All of the major joints in the body can be replaced with a plastic or metal joint called a prosthesis. Shoulder, elbow, hip, and knee replacements are common operations. Now, scientists are turning their attention to the back — in particular, to the discs between the bones of the spine.
The disc is a soft cushion between each vertebra that helps cushion and spread out the load. The center part of the disc, called the nucleus, also acts as a pump to bring in fluid for shock absorption. The discs often wear away or collapse as the body ages. The most common surgery for this problem is a discectomy. A discectomy involves removing the disc. Sometimes, the bones are also fused together.
A discectomy isn’t a perfect solution to the problem, because the spine still needs the disc. Without the disc to cushion the bones, wear and tear increases in the spine. Nearby discs take up the extra workload. This puts them at risk for damage.
Scientists are now testing a nucleus prosthesis. They are loking at different ways to remove only the center of the damaged disc and replace it with plastic or rubber material. The new nucleus has to be acceptable to the body. This is called biocompatibility. It also has to last a long time and not leak while giving the spine the support it needs.
There are several nucleus prosthesis designs being tested in the United States. None is on the market yet. Studies are done first on cadavers (human bodies used for study) and then on living humans. In this case, animals are not good models because there are too many differences in spine load and movement. Nucleus replacement may provide another solution for disc problems that require surgery.