Doctors sometimes suggest surgery to take out a herniated disc in the cervical spine (the neck). Most times, a graft of bone is placed between the two vertebrae where the disc was removed. The graft connects–or fuses–both vertebrae into one solid bone, a procedure called arthrodesis. This often takes away pain and other symptoms caused by the injured disc. However, the fused part of the neck can no longer move. In addition, doctors fear that the vertebral joints above and below the fused section tend to degenerate quicker.
These complications have launched the medical quest for an artificial disc. An artificial disc (also called a disc prosthesis) could be used in place of a herniated disc that has been removed, and there would no longer be any need to fuse the neck bones together. The idea is that the artificial disc would take the place of the disc without a loss of joint movement.
This author reported on his use of a new type of artificial disc in 10 patients. All patients had been having pain and other symptoms for at least three months before surgery. They each had a herniated cervical disc taken out and replaced with an artificial disc.
Of the 10 patients, two developed intense neck pain after the surgery. Follow-up X-rays were done with the neck bent down. The images of both these patients showed movement around the artificial disc. In one patient, the implant actually caused the neck joint to tilt too far forward–the joint worked like a see-saw.
The other eight patients had no pain after the initial operation. However, their X-ray tests showed that they had lost mobility in the area of the artificial disc. The bones ended up fusing together around the prosthesis.
The author rates this particular artificial disc a “total failure.” If the neck could move afterward, pain was not relieved; if the pain went away, so did neck mobility. The prosthesis simply didn’t do what it was designed to do–take away symptoms while keeping the vertebrae mobile.
Despite these disappointing results, the author “remains convinced of the need for a cervical disc prosthesis that is easy to implant.” He suggests ways to design an artificial disc that will be more successful. So the quest for an effective artificial disc goes on.