Trauma to the spinal column can injure the bony elements (vertebral fracture)
or the neural elements (spinal cord and nerve root injury), or both.
The incidence of vertebral bone fractures is unknown, but there
is better accounting of traumatic spinal cord injury because of
the creation of state and national registries.1 Data
from these organizations estimate the incidence of traumatic spinal
cord injury in the U.S. to be 40 cases per million, with a mean
age of 40 years old and a male-to-female predominance of 4 to 1.
Spinal injury occurs more frequently on weekends and holidays and
during summer months. The etiology of traumatic spinal cord injury
is estimated to be 42% due to motor vehicle collisions,
27% due to falls, 15% due to acts of violence
(primarily gunshot wounds), 8% from sports, and 8% from
The vertebral column is the central supporting structure for
the head and trunk, and provides bony protection for the spinal
cord. This column consists of 33 vertebrae: 7 cervical, 12 thoracic,
5 lumbar, 5 sacral (fused to form the sacrum), and 4 coccygeal,
which are usually fused.
Vertebrae (C1 and C2)
The axial cervical vertebrae are anatomically and functionally
unique. Along with the occiput, these two vertebrae form complex
articulations designed for rotary motion. The atlas (C1) consists
of a ring formed by anterior and posterior arches and two lateral
masses that articulate with the occipital condyles and the vertebral
column. The axis (C2) consists of an anterior body—with
a superior projection called the dens that articulates
with the inner surface of C1—and a posterior vertebral
arch that encircles the spinal cord. The dens is stabilized against
the inner surface of the C1 ring by the transverse ligament.
In general, the vertebrae below C2 are fundamentally the same.
In accordance with their weightbearing function, the vertebrae become
larger toward the lower end of the vertebral column. A typical vertebra
is composed of an anterior body and a posterior vertebral
arch (Figure 255-1). 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 articular
processes form synovial joints that act as pivots of the spinal
column. The orientation of these articular facet joints changes
at different levels of the spine. Differences in orientation of
the facet joints account for variations in motion of specific regions
of the vertebral column.
Vertebral anatomy. Each vertebra consists of a vertebral
body and posterior element. Vertebrae are stabilized by an anterior longitudinal
ligament, posterior ligament, and interspinous ligament.
A series of ligaments serve to maintain alignment of the spinal