Patients with damaged discs have traditionally been treated by removing a disc or placing a bone graft in the spine to fuse two bones together. Now, an artificial disc which is being studied as a replacement is in the second phase of trials. The phase one study that was recently completed compared the prosthesis to traditional fusion. While in the first phase of trials patients were randomized, with one having a fusion operation for every two that received the artificial disc, in the second phase all patients who qualify to participate in the study will receive the artificial disc.
A healthy disc is a complex structure between the bones of the spine. The nucleus, sandwiched in the center of the disc, contains fluid that serves as a cushion. Layered collagen fibers of the adjacent annulus provide strength. When the components work together, they give the back both stability and flexibility. But when a disc is damaged, the cushion can deflate, bulge or leak, and the collagen loses its elasticity. Pain is often intense, especially when nerves get caught between degenerating components. While fusion may relieve the pain, it prevents natural, independent motion.
The artificial disc being studied would be inserted by surgeons through the the abdomen, just below the navel, sparing the large muscles of the back. Compared to traditional fusion surgery, inserting the disc takes lesser time at the operating table (about one and half years) and the patients are mobile right away contrary to those undergoing fusion surgery, who have their motion restricted for up to a year. The other major benefit that the artificial disc appears to offer is that motion remains at the disc, which does not put additional stress on adjacent discs.
In fusion surgery, in the long term, people often come back with problems at the next disc, and they may need another operation. The artificial disc may prove to be a viable alternative, especially for younger, active patients. The Food & Drug Administration is yet to approve the device for general use throughout the United States as it waiting for the results of the second phase of the trials. The drug has already been approved in Europe.