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INTRODUCTION AND EPIDEMIOLOGY
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Trauma to the spine can cause a vertebral spinal column injury, a spinal cord injury, or both. A few studies have tried to estimate the annual incidence of spinal column injury in the general population with results ranging from 11.8 to 64 cases per 100,000,1,2 but no current figures are available for the U.S. population. In contrast, the estimated annual incidence of spinal cord injury in the United States is 40 cases per million or 12,000 new cases per year, with 81% male victims, a mean age of 42.6 years, and a 67% Caucasian predominance.3 Since 2010, the leading causes of spinal cord injury are vehicular (37%), falls (29%), and violence (14%). Lifetime costs for spinal cord injury victims vary according to age at time of injury, severity of injury, and socioeconomic status; however, estimates range in millions of dollars per patient.3
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The vertebral column is composed of 33 vertebrae: 7 cervical, 12 thoracic, 5 lumbar, 5 fused sacral, and 4 (usually fused) coccygeal. The axial vertebrae (C1 and C2) are anatomically unique in that they are designed for rotary motion. The odontoid (dens) of the axis (C2) is held against the atlas (C1) by the strong transverse ligament. The remaining vertebrae share some common anatomical features (Figure 258-1). A typical subaxial vertebra is composed of an anterior body and a posterior vertebral arch. The vertebral arch is comprised of two pedicles, two laminae, and seven processes (one spinous, two transverse, and four articular). These articulations enable the spine to engage in flexion, extension, lateral flexion, rotation, or circumduction (combination of all movements). The orientation of these articular facet joints changes at different levels of the spine and accounts for variations in motion of specific regions of the vertebral column. Due to its inherent flexibility, the cervical spine is the most commonly injured region of the spinal column, with most injuries occurring at the C2 level and from C5 to C7.4 The second most common region of injury is in the thoracolumbar transition zone.
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A series of ligaments serves to maintain alignment of the spinal column. The anterior and posterior longitudinal ligaments run along the vertebral bodies. Surrounding the vertebral arch are the ligamentum flavum and the supraspinous, interspinous, intertransverse, and capsular ligaments. Between adjacent vertebral bodies are the intervertebral disks, consisting of a peripheral annulus fibrosus and a central nucleus pulposus. The intervertebral disks act as shock absorbers to distribute axial load. When compressive forces exceed the absorptive capacity of the disk, the annulus fibrosus ruptures. This allows the nucleus ...