First, we should understand that spinal fusion is a restrictive surgical procedure. They designed it to stop pain, but it also stops movement of the treated bones in the spine. With each fusion, the patient experiences incremental loss of flexibility and range of motion. Depending on a few variables, the loss of motion can be 7 - 10 degrees for each fusion.
Another problem for fusion is that when you fuse one level of the spine, you not only stop the flexibility of that level, you add new structural pressure on adjacent levels. Levels above and below the fusion will move more than is usual to compensate for the neighbor level that's been immobilized by the fusion. Structural stress transfers to the entire spine and increases wear and tear on adjacent discs, bones, and cartilage. That’s why one fusion often leads to additional ones. Some patients end up with two- or three-level fusions; sometimes more.
