The Spine

Overview. The vertebral column, or spine, is the central supporting structure of the trunk and back. Note the concave curves of the cervical and lumbar spine and the convex curves of the thoracic and sacrococcygeal spine. These curves help distribute upper body weight to the pelvis and lower extremities and cushion the concussive impact of walking or running.

The complex mechanics of the back reflect the coordinated action of:

■ The vertebrae and intervertebral discs

■ An interconnecting system of ligaments between anterior vertebrae and posterior vertebrae, ligaments between the spinous processes, and ligaments between the lamina of two adjacent vertebrae

■ Large superficial muscles, deeper intrinsic muscles, and muscles of the abdominal wall.

Viewing the patient from behind, identify the following landmarks:

1. Spinous processes, usually more prominent at C7 and T1 and more evident on forward flexion

2. Paravertebral muscles on either side of the midline

3. Scapulae

4. Iliac crests

5. Posterior superior iliac spines, usually marked by skin dimples.

A line drawn above the posterior iliac crests crosses the spinous process of L4.

Bony Structures. The vertebral column contains 24 vertebrae stacked on the sacrum and coccyx. A typical vertebra contains sites for joint articulations, weight bearing, and muscle attachments, as well as foramina for the spinal nerve roots and peripheral nerves. Anteriorly, the vertebral body supports weight bearing. The posterior vertebral arch encloses the spinal cord. Review the location of the vertebral processes and foramina, with particular attention to:

■ The spinous process projecting posteriorly in the midline and the two transverse processes at the junction of the pedicle and the lamina. Muscles attach at these processes.

■ The articular processes—two on each side of the vertebra, one facing up and one facing down, at the junction of the pedicles and laminae, often called articular facets

■ The vertebral foramen, which encloses the spinal cord, the intervertebral foramen, formed by the inferior and superior articulating process of adjacent vertebrae, creating a channel for the spinal nerve roots; and in the cervical vertebrae, the transverse foramen for the vertebral artery.

The proximity of the spinal cord and spinal nerve roots to their bony vertebral casing and the intervertebral discs makes them especially vulnerable to disc herni-ation, impingement from degenerative changes in the vertebrae, and trauma.

Joints. The spine has slightly movable cartilaginous joints between the vertebral bodies and between the articular facets. Between the vertebral bodies are the intervertebral discs, each consisting

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