Understanding Degenerative Spondylolisthesis

Article written by Alok Sharan, MD

The spine is comprised of 30 bony segments or vertebrae. 24 of these vertebrae are mobile and connected to one another via joints. As part of the normal aging process, the joints in the spine undergo a degenerative process similar to the process that occurs in other joints in the body. This results in arthritis in these joints that can sometimes lead to pain, stiffness, and/or instability of the joint.

In each spinal vertebra there are 2 joints composed of inferior and superior articular processes. These are called facet joints and are the main articulations between adjacent vertebrae. The facet joints are held in place by fibrous tissue called capsules. As part of the normal degenerative process, the facet capsules become thin and weakened. This results in a stretching of the capsule and a sliding of one vertebra on another. This sliding of one vertebra on another is called spondylolisthesis. As a result of this sliding, there is instability in the joint and the body responds via a thickening (hypertrophy) of the facets. This hypertrophy can sometimes compress the structures adjacent to the bony facets, such as the nerves or spinal canal. This results in spinal stenosis (pressure on the nerves in the low back). Spinal stenosis is commonly seen with degenerative spondylolisthesis and is a cause for the many symptoms seen with this disease.

Many patients do not realize that they have degenerative spondylolisthesis until it is seen on an x-ray at a physician’s office. Sometimes this forward slippage can cause back pain but often it does not. Unfortunately some patients do have pain that can result in a significant deterioration in their quality of life.

Symptoms
Degenerative spondylolisthesis and spinal stenosis typically causes lower back pain, muscular spasms, and/or pain with radiation to the buttocks or legs. It may also cause lower extremity weakness or numbness although this is rare. A typical patient with degenerative spondylolisthesis will complain of pain that relates to the position of their back. Some will complain of pain that comes on with activity, with difficulty during walking.

Non-operative Therapy
Treatment for a degenerative spondylolisthesis is based on the characteristics of the patient’s symptoms. Acute symptoms may sometimes be relieved with 1-2 days of bedrest. In addition, medications such as anti-inflammatories or narcotics can be given to help alleviate some symptoms.

Braces have a minor role in treatment as they can help stabilize the spine. This could be worn for comfort as needed, for a short period of time. Physical therapy is often prescribed to increase back conditioning. Typically when a patient has degenerative spondylolisthesis the muscles in the back have become deconditioned. Muscle strengthening can help by reducing the frequency and intensity of the spasms that occur with degenerative spondylolisthesis. There is also a role for epidural steroid injections to help alleviate any inflammation that may exist.

Operative Therapy
Surgery for degenerative spondylolisthesis is considered absolute only when there is an acute neurologic deficit (significant leg weakness). Typically when there is forward slippage of one vertebra on another there is minimal affect on the nerves. Unfortunately as the slip progresses it can pull on the nerves exiting the spinal canal causing pain, numbness and/or weakness. At this time, consideration should be given to surgery. Otherwise surgery is indicated if the pain continues to progress after all methods of non-operative therapy have been exhausted.

Surgical treatment for degenerative spondylolisthesis requires fusing the slipped vertebrae to the adjacent vertebrae. This will prevent the instability that causes pain. There are many ways that a surgeon can perform a fusion. One method is to take bone from the pelvis (autograft) and place it between the slipped vertebrae. Over time this bone grows in between the two vertebrae and fuses the two bones together, preventing the painful motion. There are reports that have indicated that a fusion is more likely to be successful if instrumentation is added to the procedure. This typically involves placing screws into the pedicles of the spine. The screws are connected by metal rods that hold the adjacent vertebrae together. The screws provide additional support to the spine while the fusion occurs. If spinal stenosis co-exists with the degenerative spondylolisthesis then a decompressive procedure (lumbar laminectomy) may also be performed.

Conclusion
As the spine degenerates with age, arthritis and spondylolisthesis are fairly common problems. Fortunately this does not uniformly result in disabling pain. For those patients that do have pain, a proper course of non-operative treatment can be very successful. For those who have failed this, fusion can be very successful in the right patient.