Degenerative changes in the spine may be assigned any of a number of diagnostic labels. These would include degenerative spinal arthritis, osteoarthritis of the spine, discogenic spondylosis and spondyloarthrosis. These changes, often attributed to aging and "wear and tear," affect the spine in multiple ways and can vary considerably in their severity.
Disc Changes
The earliest detectable degenerative changes in the spine tend to occur in the discs. In their classic text, "Clinical Biomechanics of the Spine," White and Panjabi describe how the water content of the disc diminishes, and the ability of its component structures to be nourished may be altered. There may be an element of fatigue failure of the outer disc fibers that occurs as well. The earliest changes may be detected on MRI imaging. Later, as the disc dries and shrinks, narrowing of the space between the vertebrae may be seen on X-ray.
Facet Joint Changes
In addition to the discs that separate the vertebrae, there is a pair of joints between the segments located on the backsides of the vertebrae. These joints, called facet joints, are classified as synovial joints. That means that the bone ends are covered in a smooth cartilage; the joints are surrounded by an elastic "capsular" ligament, and there is a slippery fluid inside the joint providing lubrication. Dr. J. A. Buckwalter and his colleagues at the University of Iowa, Department of Orthopaedic Surgery describe a process where the structural integrity of the cartilage is somehow compromised along with the ability of the cartilage to process nutrients and waste products. The result is a breakdown of the protective cartilage and increased stress on the underlying bone.
Bone Spurs
When the discs and joint cartilage become compromised, there is a loss of the shock absorbing capacity between the vertebrae. In response to the added loading, the underlying bone tends to thicken and harden. Often the margins of the vertebral joints will develop bone spurs. These spurs, which are easily identified on X-rays, tend to contribute to further stiffening of the spine over time. For some, the gradual reduction in mobility of the spine may be the only noticeable symptom.
Nerve Issues
An unfortunate potential consequence of severe spinal degeneration occurs when the combined effects of cartilage loss, disc thinning and bone spur formation result in crowding of the delicate spinal nerves. The spine, which normally protects these nerves, can end up compressing them. This may result in radiating pain, numbness, weakness or other neurological deficits. In cases of severe nerve compression, spine surgery may become necessary.
References
- "Clinical Biomechanics of the Spine"; A.A. White III and M.M. Panjabi; 1978
- "Instructional Course Lectures"; Synovial Joint Degeneration and the Syndrome of Osteoarthritis; J.A. Buckwalter, J. Martin and H.J. Mankin; 2000
