Bony Anatomy

The vertebral bodies are relatively large weight-bearing cuboid structures that are connected to each other by the intervertebral disc. The uncinate process or uncus is a cranial extension at the posterolateral corner of the vertebral body. The uncus is responsible for resistance to lateral bending, lateral listhesis, and rotation. With aging or degenerative processes the uncus can hypertrophy, narrowing the neuroforamina, which are located directly behind. Preexisting foraminal stenosis may predispose to neural injury, especially in hyperextension injuries. Short transverse processes extend lateral from the body about midlevel in anteroposterior direction and are confluent with vestigial ribs forming the foramen transversarium. Within this structure lies the vertebral artery and venous plexus except at C7, which is void.

The pedicles extend posteriorly and outward from the cranial aspect of the posterior wall of the body to the lateral masses. These short tubular structures may be cannulated with screws but, because of the close proximity of the vertebral arteries, this technique is often considered dangerous and supplanted by the use of the lateral masses as screw anchorage sites. The lateral masses or pillars when viewed laterally are parallelogram in shape and appear square when viewed ventrally or dorsally. They have cranial and caudal projections, the superior and inferior articular facets, respectively. These have cartilage surfaces that form the facet articulations. The superior facet is located behind the neuroforamen and, when fractured, may cause root injury. The laminae are thin plates of bone that extend from the lateral mass obliquely posterior and meet each other at the base of the spinous process. The spinous processes project posteriorly, angling downward, and are progressively larger from cranial to caudal direction. The spinous process of C3 to C5 is always bifid, whereas C6 may be and C7 is never bifid.

Ligamentous Anatomy

The ligaments of the cervical spine are essential to maintain both stability and range of motion. The anterior and posterior longitudinal ligaments lie on the respective surfaces of the vertebral body. The latter extends laterally at each disc and narrows behind the body. The annulus joins the corresponding vertebral bodies and is the primary restraint to all directions of movements. All cases of traumatic subluxation or dislocation indicate injury to this structure.

The posterior ligamentous complex consists of the nuchal ligaments, ligamentum flava, facet joint capsules, and all bony attachments. The nuchal ligaments include the ligamentum nuchae, which is a thick band strongly attached to the spinous processes of C2 and C7 and which extends fibers downward attaching to the tips of the C3-C6 spinous processes. The ligamentum nuchae blends with the supraspinous ligament, which bands together each spinous process at their tips. Between the spinous processes are the interspinous ligaments. The ligamentum flava attaches to the underside of the cranial lamina and top-most aspect of the caudal vertebrae. These elastic structures afford flexion and, when disrupted, indicate a significant failure from that direction. Each facet articulation has relatively redundant facet capsules that offer only a small amount of stability but when disrupted, like the ligamentum flava, indicate significant injury.

Neurovascular Anatomy

The neural anatomy is important to explain neurologic injury and to plan treatment. Advanced imaging affords an excellent means of visualizing the pertinent neuroanatomy and must be judiciously analyzed before placement of any fixation devices. The spinal cord is an elastic structure that lies inside the spinal canal. In adults its anteroposterior diameter measures about 8 mm and cross-section is slightly oval. At each disc level ventral and dorsal roots sprout and join laterally, forming the spinal nerve in the neuroforamina. The neuroforamen is a truncated cone angling outward. It is bordered anteriorly by the posterior lateral corner of the disc and uncus, above and below by pedicles and posteriorly by the superior articular facet and lateral mass. After exiting from the neuroforamen, the spinal nerve divides into ventral and dorsal primary rami.

The vertebral artery ascends from the subclavian artery to pass within the foramen transversarium at C6, although in 1% of cases this can occur aberrantly at C7 or higher levels. It exits the foramen transversarium of C2 turning anteriorly and medially in C2 and then again laterally into C1. The vertebral artery being enclosed within the spinal column may be injured due to intervertebral distraction, fractures about the foramen transversarium, and translational injuries such as facet dislocations. Further, the vertebral arteries may be damaged intraoperatively by lateral mass or pedicle screw placement.

Biomechanics and Kinematics

The subaxial cervical spine has complex motions that are controlled by the disc annulus complex, various ligaments, and bony projections including the facets and uncus. The motions are usually coupled combining angulations along more than one axis or angulations with translation. For example, during flexion-extension, 1 to 2 mm of obligatory translation occurs. Similarly, in rotation, both lateral bending and rotation occurs simultaneously.

Kinematically each segment of the subaxial spine normally has approximately 11, 5, and 5 degrees of movement in flexion-extension, lateral bending, and rotation.⁶ Small amounts (1 to 2 mm) of translation occur in both anterior-posterior and lateral directions. Normal passive motion requires little application of load, which is measured by the neutral zone. Injury will increase the dimension of the neutral zone and when this exceeds certain thresholds such that the neural structures are at risk, the spine is deemed unstable.

Anatomic Considerations for Surgery

Understanding anatomy is essential for the avoidance of adverse events during surgery. Anomalies are not uncommon in the cervical spine and should be carefully interpreted. An important axiom is that congenital bony malformations are associated with vascular malformations. Therefore when anomalies are present, a preoperative computed tomography (CT) angiogram or magnetic resonance angiography should be considered.

Anterior decompression is well described using the standard Smith-Robinson approach. If required, corpectomies can be performed after removal of the disc. If possible, the posterior longitudinal ligament should be left intact. Distraction either by pins placed into adjacent vertebral bodies or with cranial tongs can restore axial length. Decompression should be oriented to the midline and be at least 16 mm wide depending on the transverse distance between the foramen transversarium. Common errors are biasing the decompression usually to the side opposite that from which the surgeons stands or too narrow a decompression. A plate with unicortical screws may be placed after insertion of a graft or a cage. The plate should be oriented so that screws have purchased into the body and not adjacent discs or laterally into the foramen transversarium.

The posterior cervical spine is dissected carefully as disruption of ligamentum flava exposes the spinal canal to risk of iatrogenic damage. Further, laminar fractures may be displaced downward onto the spinal cord. The joint capsules should be preserved to avoid any further destabilizing injury. In younger patients, simple exposure of noninvolved levels may result in spontaneous fusion.

Screw fixation into the lateral masses requires identification of a proper starting point and screw direction. The lateral mass is first examined and its borders defined. The cranial and caudal borders are the corresponding facet joints, the lateral border is the edge of the lateral mass, and the medial border is the valley at the junction of the lamina and lateral mass. Several starting points have been described.^7–9 However, with modern fixation most authors use a modified technique where the starting point is 1 to 2 mm medial to center of the lateral mass. The author marks this point with a small burr so that when a pilot hole is started it is located at the selected point. The pilot hole is oriented upward attempting to be parallel to the facet articulations and outward about 15 to 30 degrees. This outward orientation is essential to avoid injury to the vertebral artery, which lies directly anterior to the starting point as seen on axial images. The outward angulation is often limited by the next caudal spinous process.

Clinical Examination

The clinical examination is an essential component of the evaluation process. It depends on cooperation between examiner and patient, requiring normal mentation. Sensitivity is reduced by the patient’s inability to report symptoms due to conditions such as distracting pain, mild head injuries, or intoxication.¹⁰ The clinical examination is performed by reviewing the history of injury and symptoms of cervical pain, numbness, weakness, or paresthesias. The examination assesses spinal tenderness, which is best achieved by carefully logrolling the patient and palpating from the occiput to sacrum. Tenderness, swelling, hematoma, and gaps between spinous processes are indications for further evaluation.

The neurologic examination is performed using standards established by the American Spinal Injury Association (Fig. 77–1).¹¹ These should be recorded in the medical record in a timely manner. The neurologic examination includes testing of cranial nerves, motor and sensory function, and perineal function. Motor function of key muscle groups in the arms and legs are assessed from grades 0 to 5 (Table 77–1). Several sensory functions including pinprick, light touch, and proprioception or vibratory function are tested in both the upper and lower extremities. Sensory function is graded 0, 1, or 2 (absent, hypoesthesia, and normal, respectively). Deep tendon and pathologic reflexes are determined. Hyperreflexia and findings of clonus, Babinski signs, or Hoffmann signs are indications of spinal cord compression, although in cases of acute spinal cord injury areflexia is initially common. The level of spinal cord injury is defined as the lowest-functioning root level with at least grade 3 motor function. Complete spinal cord injuries are defined as the absence of any motor or sensory function including sacral roots distal to the zone of injury. Incomplete cord syndromes have some retained motor or sensory function and have a significantly better prognosis than complete lesions. The overall impairment is graded by the modified Frankel (ASIA) scale: A—motor and sensory complete; B—motor complete with sensory sparing; C—motor and sensory sparing but not functional strength; D—motor and sensory sparing with functional strength; E—normal motor and sensory.¹¹

FIGURE 77–1 Chart illustrating (A) Frankel (ASIA) grading of spinal cord injury severity and (B) the sensorimotor examination used in determining the level of spinal cord injury and ASIA motor score.

TABLE 77–1 Key Muscle Groups

Examination of the perineum is an important component of the clinical examination. The perianal skin is tested for pinprick sensation. Digital rectal examination is performed assessing tone and the presence of voluntary contraction. Finally, sacral reflexes are assessed. The anal wink is obtained by gently scratching the perianal skin and observing a contracture. The bulbocavernosis reflex is tested during digital rectal examination by compression of the glans penis or clitoris or alternatively by pulling on a Foley catheter. During this maneuver an anal contracture should occur.

Interpretation of the perineal examination depends on the level of injury and time from injury. In cervical cord injuries the perineal function may be initially absent, but the bulbocavernosis reflex may return in several days, indicating resolution of spinal shock, which is an initial depolarization of axonal tissue after injury. If the patient has not made any distal recovery at this time, the prognosis is grave. In some cases only sacral function is spared, changing the patient from complete to incomplete with a dramatic change in prognosis. Injuries at the conus or cauda equina that have retained perineal function or bulbocavernosis reflex have excellent prognosis for bladder and bowel function.

Patient Presentation

After the clinical examination, a decision is made whether radiologic studies are indicated. To determine the proper course, patients can be divided into one of four groups: asymptomatic; temporarily nonevaluable but asymptomatic; symptomatic; and obtunded. Asymptomatic patients are those who have no pain, no cervical tenderness, neurologic signs and symptoms and who are awake, alert, and nonintoxicated.¹ Additionally, they do not have any distracting injuries that may preclude pain assessment of a potential cervical spine injury. Distracting injuries include long bone fractures, burns, visceral injury, dislocations, and craniofacial or thoracic trauma. The temporarily nonevaluable patient is otherwise asymptomatic but is either intoxicated where sobriety is expected within 24 hours or will have resolution of other painful injuries through reduction or fixation. It is hypothesized that these patients can be evaluated similar to the asymptomatic patients in a delayed fashion.¹² Symptomatic patients have cervical pain, tenderness, or neurologic symptoms such as paresthesias, weakness, or numbness. The obtunded patient is one who will not be able to fully participate in the clearance process and at the same time is at highest risk for injury. Included in this group are disabled and infant patients.

Cervical Spine Injury Severity Score

The Cervical Spine Injury Severity Score (CSISS) is based on independent analysis of four columns (anterior, posterior, right column, and left lateral column) (Table 77–2).²⁵ The anterior column includes the body, disc including the annulus, anterior and posterior longitudinal ligaments, and transverse processes. Each lateral column is scored separately and includes the facet projections, lateral mass, pedicles, and facet joint capsules. The posterior column includes the lamina, spinous process, ligamentum flavum, and nuchal ligaments (Fig. 77–2A).

TABLE 77–2 Cervical Spine Injury Severity Score (CSISS)

^* Scores < 5 are generally treated nonoperatively. Scores > 7 are usually treated surgically.

FIGURE 77–2 A, The Cervical Spine Injury Severity Score (CSISS) is based on analysis of four anatomic columns: anterior, each lateral column, and posterior. B, Each column is scored independently using the analog scale from 0 to 5. A nondisplaced fracture is valued at “1,” while increasing scores are given proportionally to the amount of displacement. A “5” is given for the worst injury to a given column that is possible. Fractional values may be used. The CSISS is the sum from each column ranging from 0 to 20.

Each column is scored using a 0-5 analog scale (Fig. 77–2B). Fractional scores can be used. Scores increase proportional to either displacement of fracture fragments or separation as a result of soft tissue injury. For example, a nondisplaced fracture is scored 1 while the worst injury possible for that column (e.g., facet fracture dislocation with 10-mm displacement) is a 5. Each column is scored independently and summed, giving the CSISS ranging 0-20.

Anderson and colleagues²⁵ assessed reliability in 34 cases with 15 examiners. Both intraobserver and interobserver reliability were excellent. Construct validity was also good as all patients with scores equal to 7 had surgery, whereas only 15% less than 5 had surgery (Fig. 77–3). Caput and colleagues²⁶ retrospectively correlated CSISS score to surgical approach in 70 patients. They found a significant correlation with high CSISS scores (>11) to a posterior or combined anteroposterior approach. The anterior approach had lower scores with a mean 6.3, indicating that anterior surgery was used for less severe injuries, in accordance with well-known biomechanical studies.

FIGURE 77–3 A, Sagittal reconstruction showing C5 flexion-axial loading injury. There is a small teardrop fragment and the body is retropulsed into the spinal canal. The patient was a Frankel C quadriplegia. B, The next sagittal image shows wide separation of the spinous processes, indicating disruption of the posterior osseous-ligamentous complex. The CSISS anterior and posterior columns are scored 4 and 5, respectively. C and D, Subluxation of the left and right sagittal computed tomography (CT) in the plane of the lateral masses is present. The CSISS is 2 for each lateral column. E, Axial CT. Note the displaced laminar fracture. F, Traction lateral radiograph after applying 50 pounds. Alignment is significantly improved and retropulsion of C5 is reduced. G, The CSISS score totaled 13, indicating a highly unstable fracture and the need for surgery. The patient was treated by anterior corpectomy and fusion with fibular allograft and translational plate. Neurologically the patient improved to Frankel D and healed the fusion.

Subaxial Cervical Spine Injury Classification

The Subaxial Cervical Spine Injury Classification system (SLIC) evaluates fracture morphology, the discoligamentous complex, and neurologic function, creating a comprehensive system to aid treatment decision making (Table 77–3).²⁷ The system assigns points for each domain and if the score exceeds a threshold, surgery would be indicated.

Overall Subaxial Cervical Spine Injury Classification Score

The SLIC score is the sum of the individual components. A patient with an SLIC score equal to 3 is treated nonoperatively, whereas surgery is recommended in a patient with a score equal to 5 (Fig. 77–4). Scores of 4 can be treated either operatively or nonoperatively.

FIGURE 77–4 A, Sagittal computed tomography (CT) showing C7 burst fracture. The patient was neurologically intact. The discoligamentous complex is intact. The SLIC score is 2 (2 for burst fracture, 0 for DLC, and 0 for neurologic). The Cervical Spine Injury Severity Score is 6 (4 for anterior, 1 for each facet diastasis, and 0 for posterior). The patient was treated successfully nonoperatively in halo vest. B, Diastasis (arrow) of both facet joints (left shown) is present. C, Retropulsion of bone from C7 burst fracture is seen on axial CT. D, Traction of 25 pounds reduced the fracture. E, The patient was treated in a halo vest. The lateral radiograph at 12 months shows excellent alignment and healing of the burst fracture.

Vaccaro and colleagues²⁷ tested the reliability of the SLIC system. Interobserver reliability was only moderate, and both injury morphology and discoligamentous complex scores were only fair. Intraobserver reliability was excellent for overall and individual components. Similar to the CSISS, the system was valid when tested against treatment decisions. The SLIC system predicted accurately what the individual observers would recommend in 91% of cases.

These quantitative systems do not “name” or describe the injuries. Both authors of the aforementioned studies recommend using common colloquial terms that have a long history of use. Examples of these are facet dislocations, lateral mass fractures, and flexion/axial loading injuries. Unfortunately, injuries may be combined or similar so that distinguishing between any two fractures may be difficult.

Anterior Column Injuries

Anterior column injuries include compression fractures, burst fractures, flexion axial loading injury, and disc distraction injuries (Table 77–4). Transverse process fractures are included in this group, although they have no effect on spinal stability but may be associated with vertebral artery injury. Most anterior column injuries are easily recognizable on plain radiographs or CT. When present, they suggest a hyperflexion mechanism and a search for a concomitant injury to the posterior ligamentous complex should ensue. The notable exception is the disc-distraction injury resulting from opposite forces (i.e., extension and posterior shear). These injuries can be subtle, especially in patients with preexisting spondylosis.

Anterior Compression Fractures

Burst Fractures

Flexion Axial Loading Injury

Transverse Process Fractures

Transverse process fractures are quite common, occurring in isolation or in association with other more severe injuries. These fractures are not involved with spinal stability and therefore are not significant in treatment decision making for the spine. However, transverse process fractures at C6 and above may warn of possible vertebral artery injury.²⁹ No consensus has been reached regarding whether routine vascular evaluation and subsequent treatment with anticoagulants are required in patients with these injuries. This topic is discussed in detail in Chapter 82.

Disc-Distraction Injury

Radiographic Analysis

A variety of fracture patterns are encompassed with this moniker. Typically the disc space is wider than normal or is hyperlordotic. This may be difficult to discern, especially in spondylotic spines. Retrolisthesis is usually present, although its magnitude, usually around 1 to 2 mm, is often underestimated in terms of its significance. Large degrees of displacement, up to 50% translation, can occur but are rare. Because of the injury to the anterior longitudinal ligament, soft tissue swelling will usually be present. Small avulsions of the anterior endplate can be confused with fractured osteophytes. Impaction of the spinous process can cause their fracture, also involving the lamina, which may be displaced into the spinal canal. Similarly, lateral mass fractures from impaction can occur.

MRI is useful to identify questionable cases. Classic findings are increased signal in anterior soft tissues both rostral and caudal to the injured disc. Increased signal intensity across the disc space transversing the anterior annulus and anterior longitudinal ligament is pathognomonic (Fig. 77–5). Rarely the posterior longitudinal ligament will be involved. Disc herniation and spinal cord compression from stenosis or malalignment may be present as well. Posterior increased signal in the facet joints and ligamentum flavum are indicative of more extensive injury and greater instability.

FIGURE 77–5 A, Lateral sagittal computed tomography (CT) of 57-year-old neurologically intact male with an ankylosed spine from diffuse idiopathic spinal hyperostosis who sustained a hyperextension disc distraction injury at C7-T1. The disc is hyperlordotic and laminar fractures are visualized. Widening between spinous processes indicates probable injury of the posterior ligamentous complex. The patient is neurologically intact. The Cervical Spine Injury Severity Score is 11 (anterior—4, left—2, right—3, posterior—2). The Subaxial Cervical Spine Injury Classification is 5 (distraction—3, DLC—2, neurologic—0). B, Left sagittal reconstruction. Comminuted facet fracture is seen. C, Right sagittal reconstruction demonstrates subluxation of the C6-7 facet and C7 pedicle fracture (arrow). D, Axial CT shows displaced laminar fracture of C7 (arrow). E, Postoperative lateral radiograph following posterior instrumentation of C4-T3. F, Postoperative anteroposterior radiograph.

Treatment of Anterior Column Injuries

Anterior column injuries with low SLIC or CSISS scores can be treated non-operatively (Table 77–5). These include compression injuries, stable forms of burst fractures and flexion/distraction injuries, and most disc-distraction injuries (see Fig. 77–4). Less significant injuries can be treated with a cervical collar, while burst fractures and flexion/axial loading injuries can be treated with a cervical thoracic orthosis (CTO) or halo vest.

TABLE 77–5 Treatment of Anterior Column Injuries

CTO, cervicothoracic orthosis.

Authors’ recommendations are in bold capitals.

Surgical indications for anterior column injuries are those with evidence of disruption of the posterior ligamentous complex as demonstrated by high CSISS and SLIC scores (see Table 77–5). In the case of compression fractures when surgery is warranted, the author recommends posterior fusion because a single-level anterior fusion may fail in the face of a vertebral fracture at the location of caudal screw fixation. Burst fractures and flexion/axial loading injuries can be reduced or significantly improved with tong traction. Although both anterior and posterior approaches may be used, the authors recommend addressing pathology at its major location (i.e., anteriorly) (see Fig. 77–3). After strut grafting or insertion of a cage, an anterior plate is applied. Although a rigid locked plate has theoretical advantages over a translational plate, the author has not observed any clinical differences in outcomes between the two plates. In rare cases of extensive comminution, associated facet dislocations, or those having residual displacement of lamina fractures, combined anterior and posterior approaches are indicated.

Surgical indications for disc distraction injuries are cases with any significant displacement, ongoing neurologic symptoms, or chronic pain. Anterior discectomy and fusion are indicated in neurologically intact patients and those with radiculopathy. Patients with cord injuries require individualized care. If stenosis is limited to the injured level, then anterior cervical discectomy and fusion are recommended. Not uncommonly, patients will have developmental narrowing of the spinal canal and multilevel stenosis. Several options are available including single-level anterior cervical discectomy and fusion combined with posterior decompression (laminoplasty) or posterior decompression (laminoplasty or laminectomy) with posterior fusion.

Outcomes: Anterior Column Injuries

Two nonrandomized clinical trials have compared outcomes of halo vest with anterior decompression and stabilization with a plate for the treatment of cervical burst fracture and flexion distraction injuries. Fisher and colleagues³⁰ noted better radiologic alignment but no differences in pain and function and could not correlate greater kyphosis in the halo group to long-term problems. Approximately 20% of halo patients failed and subsequently required surgery. Koivikko³¹ found significantly improved neurologic recovery presumably due to the better decompression in operatively managed patients over the halo vest. Toh and colleagues³² compared anterior with posterior stabilization for these injuries. They found better decompression and improved neurologic outcomes in the anterior group. In all of these trials single-stage anterior decompression and plate fixation resulted in successful fusion, satisfactory alignment, and better neurologic recovery.

Vaccaro and colleagues retrospectively reviewed outcomes of 24 patients with disc distraction injuries, 16 of whom were treated surgically by anterior fusion.³³ All surgical patients fused, although three patients developed neurologic deterioration from overdistraction of the disc space. These results were similar to those published in a systematic review by Hadley.³⁴ Mortality rate was 38% in operative and 63% in conservatively treated patients secondary to an aged population that sustained spinal cord injuries.

Posterior Column Injuries

Isolated injuries to the posterior column are less common than those that are combined with other fractures. Isolated injuries include spinous process and lamina fractures and disruption of the posterior ligamentous complex without facet subluxation (Table 77–6).

Spinous Process and Lamina Fractures

Posterior Ligamentous Injury without Subluxation

Treatment of Posterior Column Injuries

Management of isolated spinous process and lamina fractures is with simple collar immobilization (Table 77–7). Because they may be associated with complete posterior ligamentous complex disruption, kyphosis or progressive subluxation may occur. Patients should be informed that spinous process fractures may not heal due to the displacement from muscle contractions, although this rarely leads to chronic pain or further surgical treatment.

TABLE 77–7 Treatment of Posterior Column Injuries

CTO, cervicothoracic orthosis.

Authors’ recommendations are in bold capitals.

Isolated posterior ligamentous injuries without subluxation have a worse prognosis. The true state of instability may not initially be known because proper positioning of the motion segment will be in a relatively reduced position. Initial management of these injuries unless there is MRI evidence of complete disruption is nonoperative in a collar or CTO. The latter is preferred at the lower cervical spine (C5-C7). If upright radiographs demonstrate increasing deformity or excessive motion after 8 to 10 weeks of immobilization, surgery is recommended. Patients with complete ligamentous disruption without subluxation have two options; attempt nonoperative care or posterior surgery. Surgical treatment may be either an anterior or posterior approach. Before surgery, MRI should be performed to examine the status of the intervertebral disc, which if displaced into the spinal canal would warrant an anterior approach.

Isolated Facet Fractures

Mechanism of Injury

Isolated facet fractures occur from forced impaction against the neighboring facet, usually with a component of anterior shear. Thus these may result in loss of the stabilizing buttress to anterior shear and should always be evaluated with the suspicion that greater instability is present (Fig. 77–6).

FIGURE 77–6 A, 35-year-old male motorcyclist presented with neck pain and normal neurologic examination. Computed tomography (CT) showed normal alignment. B, Left lateral column is normal. C, A right superior facet fracture without subluxation is seen on sagittal CT. D, A nondisplaced fracture is seen in right facet. E, On the basis of low Cervical Spine Injury Severity Score (1) and SLIC (1) scores, a trial of nonoperative care using a hard collar was attempted. The upright radiograph shows increased translation and kyphosis at C5-6. The arrow shows interspinous widening indicating disruption of the posterior ligamentous complex. F, T2 magnetic resonance imaging confirms ligamentous disruption (arrow) and discoligamentous injury. G, A right-sided (*) cerebellar stroke has occurred secondary to disruption of right vertebral artery. H, The patient was treated with aspirin and anterior discectomy and fusion. One year later the fusion has healed with excellent alignment.

Lateral Mass Fractures

Assessment

Type I and type II lateral mass fractures have moderate CSISS scores, depending on the amount of translation (4-1). The SLIC scores are usually also moderate with a range of 3 to 7. The type III split fractures are more stable due to the facet invagination and have lower CSISS (3 to 6) and SLIC (1 to 2) scores. The type IV traumatic spondylolisthesis fractures are highly unstable, having CSISS of 10 to 20 and SLIC of 3 to 7.

Facet Dislocations

Facet dislocations represent a wide range of injuries because they may be unilateral, bilateral, and with or without facet facture. Many other associated injuries such as disc herniation and posterior ligamentous complex disruption may exist. In addition, neurologic injury is common and there is significant potential for neurologic deterioration. All of these factors will need to be assessed for treatment decisions. This discussion broadly groups injuries into unilateral and bilateral facet dislocations.

Unilateral Facet Dislocations

Bilateral Facet Dislocation

Bilateral facet dislocations are devastating injuries frequently resulting in quadriplegia. Unfortunately, the diagnosis may be delayed and improper treatment can result in neurologic deterioration.

Treatment of Lateral Column Injuries

Facet Dislocations

No consensus has been reached as to the treatment of unilateral facet dislocations.³⁸ Several issues are important to consider. The injury includes disruption of the annulus in almost all cases, and disc herniation occurs in 56% of unilateral and 82.5% of bilateral dislocations.³⁷ These disc herniations have been reported to persist behind the cranial vertebral body, increasing spinal cord compression and neurologic deterioration after reduction.³⁹ To avoid this, several strategies have been recommended. One strategy is to obtain an MRI before any attempt at reduction in the neurologically intact or incomplete patient. If a disc herniation is present, then anterior discectomy is recommended before reduction (Fig. 77–7). In this case, an open reduction can be performed anteriorly with interbody fusion and plate. Alternatively, another strategy in an awake, alert, and cooperative patient is to attempt a closed skeletal reduction before MRI. Both strategies are well accepted methods of treatment. Cranial tong traction can be used with the protocol described as follows. Following any closed reduction, an MRI must always be performed before surgical intervention to access for the presence of a traumatic disc herniation or other space-occupying lesion. In patients with facet dislocations and spinal cord injury, early reduction is recommended before obtaining MRI to assess the disc state.

FIGURE 77–7 A, 37-year-old male with bilateral C7 radiculopathy following motor vehicle crash. Computed tomography (CT) shows 20% subluxation and widening between spinous processes. B, The left facet is perched on sagittal CT (arrow). C, There are fractures of both superior and inferior facets (arrow) with subluxation. D, Axial CT shows left facet fracture and narrowing of foramina. E, Before reduction, magnetic resonance imaging (MRI) was performed because of the chance of a traumatic disc herniation, which is seen compressing the ventral aspect of the spinal cord behind the C6 body on this short tau inversion recovery sequence. Additionally, complete ligamentous disruption is identified (arrow). F, MRI at C6-7 showing disc herniation with cord compression. G, Anterior discectomy and fusion were performed. A large fragment of disc was found behind the C6 body. Allograft and a rigid plate were used.

In patients with reduced unilateral facet dislocations, nonoperative care using a halo vest or CTO can be attempted. If the dislocations cannot be reduced, then open reduction is easily achieved with a posterior approach. Unilateral facet fracture-dislocations are best managed operatively. Recurrence of displacement is likely to occur even after successful closed reduction. This is especially true if the length of the facet fracture exceeds 40% of the total facet height.⁴⁰ Either anterior discectomy and fusion or posterior fusion can be performed (see Fig. 77–6). In cases of associated vertebral body fractures, posterior surgery is warranted, whereas if comminution is posterior then an anterior fusion should be considered.

In almost all cases bilateral facet dislocations should be treated surgically. Biomechanical studies confirm the advantages of posterior instrumentation over anterior plates. However, this has not been shown to be important clinically.⁴¹ Both anterior and posterior fixation with screw fixation is adequate and rarely combined anterior-posterior surgery is necessary. The choice of approach is often dictated by the presence of disc herniation or posterior comminution, which would favor an anterior approach (see Fig. 77–7). Alternatively, the presence of vertebral body fractures would favor a posterior approach. Combined anterior-posterior procedures are indicated when comminution will prevent solid fixation or in cases of extreme ligamentous avulsion such as distraction injury.

Outcomes of Lateral Column Injuries

Long-term outcomes of unilateral facet fracture-dislocations have been investigated. In retrospective case series, Beyer and colleagues correlated pain to residual deformity, which was more common in nonoperatively treated patients.^42,43 Lee and Sung compared rotational unstable lateral mass fractures treated nonoperatively with those treated with anterior fixation.⁴⁴ He found that 12 of 15 patients treated conservatively failed and underwent surgery. Surgical results were excellent except in three cases of type I lateral mass fractures (fracture separations) that had only a single segment fusion and then developed subluxation at adjacent level. Dvorack and colleagues⁴⁵ reviewed 90 patients (72 operative and 18 nonoperative) at 2 years using health-related quality-of-life assessments. Both groups had more pain and disability than normative subjects adjusted for age. However, operatively treated patients had significantly better SF-36 scores than nonoperatively treated patients. Kwon and colleagues⁴⁶ performed a randomized controlled trial of unilateral facet dislocations comparing anterior with posterior fixation. He found no significant differences except in higher rates of wound infections in the posterior group and dysphagia in the anterior group. Anterior plate fixation, however, may be associated with failure when used in the presence of vertebral endplate fracture.⁴⁷

Current management of bilateral facet dislocations is primarily operative, although past descriptions of successful halo-vest treatment have been reported.³⁴ In these series, up to 30% of patients had recurrent deformity and required surgery. Comparisons between operative and nonoperative treatment using modern patient-centered outcomes are not available. Both anterior plate fixation and posterior lateral mass fixation are associated with satisfactory radiologic outcomes.^{7,34,41,48,49}

Special Injury Types

Several patterns of injury do not fit conveniently into anatomic categories. These include fractures in ankylosed spines, injuries in patients resulting in central cord syndrome, vertical distraction injuries, and fractures in the elderly (Table 77–10). Fractures in pediatric patients are discussed in Chapter 28.

Ankylosed Spines

Patients who have ankylosed spines from ankylosing spondylitis, diffuse idiopathic spinal hyperostosis (DISH), or surgery have increased risk of spinal column and cord injury. The loss of intervertebral disc decreases elastic deformation following trauma further amplified by long lever arms increasing the risk of fractures. Ankylosing spondylitic patients in particular may be osteoporotic and have potential for epidural bleeding, which can expand cranially and caudally causing spinal cord injury.

Central Cord Syndrome

The central cord syndrome classically occurs from a hyperextension injury in patients with narrow spinal canals, usually from spondylosis. Radiographically no significant injuries are noted. Neurologic examination is a picture of greater involvement of the upper extremities than the lower extremity and sacral roots. Neurologic manifestations reflect injury to the central gray matter and surrounding white matter in the central spinal cord. The axonal tracts to the upper extremities are located more centrally than the lower extremity and sacral regions and therefore are injured to a greater degree leading to the classic pattern of neurologic findings. Additional foraminal stenosis is not uncommon, further impairing upper-extremity function. The overall prognosis for this injury is good, although hand function may remain poor.

Radiographic Characteristics

Patients with central cord syndrome secondary to hyperextension injury have small spinal canals with midsagittal diameters less than 10 mm. This may be focal, especially at C3-4, or involve the entire subaxial cervical spine. The spine is generally spondylolytic with loss of disc height and osteophytes at multiple levels (Fig. 77–8). Signs of discoligamentous injury include endplate avulsion, retrolisthesis (thought to be preexisting), and disc distraction or hyperlordosis. The latter may be inaccurately thought to be normal. Retropharyngeal swelling is suggestive of hyperextension injury and should elicit concern for a discoligamentous injury. Posterior displacement of even small amounts may critically narrow spinal canals when stenosis is present. Various findings of posterior column injury may be present. If vertebral body displacement occurs, the facet joints will demonstrate diastases greater than 2 mm, indicating capsular disruption. Spinous process and lamina fractures secondary to impaction injury are suggestive of a hyperextension injury.

FIGURE 77–8 A, A 49-year-old male involved in a motorcycle accident presented with a severe central cord syndrome. He had no motor function in his upper extremities and only a toe flicker in his lower extremities. No skeletal injury is seen on computed tomography. Spinal canal stenosis at C5-6 and C6-7 due to osteophytes is present. No skeletal injury is present, so Cervical Spine Injury Severity Score is 0 and Subaxial Cervical Spine Injury Classification is 4 based on neural compression in a patient with neurologic deficits. B, T2 magnetic resonance imaging (MRI) shows a swollen cord with increased signal intensity (arrow). Signal changes in vertebral bodies were thought to be secondary to degenerative changes. C, Axial MRI at C5-6 similarly showing spinal stenosis. D, The patient was treated on day of injury with C4-C7 laminoplasty. He made rapid neurologic recovery, regaining the ability to walk and use his hands. One year postoperative lateral radiograph. E, MRI one year after injury. A large cyst is seen representing spinal cord injury.

MRI is essential when treating patients with central cord syndrome. Spinal cord compression can be present focally at one level (often C3-4) or over multiple levels. Increased signal on T2 in the spinal cord represents edema or necrosis, whereas decreased signal on T1 imparts a much poorer prognosis. Fat suppression techniques are important to visualize discoligamentous injuries such as disruption of the anterior longitudinal ligament and increased signal in the disc space. Increased retropharyngeal signal attests to injury along the anterior aspect of the spine.

Vertical Distraction Injury

This is a rare devastating injury where there is vertical separation between the vertebral segments through the disc space and facet articulations. Complete spinal cord injury is always present and vascular abnormities should be anticipated.

Fractures in Geriatric Patients

The incidence of cervical fractures in the elderly is increasing and presents challenges for treating physicians. Elderly patients are more prone to injury due to osteoporosis, generalized sensory imbalance with aging, developmental stenosis with increased risk of spinal cord injury, and a higher rate of vehicular accidents per mile driven. The subaxial cervical spine is the second most common location for trauma in the elderly after C2.

Mortality of geriatric patients with cervical fractures ranges 30% to 50%, similar to that of hip fracture. Treatment by traction, prolonged bed rest, and the halo vest are associated with increased mortality and should be avoided. Patients often have multiple medical comorbidities that are exacerbated by the injury and its treatment. Geriatric patients are particularly prone to aspiration pneumonia due to retropharyngeal soft tissue swelling and dysphagia. Swallowing dysfunction is further aggravated by bracing and anterior neck surgery. Cervical orthoses are poorly tolerated and have a higher incidence of decubitus ulceration.

Ankylosed Spines

Ankylosing spondylitic patients often have delayed diagnoses with neurologic deterioration and therefore making the initial diagnosis is essential. CT imaging should be obtained in any ankylosing spondylitic patient who has spine pain following trauma. If CT is unrevealing, MRI should be obtained. Even nondisplaced or questionable injuries are likely to behave poorly with resultant neurologic deficits. Noncontiguous fractures are present in up to 20% of cases and therefore the entire spinal column should be imaged.

TABLE 77–11 Treatment of Special Fracture Types

CTO, cervicothoracic orthosis.

Authors’ recommendations are in bold capitals.

The treatment of subaxial fractures in patients with ankylosing spondylitis is surgical unless medically contraindicated.⁵² The aggressive approach is warranted by the high incidence of displacement and resultant neurologic injury or kyphosis that can occur with nonoperative treatment.⁵³ Traction is generally not recommended because there are no ligaments to be used to guide reduction or restrain overdistraction. If necessary, a two-vector technique has been described for these patients.⁵⁴ The surgical treatment is best performed with posterior instrumentation over many segments because there is no concern over fusing many segments. If possible, we recommend three levels above and below the injured segment. In the thoracic spine pedicle screws are used, while lateral mass screws are used in the cervical spine. Bone graft is not necessary, although local bone graft can be added at the fracture site.

Central Cord

The treatment of patients with central cord syndrome remains controversial. Decisions are based on the initial severity of neurologic deficit, injury type, degree of instability, and location of residual cord and root compression. Classically, initial nonoperative treatment was employed, stating that patients will likely demonstrate slow neurologic recovery.⁵⁵ If recovery was not satisfactory, then a late decompression was performed.⁵⁶ More recently an aggressive surgical approach has been advocated with the goals to speed recovery, shorten hospitalization, and reduce morbidity. It appears that the surgical treatment is safe and may offer better neurologic recovery, although adequate studies are lacking (see Fig. 77–8).⁵⁵

Patients with unstable injuries should be treated surgically. Stabilization can be performed either anteriorly or posteriorly depending on where decompression is required. Those patients with focal (one to two levels) cord compression are good candidates for anterior decompression and fusion. Patients with multilevel disease can be treated with posterior decompression by laminoplasty or laminectomy. Fusion is indicated for cases with instability (CSISS > 7 or SLIC > 5) (see Fig. 77–8).

Vertical Distraction

Traction is contraindicated and reduction is best achieved either surgically or by halo vest. Definitive treatment by combined anteroposterior fixation is recommended.

Fractures in Geriatric Patients

Fractures in geriatric patients require early decisions, avoidance of prolonged immobilization, and multidisciplinary care to avoid medical complications. The halo vest should be avoided and, if medical conditions allow, rigid stabilization should be considered for any marginal or unstable injury. The authors prefer posterior fusions in order to avoid anterior approaches and the consequent risk of airway or swallowing complications. The goal of surgery is usually stabilization and therefore longer fusion constructs may be appropriate. Consultation with a speech pathologist should be considered in patients having dysphagia:

Indications for Nonoperative Treatment

Nonoperative treatment is indicated in patients with mild to moderate instability. Using the CSISS and SLIC scoring systems, these patients have scores less than 7 and 4, respectively. Further features are absence from symptomatic neural compression, less than 3 mm of translation, no significant widening of the distance between the spinous processes, and an ability to tolerate nonoperative care. Specific fracture types that are candidates for nonoperative care are discussed as follows.

Surgical Treatment

Surgery is warranted in a majority of patients with neurologic deficits and for some patients with unstable fractures. The goals of surgery are to decompress the neural elements (when required), reduce and maintain spinal alignment, and stabilize the spine until bony healing can occur. The long-term goals are to maximize neurologic recovery and provide a stable, painless, functioning spinal column. This should be accomplished with the least postoperative immobilization and with the fewest levels fused as possible. Further adverse events should be minimized.

Timing of Surgery

The timing of surgical intervention in patients with spinal cord injuries remains controversial due to lack of adequately designed clinical trials. Strong experimental evidence suggests that early decompression results in improved neurologic recovery.^64–66 Further, there may be a short window of opportunity when spinal cord injury can be reversed or prevented.⁵⁷ These observations are confirmed by careful study of the pathophysiologic changes that occur after spinal cord trauma as discussed in Chapter 75. However, to date it is unknown whether these observations apply to humans, although it is likely.

Fehlings and Perrin⁶⁷ performed a systematic review of the timing of surgery in spinal cord injuries. They found that early surgery (<24 hours) can be performed safely. The evidence for benefits of acute surgical decompression (<24 hours) is weak due to lack of nonoperative controls. Fehlings and Perrin⁶⁷ recommend this as only an option. The same authors are the principle investigators of an ongoing study that is comparing early versus delayed decompression. Early results show improved neurologic recovery in the group treated within 24 hours of injury; however, because of inadequate study power, the results are not statistically significant at this time.

In some cases such as bilateral facet dislocations or burst fractures, decompression can be achieved by immediate reduction with tong traction.⁵⁷ Case reports of reduction of bilateral facet dislocations have demonstrated immediate neurologic recovery. These, along with large case studies, demonstrate safety and efficiency of closed reduction in these cases. Fehlings and Perrin⁷⁶ recommend urgent decompression in incomplete quadriplegia at the level of a guideline. Another potential advantage of early surgery is that it allows immobilization and avoidance of potential problems of bed immobilization in critically injured patients. Results of comparison between early and delayed (>72 hours) surgical intervention in spinal cord injuries is inconclusive. Mirza, Mckinley, and colleagues have shown fewer complications and shorter hospitalizations and length of stay, whereas others such as Vaccaro, Waters, and Fehlings have shown no differences.^68–72

Anesthesia Considerations

Patients with unstable cervical spines present anesthetic challenges that should be discussed with the anesthesiologist before surgery. The spinal cord–injured patient should be hemodynamically stable, having a mean arterial pressure of at least 80 mm Hg and adequate oxygenation. During surgery, adequate blood pressure should be maintained and hypotension treated aggressively. Intubation is best performed with a fiberoptic technique without change of head position. Surgeons should be present and available to stabilize the head if necessary. Extubation at the end of the procedure may be complicated by further respiratory difficulties due to swelling, retropharyngeal hemorrhage, or neurologic impairment. Supine positioning is done by transfer with the surgeon holding the head. Prone positioning onto a special table such as the Jackson table is performed by log roll or with the turning frame technique with the latter being theoretically safer. In both cases immediate radiographs are obtained to check alignment.

Surgical Approaches

Both anterior and posterior approaches have been shown to be effective for the treatment of cervical spine fractures. The details of surgical techniques relative to anterior and posterior decompression and fusion with instrumentation are given in detail in Chapter 70. Many factors should be considered when choosing between these approaches. Most important is the need to decompress the neural elements, which will dictate the approach. In most cases this will be anterior, although displaced lamina or facet fractures occasionally require posterior decompression. Secondly, the bony structure where internal fixation (screws or wires) is to be applied should be considered. Fracture at fixation sites risks failure or may require larger constructs, thus making the opposite approach more efficacious. An example is a facet dislocation associated with a vertebral body endplate fracture that is best treated from a posterior approach, whereas a comminuted facet fracture may be better treated by an anterior discectomy and fusion. The approach should allow the fewest segments fused as possible. This would favor an anterior approach except when multiple fractures are present. Other considerations are patient’s comorbidities, disc injuries, bone quality, and forms of postoperative bracing.