Summary of Key Points
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Occipitocervical injuries should always be suspected in cases of high-impact trauma.
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It is relevant to evaluate for additional injuries.
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Special attention should be paid to pure transverse ligament injuries that cannot expect to heal with nonoperative management.
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When appropriate, incomplete spinal cord injuries with compressive lesions warrant surgical intervention as soon as possible.
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When possible, early surgical intervention is desirable to promote early mobilization and rehabilitation.
The occipitocervical junction includes the skull base at the foramen magnum, C1, C2, and the associated ligamentous, neural, and vascular structures. Because of the important neural and vascular structures in the region, occipitocervical junction injuries have the potential to cause significant neurologic morbidity or mortality. Therefore, careful recognition, diagnosis, and management of these injuries are essential. The association with high-impact trauma and occipitocervical junction injuries is well recognized. However, the potential for injuries even with relatively minor trauma should be remembered, especially with abnormal bone (e.g., osteoporosis) or ligaments (e.g., rheumatoid arthritis).
Occipitocervical junction injuries can be classified in several ways ( Box 127-1 ). One useful system describes occipitocervical junction injuries as isolated ligamentous injuries, isolated fractures, or mixed ligamentous and bony injuries. Occipitocervical junction trauma can also be described by the site or level(s) of injury. At most sites, classification systems have been developed for specific injury patterns (e.g., C2 odontoid fractures). Finally, occipitocervical junction injuries can be described on the basis of their stability. Stability is generally determined with clinical and radiographic assessment, sometimes using dynamic flexion/extension radiographs. A stable injury does not demonstrate significant radiographic deformity, pain, or neurologic dysfunction with normal physiologic loads and movement. An example of a stable injury would be an isolated C2 spinous process fracture that meets the preceding criteria. Some injuries are clearly unstable, such as occipitocervical dislocations. Other injuries may initially appear stable but have a reasonable chance of developing delayed instability with time, gravity, movement, or relaxation of paraspinal muscle spasm. This category reflects the reality that clinical and radiographic assessment of long-term stability may be indeterminate.
A
Location of Bone or Ligamentous Injury
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Pure ligamentous injuries
Occipitoatlantal dislocations
Transverse ligament injuries
Rotatory C1-2 dislocations
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Isolated fractures
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Occipital condyle fractures
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C1 (lateral mass, ring)
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C2 (odontoid, body, hangman, dorsal element)
- •
- •
Mixed ligamentous and bony injuries
B
Site/Level of Injury
Occipital bone (C0) (e.g., condyle fracture)
C0-1 ligaments (e.g., occipitoatlantal dislocation)
C1 (e.g., lateral mass, ring fractures)
C1-2 ligaments (e.g., transverse ligament injuries)
C2 (odontoid, body, hangman, dorsal element fractures)
C
Degree of Stability
Stable
Low probability of delayed instability
High probability of delayed instability
Unstable
The preceding classification systems are helpful in injury assessment and planning management. However, the management of a patient with occipitocervical junction trauma is best determined by considering the nature of the injury (including associated injuries), patient characteristics (e.g., age, medical risk factors, bone quality, desire and ability to tolerate use of a halo orthosis), and the physician’s experience. Although much less common, penetrating trauma to the occipitocervical junction presents unique issues that relate to the specific location and trauma modality (e.g., bullet, knife). This class of injuries is not specifically discussed in this chapter but is addressed in Chapter 142 . Although most of the principles from blunt trauma are applicable to penetrating trauma, it is important to point out some important differences. Compared with blunt trauma, penetrating trauma typically results in less ligamentous injury and, therefore, for a similar fracture, may be more stable. However, penetrating trauma more commonly results in trauma to vascular or other important regional structures.
General Principles
The initial management of occipitocervical junction injuries is focused on basic trauma management principles, including the establishment and maintenance of airway, breathing, and circulation; careful immobilization and transportation; and recognition and management of any associated injuries. These principles have evolved over time and have been published in numerous settings.
Occipitocervical junction injuries are frequently recognized on routine cervical spine imaging. However, these injuries may be difficult to detect on initial diagnostic studies. Clinical suspicion based on history and physical examination can aid recognition. Routine radiographs and clinical assessment are often inadequate to fully characterize the injury, and more specialized imaging is usually indicated. Coronal, curved coronal, sagittal, or three-dimensional computed tomography (CT) reconstruction views can be extremely helpful in characterizing the presence and nature of injury. Magnetic resonance imaging (MRI) may be difficult or impossible to obtain acutely but can often provide essential information on spinal canal compromise and may suggest the presence and degree of ligamentous injury. Dynamic imaging with plain radiographs, CT, or MRI can be valuable in assessing stability but should be performed carefully. Occasionally, stability is checked with real-time fluoroscopy during careful flexion and extension controlled by a qualified examiner. For example, fluoroscopic flexion/extension imaging may be helpful when there is urgent need to assess the stability of the cervical spine in an unresponsive patient but there is still controversy about its interpretation.
Once occipitocervical junction injuries are diagnosed, management decisions are based on several factors, including the extent and stability of injury, the presence or progression of neurologic deficits, and patient-specific factors that influence the risks with different treatments. Nonoperative management typically includes some type of rigid (halo) or semirigid (collar) orthosis. Operative management is generally indicated for injuries that are unstable, have significant potential for delayed instability, have progressive neurologic deficits, or cause significant deficits or symptoms that are not controlled with nonoperative measures. Operative planning may include obtaining additional imaging (e.g., dedicated studies for image guidance), ensuring the availability of appropriate instrumentation, and arranging neurophysiologic monitoring where appropriate.
Diagnosis and Management
Atlantooccipital Dislocations
Atlantooccipital (AODs) dislocations are relatively uncommon ligamentous injuries that usually result from hyperflexion and distraction during high-impact blunt trauma that is more common in pediatric patients due to flatter condyles and increased ligamentous laxity. These injuries are highly unstable, frequently fatal, and usually result in significant neurologic injury from stretching, compression, or distortion of the spinal cord, brainstem, and cranial nerves. In addition, significant morbidity and mortality can result from associated cerebrovascular injury, which varies significantly among trauma series (0.53% to 88%), diagnosis test used (computed tomography angiography [CTA], conventional angiogram), and severity of injuries. Recognition and rapid management of these injuries may limit further injury, but even with appropriate care, neurologic deficits can progress. Although these were initially felt to be rare, several series of trauma fatalities have revealed an incidence between 8% and 19%.
Lateral cervical spine radiographs may recognize atlantooccipital dislocations (sensitivity, 0.57), especially in severe injuries. However, these injuries can be difficult to diagnose with plain radiographs alone, especially with less severe dislocations. In addition, the frequent presence of coexisting significant head trauma can delay recognition of spinal injury. Diagnostic clues include prevertebral soft tissue swelling, an increase in the dens-basion distance, and separation of the occipital condyles and C1 lateral masses ( Fig. 127-1 ). CT imaging with reconstruction views (sensitivity 0.84) usually provides a better assessment of fractures and alignment than plain radiographs do. The presence of subarachnoid hemorrhage supports but does not confirm the diagnosis. MRI can be helpful for diagnosis (sensitivity 0.86), to assess the extent of spinal cord compression and injury, and to demonstrate compressive hematoma lesions.
On the basis of the injury pattern, Traynelis and colleagues classified atlanto-occipital dislocations into four types: type I (anterior), type II (longitudinal), type III (posterior), and “other” (complex). Multiple diagnostic radiographic criteria have been described to assess the relationship between the skull base and the cervical spine ( Fig. 127-2 ). Although developed for lateral plain radiographs, these criteria can also be used on sagittal reconstruction CT views, provided that there are no significant artifactual distortions. Currently, if a radiologic method for measurement is used to determine AOD on the lateral radiograph, the basion-axial interval–basion dental interval (BAI-BDI or Harris) method is recommended. This method demonstrated increased diagnostic accuracy compared with the Powers ratio. A BDI above 12 mm in adults and children is considered abnormal. The BAI is mainly used for anterior or posterior AOD (Traynelis type I and III) and measures the distance between basion and a line drawn tangentially to the posterior cortical surface of C2 with rostral extension (also known as the posterior axial line), and its normal values range from −4 to 12 mm in adults and from 0 to 12 mm in children. The Wackenheim clival line extends along the dorsal surface of the clivus and should be tangential to the tip of the dens. Ventral or dorsal translation of the skull in relation to the dens will shift the clival line to either intersect or run dorsal to the dens, respectively. The Powers ratio is based on the relationship of the B–C line (from the basion to the C1 dorsal arch) and the O–A line (between the opisthion and the C1 ventral arch). Normal B–C/O–A ratios average 0.77, whereas pathologic ratios (> 1) typically represent occipitocervical dislocations. However, false negatives can occur with longitudinal or dorsal dislocations. The Wholey dens-basion technique assesses the distance from the basion to the dens tip. Although variability is common, the average distance in adults is about 9 mm, and pathologic distances are greater than 15 mm. The Dublin method, the least reliable method, measures the distance from the mandible (posterior ramus) to the ventral part of C1 (normally 2 to 5 mm) and C2 (normally 9 to 12 mm).
Initial management of these injuries focuses on immobilization, almost always with a halo orthosis. Cervical collars are potentially dangerous because they may produce distraction and thereby promote further injury. Similarly, traction can cause neurologic worsening (2 of 21 patients) and should be avoided or used with extreme caution. Nonoperative management does not provide definitive treatment of these injuries because of the significant ligamentous disruption that cannot be expected to heal even with prolonged rigid (halo) external immobilization (11 of 40 patients had a nonunion or neurologic deterioration). Operative stabilization consists of an occipitocervical arthrodesis with rigid internal fixation (discussed later and in Chapter 53 ). Decompression and restoration of alignment may also be necessary to maximize neurologic recovery.
Transverse Ligament Injuries
Isolated traumatic transverse ligament injuries are unstable injuries that can result in significant upper cervical spinal cord injury either during the initial trauma or afterward. These injuries are more common in hyperflexion injuries. Because transverse ligament injuries may be difficult to recognize on initial (neutral) plain radiographs, an elevated index of suspicion is required in some settings—for example, high-impact trauma.
Transverse ligament injuries are suggested or diagnosed indirectly with radiographic imaging. A widened atlantodental interval (ADI) on flexion lateral cervical radiographs (> 3 mm in adults, > 5 mm in children) suggests transverse ligament insufficiency. Thin-cut CT imaging with reconstruction views may suggest the diagnosis by demonstrating a C1 lateral mass avulsion fracture at the ligamentous insertion. Thin-cut MRI with attention to the transverse ligament when using gradient echo sequences can directly demonstrate a transverse ligament injury. If the diagnosis is uncertain, dynamic (flexion/extension) imaging is appropriate for cooperative patients. On the basis of CT and MRI, traumatic transverse ligament injuries can be classified into two categories ( Fig. 127-3 ). Type I injuries involve disruptions of the midportion (IA) or periosteal insertion laterally (IB). Type II injuries involve fractures that disconnect the C1 lateral mass tubercle for insertion of the transverse ligament via a comminuted fracture (IIA) or an avulsion fracture (IIB).
The management of transverse ligament injuries should be individualized. In a retrospective series of 39 patients by Dickman and colleagues, type I injuries that affect mainly ligamentous tissue were managed surgically with dorsal C1-2 arthrodesis and fixation. The surgical options included C1-2 dorsal wiring, C1-2 Halifax clamps, C1-2 transarticular screws, or C1-2 segmental screw fixation (discussed later and in Chapter 53 ). Type II injuries were considered to have a much higher chance of healing with halo immobilization (up to 74%). If a nonunion was still present after a prolonged period of immobilization (> 3 months), then operative stabilization was considered appropriate.
Rotatory C1-2 Subluxations
Rotatory C1-2 subluxations are ligamentous injuries that are more common in children and adolescents with less morbidity and mortality than AOD. These injuries typically present with neck pain and a fixed, rotated “cock-robin” head position. Open-mouth radiographs may demonstrate an asymmetry of the C1 and C2 lateral masses. CT imaging can confirm the rotatory subluxation diagnosis and demonstrate coexisting fractures. C1-2 axial rotation greater than 47 degrees confirms the diagnosis. Three-view CT imaging (15 degrees to the left, neutral, and 15 degrees to the right) can also be helpful in establishing the diagnosis. MRI may detect a coexistent transverse ligament injury.
The treatment of C1-2 rotatory subluxations is generally nonoperative. Axial traction with a halter device or Gardner-Wells tongs can usually achieve reduction of the injury. Prolonged traction or the use of muscle relaxants may be needed. Periodic imaging may help to assess progress, but clinical improvement in the alignment and symptoms often provides confirmation of a successful reduction. Operative reduction and fixation are reserved for irreducible injuries, recurrent subluxations, and transverse ligament injuries.
Occipital Condyle Fractures
Occipital condyle fractures generally occur with axial trauma and are almost always unilateral (> 90%). The historical classification according to Anderson and Montesano described three types of injuries: type I injuries are comminuted fractures that result from axial trauma; type II fractures are extensions of linear basilar skull fractures; type III injuries are avulsion fractures of the condyle that can result from a variety of mechanisms. The incidence of occipital condyle fractures has been estimated to be between 1% and 3% of blunt craniocervical trauma cases. Although plain radiographs (usually open-mouth radiographs) may occasionally identify the injury, they have an unacceptably low sensitivity (estimated at 3.2%) and should not be relied on when the diagnosis is suspected. CT imaging with reconstruction views provides the best assessment of fracture pattern and alignment.
Occipital condyle fractures are generally stable and therefore are typically managed with an external nonrigid orthosis (collar) until the fracture heals (often 12 weeks). If occipitocervical misalignment is identified upfront, occipitocervical fusion or halo fixation is recommended.
C1 Fractures
Isolated C1 fractures account for approximately 5% of cervical spine fractures. These injuries occur with axial trauma with or without lateral bending. Open-mouth radiographs may suggest the injury, but CT imaging with reconstruction views provides the best assessment of fracture pattern and alignment. Fractures can include almost any part of the ring or lateral masses of C1. Aside from unilateral lateral mass fractures, the fractures usually occur at multiple sites ( Fig. 127-4 ). Jefferson fractures are four-part fractures with bilateral ventral and dorsal ring fractures. The assessment of these injuries is focused on evaluating the integrity of the transverse ligament and on recognizing any additional fractures.
The management of C1 fractures is based on the integrity of the transverse ligament that can be assessed indirectly with several radiographic criteria such as a widened atlantodental interval (> 3 mm) and increased spread of the lateral masses of C1 over C2 (> 6.9 mm, rule of Spence) or directly through high-resolution MRI ( Fig. 127-5 ). If the transverse ligament is intact, isolated C1 fractures are generally stable and can be treated with an external orthosis (e.g., sterno-occipital-mandibular immobilization [SOMI] device) primarily for symptom control until the fracture heals. With transverse ligament insufficiency, operative stabilization is indicated by using a C1-2 fusion technique such as dorsal C1-2 wiring techniques, C1-2 transarticular screws, C1 lateral mass-to-C2 pars/pedicle/translaminar screws, or ventral C1-2 screw fixation (see Chapter 143 ). The surgical choice is based primarily on patient anatomy and fracture pattern as well as the surgeon’s experience and preference. Postoperatively, most operations employing rigid internal fixation can be managed with a nonrigid external orthosis (e.g., a collar, SOMI), but C1-2 dorsal wiring without additional instrumentation generally warrants the use of a halo.
C2 Fractures
C2 fractures make up about 20% of all cervical spine fractures and are classified as odontoid, body, or other fractures (e.g., hangman, laminar, or spinous process).
Odontoid Fractures
C2 odontoid fractures can occur from a number of mechanisms but most often are caused by hyperextension injuries. Although lateral cervical spine radiographs may demonstrate some fractures, especially those with displacement, this technique can easily miss fractures, especially those with degenerative changes or minimal displacement. Open-mouth radiographs are very helpful for diagnosing most odontoid fractures, but these also may be inconclusive. Thin-cut CT images with sagittal and coronal view reconstruction views are the best way to diagnose and characterize odontoid fractures as well as to find associated fractures and plan treatment.
Anderson and D’Alonzo classified odontoid fractures into three types based on the location of the fracture line through the odontoid tip (type I), odontoid base (type II), or C2 body (type III) ( Fig. 127-6 ). Type I fractures are essentially avulsion fractures of the odontoid tip and are rare, generally stable, and usually managed with an external semirigid (collar) or rigid (halo) orthosis. Type II fractures are the most common type of odontoid fracture. These fractures are unstable and prone to nonunion because they occur in an area of relatively reduced osseous vascularity. Therefore, rigid halo immobilization or surgical stabilization is often necessary. Hadley and associates described type IIA fractures that are comminuted fractures at the base of the dens with associated free fragments. These fractures are considered particularly unstable, and surgical stabilization is advisable, usually with a dorsal C1-2 fusion. Type III fractures involve the vertebral body and are discussed later.
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