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When the Spine Degenerates, Everything Changes

When a disc in your spine thins out, the joints are affected, too. The small joints on each side of the back of the spine are called facet joints.

Degenerative disc disease causes a loss of disc height. The facet joints actually change shape. Decreased disc height leads to increased rotation in the spine. The load gets transferred to the facet joints. Increased motion at the joint from loss of disc height affects the joint capsule, too. The fibrous capsule changes to try to protect the joint.

The authors of this study took a look at the chemistry behind these changes. They studied the entire facet joint in 14 patients. Each patient had a spinal fusion with removal of the joint. The authors noticed that changes in the facet joints are often greater on one side than the other. The cartilage lining the joint and the capsule around the joint are also changed. The cartilage is worn away or cracked and fissured.

They also noted certain types of changes in the capsule. The capsule was hypertrophied, or increased in size. In this way, the capsule limits the increased rotational forces that occur with loss of disc height. Bone spurs form around the joint. This changes the joint shape even more and limits joint motion.

The authors conclude that damage to the joint occurs only after the capsule changes. Early signs of capsule changes might alert doctors to upcoming joint changes. In the future, CT or MRI imaging may help point out these early changes in time to do something about them.

References: Bronek Boszczyk, MD, et al. Immunohistochemical Analysis of the Extracellular Matrix in the Posterior Capsule of the Zygapophysial Joints in Patients with Degenerative L4-5 Motion Segment Instability. In Journal of Neurosurgery: Spine. July 2003. Vol. 99. No. 1. Pp. 27-33.

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