injuries during birth or because of child abuse. Injuries in this age group involve the occiput, C1, or C2 and are usually of a spinal cord injury without radiographic abnormality (SCIWORA). Young children usually sustain cervical spine injuries from falls or MVAs. Older children and adolescents’ neck injuries may be sports related or caused by bicycle, motor vehicle–pedestrian, or all-terrain vehicle accidents.
Cervical spine injury can occur through various mechanisms, and the type of deforming forces may predict the type of injury and radiologic findings. Hyperflexion injuries are the most common and may cause wedge fractures of the anterior vertebral body along with injury of the posterior elements. Hyperextension injuries may cause compression of the posterior elements and a tear of the anterior longitudinal ligament. Axial loading may cause burst or comminuted fractures of the arches of the upper cervical spine or compression fractures of the lower cervical vertebra. Rotational injuries may cause a fracture or dislocation of the facets.
The most common symptoms are localized neck pain, decreased ROM, and muscle spasm. The patient may also report transient paresthesias or weakness. The history should include symptoms present at any time after the injury even if they are transient. Transient symptoms may be the only indication of SCIWORA, and it is important to have a high index of suspicion and to ask specifically about transient symptoms in any patient whose mechanism of injury is consistent with cervical spine injury. Patients who have sustained serious trauma, multiple injuries, or both are particularly at risk for unrecognized neck injuries. Physical examination should include assessment of vital signs, a neck examination, and a neurologic examination. Midline cervical tenderness is more common than paraspinous muscular spasm or tenderness in the presence of a cervical spine injury. The neurologic assessment should include evaluation of tone, strength, sensation, and reflexes. Up to half of children with cervical spine trauma also have neurologic deficits. Children who have findings suggestive of spinal injury should have immobilization maintained and undergo immediate radiologic evaluation.
Although by 8 to 10 years of age the child’s spine is similar to that of an adult, interpretation of cervical spine radiographs in children is difficult. Normal variants at various ages must be distinguished from pathologic findings. The tip of the odontoid process shows a cartilage line until the 12 years of age, and the vertebral ring apophyses do not fuse until 25 years of age. In the open-mouthed AP view, the odontoid process appears sandwiched between the neural arches. Between 3 and 6 years of age, the odontoid fuses with the neural arches and the body of C2. Therefore, no physis should be seen at the odontoid of a child 6 years of age or older. Vertebrae C3 through C7 arise from three ossification centers: one for the anterior vertebral body and one each for the neural arches. Between 3 and 6 years of age, the neural arches fuse with the anterior segment. On the lateral view, the child’s vertebral bodies appear wedge shaped until the age of 7 years, at which time they develop the more “squared-off” appearance.
Criteria have been developed to identify those with low probability of cervical spine injury to determine when radiographic evaluation is not necessary. In children older than 8 years of age, if they meet all five of these criteria, radiographs can safely be avoided: no midline cervical tenderness, no focal neurologic deficit; normal alertness; no intoxication; and no painful, distracting injury. If radiographs are indicated, three views of the cervical spine are recommended: cross-table lateral, AP, and open-mouth odontoid. The cross-table lateral identifies the majority of fractures, subluxations, and dislocations. The most common cause of an overlooked vertebral fracture is an inadequate film series so obtaining appropriate views is essential. Flexion-extension views may identify cervical instability and may be useful when the three views are negative despite the presence of cervical pain, tenderness, or spasm. They do require that the patient is alert and cooperative. MRI is the imaging procedure of choice in any patient with neurologic signs or symptoms and normal plain radiographs.
The lateral view should be systematically evaluated looking for bony integrity, alignment of the three cervical spine contour lines ( Figure 10-5 ), and soft tissue spaces. Absence of cervical lordosis may be attributable to muscle spasm and may be normally absent in children up to age 15 years. The examiner should be aware that the spinolaminal line is not as easily seen in children as in adults. Some children demonstrate significant anterior subluxation of C2 on C3 often accentuated by neck flexion ( Figure 10-12 ). This is because of the increased mobility of the child’s cervical spine and to the horizontal orientation of the facet joints. If the patient has no history of neck injury or neck pain and has normal neck ROM, “pseudosubluxation” can be presumed. The posterior cervical (Swischuk) line between the anterior aspects of the C1 and C3 spinous processes is used to distinguish pseudosubluxation from true subluxation. True subluxation should be suspected if the posterior cervical line misses the anterior aspect of the C2 spinous process by 2 mm or more.