Removing the main body of the vertebral bone is called a corpectomy. Once this is done, the spine is fused with a bone graft at that level. Sometimes a metal plate is also inserted. The plate gives the spine extra support until the graft fills in. This keeps the spine from further collapse.

The main problem after corpectomy is degeneration of the spine at the segment above or below. This is called the adjacent segment. Studies show adjacent degeneration occurs in up to 75 percent of all patients. Some researchers have tried to prove the changes are just the result of a natural aging process.

The majority of studies report changes occur, but it hasn't been proven to be caused by the fusion itself. Most scientists think the corpectomy and fusion causes a shift of the load through the spine to the nearby vertebrae.

The authors of a recent study suggest the altered loads occur because of changes within the spinal ligaments. It's possible that increased motion at the segment above and below the fused spine causes the ligaments to increase in size or hypertrophy. The ligaments put increased pressure on the spine, not the lack of motion at the fused site.