Cervical Spine Trauma
- DOI:
- 10.1093/med/9780199350940.003.0007
• Trauma patients should be assumed to have injury to the cervical spine until proven otherwise.
• Patients with histories involving traumatic mechanisms that could cause cervical spine injury must be immobilized in a rigid cervical collar until a specialized examination is performed.
• The forces involved at the time of injury need to be assessed. These might include compressive, distractive, hyperextension, hyperflexion, lateral flexion, rotational, or translation forces.
• Cranial nerves may be injured in tandem with high cervical spine fractures and dislocations and must, therefore, be closely examined as part of the cervical spine trauma evaluation.
• The cervical spine cannot be cleared clinically for patients who are not alert or who have distracting injuries.
• Many, but not all, cervical fractures and dislocations can be identified on the lateral cervical radiograph. Inspection can begin with examination of the continuity of the anterior vertebral, posterior vertebral, spinolaminar, and spinous process lines. It is important to include the cervicothoracic junction in lateral cervical spine radiographs.
• In patients with acute spinal cord injury, early intervention to decompress the spinal cord increases the chance of neurologic recovery.
• Atlanto-occipital dissociation or dislocation can be diagnosed using the Powers ratio, calculated as the distance from the basion to the posterior arch of C1, divided by the distance from the anterior arch of C to the opisthion. Ratios of more than 1 are concerning for anterior dislocation of the occiput in relation to C1.
• Type II odontoid fractures have a high rate of nonunion. Risk increases with patient age of more than 50 years, displacement of more than 5 mm, posterior displacement, and angulation of more than 10 degrees.
• The Allen-Ferguson classification system divides subaxial fractures and dislocations according to the dominant forces and spinal position at the time of injury: compressive flexion, distractive flexion, lateral flexion, compressive extension, distractive extension, and vertical compression.
• The subaxial injury classification system grades injuries according to the morphology of the injury, the extent of discoligamentous complex damage, and the extent of neurologic compromise. Patients with higher scores are more likely to require surgery.
• Surgical interventions for cervical spine trauma aim to reduce spinal cord or nerve root compression and provide short-term and long-term mechanical stability to the cervical spine, thereby preventing pain, deformity, and further neurologic injury.
• It is important to consider the specific patient-related factors such as previous level of function, medical comorbidities, associated injuries, and the patient’s personal beliefs and wishes when determining the optimal treatment.
Injuries to the cervical spine typically result from high-energy trauma such as motor vehicle accidents, falls from heights, high-impact sports (e.g., football, diving), and violence. Trauma patients should be assumed to have cervical spine injury until proven otherwise. Missed injuries can lead to permanent disability. Approximately 2.5% of blunt trauma patients have fractures to the cervical spine.1 Age older than 65 and male sex are significant risk factors for injuries to the cervical spine in trauma victims, each factor having a relative risk approximately twice that of younger victims.2 C2 is the most common cervical vertebrae injured, representing 24% of fractures. C6 and C7 account for an additional 39% of fractures, with the subaxial spine (C3–7) accounting for 65% of cervical fractures and 75% of cervical dislocations and subluxations.1
It is essential to obtain details about the mechanisms of injury when evaluating trauma patients. High-energy motor vehicle accidents, falls from heights, and associated head injuries should raise suspicion for cervical spine injury. As discussed below, various injury patterns can result from different forces on the neck and head. Therefore, one should determine whether compressive, distractive, hyperextension, hyperflexion, lateral flexion, rotational, or translation forces were at play at the time of injury. Distractive forces, for example, can cause ligamentous injury that may not be obvious on initial radiographic imaging, and knowledge of the mechanism of injury may lead one to investigate further. It is also important to identify preexisting cervical spine conditions such as diffuse idiopathic skeletal hyperostosis, ankylosing spondylitis, cervical radiculopathy or stenosis, previous cervical spine surgery, and any associated baseline neurologic deficits. The patient should be questioned about the presence and quality of numbness, pain, weakness, or paresthesias in the neck and extremities. The timeline of progression of symptoms should be reviewed as well.
Trauma patients who are suspected of having a cervical spine injury must have the neck immobilized in a rigid cervical collar until a specialized examination is possible. The neck should be kept in neutral flexion–extension and the collar fitted snugly so that no more than two fingers can be placed between the patient’s closed jaw and the chinrest of the collar. Any deformity of the neck should not be forcibly corrected when placing the cervical collar.
Key Physical Examination Maneuvers
As in any trauma evaluation, it is important to begin the physical examination by assessing airway, breathing, and circulation. Ecchymosis across the abdomen and chest (seatbelt sign) should raise suspicion for flexion–distraction injuries of the spine. During the secondary survey, the immobilization collar should be removed carefully and the neck inspected for rotational deformities. The posterior cervical spine should be palpated for the presence of tenderness, step-offs, or crepitus. Midline bony tenderness should be differentiated from paraxial muscular pain. Next, the cervical collar should be reapplied, the patient logrolled carefully, and the remaining spine visualized and palpated. A neurologic examination should be performed, including testing of the cranial nerves, which can be injured in high cervical spine injuries.
The following are several examination maneuvers that may assist with evaluation of the cervical spine (maneuvers involving neck motion should be deferred until imaging is reviewed3):
1. Hoffman sign. The examiner flicks the nail of the distal phalanx of the middle finger and watches for reflexive contraction of the thumb. The presence of this reflex may indicate cervical myelopathy because it represents a hyperactive deep tendon reflex.
2. Lhermitte sign. The patient is asked to maximally flex the neck and trunk. Radiating pain or paresthesia down the arms or spine suggests the presence of cervical spinal stenosis.
3. Romberg sign. While standing, the patient is asked to keep the arms outstretched forward with palms up while the eyes are closed. Inability to maintain balance suggests possible myelopathy and, specifically, injury to the dorsal column of the spinal cord.
4. Spurling sign. The examiner stands behind the patient, slowly extends and rotates the patient’s head to the side of suspected neural impingement, and applies gentle axial compression. Radiating pain or paresthesia down the arm indicates cervical foraminal stenosis.
Cervical Spine Clearance and Removal of Cervical Collars
According to the National Emergency X-Radiography Utilization Study (NEXUS) low-risk criteria,4,5,6 trauma patients who have been placed in a cervical collar but have no apparent spinal injury may be cleared clinically and without radiographic imaging if they meet the following criteria:
1. The patient must be awake and alert.
2. The patient cannot be intoxicated.
3. There must be no neurologic deficits.
4. There must be no painful, distracting injuries.
5. There must be no posterior midline cervical spine tenderness.
If the patient meets all of the above criteria, the NEXUS criteria suggest the cervical spine can be cleared clinically without need for any radiographic imaging. An alternative algorithm known as the Canadian C-spine rule (CCR) has been shown to have higher sensitivity and specificity for cervical spine injury than the above criteria and would potentially decrease the rates of radiography (Fig. 7.1).7,8 Importantly, the CCR assesses whether there are specific high-risk or low-risk factors that might suggest the need for imaging and requires the patient to be able to rotate the neck actively by 45 degrees to the left and right to be cleared without radiography.
Figure 7.1. The Canadian C-spine rule.
Reprinted with permission from Stiell IG, Clement CM, McKnight RD, Brison R, Schull MJ, Rowe BH, et al. The Canadian C-spine rule versus the NEXUS low-risk criteria in patients with trauma. N Engl J Med. 2003;349(26):2510–2518, Figure 1.
Just as it is important for the cervical spine to be placed in a rigid cervical collar promptly, it is also important that the cervical spine be assessed for injury and that the collar is removed when not needed, to prevent complications such as aspiration and ulcers (typically occipital and submandibular).
If the cervical collar cannot be cleared clinically, radiographs and/or computed tomography (CT) scans should be obtained to assess for spinal injury. The standard cervical spine radiographic series consists of anteroposterior (AP), lateral, and odontoid views. On the lateral view, spinal alignment should be evaluated by inspecting the anterior vertebral line, posterior vertebral line, spinolaminar line, and spinous process line (Fig. 7.2). The soft tissue line should also be evaluated. A swimmer’s view or CT scan can be obtained if there is difficulty capturing the cervicothoracic junction. Oblique views can help to assess for foraminal stenosis. If standard radiographs are negative and there is suspicion for instability, flexion–extension radiographs can be obtained, but these should be performed only for an awake and alert patient who has no neck pain or neurologic injury and shows full range of motion. All radiographs should be inspected for fracture, segmental angulation, listhesis, kyphosis, and thickened prevertebral soft tissues. Prevertebral soft tissues are normally approximately 6 mm or less at C2 and 18 mm at C6.9,10
Figure 7.2. Key spinal lines on a lateral cervical radiograph. Most cervical fractures and dislocations can be identified on a lateral cervical radiograph. Inspection can begin with examination of the continuity of the anterior vertebral, posterior vertebral, spinolaminar, and spinous process lines. The soft tissue line should also be evaluated carefully.
At many trauma centers, CT has replaced radiography as the initial imaging technique to assess for spinal injury because of its higher sensitivity for detecting spinal injury and quicker speed to obtain acceptable images. Otherwise, CT should be performed whenever abnormalities are seen on radiographs or when acceptable radiographs cannot be obtained. Some authors will clear cervical collars on the basis of negative imaging alone, whereas others will wait until clinical criteria are met as well (e.g., in the case of an intoxicated patient). If there is suspicion for neurologic or soft tissue (e.g., ligamentous) injury, magnetic resonance imaging (MRI) should be obtained. This technology can detect posterior ligamentous complex disruption, disc herniation, and spinal cord injury. Magnetic resonance angiography and CT angiography can assess for vertebral artery injury.
Operative Versus Nonoperative Treatment
Before discussing specific categories of cervical spine injuries, it is important to emphasize the broad goals of surgical treatment. Any surgical intervention aims to reduce spinal cord or nerve root compression and provide short-term and long-term mechanical stability to the cervical spine, thereby preventing pain, deformity, and further neurologic injury. Although many guidelines exist to assist surgeons when selecting operative versus nonoperative treatment for particular cervical spine injuries, it is important to consider the specific patient-related factors such as previous level of function, medical comorbidities, associated injuries, and the patient’s personal beliefs and wishes.3
Neurologic deficits after cervical spine injuries follow various patterns that can range from transient symptoms to permanent disabilities.
Stingers or Burners
Injuries to the cervical nerve roots and brachial plexus can present as “stingers” or “burners.” These transient neurapraxia injuries commonly take place during contact sports. During football, for instance, they can result from a tackle in which the player’s neck is flexed laterally.11 This places the ipsilateral cervical foramina in maximal compression and the brachial plexus contralateral to the direction of neck flexion in maximal tension. Patients report sensations of burning or stinging down one arm, which often subsides after a few minutes. Although sensory changes and paresthesias are the most common symptoms, motor weakness can follow up to 7 days later.12
Nerve Root Injury
Radicular symptoms that do not quickly subside, as in the case of stingers, often result from nerve compression by herniated intervertebral discs, dislocated segments, or fracture fragments. Such injuries can cause decreased sensation and paresthesias in a particular dermatome or weakness in a myotome. They can also present more subtly, with absence of deep tendon reflexes at a particular level, even in the presence of full voluntary motor function.
Transient Quadriparesis
Whereas stingers involve a single or limited number of cervical nerve roots, transient quadriparesis or quadriplegia refers to short-lasting neurapraxia involving the entire cervical spinal cord. Patients present with weakness and sensory changes in more than one limb that can last from minutes up to 36 hours. Often, this condition is associated with stenosis of the cervical spinal canal.13 Although transient quadriparesis can occur even in the absence of acute fracture or ligamentous injury, radiographs and MRI scans may show acute cervical abnormalities.14
Spinal Cord Injuries
Spinal cord injuries can be divided into complete and incomplete injuries. According to the American Spinal Injury Association (ASIA) classification of spinal cord injury, the neurologic level of injury refers to the most caudal level of the spinal cord with intact sensation and antigravity muscle strength (3 or greater), provided that more rostral levels have normal sensory and motor function.15 A complete spinal cord injury refers to absence of any motor or sensory function below the injured level, including loss of voluntary anal contraction and sensation. Importantly, certain reflexive movements such as spontaneous limb flexion can occur after a complete spinal cord injury, and these should not be confused with voluntary movements. Deep tendon reflexes are often hyperreflexive in the later stages after acute spinal cord injury (initially, they may be absent or hypoactive). Patients with incomplete spinal cord injuries retain some motor or sensory function (motor incomplete or sensory incomplete spinal cord injury, respectively). Central spinal cord injury is an incomplete injury that results from a hyperextension mechanism and presents with deficits that affect the upper extremities more than the lower extremities. Patients may present with burning and paresthesias in both upper extremities.
In patients with acute spinal cord injury, early intervention to decompress the spinal cord increases the chance of neurologic recovery.16 Administration of high doses of steroids (e.g., methylprednisolone) remains controversial in acute spinal cord injury.17,18,19
Fractures of the occipital condyles can result from axial loading of the skull on the lateral masses of C1. Lateral hyperflexion can also create the compressive force needed to cause this high-energy fracture. These injuries can be missed on conventional radiographs and are more likely to be diagnosed using CT. Cranial nerves (particularly IX–XII) should be tested because of the proximity to the zone of injury. The Anderson and Montesano classification20 divides these injuries into three categories:
1. Type I: Compression/impaction-type fracture leading to comminution of the occipital condyle
2. Type II: Shear-type fracture extending into the skull base, resulting from a direct blow to the skull
3. Type III: Condylar-alar ligament avulsion fracture caused by forced rotation and lateral bending.
Most type I and type II fractures are considered stable injuries because of preservation of the alar ligaments and tectorial membranes. If the occipital condyle fracture is stable and there is minimal fragment displacement into the foramen magnum, it can often be treated with cervical orthosis and analgesics. Type III fractures are more likely to be unstable and may require halo immobilization or occipitocervical fusion. Other indications for surgical intervention and possible fusion include neural compression from displaced fracture fragments and associated injuries to the upper cervical spine.
Atlanto-occipital Dissociation
Dissociation of the skull from the cervical spine typically occurs after high-energy injuries that cause tears of the alar ligaments and tectorial membrane. This injury is often fatal, and the cervical spines of patients who have sustained such an injury should be considered highly unstable. The Traynelis classification21 divides atlanto-occipital dissociations as follows:
1. Type I: Anterior dislocation (occiput translated anteriorly relative to the cervical spine)
2. Type II: Longitudinal dislocation (distraction causes the condyles to dissociate from the atlas without associated translation)
3. Type III: Posterior dislocation (occiput translated posteriorly relative to the cervical spine).
Anterior atlanto-occipital dissociation or dislocation can be diagnosed using the Powers ratio,22 which is calculated as the distance from the basion to the posterior arch of C1, divided by the distance from the anterior arch of C1 to the opisthion (Fig. 7.3). A Powers ratio of more than 1 is concerning for anterior dislocation of the occiput in relation to C1. A distance between the basion and dens (the basion–dens interval) of more than 9 to 12 mm is another sign that is concerning for atlanto-occipital dissociation.23,24
Figure 7.3. Powers ratio. Sagittal reconstructed CT image. Powers ratio (BC/OA) is calculated as the distance from the basion (B) to the posterior arch of C1 (C), divided by the distance from the opisthion (O) to the anterior arch of C1 (A). Ratios of more than 1 are concerning for anterior dislocation of the occiput in relation to C1.
These injuries are often highly unstable, requiring posterior occipitocervical fusion for long-term stabilization.
C1–2 Subluxation (Atlantoaxial Instability)
A widened atlanto–dens interval (ADI) provides radiographic evidence of atlantoaxial instability (Fig. 7.4). In healthy adults, ADI is typically less than 3 mm for men and less than 2.5 mm for women. In children less than 15 years old, ADI is typically less than 5 mm. In those with atlantoaxial instability, flexion–extension radiographs can show dynamic changes to the ADI. However, flexion–extension radiographs are often contraindicated in the acute traumatic setting, especially when neurologic deficits are present or radiographs already show strong evidence for spinal instability. In the setting of trauma, C1–2 subluxation typically results from forced flexion leading to rupture of the transverse ligament or an avulsion fracture from the C1 lateral mass via the ligament. CT can show an avulsed lateral mass fragment, whereas MRI can provide more direct visualization of a ruptured ligament. Traumatic atlantoaxial instability involving avulsed lateral mass fragments can be treated with halo immobilization until osseous healing is observed, whereas C1–2 fusion is often indicated for instability resulting from direct transverse ligament tears.
Figure 7.4. Atlantoaxial instability. The length between the two arrowheads represents the atlanto–dens interval (ADI). In healthy adults, ADI is typically less than 3 mm for men and less than 2.5 mm for women.
Reprinted with permission from Zebala LP, Buchowski JM, Daftary A, O’Brien JR, Carrino JA, Khanna AJ. The cervical spine. In: Khanna AJ, ed. MRI Essentials for the Spine Specialist. New York: Thieme, 2014:111–154, Figure 6.13B.
Atlantoaxial rotatory subluxation is caused by a flexion–extension injury mechanism combined with a rotational component and sometimes occurs spontaneously without any clear traumatic history. The Fielding classification divides these injuries according to pivot point (odontoid or facet), transverse ligament competence, and ADI.25 In approximately half of these injuries (Fielding type I), the odontoid serves as the pivot point, leaving the transverse ligament intact with an ADI of less than 3 mm. These subluxations can often be treated with gradual cervical halter traction while the patient is supine. Rarely will they require surgical intervention such as C1–2 fusion.
High-energy axial loads on C1 can result in a range of fracture patterns, including isolated fractures to the anterior arch, posterior arch, or transverse processes; comminuted fractures of the lateral masses; and combined fractures of the anterior and posterior arches (known as burst fractures).26 These fractures often do not cause neurologic injury because of the large space available for the spinal cord at this vertebral level. Burst fractures, also known as Jefferson fractures, force the lateral masses to displace laterally away from the canal. T2-weighted MR images allow assessment for rupture of the transverse ligament, which provides C1–2 relational stability and is a critical factor in surgical decision-making. When the right and left overhang distances of C1 lateral masses (relative to the lateral aspect of C2) are 7 mm or more on the open mouth radiographic view, the transverse ligament is deemed ruptured and the fracture is considered unstable.
Aside from Jefferson burst fractures with a lateral mass overhang of more than 7 mm, C1 ring fractures rarely require surgery and can be treated with rigid cervical orthosis or halo immobilization. Indications for surgical stabilization include midsubstance tear of the transverse ligament and deformity resulting from associated rotatory instability. For unstable fracture patterns, posterior C1–2 fusion is preferred versus occipitocervical fusion if adequate C1 purchase can be achieved.
C2 fractures are broadly categorized into odontoid process fractures, lateral mass fractures, and pars fractures (also known as hangman’s fractures).
Odontoid Process Fractures
Approximately half of axis fractures are odontoid fractures, which can result from hyperextension or hyperflexion injuries. The vascular supply to the odontoid process arrives via vessels at the apex and the C2 vertebral body below its base, which results in a watershed area at the base of the dens. Odontoid fractures27,28 are classified in relation to this watershed area:
1. Type I: Apical avulsion fracture (typically involving the alar ligament)
2. Type IIA: Base fracture (at the junction of the odontoid process and C2 body)—minimally displaced or nondisplaced (Fig. 7.5)
3. Type IIB: Base fracture—displaced, with oblique, anterosuperior-to-posteroinferior fracture line
4. Type IIC: Base fracture—displaced, with oblique, anteroinferior-to-posterosuperior fracture line
5. Type III: Body fracture involving cancellous bone of C2. May extend into the lateral facets.
Figure 7.5. A, Sagittal T2-weighted MR image showing a type IIA odontoid fracture (arrow). Note the prevertebral edema or hematoma (arrowhead). B, Artist’s sketch.
Reprinted with permission from Zebala LP, Buchowski JM, Daftary A, O’Brien JR, Carrino JA, Khanna AJ. The cervical spine. In: Khanna AJ, ed. MRI Essentials for the Spine Specialist. New York: Thieme, 2014:111–154, Figures 6.12A and B.
If isolated, type I and type III fractures are typically stable and can be treated nonoperatively with cervical collar (type I) or halo immobilization (type III). Type II fractures have a high rate of nonunion (risk increases with patient age, displacement of more than 5 mm and posterior displacement, and angulation of more than 10 degree).29,30,31,32 Type II fractures with high risk of nonunion can benefit from surgical fixation such as anterior screw fixation by lag technique (type IIB is most amenable) or C1–2 fusion.
C2 Lateral Mass Fractures
These fractures can result from combined axial compression and lateral bending. Initial treatment typically involves cervical collar immobilization. Chronic pain associated with the fracture may be an indication for fusion at a later stage.
C2 Pars Fractures (Hangman’s Fractures)
Traumatic anterior spondylolisthesis of C2 is typically caused by hyperextension with axial loading, resulting in fracture of the bilateral pars interarticularis of C2. It can occur in diving injuries. The Levine and Edwards classification system33 categorizes these fractures according to the level of displacement, angulation, translation, and C2–3 disc disruption:
1. Type I: Nondisplaced fracture, less than 3 mm of translation and no angulation, C2–3 disc intact
2. Type II: Displaced fracture, substantial angulation at C2–3, more than 3 mm of translation, C2–3 disc disrupted
3. Type IIA: Displaced fracture, severe angulation at C2–3 but no translation, severe disruption of the C2–3 ligamentous complex, hinges on the anterior longitudinal ligament
4. Type III: Associated unilateral or bilateral C2–3 facet dislocation.
Type I fractures can often be treated with cervical orthosis. Type II fractures with less than 5 mm of displacement can be reduced using axial traction plus extension and then immobilized in a halo for at least 6 weeks. Displacement of more than 5 mm often requires surgical stabilization. Type IIA fractures should not be placed in traction because of insufficiency of the C2–3 ligamentous complex, which can lead to exacerbation of symptoms. Rather, they should be reduced using hyperextension alone followed by halo immobilization. Type III fractures typically require halo traction followed by open reduction and internal fixation (of C2) and/or fusion (C2–3 or C1–3).
Allen-Ferguson Classification System
The Allen-Ferguson classification system,34 described in 1982, divides subaxial fractures and dislocations according to mechanism of injury and was derived from static radiographs of 165 patients (Fig. 7.6). Six categories of injuries are described according to the dominant forces and spinal position when the injury occurred:
Figure 7.6. The Allen-Ferguson classification system for subaxial cervical spine injuries.
Reprinted with permission from Chapman JR, Anderson PA. Cervical spine trauma. In: Frymoyer J, Ducker TB, Hadler NM et al, eds. The Adult Spine: Principles and Practice. 2nd ed. Philadelphia, PA: Lippincott-Raven; 1997:1245–1295.
1. Compressive flexion
2. Vertical compression
3. Distractive flexion
4. Compressive extension
5. Distractive extension
6. Lateral flexion.
These six categories are subdivided into stages according to the extent of injury and anatomic disruption.
Subaxial Injury Classification System
The more recently introduced subaxial injury classification (SLIC) system (Table 7.1)35 builds on the Allen-Ferguson classification system and grades injuries according to the following:
Table 7.1. Subaxial Cervical Spine Injury Classification System Scale.
|
Characteristic |
Points |
|---|---|
|
Morphology |
|
|
No abnormality |
0 |
|
Compression |
1 |
|
Burst |
+1 = 2 |
|
Distraction* |
3 |
|
Rotation/translation† |
4 |
|
Discoligamentous complex |
|
|
Intact |
0 |
|
Indeterminate¶ |
1 |
|
Disrupted** |
2 |
|
Neurologic status |
|
|
Intact |
0 |
|
Root injury |
1 |
|
Complete cord injury |
2 |
|
Incomplete cord injury |
3 |
|
Continuous cord compression in setting of neurologic deficit |
+1 |
*E.g., facet perch, hyperextension.
†E.g., facet dislocation, unstable teardrop, or advanced-stage flexion–compression injury.
¶E.g., isolated interspinous widening, MRI signal change only.
**E.g., widening of disc space, facet perch, or dislocation.
Adapted from Vaccaro AR, Hulbert RJ, Patel AA, Fisher C, Dvorak M, Lehman RA, Jr., Anderson P, Harrop J, Oner FC, Arnold P, Fehlings M, Hedlund R, Madrazo I, Rechtine G, Aarabi B, Shainline M, Spine Trauma Study Group. The subaxial cervical spine injury classification system. A novel approach to recognize the importance of morphology, neurology, and integrity of the disco-ligamentous complex. Spine (Phila Pa 1976). 2007;32:2365–2374, Table 1.
1. Morphology of the injury
2. Extent of discoligamentous complex damage (best evaluated on MRI)
3. Extent of neurologic compromise.
Injuries with higher scores on the SLIC scale are more likely to require surgical treatment. A surgical algorithm based on the SLIC scale was described by Dvorak et al.36 in 2007.
Compressive Flexion Injuries
These injuries occur when the spine is axially loaded while in a flexed position and can range from relatively stable to highly unstable injuries. In the most minor stage of this injury, patients present with compression fractures of the anterosuperior endplate. In the most severe injuries, patients develop a “teardrop” (triangular) or quadrangular fracture anteriorly, complete disruption of the posterior ligamentous complex, and retrolisthesis of the inferoposterior margin of the vertebra into the neural canal (Fig. 7.7). Patients with neurologic injury should be evaluated with MRI to evaluate for an acute disc herniation. Whereas compression fractures without neurologic compromise typically can be treated with a cervical orthosis, teardrop and quadrangular fractures often require acute anterior decompression (e.g., corpectomy) and surgical stabilization with anterior bone graft, plating, and often posterior instrumentation.
Figure 7.7. Quadrangular fracture from compressive flexion injury. Sagittal reconstructed CT image.
Reprinted with permission from Khanna AJ, Kwon BK. Subaxial cervical spine injuries. In: Rao RD, Smuck M, eds. Orthopaedic Knowledge Update: Spine 4. 4th ed. Rosemont (IL): American Academy of Orthopaedic Surgeons, 2012:221–233, Figure 3.
Vertical Compression Injuries (Burst Fractures)
Pure axial loading of the cervical spine can lead to burst fractures (Fig. 7.8). Displacement of vertebral body fragments into the neural canal (a complete burst fracture) is rare in the cervical spine and typically occurs in more caudal vertebra. It is important to obtain an MRI scan to assess for injury to the disc and posterior ligamentous complex. Depending on the extent of fragment retropulsion and neural compromise, these injuries may require anterior decompression and reconstruction combined with posterior instrumentation.
Figure 7.8. Cervical burst fracture. Artist’s illustration of (A) sagittal and (B) axial views showing cord compression. The white arrow in A shows fractured vertebral body. The two black arrows in B show retropulsion of vertebral body fragments into the spinal cord.
Reprinted with permission from Zebala LP, Buchowski JM, Daftary A, O’Brien JR, Carrino JA, Khanna AJ. The cervical spine. In: Khanna AJ, ed. MRI Essentials for the Spine Specialist. New York: Thieme, 2014:111–154, Figures 6.11B and D.
Distractive Flexion Injuries (Facet Joint Dislocations and Fractures)
On lateral radiographs, facet joints should align well with the rostral and caudal segments, and the joints should not be wider than 2 mm. Widening of the joints, or perched facets, suggests facet subluxation or dislocation, which can be associated with ligamentous or bony injury. The Allen-Ferguson classification system categorizes distractive flexion injuries into four stages: facet subluxation, unilateral facet dislocation, bilateral facet dislocation with 50% displacement, and bilateral complete facet dislocation. A locked facet dislocation, or “jumped facet,” occurs when the inferior articular process of one vertebra is translated anteriorly over the superior articular process of the caudal vertebra (Fig. 7.9). Dislocations occur most commonly at C5–6 and C6–7. Unilateral facet dislocations often involve less than 50% translation of the vertebral body, whereas bilateral facet dislocations typically involve more than 50% translation. Bilateral facet dislocations are associated with high rates of cervical spinal cord injuries, with approximately 30% of patients having complete spinal cord injuries.37
Figure 7.9. Bilateral facet dislocations. A, Sagittal T2-weighted MR image shows translation of C7 over T1 and cord compression caused by a disc extrusion (arrow). B, Parasagittal T2-weighted gradient-echo image demonstrating facet dislocation (black arrow and arrowhead).
Reprinted with permission from Zebala LP, Buchowski JM, Daftary A, O’Brien JR, Carrino JA, Khanna AJ. The cervical spine. In: Khanna AJ, ed. MRI Essentials for the Spine Specialist. New York: Thieme, 2014:111–154, Figures 6.5A and C.
Many authors recommend obtaining an MRI before reduction to rule out a herniated disc, which occurs in approximately 7% of cases. If MRI shows a herniated disc, then open anterior decompression before reduction is recommended. If there is no herniated disc and the patient is alert and cooperative, then closed reduction may be attempted. The procedure is as follows.
Gardner-Wells tongs are applied to the head symmetrically 1 cm above the pinna of each ear and in line with the external auditory meatus. Slight posterior placement of the pins can apply a flexion force to the skull and thereby assist in reduction (note that anterior placement of pins can apply a harmful extension force and places the superficial temporal vessels and temporalis muscles at risk). Serial radiographs are taken as 10 pounds of weight is sequentially added to the traction. The maximum allowed weight is controversial, with some suggesting a safe limit of 70 pounds and others reporting successful application of 100 to 140 pounds. When radiographs show the proximal facet perched just over the caudal facet, one can proceed with the reduction maneuver. For unilateral facet dislocations, the head should be rotated 30 to 40 degrees in the direction of the dislocation. For bilateral facet dislocations, the spinal process step-off posteriorly should be palpated, and pressure should be applied upon the caudal spinous process anteriorly. Then the head should be rotated 40 degrees in one direction and then 40 degrees in the other direction. Any development or worsening of neurologic symptoms should be followed immediately by removal of weights and MRI if not previously obtained.
Surgical stabilization is typically required in cases of facet dislocation, and interventions require anterior-only, posterior-only, or combined anterior and posterior approaches, depending on the extent of anterior compression causing neurologic compromise and the difficulty of open reduction if an anterior approach is taken.
Extension Injuries
The Allen-Ferguson system classifies cervical spine extension injuries as compressive extension injuries or distractive extension injuries. Compressive extension injuries range from a unilateral vertebral arch fracture to bilateral vertebral arch fractures and anterior displacement of the rostral vertebral body (with ligamentous failure anteroinferiorly and posterosuperiorly). In distractive extension injuries, distractive tension placed on the anterior column results in anterior longitudinal ligament failure or transverse fracture of the vertebral body (Fig. 7.10). In stage 1 injuries, there is no displacement of the vertebral body into the neural canal. In stage 2 injuries, there is failure of the posterior ligamentous complex as well, which leads to posterior displacement of the vertebral body into the canal.
Figure 7.10. Distractive extension injury. A, Sagittal reconstructed CT image shows avulsion of C4 (arrow) from a hyperextension injury. B, Sagittal T2-weighted MR image shows bright signal (arrow) within the anterior disc consistent with tensile failure. Note the anterior soft tissue edema (arrowheads).
Reprinted with permission from Khanna AJ, Kwon BK. Subaxial cervical spine injuries. In: Rao RD, Smuck M, eds. Orthopaedic Knowledge Update: Spine 4. 4th ed. Rosemont (IL): American Academy of Orthopaedic Surgeons, 2012:221–233, Figure 5.
Lateral Flexion Injuries
Lateral flexion injuries result from blunt, laterally direct trauma to the head or neck. This causes a distractive force on the side ipsilateral to the trauma and a compressive force contralaterally. In stage 1, these injuries result in asymmetric vertebral body compression fractures combined with a vertebral arch fracture. In stage 2, ligamentous failure can lead to vertebral body and arch displacement.
Lateral flexion injuries, as well as hyperextension and rotational injuries, can also result in cervical lateral mass fractures, particularly of the comminution type described by Kotani et al.38 The Kotani classification system38 divides these fractures as follows (Fig. 7.11):
1. Separation type: Involves fracture lines at the lamina and pedicle unilaterally
2. Comminution type: Multiple, comminuted fracture lines in and around the lateral mass
3. Split type: Vertical fracture line in the lateral mass caused by the superior articular process of the caudal vertebra hitting the inferior articular process of the rostral vertebra
4. Traumatic spondylolysis type: Bilateral pars interarticularis fractures causing complete separation of the anterior and posterior elements of the vertebra.
Figure 7.11. Kotani classification system of lateral mass fractures. A, Separation type. B, Comminution type. C, Split type. D, Traumatic spondylolysis type.
Reprinted with permission from Kotani Y, Abumi K, Ito M, Minami A. Cervical spine injuries associated with lateral mass and facet joint fractures: new classification and surgical treatment with pedicle screw fixation. Eur Spine J. 2005;14(1):69–77, Figure 1.
Many lateral mass fractures require surgical stabilization, such as posterior decompression and two-level instrumented fusion or anterior plating and interbody fusion. Certain types of lateral mass fractures without gross instability can be stabilized directly with a single posterior pedicle screw on the side of the fracture.
Cervical Spinous Process Avulsion Fracture (“Clay Shoveler’s Fracture”)
This refers to an avulsion fracture of the spinous processes in the lower cervical and/or upper thoracic spine (most commonly at C7). It can result from a strong musculoligamentous pulling force during flexion or extension (classically when shoveling hard, unyielding clay) or a direct trauma to the spinous process. These fractures can often be treated nonoperatively and have good rates of union. Chronic pain from a nonunion can be treated with surgical excision.
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