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29Injuries of the Lower Cervical Spine Injuries of the Lower Cervical Spine

zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzSohail K Mirza, M.D. Paul A. Anderson, M.D.

Patients with blunt trauma injuries have a 2% to 6% prevalence of cervical spine injury. Victims of motor vehicle crashes, a subgroup of blunt trauma, have a higher rate of cervical injury (12%). The risk of cervical injury in specic settings can be further estimated by patient age, circumstances of the injury, and ndings at initial evaluation24 (Table 291). The clinical ndings in the initial evaluation dene the relative risk of a cervical spine injury, and combining these factors further identies the population at risk for such injury. These risk estimates can serve as a guide for the initial management of high-risk patients, as well as for prioritization of the subsequent clinical and radiographic evaluation.

Anatomic Considerations Specic to the Lower Cervical SpineThe vertebrae and articulations of the subaxial cervical spine (C3C7) and the rst thoracic vertebrae have similar morphologic and kinematic characteristics (Fig. 291). Injuries and disease processes usually behave similarly in this region. However, important differences in lateral mass anatomy and in the course of the vertebral artery exist between the mid and lower cervical spine. Surgical techniques place special emphasis on detailed knowledge of cervical anatomy to avoid neurovascular complications. NEURAL ELEMENTS The size and conguration of the spinal canal vary among humans and are important factors in determining the severity of spinal cord injuries.81, 120 Spinal cord dimensions, however, have remarkably little variation in humans. The midsagittal diameter of the spinal canal is measured from the base of the spinous process to the posterior margin of the vertebral body. In the subaxial spine, the spinal cord has an average midsagittal diameter of 8 to 9 mm. Cervical spinal canal stenosis exists when the midsagittal diameter is less than 10 mm. The Pavlov ratio may be used to estimate the size of the spinal canal229 and is dened as the ratio of the midsagittal diameter to the anteroposterior (AP) diameter of the vertebral body. If this ratio is less than 0.8, cervical stenosis is present. Cervical stenosis correlates with neurologic injury in patients with cervical fractures.81 The spinal nerves form from the ventral and dorsal roots and pass through the neural foramina. The boundaries of the neural foramina are the pedicles above and below the facet joint and the capsules posteriorly. Anteriorly, the foramina are above and below the disc annulus, the posterior vertebral body, and the uncinate process. The size of the neural foramina can be affected by displaced bone and disc fragments, by malalignment, or by loss of disc height. Patients with spinal cord injuries should be

INJURY PATTERNS

zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz Categorization of lower cervical spine injuries is variable, inconsistent, and problematic. Difculties are partly due to the inherent structural complexity of this region of the spine. With intertwined neural and vascular elements, load-bearing articular joints, and highly mobile articulations, the lower cervical spine is indeed complex. Variation in the interpretation of imaging studies adds to this complexity. Because injuries with distinct clinical implications require recognition rst and foremost, injury classication schemes that attempt comprehensive inclusion of all possible injury patterns have generally been too elaborate to be clinically useful. Simpler schemes fail to capture the essential dening characteristics of individual injuries. For simplicity and clarity in discussing important characteristics, we have divided the presentation of injury patterns in the lower cervical spine into separate anatomic, mechanistic, and morphologic considerations. However, it is important to keep in mind that evaluation of each injury involves a component of all three general categories of assessment.814

CHAPTER 29 Injuries of the Lower Cervical Spine TABLE 291

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Frequency of Cervical Spine Fracture in Patients Admitted to the Emergency Room of a Regional Trauma Center

zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzPrevalence of Cervical Spine Fracture (%) 19.7 7.2 2.2 1.9 1.1 0.5 0.4 0.04

Clinical Characteristics Trauma patient with focal decit Trauma patient with severe head injury Trauma patient, no focal decit, no severe head injury, moderate-energy cause, age >50 Trauma patient, no focal decit, high-energy cause Trauma patient, no focal decit, high-energy cause, age 50 Trauma patient, no focal decit, no severe head injury, moderate-energy cause, age 11 Resting radiographs 2 Sagittal plane displacement 3.5 mm or 20% 2 Relative sagittal plane angulation > 20 1 Abnormal disc narrowing 1 Developmentally narrow spinal canal (sagittal diameter < 13 mm or Pavlovs ratio < 0.8) 2 Spinal cord damage 1 Nerve root damage 1 Dangerous anticipated loading Point total of 5 or more = UNSTABLE INJURY treat with prolonged immobilization or surgery.

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kyphotic angulation may be reduced, thereby obscuring the presence of this injury. Interspinous widening is one of the most consistent ndings in this sort of injury, but it is often overlooked. The widening may be better visualized on AP radiographs. The use of exion-extension radiographs to assess stability and potential ligamentous injuries is a controversial subject. We personally recommend MRI with fat suppression technique to evaluate the posterior ligaments (Fig. 2910). If these images demonstrate high-intensity signals between the spinous processes, our patients are treated as they would be for a severe ligamentous injury. Again, patients are evaluated with the White and Panjabi criteria; when the point value is greater than 5, they are considered to have an unstable severe ligamentous injury. Nonspecic Soft Tissue Injury (Whiplash). Posterior ligamentous injuries most often result from hyperexion and distractive forces, and more severe injuries occur when small degrees of rotation are added. Posterior ligamentous injuries proceed in a dorsal-to-ventral direction. The nuchal ligaments are injured rst, followed by injury to the facet joint capsules, the ligamentum avum, and the intervertebral disc. Clinically, a variable amount of ligamentous disruption may be observed and, therefore, varying degrees of instability. No formal, clinically useful classication of these injury patterns has been universally accepted. Mild injuries are partial ligament injuries with focal tenderness but normal alignment and structural integrity. Moderate injuries have

CHAPTER 29 Injuries of the Lower Cervical Spine TABLE 297

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White and Panjabis Guidelines for Applying Interpreting the Instability ChecklistGENERAL CONSIDERATIONS

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The checklist is not validated in an applied clinical setting. Checklist functions as a safety factor, like a pilots checklist. Checklist is helpful in determining which patients need surgery or prolonged immobilization. Instability threshold is arbitrarily set at 5 to balance unnecessary surgery versus irreversible catastrophe. If any criterion has a borderline decision, add 12 the value to the sum. Checklist is not applicable to children < 7 years. ANATOMIC CONSIDERATIONS All anterior or all posterior elements destroyed potentially unstable Anterior elements destroyed more unstable in exion Posterior elements destroyed more unstable in extension Developmentally narrow canal lower threshold for neurologic problems with spinal injury RADIOGRAPHIC CONSIDERATIONS Translation measurement is based on a x-ray tube to lm distance of 72 inches. Sagittal plane translation: 3.5 mm on a static lm or F/E views (3.5 mm = 2.7 mm lab value + 30% magnication) or ratio of (translation distance) / (vertebral body diameter) > 20% Sagittal plane rotation: > 20 on F/E views or at least 11 more than FSU above or FSU below the level on a static view Stretch test: more than 1.7 mm difference in interspace separation pre- and post-test or more than 7.5 angulation Disc space height: disc narrowing may suggest annulus disruption and instability; disc space widening may also indicate annulus disruption and instability. Canal width: canal AP diameter < 15 mm or Pavlov ratio < 0.80 (Pavlov ratio = (midlevel posterior vertebral body to nearest point on spinolaminar line ) / (midlevel vertebral body AP diameter); normal 1) NEUROLOGIC CONSIDERATIONS If the trauma is severe enough to cause initial neurologic damage, the support structures have probably been altered sufciently to allow subsequent neurologic damage, and the injury is clinically unstable. Root involvement is a weaker indicator for clinical instability (one point) vs. cord injury (two points). PHYSIOLOGIC CONSIDERATIONS Anticipated dangerous loads are in occupations such as heavy laborer, contact sport athlete, or motorcyclist. Intractable pain also indicates instability.

highly unstable and, according to Webb and colleagues, frequently overlooked.246 Disruption of the Anterior Longitudinal Ligament. Hyperextension creates tensile forces in the anterior longitudinal ligament, occasionally resulting in failure (Fig. 2911). This injury leads to failure of the anterior longitudinal ligaments and disc annulus. In cases involving more severe extension (50% or greater), retrolisthesis can occur. When retrolisthesis does develop, increased widening or excessive lordosis of the intervertebral disc will be visible radiographically. MRI will show high signal intensity in the disc and retropharyngeal spaces on T2-weighted images. Traumatic Disc Disruption. Forced hyperextension with injury to the disc and longitudinal ligaments can result in traumatic retrolisthesis (see Fig. 2911). Usually, only a subtle degree (2 to 3 mm) is present, and it is easily overlooked or else thought to be secondary to preexisting spondylosis. In patients with congenitally narrow spinal canals, even these small amounts of retrolisthesis can cause a signicant amount of cord compression. Rarely, 50% or greater retrolisthesis develops. These injuries are highly unstable and difcult to reduce, and any reduction is difcult to maintain. Extension injuries are frequently associated with 2 to 4 mm of posterior vertebral subluxation (Fig. 2912). This injury has commonly been called traumatic retrolisthesis. Extension injuries are of intermediate instability. This degree of traumatic retrolisthesis may be difcult to differentiate from the retrolisthesis caused by degenerative changes. MRI with fat suppression can clearly identify traumatic discoligamentous injuries in questionable cases. Treatment of traumatic retrolisthesis is based on neurologic involvement. Patients who are neurologically intact may be

TABLE 298

General Categories of Spinal Column Disruption in the Lower Cervical SpineInjury Soft tissue injury Nonspecic soft tissue injury Avulsion of the anterior longitudinal ligament Traumatic disc disruption Isolated fractures Spinous process fracture Transverse process fracture Lamina fracture Vertebral body injuries Extension teardrop fracture Compression fracture Burst fracture Flexion teardrop fracture Facet injuries Unilateral facet fracture Lateral mass fracture-separation Unilateral facet dislocation Bilateral facet dislocation Fracture-dislocations Shear fractures with displacement Distraction-dissociation injury

zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzGeneral Treatment Category Soft collar Hard collar Surgery Hard collar Hard collar Hard collar Hard collar Hard collar or halo device Halo device or surgery Surgery Hard collar or surgery Hard collar or surgery Surgery Surgery Surgery Surgery

zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzassociated pain with some displacement. Radiographs show isolated kyphosis and spreading of the spinous processes. However, the displacements do not meet the criteria of White and Panjabi and produce a score of less than 5 on the clinical instability checklist. Severe cases are associated with pain and instability and complete ligament disruption. Radiographs demonstrate widening of the spinous processes, increased local kyphosis when compared with adjacent levels, small amounts of anterior subluxation, and facet subluxation or even facet perching. Severe posterior ligamentous injuries score greater than 5 on the clinical instability checklist. Posterior ligamentous injuries associated with vertebral body compression fracture are

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830TABLE 299

SECTION II Spine

ASIA Impairment ScaleScale A B C Type of SCI Complete Incomplete Incomplete

zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzDescription of SCI Pattern No motor or sensory function in the lowest sacral segment (S4S5) Sensory function below neurologic level, and in S4S5 no motor function below neurologic level Motor function is preserved below neurologic level and more than half of the key muscle groups below neurologic level have a muscle grade < 3 Motor function is preserved below neurologic level and at least half of the key muscle groups below neurologic level have a muscle grade 3 or better Sensory and motor functions are normal

the result of major injury vectors (see Fig. 297). They are stable as long as the facet articulations are competent and no vertebral body translation is involved. Rarely, lamina fractures can be displaced into the spinal cord; when such displacement occurs, extraction is required. Isolated fractures of the pedicles are rare because the neural arch is usually broken in two places (Fig. 2913). Vertebral Body Injuries Extension Teardrop Injury. Hyperextension can also result in an avulsion fracture of the anteroinferior vertebral body (see Chapter 28). This fracture is associated with discoligamentous disruption and occurs most commonly at the C2C3 interspace. Such fractures have been termed extension teardrop fractures, and they must be differentiated from the exionaxial loading teardrop fracture described by Lee, Schneider, and their co-workers.129, 204 A frequent source of confusion is osteophyte formation. The osteophytes may be fractured or incompletely ossied and therefore called a fracture. MRI has been useful in identifying acute extension injuries that result in disc annular disruption. Compression Fractures. Vertebral body compression fracture can occur from hyperexion or axial loading (Fig. 2914). When viewed radiographically, the body is wedge shaped, but the posterior vertebral body wall is intact. In isolated compression fractures the posterior osteoligamentous complex is also intact. These isolated fractures are stable. However, compression fractures frequently occur in association with disruption of the posterior ligaments; the disrupted ligaments are notoriously unstable and usually fail if treated nonoperatively. Burst Fractures. Burst fractures are characterized by vertebral body comminution with retropulsion of the

D

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zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzAbbreviation: SCI, spinal cord injury.

treated in a collar or cervicothoracic brace, as outlined earlier. The height of the collar should be carefully assessed to avoid extension. Patients with a transient or persistent neurologic decit should be placed in tongs traction and undergo MRI. If the neural decits do not resolve, anterior discectomy and fusion with plate xation are warranted. Isolated Fractures Isolated fractures of the spinous processes, lamina, and transverse processes occur frequently and are most often

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FIGURE 2910. A, Initial radiograph shows minimal separation of the C3C4 spinous processes (arrowheads). B, Upright radiograph 3 days later shows near-dislocation (arrowheads) despite immobilization in a collar. C, Magnetic resonance imaging (MRI) T2-weighted image demonstrates a high-intensity signal in the nuchal ligaments (arrowhead) due to edema and hemorrhage. A small traumatic disc herniation is seen ventral to the cord.

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Contusion of cord Torn anterior longitudinal ligament

Infolded ligamentum flavum

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posterior retrolisthesis into the spinal canal. Posteriorly, interspinous widening or comminution of the lamina and spinous processes is observed. Teardrop fractures are often seen in trauma from diving accidents and football injuries, and they are usually associated with signicant spinal cord injury. The classic neurologic syndrome is anterior spinal cord injury with loss of all motor and sensory functions except proprioception. Teardrop fractures differ signicantly from burst fractures in that the neural injury is due to the posteroinferior corner of the body rotating into the canal and not from retropulsion of the posterior body wall. In general, a teardrop fracture is more unstable than a burst fracture. Similar to burst fractures, varying degrees of instability of exion teardrop injuries exist. Mild cases have less than 3 mm of vertebral body displacement and minimal disruption of the posterior ligaments. In more severe cases, the spine is unstable because of the combination of vertebral body displacement and disruption of the posterior ligaments. Facet Injuries Isolated Facet Fracture. Isolated fractures of the facet or lateral masses must be examined and observed with extraordinary care because they may represent a more unstable injury than rst appreciated. These fractures are often missed on initial radiographs. They are best recognized from the lateral radiograph or sagittal CT reconstructed image. Isolated fractures not associated with any AP subluxation are stable. This may be deceiving as both the radiograph and the CT scan are done in the supine position and displacement may occur when the patient is upright. Missed facet fractures are the cause of chronic neck pain after trauma. Lateral Mass Fracture-Separation. Fractureseparation of the lateral mass occurs from lateral extension and rotation forces132, 198 (Fig. 2917). Compressive forces on the lateral masses create fracturing of the pedicle and the lamina at its junction with the lateral mass. When a fracture occurs, the lateral mass is separated from the vertebral body and lamina and thus becomes free oating. The side becomes rotationally unstable and allows forward rotation of the vertebral bodies. All the facets of the lateral mass work to stabilize both at a cranial and caudal level, and when a fracture-separation takes place, two motion segments may be affected. Initially, minimal translation may be present, although progressive deformity can occur despite bracing. Radiographically, malrotation of the entire facet is visible from lateral views. The AP view demonstrates facet joints rotated into view in the articular pillars. Though easily visible, fracture of the lamina at the junction of the lateral mass is often overlooked. Unilateral Facet Dislocation. Unilateral facet dislocations and unilateral facet fractures with subluxation have varying mechanisms of injury and prognosis (Fig. 2918). Typically, unilateral facet fractures and dislocations result from exacerbated kinematics of the normal cervical spine.209 In lateral bending and rotation, coupled motion enables one facet to move upward and the contralateral facet to move downward. The spinous process moves laterally toward the convexity of the curve. With excessive

BFIGURE 2911. Traumatic retrolisthesis is associated with disruption of the arterial longitudinal ligament and disc annulus, allowing varying degrees of posterior translation. A, In less-severe cases, 2 to 3 mm is present. B, In more severe cases, up to 50% retrolisthesis can occur. This causes compression of the spinal cord between the posterior body of the cranial vertebrae and the lamina of the caudal vertebrae. (B, Redrawn from Harris, J.H.; Yeakley, J.W. J Bone Joint Surg 74B:567570, 1992; from Forsyth, H.F J Bone Joint Surg Am 46:1792, 1964.) .

fracture fragments into the spinal cord (Fig. 2915). Viewed radiographically, both the anterior and posterior vertebral body height is shortened, and the interpedicular distance is widened. Burst fractures are associated with a variable amount of posterior ligamentous disruption, depending on the degree of exion or distraction present during injury. If intraspinous widening is observed or if facet disruptions are present, the lesion should be considered unstable and treated surgically. Flexion Teardrop Injury. A exion teardrop fracture is a complex injury often associated with spinal cord injury.204, 230 The teardrop is a small bony fragment located off the anteroinferior corner of the body that is rotated anteriorly (Fig. 2916). More importantly, the vertebral body is fractured coronally and has undergone

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FIGURE 2912. A 30-year-old patient sustained a central cord injury from hyperextension during a fall while skiing. A, Plain radiographs show 2-mm retrolisthesis with a congenitally small canal at C4C5. B, Increased signal intensity in the spinal cord is seen on the MRI scan. C, Because of persistent neurologic decits, an anterior decompression, fusion, and anterior plate xation with cervical spine locking plate (CSLP) was performed.

Superior facet fracture Pedicle fracture Facet fracture Print Graphic Inferior facet fractureFIGURE 2913. A and B, Isolated fractures of the pedicle and facet. These are usually stable. If pedicle fractures are associated with other posterior element injuries, the injury may prove to be unstable.

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Compression Shear

Tension

BFIGURE 2914. A, Stable vertebral body compression without involvement of the posterior osteoligamentous structures. B, Disruption of the posterior ligament creates a highly unstable fracture that usually will fail nonoperative treatment. Abbreviation: MIV, major injury vector. (A, Redrawn from Holdsworth, F J Bone Joint Surg 45:620, 1963. B, . Redrawn from White, A.A., III; Panjabi, M.M. In: White, A.A., III; Panjabi, M.M., eds. Clinical Biomechanics of the Spine, 2nd ed. Philadelphia, J.B. Lippincott, 1990, p. 225.)

force, one side of the neck will move too far inferiorly while the other moves too far craniad, thereby resulting in facet dislocation. Fractures of the facet articulation and occasionally the entire lateral mass are often present. These fractures result from the addition of shear or compressive forces, which cause excessive loading on the joint surfaces. Common causes of unilateral facet dislocation are trauma sustained in vehicular crashes and in athletics.

Beatson carefully analyzed the injuries to bony and soft tissue structures associated with unilateral facet dislocation.17 He found that a single facet could be dislocated only when the interspinous ligament, ligamentum avum, and ipsilateral joint capsules were damaged. When the posterior longitudinal ligament adjacent to the side or the disc annulus was damaged, the spine could be displaced further forward to just under 50%. Reduction by in-line traction was difcult because the contralateral facet joints and ligamentous structures remained intact. A minimal amount of lateral bending to the opposite side of the dislocation, however, could facilitate reduction. Unilateral facet dislocations are commonly missed because the rotational nature of the injury is not easy to identify on standard AP and lateral radiographs. In addition, small amounts of subluxation may be present on the initial radiograph, or the patient may have a signicant degree of spontaneous reduction. Unilateral facet dislocation occurs most commonly at C5C6 and C6C7, where visualization may be obscured by the overlying shoulders. In many cases, the injury is stable in the dislocated position, thereby minimizing pain. Radiographic features include vertebral body displacement of about 25% (Fig. 2919). Rarely, a minimal compression fracture of the caudal vertebral body is present. Interspinous widening is variable and depends on the amount of distraction, as well as the initial head and neck position. An important nding in diagnosing a unilateral facet dislocation is noticing asymmetry of the facets above and below the injury on the lateral view. Normally, the right and left facets are overlapping and viewed as a single unit on the lateral view. When a unilateral facet dislocation is present, the symmetry of the left and right facets is lost and both are visualized. Most commonly, two cranial facets are seen while the caudal facets are still overlapping and can be seen as a single facet. This arrangement creates the bow tie sign, which is pathognomonic for unilateral facet dislocation. The AP radiograph requires careful scrutiny because fractures of the pedicle or the laminar mass may be present. In this situation, the spinous processes are rotated to the side of the dislocation. If the facet is rotated into a exed position, the joint surface is visualized in the articular pillar. Trauma oblique radiographs are useful in determining facet alignment and foraminal encroachment, but they must be performed without turning the patients head. CT demon-

FIGURE 2915. Cervical burst fractures are associated with comminution of the vertebral body with retropulsion into the spinal canal. A, In stable burst fractures, there is minimal involvement of the posterior osteoligamentous structures. B, In unstable burst fractures, there is fracturing or disruption of the posterior ligaments due to distractive forces.

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FIGURE 2916. Axial loading injuries to the cervical spine have several variants. A, One common variant is a teardrop fracture. The injury is predominantly a exion-axial loading injury resulting in an oblique fracture of the anterior portion of the body with the line of injury propagating through the vertebral body. It exits out through the posterior aspect of the disc at the injured level with disruption of the facet capsules and interspinous ligaments. B, Notice the spreading of the facets indicating disruption of the capsules (arrows).

A

strates fractures in more than 75% of cases. CT reformations in the sagittal and oblique planes show detailed alignment of the facets. MRI is useful in some cases to show foraminal encroachment, as well as the status of the intervertebral disc, which can be herniated into the spinal canal in up to 15% of cases. Clinically, patients with a unilateral facet dislocation have pain, radiculopathy, a spinal cord injury, or any combination of these manifestations. Radiculopathies are easily overlooked and require careful upper extremity muscle and sensory testing. Palpation of gaps between spinous processes or malrotation of a spinous process is difcult in the cervical spine. The variability in injury mechanisms, bony injuries, and their prognoses led Levine to the following tripart classication of unilateral facet dislocations. The rst category is unilateral facet dislocation, the second is unilateral facet fracture with subluxation, and the third is fracture-separation of the lateral mass.130 Each category is characterized by subluxation with 10% to 25% displacement of the vertebral body and rotation of the spinous process to the side of the facet subluxation. Unilateral facet dislocations (see Fig. 2918A) occur less frequently than fractures. Twenty-ve percent of vertebral body translation is present in dislocations, and spinal cord injury occurs in up to 25% of cases. These dislocations may be difcult to reduce with cranial traction, but fortunately, they may be stable after reduction. Unilateral facet fractures with subluxation occur in up to 80% of cases130 (see Fig. 2918C). They are associated more commonly with fractures of the superior facet and less frequently with fractures of the inferior facet (see Fig. 2919). Although these two fractures result from different

mechanisms, both are unstable because the inadequate facet makes the spine unable to prevent anterior shear or rotation to the ipsilateral side. Unlike unilateral facet dislocations, these two fracture types do not usually involve any juxtaposition of the relationship of the anterior and posterior portions of the joint. Instead, rotational deformity carries the fragment forward. Both fracture types generally reduce anatomically with axial traction. Bilateral Facet Dislocation. Bilateral facet dislocations (Fig. 2920) result from several mechanisms, most often hyperexion in combination with some rotation.250 Allen and associates described these injuries as distraction exion stage III and distraction exion stage IV lesions.5 Roaf created various spinal injuries in cadaveric models and found that pure hyperexion resulted in compression fractures of the vertebral body.188 He also discovered that small amounts of rotation pretensed the ligaments, thereby allowing bilateral facet dislocations to occur with much lower force. Others have created bilateral facet dislocations by compressive loading onto the skull with the neck placed in slight exion.209 This mechanism occurs frequently in young athletes. Regardless of the mechanism of injury, bilateral facet dislocations are highly unstable injuries and are associated with neurologic decit in most cases. Dissection of cadavers demonstrates a signicant injury to all posterior ligamentous structures and the posterior longitudinal ligament and disc annulus. The anterior longitudinal ligament is often the only structure that remains intact. Injuries to the disc annulus are of special importance. When injured, the annulus is avulsed from its vertebral attachments, and the nucleus pulposus and portions of the annulus and end-plate can then retropulse into the spinal canal and further compress neural tissues (Fig. 2921).

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FIGURE 2917. A 26-year-old woman presented 3 months after severe head injury with neck pain and bilateral C6 radiculopathy. A, On the initial chest radiograph, the C5 lateral mass is rotated into the plane of the x-ray beam because fractures of the pedicle and lamina create a fracture-separation of the lateral mass. B, The lateral radiograph 3 months later shows subluxation of C4C5 and C5C6. C, The axial computed tomography (CT) scan demonstrates the pedicle and lateral mass fractures. D, E, After reduction, she was treated by a lateral mass xation using AO reconstruction plates. Her neurologic decits completely resolved after the stabilization procedure.

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FIGURE 2918. A, Facet fractures and dislocations in the cervical spine are a result of a combination of exion and rotational forces. Depending on the relative relationship of the amount of exion and rotation, either a facet fracture or a dislocation may occur. When the forces are predominantly rotational, without a signicant exion force, a unilateral facet fracture can occur. B, However, when the rotation is preceded by exion, so that the facets are at least partially disengaged before the rotational force is applied, a unilateral facet dislocation results. C, Unilateral facet fracture-dislocation. Fracture of the superior articular facet with subluxation. (B, C, Redrawn from White, A.A., III; Panjabi, M.M. In: White, A.A., III; Panjabi, M.M. eds. Clinical Biomechanics of the Spine, 2nd ed. Philadelphia, J.B. Lippincott, 1990.)

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FIGURE 2919. This 63-year-old woman sustained a unilateral facet fracture at C3C4. The inferior facet of C3 was fractured (arrow in A) with an intact superior facet of C4. This is a less common pattern. A single level of oblique wiring cannot be done, as the wire needs to be passed through the inferior facet of the level above, which in this case is fractured. A, The oblique wire construct was extended to the inferior facet of C2, and an interspinous wire was used to augment the stability of the construct in exion. B, Follow-up radiograph at 1 year demonstrates a solid arthrodesis with anatomic alignment.

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FIGURE 2920. A, As seen in this illustration, bilateral injuries occur when the force is predominantly that of exion. B, C, If the exion is sufcient to clear the superior articular facet of the lower level, then the injury is a pure ligamentous injury with disruption of the interspinous ligament, supraspinous ligament, facet capsules, ligamentum avum, and the posterior portions of the disc. If translation occurs with a lesser degree of exion, then frequently fractures of both superior articular facets occur in addition to the ligamentous injuries.

MRI has documented that 10% to 40% of patients with bilateral facet dislocations have associated disc herniations.75, 80, 186 However, signicant disc herniations with cord compression occur much less frequently. Usually, the disc material and cartilaginous end-plate are behind the body and located under the posterior longitudinal ligament. Patients with disc herniations may deteriorate after closed reduction. Bilateral facet dislocations have 50% vertebral body translation on lateral radiographs. Fracturing of the posterior elements occurs in more than 80% of cases. Abnormal disc space narrowing is an ominous sign and often associated with disc herniation.250 The spine is kyphotic, and widening between the spinous processes is

usually present. Bilateral laminar fractures or fractures in the spinous processes are frequent and complicate posterior xation. Fracturing of the facets is common and often results in the combination of a facet dislocation on one side and fracture of the facet with displacement on the other. Rarely, bilateral pedicle fractures are present and create a spondylolisthetic condition that is difcult to reduce.146 With more severe distraction forces, the dislocation can increase to 100% or result in vertical separation between vertebral bodies. These lesions are dangerous because skull tongs traction will not be useful and can in fact result in further neurovascular injury. These injuries also appear to be associated with an increased likelihood of neuro-

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FIGURE 2921. A, A bilateral disc facet dislocation with the intervertebral disc displaced into the spinal canal. B, After reduction, the disc is causing spinal cord compression. C, This midsagittal MRI scan demonstrates postreduction disc herniation into the spinal canal. The patient sustained a bilateral facet dislocation in the lower cervical spine and was neurologically intact on presentation. Closed reduction was done, but complete anatomic restoration of alignment was not possible. However, the patient remained neurologically intact. Therefore, before surgical stabilization, an MRI scan was obtained to determine the cause of incomplete reduction. This image demonstrates disruption of the posterior longitudinal ligament and disc herniation sufcient to minimally compress the anterior surface of the cord. Note also the stripping of the anterior longitudinal ligament from the surface of the bodies. (A, B, Redrawn by permission of the publisher from Cervical intervertebral disc prolapse associated with traumatic facet dislocations by Berrington, N.R.; van Staden, J.F Willers, J.G.; vander .; Westhuizen, J., Surg Neurol 40:395399, Copyright 1993 by Elsevier Science Inc.: modied from Eismont, F et al. J Bone .J.; Joint Surg Am 73:15551560, 1991.)

logic deterioration, a higher level of neural than skeletal injury, and vertebral artery injury leading to subsequent death. Fracture-Dislocations Fractures with Dislocation. Injury patterns associated with translation displacement across the injury site imply a severe injury with complete disruption and marked instability. These injury patterns are designated fracture-dislocations, and the particular type of complete disruption may result from several different high-energy mechanisms, including compression, bending, and distraction. In severe injuries, the injury patterns acquire a common appearance of gross structural disruption, loss of stability, and damage to all components of the spinal column, including bone, ligaments, cord, nerve roots, and associated structures such as blood vessels and paraspinal muscles. The disconnected cephalad and caudad segments of the spine show translational displacement in the coronal and sagittal planes, consistent with dislocation. Distraction-Dissociation Injury. Complete disruption of the longitudinal ligaments in the lower cervical

spine results in severe instability equivalent to the instability in fracture-dislocation patterns. This injury is characterized by complete loss of structural continuity of the spinal column, and it is frequently accompanied by severe spinal cord injury. Often in distraction-dissociation injuries, the large blood vessels of the neck, the carotid and vertebral arteries, sustain a stretch injury that may result in cerebral ischemia, stroke, and death. Distraction may be associated with an extension-type injury, which is seen more often in patients with stiff spines caused by severe spondylosis, DISH, or ankylosing spondylitis. These injuries may in some cases be highly unstable fracture dislocations. If not accompanied by immediate neurologic decit, they have the potential for causing neural deterioration. Therefore, patients with these injuries should have provisional stabilization with a halo vest. Cervical traction is contraindicated, as distraction or change in position may cause further neural deterioration. Forsyth, Harris and Yeakley, and Allen and associates have identied extension fractures that result in 50% posterior vertebral body translation, as well as bilateral facet dislocations that occur from hyperextension

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mechanisms.5, 90, 109 Severe comminution of the posterior elements is often present in these fractures. Because of loss of all spine stability, the posterior dislocation can reduce spontaneously. With further head exion, the posterior dislocation can continue forward and simulate a bilateral facet dislocation. Merianos and associates documented similar cases associated with bilateral pedicular fractures.146 These injuries are difcult to reduce, and any reduction achieved is hard to maintain because of separation of the anterior and posterior spinal columns. Patients with severe traumatic retrolisthesis are difcult to manage in terms of both treatment and pain. Attempts at traction should be made, and if such attempts are successful, anterior decompression and interbody fusion with a plate should be performed. If reduction cannot be achieved or maintained, open reduction through an anterior approach is warranted. These patients may also require posterior xation with lateral mass plates to achieve alignment and spinal stability. In patients with displaced laminar fractures in whom neurologic decit is present, a laminectomy procedure is indicated in combination with stabilization.

FLEXION-EXTENSION RADIOGRAPHS Flexion-extension radiographs are often recommended to evaluate the stability of the cervical spine after injury. They must be used with caution because signicant displacement can occur even in patients who are awake, and such displacement can cause additional spinal cord injury.44 Furthermore, their usefulness is limited by muscle spasms that decrease overall neck excursion. Although such stress radiographs can demonstrate instability, the clinical evaluation of stability, as per Whites discussion, does not require dynamic radiographs. Recently, Harris and colleagues recommended a rigid protocol of exion-extension cineuoroscopy obtained from obtunded patients under anesthesia who were otherwise undergoing surgery.110 In 187 of the patients evaluated, no adverse effects occurred from this protocol. Three patients in this study were identied with unstable spines. Despite these promising initial results, further evaluation of this protocol must be performed before it is routinely accepted. Our current recommendation is to refrain from attempts to obtain exion-extension radiographs in the acute trauma setting. Instead, patients with questionable injuries are immobilized in their extraction collars and then reevaluated as outpatients, where subacute exionextension radiographs can be obtained. MRI is a helpful alternative and an excellent tool for identifying ligamentous injuries. Because ligamentous injuries are the most dangerous occult injuries, MRI is an excellent resource. STRETCH TEST The stretch test is a diagnostic procedure used to evaluate occult cervical instability. The test is based on the assumption that an occult, but unstable ligament injury can be demonstrated by the application of a controlled distraction force. Patients with an apparently minor cervical fracture but one that could have a more severe associated ligamentous injury are placed in a cervical traction apparatus. The traction apparatus may be a head halter harness or cervical traction tongs. With the patient in a supine position, incremental weights are applied, typically in 5-lb increments, up to 25 lb total weight. Alignment of the cervical spine is assessed radiographically, and the patient is examined between each weight increment. If the cervical spine shows distraction (a 50% increase in disc height) or if the patient has neurologic symptoms, instability is indicated. If none of these signs are present, the patient is deemed to have a stable cervical spine.

CERVICAL IMAGING Standard Views

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The three standard views of the cervical spine are the AP, the lateral, and the open-mouth views. Some medical centers, including ours, add right and left oblique views to the standard set. If the lateral view does not show the cervicothoracic junction, it is supplemented by a swimmers lateral view (see Chapter 26). This projection separates the shoulder overlap to allow better visualization of the lower cervical and upper thoracic vertebrae (Table 297).

Dynamic StudiesUPRIGHT RADIOGRAPHS Upright radiographs are a useful tool for diagnosing spine injuries, but they allow only one level of dynamic assessment. Upright radiographs show the cervical spine under physiologic load, and although this view is limited, it is helpful because ligament injuries not apparent on supine radiographs may become apparent with loading. Examining the cervical spine under a physiologic load results in focal kyphosis or translation at the injured segment. Minor bone injuries such as compression fractures may also show more deformation with load bearing. Upright radiographs are also useful in evaluating the success of spinal stabilization with external bracing or surgical xation. An upright radiograph allows surgeons to view change in position as it relates to the supine view, which may necessitate a change in treatment. As for other assessment tools, exion-extension radiographs and the stretch test provide other dynamic measurements.

Computed Tomography and Magnetic Resonance ImagingCT shows bone in exquisite detail. It is routinely performed on all patients with cervical spinal injuries to identify facet fractures and malalignment. CT is indicated for most patients with bony injuries, such as vertebral body fractures or fractures of the lamina or facets. Before surgery, patients should undergo CT scanning to determine the extent of the osseous injury and to help plan

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surgical treatment, especially when using newer methods of screw xation. If a fracture has been identied, CT or MRI is always recommended. In patients with neurologic injury or facet fracture-dislocation, MRI is preferred because it visualizes the cause of the cord damage and the status of the intervertebral disc.62, 201 However, MRI does not dene bony pathoanatomy as well as CT does. MRI or myelography is warranted in patients with progressive or unexplained neural decits. To assess disc pathology, foraminal patency, and possible epidural hematoma formation, these diagnostic imaging procedures should be performed before any surgical treatment is attempted. According to Eismont, Rizzolo, and their co-workers, disc herniation is associated with bilateral facet fracturedislocation in 10% to 15% of patients.80, 186 Patients with hyperexion-type injuries may have increased signal intensity in the posterior nuchal ligaments on MRI, which is indicative of ligamentous disruption. Fat suppression techniques such as T2-weighted or short T1 inversion recovery (STIR) sequences can be particularly helpful.

TREATMENT

zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz Errors in the initial care of spinal injury patients can have catastrophic, even fatal results.70 Minimizing these errors requires management of spinal injury patients at highly specialized centers with experienced personnel.191 It has been shown that patients with spinal cord injury benet from early transfer to a trauma center.162 For patients with spinal cord injury, early referral to a spinal cord injury center improves patient survival and neurologic recovery.123 Management of spinal injury patients requires the concerted energy and action of a talented trauma team. Experienced eld personnel, emergency room physicians, orthopaedic surgeons, neurosurgeons, rehabilitation physicians, radiologists, and general surgeons are integral members of the team. The physicians who will ultimately assume the long-term management of trauma patients are critical in directing optimal initial care.98 Denitive treatment of the spinal injury may be nonoperative or surgical.253 The surgeon must protect and immobilize the spine until injury is denitively excluded or treated, which means that all trauma patients should be in a supine position at strict bedrest on a at bed, with spine board transfers. Logrolling must be used for decubitus ulcer prophylaxis. Patients may alternatively be placed in a rotating frame for improved pulmonary mechanics and skin care. The objective in treating any spinal cord injury includes protecting the spinal cord from further damage and providing an optimal environment for neurologic recovery. This goal requires reducing and stabilizing fractures and dislocations, decompressing the neurologic tissue, and providing the most stable, painless spine possible.55, 99, 191 An environment for maximal neurologic recovery should be created within the rst several hours after injury.72, 78, 185 The basic elements of treatment are resuscitation of the patient with advanced trauma life support

principles, identication of the fracture pattern, classication and assessment of fracture stability, early closed reduction if possible, pharmacologic treatment (if indicated), and nally, denitive treatment. Denitive treatment is aimed at achieving complete decompression of the neural tissues in patients with neurologic decits and providing sufcient stabilization to allow patient mobilization. This goal can be achieved by either operative or nonoperative methods. Patients with persistent neural compression who are neurologically intact do not usually require decompression. Surgical stabilization, if selected, should include as few motion segments as possible. In neurologically impaired patients, stabilization should allow mobilization of the patient without the use of a halo brace. Although experimental treatments have shown that neurologic recovery can be improved by decompressive surgery in animal models, only the use of corticosteroids and correction of adverse mechanical factors have been demonstrated to be effective in minimizing neurologic decits in humans. The timing of surgery for a cervical injury remains a controversial topic. No denitive data have demonstrated that early treatment in humans has any inuence on neurologic recovery.118 Opponents of early surgical intervention insist that the stress of an operation adds to the rapidly changing biochemical, vascular, and cellular events that invariably follow spinal cord injury and that these events will ultimately be harmful to the patient.33, 140 This scenario may occur in patients with bilateral facet dislocations and is discussed later.80, 186 Marshall and co-workers performed a prospective study of neurologic deterioration in 283 spinal cordinjured patients.140 They found that four patients who had undergone surgery within 5 days of injury experienced deterioration. No patient who had surgery after 5 days had deterioration. However, ve patients had evidence of deterioration during nonoperative treatment while awaiting surgery, including two cases of deterioration from halo vest placement, two from rotation of a Stryker frame, and one from loss of reduction. Conversely, other researchers insist that early operative stabilization enhances neurologic recovery and decreases the morbidity associated with long periods of immobilization. Studies by Schlegel and associates203 and by Anderson and Krengel8 showed no difference in complications, but better patient outcome in patients treated early. The protocols for spinal cord injury at our particular institution call for early fracture reduction, stabilization, and decompression of neural tissues. Animal studies have consistently shown a strong inverse relationship between the timing of decompression and neurologic recovery. Shorter time to decompression has been shown to lead to greater recovery.15, 29, 72, 74, 77, 185 Delamarter and colleagues placed constricting bands in beagles that narrowed the spinal cord to 50%.72 The animals had decompression (removal of the constricting bands) at time 0, 1 hour, 6 hours, and 24 hours. Animals that had early removal (0 and 1 hours) made full clinical neurologic recovery, whereas those decompressed later (6 and 24 hours) did not. This outcome correlates well with histopathologic ndings demonstrating that the axonal tracts in the white matter are intact immediately after experimental trauma.15, 77 However, these results were followed by progressive

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destruction over a period of 24 to 48 hours because of secondary injury from adverse mechanical, biochemical, and vascular factors.115, 117, 209, 257, 260 A short window of opportunity may exist in which reduction of the deformity combined with reestablishment of spinal cord perfusion can completely reverse the spinal cord injury.72, 128 We have observed six such cases in patients who underwent reduction of a bilateral facet dislocation within 2 hours of trauma. All experienced immediate reversal of their quadriplegia. From these observations and studies, it appears that neurologically injured patients should indeed have fracture reduction performed in a timely fashion.31, 40, 72, 128 Another concern in managing patients with cervical spinal injuries is the effect of prolonged traction on their general medical condition. Cranial tongs traction requires recumbency, which can lead to pulmonary, gastrointestinal, and skin complications. Schlegel and associates203 and Anderson and Krengel8 reported decreased morbidity and length of hospitalization in patients with multiple injuries if treated surgically within 72 hours of injury when compared with those treated in delayed fashion.

Provisional CareThe initial treatment of cervical spinal cord injuries consists of reduction with cranial tongs traction. Because accid patients, elderly patients, and those with ligament injuries can easily be overdistracted by traction, traction weight should be applied judiciously. In many cases, reduction can be facilitated by adjusting the relative position of the head to the thorax instead of simply adding more traction weight. Special care must be taken in positioning children, whose heads are relatively larger than their chests, and also in positioning elderly patients with preexisting thoracic kyphosis. Generally, an initial traction weight of 2.5 kg is used for injuries in the upper cervical spine and 5.0 kg is used for injuries in the lower cervical spine. Traction weight is increased in increments of 2.5 to 5.0 kg at 15-minute intervals to allow for soft tissue relaxation. A neurologic examination should be performed and a lateral radiograph obtained after the addition of each increment of weight. Weight is increased until the fracture or dislocation is reduced. During reduction, radiographs should be scrutinized for signs of overdistraction, such as widening of the intervertebral disc or the facet joints. To facilitate unlocking a facet dislocation, the head can be gently exed by placing towels under the occiput. Burst fractures may require substantial traction weightwe have used up to 70% of the bodys weight without incurring complications. However, manual manipulation is not recommended to achieve reduction. Gardner-Wells tongs are applied in the emergency department to patients with unstable cervical injuries (see Fig. 294). In so doing, the skin is prepared with a povidone-iodine (Betadine) solution and inltrated to the level of the periosteum with a local anesthetic. Shaving the scalp is not necessary. The pins are inserted into the skull 1 cm above the tips of the ears and in line with the external auditory meatus. The pins are tightened symmetrically until the spring-loaded plunger protrudes 1 mm from the

pin surface. The locking nuts are tightened and weight applied with a rope and pulley. The pins are retightened after 24 hours and are not disturbed again. This protocol requires thinking ahead, for if an MRI study is anticipated, MRI-compatible tongs must be used from the start of treatment. The use of MRI-compatible tongs can facilitate postreduction imaging, although these tongs do not hold as much traction weight as stainless steel tongs do.25 Weights of 5 to 10 lb are then applied, a repeat neurologic examination is performed, and a lateral radiograph is obtained. If reduction has not occurred, the weight is increased by 5 to 10 lb and the process is repeated. Interval radiographs are scrutinized carefully for signs of overdistraction, such as increasing disc height or facet joint diastasis. Traction of up to 70% of body weight can be applied safely by this meticulous protocol.65 The use of C-arm uoroscopy can also facilitate reduction. Once reduction has been achieved, the traction weight can be decreased, except in some patients with burst or exion teardrop fractures. Cranial tongs traction is contraindicated in patients with skull fractures or large cranial defects. Traction should also be used judiciously in patients with complete ligamentous injury. After reduction, patients should be imaged by MRI. Those with persistent cord compression are considered candidates for surgical decompression and stabilization. In most patients who achieve indirect decompression by fracture reduction, the choice of treatment is based on the clinical course and fracture type, as described later. Indications for immediate surgery include neurologic deterioration and ongoing compressive lesions or malalignment. Patients with failure of reduction by closed technique should also be considered candidates for early surgery within the rst 24 hours.31, 211 Cervical injuries almost always require skull traction. The only exception to this rule is the case of a distraction injury. Distraction at the skull-spine junction or between any vertebrae indicates complete ligament disruption. These injuries are the most unstable spine injuries, and skull traction in these patients will lead to catastrophic iatrogenic neurologic and vascular injury. Patients with these injuries are better immobilized with sandbags and tape or a halo apparatus. Even when immobilized in the halo apparatus, patients should be kept in strict bedrest with full spine precautions until denitive surgical stabilization. Hemodynamic instability is commonly seen after spinal cord injury because interruption of the descending sympathetic bers results in vasodilatation and hypotension. Vagal predominance causes bradycardia, further lowering cardiac output. A low pulse rate can distinguish hypotension associated with spinal cord injury from hypovolemic shock. Neurogenic shock should be treated with vasopressors or agents to increase peripheral vascular resistance rather than uid resuscitation. The bradycardia may require atropine or, rarely, a pacemaker. Because of loss of autoregulation, spinal cord blood ow to the injured region is determined solely by blood pressure. Therefore, when hypotension is present, rapid correction is essential to patient survival. Minor spinal injuries include laminar fractures, spinous process fractures, lateral mass fractures without vertebral body displacement, and avulsion fractures of the anterior

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longitudinal ligament. These injuries are usually stable and occur with hyperextension; they are not associated with neurologic decits. Flexion injuries include vertebral compression fractures without posterior wall involvement and grade I or II ligament injuries. Patients suffering these more minor injuries, if the injuries are stable, are immobilized with a cervical collar. Tongs traction is applied only to patients who are to undergo concurrent procedures such as femoral intramedullary nailing or pelvic xation. Anterior vertebral translation is normally prevented by the orientation of the facets, the posterior ligamentous structure, and the disc annulus. Translation of 25% occurs under three particular conditions: unilateral facet dislocations, bilateral perched facet fractures, and facet fracturedislocations. In unilateral dislocations, the spinous process is rotated to the side of the facet dislocations on AP radiographs. Bilateral facet dislocations result in at least 50% vertebral body translation. Widening of the interspinous process is an important indicator of posterior ligament injury. In these instances, CT has been useful in identifying facet fractures and malalignment. MRI has been used successfully to identify intervertebral disc herniation in 35% of bilateral dislocations and 15% of unilateral cases.81 Methylprednisolone is given to patients with spinal cord injuries according to the protocols outlined earlier. Rapid closed reduction is accomplished by tongs traction and weights. In the case of spinal injury, because all the major surrounding ligaments are potentially damaged, overdistraction is always a potential and painstaking effort must be taken to avoid this peril. If reduction cannot be achieved by closed methods, open reduction and internal xation are indicated. Closed manual manipulation is not recommended. Axial loading can fracture the vertebral body and retropulse bony fragments into the spinal canal. When this mechanism is combined with exion, as it often is in the case of diving injuries, a teardrop fracture is produced.120 In this injury, the fractured anterior-inferior corner of the vertebral body forms a teardrop shape and the remaining vertebral body is rotated posteriorly into the canal. In addition, rupture of the posterior ligament structures produces kyphosis and a highly unstable fracture (see Fig. 2920). Under these conditions, spinal cord damage is often severe. In treating a teardrop fracture, spinal realignment and reduction of the retropulsed fragments can be achieved by axial traction. Up to 70% of body weight can be used without incurring complications in burst fractures. After reduction, the amount of traction weight can be reduced, but the fracture must be monitored radiographically to ensure maintenance of reduction. Schneider and Knighton described a syndrome involving damage to the cervical spinal cord in patients without any obvious spinal fractures.206 This syndrome is due to hyperextension in patients with narrow spinal canals and results in compression of the spinal cord between the bulging disc and the infolded ligamentum avum. Neurologically, this injury produces a central cord syndrome in which patients retain better lower extremity than upper extremity function. The prognosis for recovery in the lower extremities is good, although many patients suffering from this syndrome experience residual loss of hand

function. Patients who have sustained an extension injury concurrently with a central cord syndrome should be placed in traction even when radiography reveals no evidence of an acute injury. This precaution protects the cord from further injury and reduces small malalignments, such as 1 to 2 mm of retrolisthesis. Traction can be used to open the canal by applying tension to the ligamentum avum and pulling it out of the spinal cord.

Closed ReductionClosed reduction in cervical spine injuries has proved safe and effective.124 It is possible that successful reduction may require weights higher than 140 lb. Sabiston and colleagues provided evidence that traction weight totaling up to 70% of body weight is safe.200 However, weight heavier than 80 lb should not be applied to most carbon ber MRI-compatible tongs. The traditional steel GardnerWells tongs are less likely to slip with larger weights. Traction should not be applied to patients with injuries involving distraction of the spinal column. Decompression of spinal cord injury should proceed immediately.71 Emergency attempted closed reduction is the treatment of choice for alert cooperative patients with acute cervical spine dislocations.216 In these patients, imaging is not necessary before reduction and should be avoided so that reduction is not delayed.128 Open or closed reduction under general anesthesia in an uncooperative or unconscious patient can be preceded by an MRI scan. In this situation, a herniated disc may be treated by surgical decompression before reduction.187 Patients with highly unstable injuries, such as craniocervical dissociation, can undergo reduction and be provisionally immobilized with a halo device.151 Closed reduction decreases the need for more complicated surgical procedures.221 Reduction also improves stability by preventing neurologic deterioration in the interval preceding denitive treatment.137 Closed reduction can improve neurologic status.210 Spinal cordinjured patients may have an excellent capacity for spinal cord recovery regardless of the initial ndings.42 Reduction within the rst few hours of injury may lead to dramatic improvement in neurologic status. Reduction within 2 hours of injury may reverse tetraplegia.95 Although case reports have described neurologic deterioration during reduction,163 larger series have not noted neurologic deterioration with closed reduction.65

Denitive CareCLOSED TREATMENT Closed treatment remains the standard of care for most spinal injuries. Clinical observation reports, biomechanical investigations of stability, and radiographic measurements of stability have not produced denitive recommendations applicable to specic cases in terms of certain decisions regarding closed or operative treatment. The only consistent indication for surgical treatment may be skeletal disruption in the presence of a neurologic decit. One consistent contraindication to closed treatment is a purely ligamentous and unstable spinal column injury in a

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skeletally mature patient. Although these injuries may heal adequately in pediatric patients who still have signicant growth remaining, in adult patients, the healing response does not restore sufcient strength to provide spinal column stability, regardless of the length of bedrest or external immobilization. Unstable ligamentous injuries always require fusion. Osseous injuries will heal adequately but require treatment to control deformity. Closed treatment options are bedrest, a halo apparatus, an external orthosis, or a cast.83 Bedrest as denitive treatment may be indicated in rare patients unable or unwilling to undergo bracing or surgery. Such patients may include those with a severe preexisting deformity, morbid obesity, or medical co-morbidity, or it may simply be their personal preference. Bedrest for the initial few weeks preceding bracing is an option for severely unstable injuries. The level of injury serves as a guide for the category of external orthosis (see Table 296). Most commercially available braces within each category are equally effective.149 Custom-molded trunk orthoses provide added rotational control, and casts can be applied in hyperextension to improve kyphosis. Bracing is continued until bone healing is sufcient for load bearing. The guideline for load bearing is 8 weeks for cervical injuries and 12 weeks for thoracolumbar injuries. Mild Soft Tissue Injury Neck pain or tenderness without associated imaging abnormalities is generally treated with initial immobilization in a collar. Flexion-extension radiographs are obtained when the tenderness resolves, typically 2 to 6 weeks after injury. Instability on exion-extension views requires surgical treatment. If dynamic studies do not show instability and the patient remains symptomatic, a short course of physical therapy for strengthening plus the addition of mobility exercises is usually helpful. Patients with chronic symptoms require specialized pain management. Isolated Minor Fractures Isolated pedicle or facet fractures without vertebral subluxation are usually stable and can be treated in a cervical orthosis for 6 to 8 weeks. Careful follow-up is required because of the potential for late subluxation. Patients with chronic neck pain after trauma may have occult fractures of the facet that are not easily discernible on plain radiographs. These injuries can be identied by bone scanning or CT and can be treated with late posterior fusion. Vertebral Body Injuries Extension Teardrop Injury. Patients with extension injuries but without a fracture can be mobilized in a cervical collar after 5 to 7 days in traction. Because the prognosis for nonoperative management of these injuries is generally good, no initial surgical treatment is required. If a patient fails to make a satisfactory recovery and cord compression is documented by myelography or MRI, late anterior decompression should be considered. Stable extension injuries of the anterior column include rupture of the anterior longitudinal ligament, rupture of the disc annulus, and an extension teardrop fracture without vertebral body subluxation. In all cases, spinal

alignment should always be evaluated because small degrees of retrolisthesis are easily overlooked. Patients with anterior longitudinal ruptures can be identied radiographically by the notable increase in disc space. Occasionally, these patients will also have increased lordotic angulation. These injuries reduce easily with upright positioning. The most effective treatment of an anterior longitudinal ligament injury is the use of an orthosis for 6 to 8 weeks, as outlined previously for the treatment of stable injuries. Compression Fractures. Compression fractures are best treated with external bracing. A hard cervical collar or a Minerva-type brace for 6 to 8 weeks is usually adequate. Flexion-extension views should be obtained at the end of bracing to exclude any residual ligamentous instability. Patients with vertebral body compression fractures should be carefully examined for disruption of the posterior osseous ligament. Symptoms of this condition include tenderness along the spinous processes, gaps between the spinous processes, interspinous widening on plain radiographs, an abnormal signal in the nuchal ligaments on MRI, or any combination of these signs and symptoms. Compression fractures associated with ligamentous injuries are treated surgically by posterior interspinous fusion. Webb and colleagues identied hidden exion injuries that initially appeared to be simple wedge compression fractures.246 These injuries are caused by hyperexion forces and consist of an anterior vertebral fracture with posterior osteoligamentous disruption. They are unstable, and when carefully analyzed, they will exceed 5 points on the White and Panjabi scale. This injury is sinister and notorious for slow progression of increasing deformity until dislocation or facet perching occurs. Burst Fractures without Associated Neurologic Injury. Burst fractures of the cervical spine have an appearance similar to fractures of the thoracolumbar junction. Their stability and treatment depend on the stability of the posterior elements. These injuries often occur at C6 and C7 and can be missed easily if radiographs are inadequate. CT and MRI should be performed to fully evaluate the posterior osseous ligamentous structures. The initial treatment of all burst fractures is reduction with cranial tongs traction. In most cases, the posterior longitudinal and anterior longitudinal ligaments are spared, and therefore large traction weights can be safely used. Initially, 10 to 15 lb is applied and then progressed up to 70% of body weight to obtain the most complete reduction.66 Denitive treatment is based on fracture stability and neurologic function. Patients with stable fractures that do not involve the posterior elements can be treated with halo immobilization for 12 weeks. The halo vest cannot maintain axial distraction, and therefore some loss of reduction will necessarily occur, including retropulsion of bone into the canal. Patients with unstable fractures and injury to the posterior osseous and ligamentous structures are best treated with surgical stabilization. Before the development of effective and safe anterior cervical plates, these injuries were successfully treated by posterior wire xation with or without a postoperative halo vest. However, modern-day surgery has proved that plate xation of the lateral masses is biomechanically more effective than interspinous wire

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xation in controlling the axial forces. Anderson and associates reported successful outcomes in 12 patients with unstable burst fractures and exion teardrop fractures treated with AO reconstruction plates applied to the lateral masses.13 However, the anterior approach with the use of rigidly locked plates is our particular recommended treatment. This technique allows removal of the fractured vertebral body and displaced discs, as well as reconstruction with a strut graft and plate spanning the two injured motion segments. Others have recommended combined anterior and posterior surgeries performed sequentially for these highly unstable fractures. We have found that this approach is rarely warranted because of the effectiveness of anterior cervical plate stabilization.41 Cervical burst fractures in patients with neurologic injury should be treated by anterior decompression and fusion with anterior cervical plates. Anterior decompression is the most viable method because it removes displaced bone and disc fragments and may allow viable, but nonfunctional neural tissue to recover. Patients with stable burst fractures but no associated neurologic injuries are treated in a halo vest for 12 weeks. Anterior decompression and strut fusion are performed in patients who have sustained stable burst fractures with associated neurologic injuries. Late anterior decompression is indicated in patients who fail to improve neurologically and for those with persistent cord compression. The technique of posterior cervical fusion for burst fractures or facet fracture-dislocations requires communication and careful coordination between the anesthesiologist and the surgeon. Nasotracheal intubation is performed with a beroptic light system on an alert patient. The patient is transferred to a Stryker frame and placed in a prone position. After a neurologic examination is repeated and a lateral radiograph is obtained to conrm adequate alignment, general anesthesia is administered. Spinal cord monitoring is performed when intraoperative reduction is anticipated. A modied Rogers wiring technique provides adequate xation for ligament injuries with intact bony structures.61 Posterior cervical plate xation is indicated for fractures with associated posterior ligament instability and for burst fracture patterns.102 In this technique, the fracture is reduced by traction weight and xed internally with 2.7- or 3.5-mm reconstruction plates afxed to the lateral masses with screws (see Fig. 2921). Autogenous iliac cancellous bone graft is placed in the decorticated facet joint and along the lamina and spinous processes. Extension Injuries Anterior Longitudinal Ligament Avulsion and Extension Teardrop Injury. An extension teardrop fracture is a small, triangular bone fragment displaced from the anterior inferior corner of the vertebral body. In some cases, the fracture may be an osteophyte or it may be confused with incomplete ossication of an osteophyte. This injury is stable but must be differentiated from a exion teardrop fracture with associated comminution of the vertebral body, nor should it be confused with retropulsion of the spinal canal with interspinous disruption. Treatment of these injuries involves the use of a collar or cervicothoracic brace for 6 to 8 weeksthe same treatment outlined earlier for stable injuries.

SURGICAL TREATMENT Surgical management of patients with spinal cord injury is based on reports of experience and observation as opposed to rigorous clinical trials. Surgical stabilization of the spinal column is an essential technique because it can prevent further mechanical injury to the damaged cord tissue. Removing any residual compressive mass effect, as when reducing a vertebral dislocation or removing bone fragments pressing on the spinal cord, may also allow better neurologic recovery. Closed treatment of unreduced injuries may lead to chronic pain requiring surgical treatment.21 According to recent studies, time plays a potentially pivotal role in neurologic recovery. Early intervention in this setting is not dened in terms of days after injury, but rather in terms of minutes and hours. Animal studies have suggested that a potential window of opportunity occurs in the rst 3 to 6 hours after injury. It is during this time that signicant neurologic recovery may be possible48, 72 (see Table 294 and Figs. 296 and 298). Patients suffering multiple injuries with burns should be managed with early surgical treatment of fractures.76 Mortality rates in trauma patients are determined more by severe head injury than by injury to any other organ system.62 A prognosis based on the Injury Severity Score or Glasgow Coma Scale should not deter the surgical team from optimal management of orthopaedic injuries. Surgery for spinal injuries always involves fusion except in the two rare exceptions of odontoid fractures and C2 arch fractures. Under specic circumstances, these two injuries may be treated with internal xation osteosynthesis.26 Some researchers believe that open reduction and instrumentation may be just as effective as fusion for spinal fractures.165 Early surgery reduces time in the hospital.166 Spinal cord blood ow may be adversely affected by an anterior cervical approach.63 Anterior interbody grafts are prone to displacement in patients with posterior instability or gross deformity of the vertebral body unless supplemented by xation.234 Anterior plating and posterior plating are equally successful in treating cervical trauma.86, 96 Earlier studies reported high complication rates with anterior cervical surgery.217 However, anterior plating provides immediate stabilization, even with posterior ligamentous injury.52 The strength of the xated spine is relatively unchanged by corpectomy and anterior grafting. Anterior grafting has also been shown to improve alignment,138, 196 and xation maintains the alignment.150 Anterior fusion has likewise proved to be an excellent choice of procedure because it allows early mobilization, a shorter hospital stay, and less nancial burden.223 A general approach to the treatment of patients with stable fractures resulting from any mechanism is discussed separately in this section. These types of injuries are usually isolated to one side of the spinal column and are not associated with vertebral body translation or neurologic decit. To determine treatment options, these injuries are assessed with the White and Panjabi criteria. Stable injuries are those determined to have a value of 4 or less. Common types of these stable injuries are vertebral body compression fractures, avulsion of the anterior longitudi-

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Presentation

FIGURE 2922. This 29-year-old man sustained a minor exion injury of C7 without neurologic decit. The patient was treated in a cervicothoracic orthosis for 12 weeks and healed without subsequent instability on exion-extension radiographs.

nal ligament, extension teardrop fractures, mild posterior longitudinal ligament injuries, and isolated fractures of the posterior elements (Fig. 2922). When suffering a stable fracture injury, patients are treated in a hard collar or cervicothoracic brace for 6 to 8 weeks. After orthotic placement, an upright radiograph and exion-extension radiographs are obtained to check alignment. These radiographs are repeated biweekly until healing, which usually takes another 6 to 8 weeks to be completed. During the period of immobilization, patients should perform isometric neck exercises and low-impact aerobics. Physicians must be mindful that their assessment of stability may be incorrect. Only careful follow-up with frequent radiographs can determine whether adequate alignment of the spine is maintained. Increasing pain or new neurologic decits may indicate motion of the fracture site or loss of position. What was once determined to be a stable fracture could indeed be unstable. Nonunion may develop in displaced spinous process fractures, but it is rarely symptomatic. Simple wedge compression fractures may occur from axial loading with fracture of the superior end-plate and vertebral body wedging. Minimal kyphosis and no canal compromise are present. These injuries are stable and can be treated successfully with a cervicothoracic brace, as outlined previously.

Traumatic Disc Disruption and Cord Contusion Taylor and Blackwood rst reported traumatic disc disruption and cord contusion as a particular type of spinal cord injury, and they did so in the absence of radiographic changes.227 These authors correctly postulated that the spinal cord was pinched between the disc anteriorly and the infolded ligamentum avum posteriorly. Schneider and Knighton claried the neuroanatomic basis for the development of central cord syndrome, which so often results in these extension injuries.206 They believed that the condition had a good prognosis and thus surgery was rarely warranted. To solidify these particular ndings, Marar carefully reviewed 45 spinal cord injuries caused by extension mechanisms.139 He found that the neurologic injury was more variable than Schneider and Knighton initially reported and that it did not conform to the typical central cord syndrome. Only 10 of the patients had normal radiographs. Eleven patients had retrolisthesis and 24 had extension teardrop fractures. Of the four patients who died during treatment, all had transverse fractures through the vertebral body that were not apparent on plain radiographs. Clinical outcome in the Schneider and Knighton study was correlated with initial hand strength. Thirty-one of 32 patients could ambulate at long-term follow-up. However, only those with at least grade 3 hand strength at the time of admission had recovered signicant hand function. Merriam and associates also correlated outcome with initial hand strength, as well as outcome with the presence of perineal pinprick sensation.147 The standard initial treatment of extension spinal cord injuries is the application of tongs traction. Such management may reduce any malalignment and help lengthen the spinal column, thereby indirectly decompressing the spinal cord and stabilizing the spine to prevent further injury. Denitive treatment is determined by imaging studies and the progress of neurologic recovery. Patients who are improving neurologically are mobilized in a collar for 5 to 7 days, and upright radiographs are obtained to ensure alignment. Patients whose condition is not improving or who have reached a neurologic plateau are candidates for surgical decompression. The approach for surgical decompression is dependent on the site of cord compression and the extent to which the cord is compressed. Anterior decompression is indicated in patients with one to three levels of anterior or AP cord compression or if the spine is kyphotic. Posterior decompression is indicated in rare cases when compression is localized posteriorly or when more than three levels of AP compression are present. For maximal effectiveness, posterior decompression is best performed in spines with neutral or lordotic postures. After either anterior or posterior decompression, plate xation is added in patients with traumatic cord injuries. Vertebral Body Injuries Burst Fractures with Associated Neurologic Injury. Neurologic injury in burst fractures typically occurs from posterior displacement of fracture fragments of the vertebral body. Disruption of neural structures primarily takes place during the injury event. However, persistent cord compression from displaced bone fragments can cause

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further neurologic deterioration. The most immediate goal in patients with these injuries is to indirectly decompress the spinal cord by cranial traction. Because these injuries are compressive, ligaments at the fracture site are usually intact and traction can be applied safely. Closed reduction of burst fractures can require traction weights up to and over 100 lb. If closed reduction is successful and postreduction MRI conrms that the spinal cord is no longer compressed, surgical treatment can be performed on a somewhat elective schedule. Surgery usually consists of an anterior approach, corpectomy of the fractured vertebra, interbody fusion with a structural graft, and anterior plate xation with locking screws. Although severe burst fractures are associated with concurrent posterior facet joint injury, anterior xation with a rigid plate and external brace provides xation. In rare circumstances, such as patients with osteoporosis or an injury at the cervicothoracic junction involving the C7 vertebral body, posterior xation may be the preferred treatment or could be necessary to supplement anterior xation. Decompression of an injured spinal cord is the primary objective in treating patients with a burst fracture and an associated spinal cord injury. If closed reduction is unsuccessful in this setting, direct decompression should be performed urgently through an anterior cervical approach. Reconstruction with an anterior structural graft and plate is usually adequate if supplemented with external bracing in a Minerva brace. Occasionally, additional xation may be necessary through a posterior approach. Flexion Teardrop Injury. Unfortunately, exion teardrop fractures are associated with signicant spinal cord injury and generally occur in younger patients. Similar to burst fractures, the stability and long-term healing potential of exion teardrop injuries are dependent on the degree of disruption of the posterior osteoligamentous structures. The initial treatment of patients with this injury is skeletal tongs traction. Patients with deformities should be imaged acutely to ensure adequate indirect decompression. In patients with a mild degree of instability (noted by lack of separation of the spinous process and less than 3 mm of displacement of the vertebral body into the canal), halo vest treatment for 12 to 16 weeks can be used. At the end of immobilization, exion-extension radiographs are obtained to ensure stability. Patients with unstable exion teardrop fractures who have achieved reduction are best treated surgically with stabilization over two motion segments. Patients must have documented indirect decompression of the spinal canal before any attempt at posterior xation. In most cases, the best approach is an anterior one involving the use of an autogenous iliac crest graft and plate xation (Fig. 2923). Alternatively, lateral mass xation has been used successfully in a large series of patients.13 Patients with neurologic decits or those with residual cord compression are treated by anterior decompression and reconstruction with an iliac crest strut graft and plate xation. Although some authors have recommended combined anterior/posterior approaches, we have found that a cervical locking plate is usually successful.41 Facet Injuries Posterior cervical fusion is performed on all patients with bilateral facet dislocations. In the past, surgery was

generally delayed until 5 to 7 days after injury to avoid neurologic deterioration. Neurologic deterioration occasionally occurs in quadriplegic patients treated within 5 days of trauma,212 and the previous policy of delay in surgery was intended to circumvent such deterioration. However, earlier surgery may be benecial for reducing patient complications but not for enhancing neurologic recovery. Before attempting surgical treatment, the status of the intervertebral disc is determined by CT, myelography, or MRI. If the disc is retropulsed into the spinal canal, it should be removed before posterior cervical fusion. If the facet cannot be reduced preoperatively, reduction can be accomplished easily during surgery by applying traction to the spinous process or by levering the dislocated facet joint with an elevator. Rarely, a small portion of the facet must be removed to aid in reduction. Treatment of unilateral facet dislocations remains controversial. Closed treatment in a halo vest is frequently ineffective because reduction is not successful in 50% of cases or else the reduction is not maintained.169 Better results are achieved when anatomic alignment has been maintained. Therefore, posterior cervical fusion is recommended for patients with unilateral facet dislocations and those with facet fracture-dislocations.11 Lateral Mass Fracture-Separation. Levine identied a particular fracture type characterized by two vertical fracture lines in the pedicle and lamina that create a separation of the lateral mass.130 In this fracture, the lateral mass rotates to a horizontal position, which allows subluxation of both the cranial and caudal levels. This injury is highly unstable and is best treated surgically. Because of the high degree of instability, lateral mass xation of two motion segments is recommended (see Fig. 2917). Unilateral Facet Dislocation. Unilateral facet dislocations may still remain stable even if reduction can be achieved, and therefore nonoperative treatment with a halo vest is a viable option. Extension and slight contralateral rotation may decrease the likelihood of redisplacement. Patients with this type of injury should be evaluated frequently to ensure maintenance of reduction. After 12 weeks, the halo vest can be removed, and exion-extension radiographs should then be obtained. If instability is still present, late posterior fusion is indicated. Most patients with pure unilateral facet dislocations that require posterior fusion can be treated by the Rogers or Bohlman interspinous wire technique.30, 191 Spines that have sustained unilateral facet fracturedislocations have lost their mechanical resistance to rotation and anterior translation. Reductions are usually easily performed with pure axial traction, although redisplacement occurs frequently during nonoperative treatment. Therefore, operative treatment is recommended for these injuries, and most patients respond well to posterior fusion. To increase rigidity and to resist rotatory moments, the oblique wire technique or lateral mass plate xation can be used in association with the interspinous technique13, 79 (Fig. 2924). Patients with neurologic decits should undergo MRI before surgery. If a disc herniation is present, anterior cervical discectomy plus fusion is indicated. In a small percentage of patients, foraminal stenosis is present secondary to displaced bone fragments. In these cases, posterior foraminotomy

CHAPTER 29 Injuries of the Lower Cervical Spine

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FIGURE 2923. A, Anterior corpectomy is fre