In this article, two well-known orthopedic surgeons from Rush University Medical Center in Chicago review three groups of nonfusion technologies. These include 1) total disc replacements (TDRs), 2) prosthetic nuclear implants (PNIs), and 3) posterior stabilization devices (PSDs).
When conservative care fails to reduce back pain and restore function, spinal fusion is often the final treatment plan. But long-term studies show that loss of motion at the fused level transfers the stress load to the vertebra above or below.
Degeneration of the next level has led to the development of these three alternatives to spinal fusion. The TDR reduces pressure on the nerves and restores the height of the disc. Near normal motion is also preserved. TDRs are available for the cervical spine (neck) and lumbar spine (low back).
New TDR designs have resulted in special coatings for the endplates to improve tissue compatibility and bone ingrowth. A special covering reduces friction and catches any metal ions or debris that occur.
Nuclear implants replace just the inner core of the disc. Scientists have found that degenerative changes in the disc begin inside the nucleus. If this part of the disc can be replaced early before there is a large tear or collapse of the disc space, then the patient may be spared a later disc herniation.
There are different types of nuclear implants. Some are inserted inside the disc. Others act as a filler and are injected into the space after the nuclear material has been removed. Once injected, the substance hardens into a strong but elastic mass.