Choices in back surgery are changing. Spinal fusion is the standard treatment for chronic low back pain caused by degenerating discs. But a new device, the total disc replacement (or artificial disc), is now on the market. This may change how the problem is treated.
Disc replacements come in two kinds. There’s a partial disc replacement, which replaces just the central portion of the disc. The center of a disc is called the nucleus pulposus. Moderate disc disease can be treated with a partial disc replacement, called prosthetic disc-nucleus (PDN).
For advanced disc disease, a total disc replacement may be needed. This involves removing and replacing the entire disc. The disc is made up of two parts: the nucleus pulposus on the inside and the outer covering called the annulus fibrosis.
Different types of disc implants are ready for use. Doctors working with one of these companies are testing a new way to put the device into the disc space. Until now the incision was made along the back of the spine. This approach can cause problems when bone and soft tissue is cut to gain access to the disc space. The doctor must also be careful to avoid damaging the nearby spinal nerves.
The new method gains access to the disc space through the patient’s side. Cutting through the psoas muscle along the front of the low back brings the doctor to the middle third of the disc. This approach is called the AnteroLateral transPsoatic Approach (ALPA). It can only be done at the L2-L4 spinal levels. Below that, the pelvic bone gets in the way. Later it may be possible to cut through the bone from the side and reach L5-S1 levels.
Eight patients formed the first study group for ALPA. Half the group suffered damage to the nerve sending messages to the psoas muscle. The symptoms were temporary and went away by the third month after the operation. There was a problem with the artificial disc moving forward in the disc space. The authors think this was caused by weakness in the annulus fibers. They don’t think it happened because of the ALPA method.
This first study shows promise using the ALPA technique for disc replacement. The authors propose using the method on a larger number of patients. Problems with nerve damage and implant migration will likely improve as the doctor gains experience with this new approach.