In 2001, according to the University of Washington School of Public Health and Community Medicine, 122,316 lumbar fusions were performed. That number is 113 percent higher than in 1996. Lumbar fusions increased the most for patients older than 60. The reasons to perform fusion in the lumbar spine can be complex.
Degenerative Disc Disease
Aging of the spine probably accounts for the increase in lumbar fusion rates in patients older than 60. Degenerative changes in the discs occur as the spine ages. The discs of young people are well-hydrated, plump and full. Aging dehydrates the discs, and they become flat and lose their effectiveness as shock absorbers. Daily wear can cause a tear in the annulus, the ring around the soft part of the disc. Damage to the disc can cause pain, numbness and weakness. Occasionally, there is radiation of pain down one or the other leg. Some patients may experience foot drop. Treatment for this condition can range from conservative treatment to lumbar fusion, depending on the severity of the disease.
Spinal Stenosis
Spinal stenosis is the narrowing of the spinal cord canal due to arthritic changes in the lumbar spine. As the spine ages and discs dehydrate, the vertebrae may begin to rub against each other. This causes an inflammatory reaction, and the vertebrae in response develop excess bone. These are sometimes referred to as bony spurs, which can protrude into the spinal canal and press against the spinal cord. They can also press against spinal nerves that exit through small holes in the vertebrae, causing pain, numbness and weakness in the lower extremities. According to SpinalStenosis.org, surgery is the only proven treatment for spinal stenosis. One procedure used to correct spinal stenosis is lumbar fusion.
Spinal Instability
Spinal instability can be caused by a number of etiologies. Spinal instability is defined as the loss of normal biomechanical motion of the spine, which is replaced by abnormal motion that causes pain. The spine's anatomy and structures are designed to move in particular ways as the body moves through space. When the spine is affected by tumors, arthritis and injuries, the natural motion of the spine is changed. When this action is replaced by asynchronous motion of the vertebrae, pain develops. Abnormal motion can also cause impingement on the cord and spinal nerves. According to the Mayo Clinic, lumbar fusion is a treatment option for spinal instability.
