CERVICAL, THORACIC, AND LUMBAR FRACTURES

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CHAPTER 69 CERVICAL, THORACIC, AND LUMBAR FRACTURES

Robert L. Tatsumi, Robert A. Hart

Spinal column injuries in the United States occur at a rate of 4 to 5.3 injuries per 100,000 households. The most common causes of spinal column injuries include motor vehicle accidents (45%), falls (20%), sports-related accidents (15%), violence (15%), and miscellaneous causes (5%).

During the primary survey, as outlined by the American College of Surgeons guidelines, proper head mechanics should be employed for securing the airway. Manual in-line immobilization is preferred to avoid excessive head and neck movement. All patients with suspected spinal injuries should have proper immobilization of the neck and back to reduce the risk of spinal cord damage. Patients wearing a helmet at the time of injury should continue to wear the head apparatus during transport, but may have the face mask cut to provide ventilatory access.

Means of initial immobilization include a cervical collar, tape, or straps to secure the patient’s neck/back and transportation on a firm spine board with lateral support devices. It is estimated that 3%–25% of spinal cord injuries may result from improper immobilization of the spinal column during the transport period.

The resuscitation period is a crucial time after airway management and provisional spinal stabilization have been performed. Maintaining a mean blood pressure greater than 95 mm Hg is recommended to provide adequate perfusion to the spinal cord, and has been shown to provide better neurologic outcomes. The treating physician must monitor for neurogenic shock, which presents as hypotension accompanied by bradycardia due to decreased sympathetic outflow as a result of a cervical or high thoracic spinal cord injury. Treatment consists of both volume replacement and the use of vasopressors if hypotension persists.

NEUROLOGIC INJURY

The spinal cord fills 35% of the canal at the level of the atlas and about 50% in the cervical and thoracolumbar regions. The spinal cord consists of white matter in the periphery and gray matter centrally. The gray, myelinated matter can be divided into three columns. The posterior columns conduct ascending proprioception, vibratory, and tactile signals from the ipsilateral side of the body. The lateral columns conduct ascending pain and temperature signals from the contralateral side of the body via the lateral spinothalamic tracts as well as descending voluntary motor signals from the ipsilateral side of the body via the lateral corticospinal tracts. Finally, the anterior column conducts ascending light touch signals from the contralateral side of the body via anterior spinothalamic tracts and descending fine motor control via anterior corticospinal tracts.

The end of the spinal cord (conus medullaris) is located at L1-L2 intervertebral disk. Below the level of the conus medullaris, the spinal canal is occupied by the lower motor roots called the cauda equina. As a lower motor neuron lesion, injury to the nerve roots has a much better prognosis for recovery than injury to the spinal cord (Figure 1).

Figure 1 Spinal cord cross-section demonstrating the motor and sensory tracts.

Classification of Neurologic Injury

Determining the extent of a neurologic deficit in a patient with a spinal cord injury is paramount to understanding the overall prognosis. A complete injury is one in which “no motor or sensory function exists more than three segments below the level of the injury.” Incomplete injuries retain some neurologic function further than three segments below the level of the injury with the caudal segment exhibiting greater than 60% motor strength and intact sensation.

Patients with complete injuries have less than a 3% chance of motor recovery in the first 24 hours. Patients with sacral sparing have partial continuity of the white matter long tracts and demonstrate an incomplete cord injury. The presence of the bulbocavernosus reflex, a spinal reflex mediated by the S3-S4 region of the conus medullaris, may be absent in the first 4–6 hours after injury while the patient is in “spinal shock,” but usually returns within 24 hours. If the reflex does not return after 24 hours and distal neurological function remains absent, the injury is complete.

The secondary survey in patients with spinal cord injury includes a precise definition of neurologic deficits. Classification systems are useful to compare outcomes between different studies. While a variety of clinical grading systems exist, the American Spinal Injury Association (ASIA) scale has become the most widely accepted. The ASIA scale identifies motor, sensory, and general impairment deficits, and incorporates the functional independence measure (see page 163).

Incomplete Spinal Cord Syndromes

Four incomplete spinal cord syndromes are defined based on the location of the trauma to the spinal cord. Central cord syndrome is the most common pattern of injury, resulting from gray matter destruction, which is worst in the central region of the spinal cord. This injury pattern often occurs due to hyperextension injury in a patient with degenerative cervical spinal stenosis. The patient experiences motor and sensory deficits that are worse in the upper than in the lower extremities. The overall prognosis for central spinal cord injuries is good, with 75% of the patients experiencing at least partial motor recovery and most regaining the ability to ambulate.

Anterior cord syndrome is caused by vascular injury to the anterior portion of the spinal cord that causes motor/sensory deficits (lower greater than upper) with sparing of proprioception and position sense. This diagnosis carries the worst prognosis with only 10% of patients regaining substantial function.

Brown–Sequard syndrome is caused by isolated injury of one lateral half of the spinal cord and results in ipsilateral motor and contralateral sensory deficits. This syndrome has the best functional recovery.

Posterior cord syndrome is the rarest and causes decreased position and pressure sensation.

Spinal Cord Injury

Pharmacologic intervention for spinal cord injury continues to be a controversial topic. The recommended protocols based on the National Acute Spinal Cord Injury Study are a 30 mg/kg loading dose and 5.4 mg/kg/hr of methylprednisolone for 23 hours when delivered within 38 hours of injury, and a 47-hour infusion when started within 8 hours of injury. Despite the high acuity of these studies, the differences in the outcome are small, and bleeding and infectious complications were high in the steroid group compared to the control group. As a result, most spine societies do not regard these steroid protocols as an essential feature of initial spinal cord injury management.

CERVICAL SPINE TRAUMA

Evaluation

Cervical spine clearance for trauma patients continues to be a topic of debate. Class I evidence suggests that cervical spine radiographs are necessary for patients who present with neck pain or tenderness and have a decreased level of consciousness or are intoxicated, or who have distracting injuries. A cervical spine series consisting of anteroposterior (AP), lateral and open-mouth odontoid views has 85% sensitivity. The addition of flexion-extension views in the awake and alert patient to delineate spinal instability increases the negative predictive value to 99%.

It is important that radiographs include the C7-T1 interspace to identify any pathology around the cervicothoracic junction. The AP radiograph should be evaluated for symmetric disk height, lateral mass alignment, and spinous process orientation. The lateral radiograph should exhibit smooth anterior and posterior vertebral lines and spinolaminar lines as well as symmetric disk spaces and overlap of the lateral masses. Soft tissue planes should be evaluated and should be less than 6 mm at C2 and less than 2 cm at C6.

Computed tomography (CT) is useful to identify osseous pathology not seen on radiographs and is especially helpful at the craniocervical and cervicothoracic junctions. In some centers, CT scanning with sagittal and coronal plane reconstructions is replacing plain radiography as a screening study for high energy trauma admissions. Magnetic resonance imaging (MRI) may also be helpful in limited situations to diagnose soft tissue injury, such as the ligaments, disks, and facet capsules.

Anatomy

The cervical spine consists of seven vertebrae, and is subdivided into the atlas (C1), axis (C2), and subaxial spine (C3-C7). The atlas is ring-shaped, consisting of two articular lateral masses without a body or spinous process. The axis contains the odontoid process, which articulates with the anterior arch of the axis. The transverse ligament stabilizes this joint.

The subaxial spine consists of vertebral bodies with concave superior endplates. The facet joints are encapsulated synovial joints with overlying hyaline cartilage. The facet joint angle is 45 degrees in the sagittal plane.

Spinal stability primarily stems from ligament and disk integrity. Craniocervical stability involves intact anterior and posterior atlanto-occipital membranes and articular capsules. The atlantoaxial joint is stabilized by the transverse ligament primarily with the paired alar and apical ligaments provided secondary stabilization. The posterior ligamentum nuchae, interspinous ligaments, and ligamentum flavum acts as a “tension band” to provide resistance against flexion distraction injuries. The atlantoaxial joint provides 50% of the overall cervical rotation (Figure 2).

Figure 2 Sagittal cervical spine cross-section.

(Data from Heller J, Pedlow F: Anatomy of the cervical spine. In Clark CR, Dvorak J, Ducker TB, et al., editors: The Cervical Spine, 4th ed. Philadelphia, Lippincott-Raven, 2005, p. 9.)

The vertebral artery passes through the vertebral foramina from C6 to C1 and then turns posteromedially around the superior articular process before entering the foramen magnum and joining the basilar artery. The vertebral artery follows a similar course, but enters at the C7 transverse foramina. Unilateral absence or hypoplasia of the vertebral artery is 5%–10%.

The vertebral canal sagittal diameter narrows from 23 mm at C1 to 15 mm at C7. Nerve roots exit the canal through the intervertebral foramen. The posterolateral uncovertebral joint and intervertebral disk forms the anterior border of the foramen while the posterior border is formed by the caudal superior articular facet. The C2 nerve root exits posterior to the C1-C2 facet joint, whereas the remaining cervical nerve roots exit anterior to the facet joints. The spinal nerves pass posterior to the vertebral artery at the middle of the corresponding lateral mass. The cervical plexus consists of the ventral rami of C1 through C4, whereas the brachial plexus is made up from the ventral rami of C5 through T1.

Cervical Spinal Ligamentous Instability

White and Panjabi defined instability as “the loss of ability of the spine under physiologic loads to maintain its pattern of displacement so that there is no initial or additional neurologic deficit, no major deformity, and no incapacitating pain.” Acute radiographic instability criteria of the subaxial cervical spine include greater than 3.5 mm translation or greater than 11 degrees of angulation in the lateral plane. Because of the potential for late instability following the resolution of acute pain and muscle spasm, patients with significant axial neck ache but normal radiographs are indicated for follow-up flexion/extension films at around 2 weeks postinjury.

Occipital Condyle Fracture

Occipital condyle fracture should be considered a marker for potentially lethal trauma as patients experience an 11% mortality rate from associated injuries. Anderson and Montesano classified these fractures into the following types:

Type I: Impaction fractures due to an axial load (3%)

Type II: Extension of a basilar skull fracture into the condyle (22%)

Type III: Avulsion fractures (75%)

Types I and II fractures are caused by axial loading and have intact alar and tectoral membrane ligaments. Type III fractures are caused by skull distraction and have ligamentous disruption.

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