Degenerative Disc Disease
When is surgery needed?

More than 65 million Americans suffer from low back pain annually. By age 50, 85% of the population will show evidence of disc degeneration. Luckily, most will have no symptoms.

Degeneration of the intervertebral disc, which is often called degenerative disc disease (DDD) or osteoarthritis of the spine, is a common disorder of the lower spine. Disc degeneration can lead to disorders such as lumbar spinal stenosis (narrowing of the spinal canal that houses the spinal cord and nerve roots), spondylolisthesis (forward slippage of the disc and vertebra), and retrolisthesis (backward slippage of the disc and vertebra) (Fig. 1). Actually, DDD is not a disease but, rather, a degenerative condition that can be painful and can greatly affect your quality of life. Disc degeneration is a normal part of aging and is generally not a problem by itself. However, when bone spurs grow adjacent to the discs, they can pinch or put pressure on the nearby nerve roots or spinal canal, and pain can occur.

Causes
Aging is the most common cause of disc degeneration. As the body ages, the discs in the spine dehydrate, or dry out, and lose their ability to act as shock absorbers between the vertebra. The bones and ligaments that make up the spine also become less flexible and thicken. Unlike muscles, there is minimal blood supply to the discs so they lack the ability to heal or repair themselves.

Symptoms
Often, patients suffering from DDD do not show symptoms. When symptoms are present, however, chronic low back pain sometimes radiates to the hips, or there is an aching pain in the buttocks or thighs while walking. Similar pain may be felt or may increase while sitting, bending, lifting, and twisting.

Understanding Disc Pain
It is not clear why some degenerative discs are painful and some are not. After an injury, some discs become painful because of inflammation. Some people have nerve endings that penetrate more deeply into the annulus fibrosus, or outer layer of the disc, than others, making the disc more susceptible to becoming a source of pain. Pain that radiates down the leg, known as sciatica or lumbago, is the result of the nerve root encountering the inner disc material, or the nucleus pulposus, an inflammatory substance that also puts pressure on the nerve (Fig. 2A). These conditions can cause symptoms such as severe leg pain, difficulty standing and walking, and weakness or numbness in the legs. DDD can lead to a chronic debilitating condition and can have a serious negative impact on a person's quality of life. When DDD is severe, traditional nonoperative treatment is often ineffective.

Treatment Options
Often, DDD can be successfully treated without surgery. Physical therapy, anti-inflammatory medications, and spinal injections often provide adequate relief of these troubling symptoms. Surgery may be recommended if the conservative treatment options do not provide relief within 2 to 3 months. If leg or back pain limits your normal activity, if you have weakness or numbness in your legs, if it is difficult to walk or stand, or if medication or physical therapy are ineffective, surgery may be necessary.

Currently, surgeons at The Hughston Clinic are involved in ongoing research on the use of bone morphogenetic protein (BMP) for the treatment of degenerative disc disease. The use of BMP eliminates the need for taking bone from the hip to use in the spine during surgery (Fig. 2B). This new procedure leads to a quicker recovery and better results. Several articles based on this research have recently been published in medical journals. Dr. John D. Dorchak and I are actively working on disc replacement therapies for both the cervical and the lumbar spine.

J. Kenneth Burkus, MD
Columbus, Georgia

Further Reading:
Burkus JK, et al. Anterior lumbar interbody fusion using rhBMP-2 with tapered interbody cages. J Spinal Disord Tech. 2002;15:337-349.
Burkus JK, et al. Clinical and radiographic outcomes of anterior lumbar interbody fusion using recombinant human bone morphogenetic protein-2. Spine. 2002;27:2396-2408.