Dance Anatomy & Kinesiology

The Spine 75

ferent regions from about 0.1 inch (3 millimeters) in
the cervical region to about 0.3 inches (9 millimeters)
in the lumbar region (Levangie and Norkin, 2001). In
the cervical and lumbar regions the discs are thicker
anteriorly and help form the anteriorly convex curva-
tures found in these regions. In the thoracic region the
discs are more even in thickness, and the posteriorly
convex curvature in this region is more due to the
wedge shape of the vertebral bodies.
The bodies of the vertebrae and intervertebral
discs are further connected by ligaments—the ante-
rior longitudinal ligament and the posterior longi-
tudinal ligament as seen in figure 3.4. The anterior
longitudinal ligament is a strong, broad fibrous band
that extends from the inner (pelvic) surface of the
sacrum up to the skull. This ligament covers and
connects the anterior aspects of the vertebral bodies
and the intervertebral discs. It functions to help
limit the extent of spinal hyperextension, maintain
stability, and prevent forward bulging of the annulus
of the intervertebral disc as seen in figure 3.5A. The
posterior longitudinal ligament is a narrower fibrous
band, having about half the strength of the anterior
longitudinal ligament (Levangie and Norkin, 2001).
This ligament runs along the posterior aspect of
the vertebral bodies, within the vertebral canal. It
is attached to the intervertebral discs and the pos-
terior edges of the vertebral bodies from C2 to the
sacrum. The posterior longitudinal ligament helps
limit extreme spinal flexion and posterior protru-
sion of the intervertebral discs as seen in figure 3.5B.
However, the posterolateral corner of the annulus

is poorly covered and represents a weak area where

disc protrusion frequently occurs.

Joints Between the Vertebral Arches

The superior articular process of one vertebra

articulates with the inferior articular process of the

vertebra above to form the facet joints, more tech-

nically termed zygoapophyseal or apophyseal joints

(figures 3.2 and 3.5A). These facet joints are synovial

joints of the gliding variety. Hence, they allow small

gliding movements in various directions. The shape

and facing of the given articular processes are key in

determining the extent and direction of movement

FIGURE 3.4 Primary ligaments of the spine (intertrans-
verse ligament not visible in this section).

FIGURE 3.5 Influence of (A) hyperextension and (B)

flexion on key spinal structures.

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