Degenerative Changes and Spinal Disorders

The spine, like any other area of the skeleton, is susceptible to degenerative, age-related changes. The discs can gradually lose hydration as the protein molecules in the nucleus lose their capacity to bind water, causing the discs to become thinner, more fibrotic, and compressed with age. This in turn, can cause the annulus to bulge posteriorly into the canal. Aging discs can permit abnormal motion between the vertebrae. Bone spurs can develop from the vertebral bodies as a result of abnormal stresses and motion, narrowing the canal or neural foramen. (28-29)

Facet joints are diarthrodial joints, and are subject to age related changes, such as joint enlargement, spurs, and cysts. These changes can contribute to narrowing of the canal or the neural foramen. (29) The ligamentum flavum and the posterior longitudinal ligament can thicken and become redundant as discs decrease in height. The bulging of these ligaments can occupy space in the central canal. (28)

All these degenerative changes can contribute to stenosis (Figure 2), a narrowing of the space available for the spinal cord or nerve roots. Some individuals are predisposed to developing stenosis because of short pedicles that result in a congenitally small central spinal canal. Symptoms of lumbar stenosis are lower extremity pain, weakness/fatigue, and sensory changes. Symptoms of lumbar spinal stenosis are exacerbated by standing or walking. The pain of spinal stenosis is referred to as neurogenic claudication. (30-31)

Figure 2.
Axial MRI of a patient with Spinal Stenosis.

As the discs and facet joints become less competent, abnormal motion between the vertebrae can develop, leading to spondylolisthesis, a slipping of one vertebra on another. This can cause narrowing of the spinal canal and/or neural foramen (Figure 3).

Figure 3.
Myelogram of a patient with Spondylolisthesis.

Spondylolisthesis can be stable or unstable. A determination is usually made after analysis of lateral flexion/extension x-rays. If discs age and thin asymmetrically, a degenerative scoliosis may result, narrowing the neural foramen on the concave side, contributing to nerve root symptoms (Figure 4).

Figure 4.
AP radiography of a patient with Degenerative Scoliosis.