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Artificial Intervertebral Disc

By David Borenstein, MD

In late October, 2004, the FDA approved the first artificial disc replacement in the United States. The approval occurred after a study matching spinal fusion with a metal spacer versus the disc replacement demonstrated similar levels of improvement. The overall success rate at 2 years was 64% with the disc replacement and 55% with the spinal fusion. Improvement was measured by a decrease in pain and function, and no major complications including nervous system damage. Failure to achieve significant pain relief occurred in 26% of the disc replacement and 38% of the fusion group. Although the artificial disc may offer some benefits compared to spinal fusion, this new device is appropriate for only a very specific group of patients.

Individuals who are candidates for disc replacement have one level of damage to the spine. The damage to the spinal level has to be related to the intervertebral disc. Patients with symptoms associated with joint disease or compression of a spinal nerve associated with arm or leg pain are not candidates for disc replacement. The problem is knowing for sure that spinal pain is totally generated from the damaged disc.

There are alternative therapies for spinal pain, both medical and surgical. The use of exercise, heat or cold applications, drug therapy, physical therapy, and acupuncture may be very helpful in decreasing pain. Surgical therapy includes the use of disc spacers and fusion of the spine as an alternative to disc replacement.

On a technical basis, the placement of a disc replacement is more difficult that usual spinal surgery. Most low back spinal surgery is done from the back of the spine. A more dangerous approach is from the front of the spine. A disc replacement must be placed from the frontal approach.

Disc replacements have been available in other parts of the world for an n extended period of time. The numbers of individuals who have received disc replacement compared to those with more classic spinal procedures are relatively few. The number of American surgeons with experience with the new device is relatively few compared to the number who have completed fusion procedures.

In the final analysis, disc replacement is a new procedure. The durability of these devices remains to be determined. The decision for a disc replacement needs to be done in the setting of the knowledge of the condition and the likelihood of its response to disc surgery.