We include an extensive chapter on this subject in recognition of the fact that back pain is among the most frequent of medical complaints. Up to 80 percent of adults have low back pain at some time in their lives and, according to Kelsey and White, an even larger percentage will be found at autopsy to have degenerative disc disease. The diagnosis of pain in these parts of the body often requires the assistance of a neurologist. One task is to determine whether a disease of the spine has compressed the spinal cord or the spinal roots. To do this effectively, a clear understanding of the structures involved and some knowledge of orthopedics and rheumatology is necessary.
The parts of the back that possess the greatest freedom of movement, and hence are most frequently subject to injury, are the lumbar, lumbosacral, and cervical. In addition to bending, twisting, and other voluntary movements, many actions of the spine are reflexive in nature and are the basis of erect posture.
As pains in the lower part of the spine and legs are caused by different types of disease than those in the neck, shoulder, and arms, they are considered separately in this chapter.
ANATOMY AND PHYSIOLOGY OF THE SPINAL COLUMN
The bony spine is a complex structure, roughly divisible into an anterior and a posterior part. The anterior component consists of cylindric vertebral bodies, articulated by the intervertebral discs and held together by the anterior and posterior longitudinal ligaments. The posterior elements are more delicate and extend from the bodies as pedicles and laminae, which form the spinal canal by joining with the posterior aspects of the vertebral bodies and ligaments. Large transverse and spinous processes project laterally and posteriorly, respectively, and serve as the origins and insertions of the muscles that support and protect the spinal column. The bony processes are also held together by sturdy ligaments, the most important being the ligamentum flavum, which runs along the ventral surfaces of the posterior elements and is applied to the inner surface of the laminae. The posterior longitudinal ligament lies opposite it on the dorsal surfaces of the vertebral bodies. These two ligaments bound the posterior and anterior structures of the spinal canal, respectively.
The posterior parts of the vertebrae articulate with one another at the diarthrodial facet joints (also called apophyseal or zygapophyseal joints), each of which is composed of the inferior facet of the vertebra above and the superior facet of the one below. The facet and sacroiliac joints, which are covered by synovia, the compressible intervertebral discs, and the collagenous and elastic ligaments, permit a limited degree of flexion, extension, rotation, and lateral motion of the spine. Figure 10-1 illustrates these anatomic features in representative sections of the lumbar spine. The size and shape of thoracic and cervical vertebrae and their posterior elements differ but ...