I saw the X-ray report on my back surgery. It says I have “adjacent segment disease.” What does that mean? I’m three years out from having a spinal fusion and starting to notice some low back and leg pain. That’s why they took a new X-ray.

One of the potential complications after spinal fusion is degeneration of the next level. The adjacent level can be above or below the vertebra. So, for example, if you had an L3-L4 fusion, the next level above is L2 and the adjacent level below is L5.

Once a vertebral segment has been successfully fused, movement is no longer possible at that level. This means the force that is transmitted to and through the spine at the fused level must be transferred to the next level where movement does occur.

Studies show that the level above is affected two to three times more often than the segment below. In a small number of people, areas above and below the fusion develop ASD. Over time, it appears that the added force can create a degenerative effect at the next level.

There is a wide range of change that can occur to suggest the start of a problem.
The presence of any of these changes is referred to as adjacent segment degeneration (ASD). For example, there may be a 10 per cent (or more) loss of disc height between two segments.

With a narrower disc space, increased pressure is applied to the nearby facet (spinal) joints. The added compression causes an overgrowth of tissue around the joint. This is labeled capsular hypertrophy. Then bone spurs can start to form. There may even be a vertebral compression fracture.

Any one of these changes is defined as ASD. By the time symptoms develop, several of these degenerative changes have occurred. Your new symptoms may be from ASD but not always. Your orthopedic surgeon will do a thorough exam and evaluate the X-rays along with your clinical presentation when making an accurate diagnosis.