Fusion of the neck (cervical spine) is widely used to treat disc disease. There's a problem with this treatment. Many patients get degenerative changes at the level just above or just below the fusion. It's not clear if these changes are caused by increased motion or by the natural process of the disease already present. When the fused level doesn't move, perhaps the load is passed up or down. The adjacent levels take on an added mechanical stress. Since disc disease is already present, researchers think both factors may add to the wear and tear on the nearby discs.
In this study 180 patients had neck fusion surgery. They were followed for more than five years. All patients were fused with a metal plate in front of the vertebral bone or bone graft to hold the spine in place until bone growth filled in. X- rays taken five years or more after the operation were compared to earlier X-rays taken right before or right after the surgery.
The researchers looked for disc height and any signs of degeneration. A loss of more than 50 percent of the disc height was scored as severe degeneration. A decrease of 50 to 75 percent was called moderate, and a loss of 25 percent of disc height was recorded as mild. Bone spurs were also graded as mild, moderate, or severe and used as a measure of surgery success.
The authors report that 92 percent of all patients had increased spine degeneration after fusion. The greater the time interval after the operation, the more damage was present. Age at the time of surgery didn't seem to make a difference. Whether or not a plate was used to fuse the spine didn't seem to make the changes worse. The researchers conclude that the need for reoperation will increase the more time goes by after fusion.