What Is Adjacent Segment Disease?

Adjacent segment disease — sometimes called adjacent segment degeneration — refers to accelerated degeneration of the spinal levels immediately above or below a prior spinal fusion. It is one of the most discussed long-term complications of spinal fusion surgery and a significant reason why patients return to spine surgeons years after an initially successful procedure.

Why it happens

When a segment of the spine is fused, it eliminates motion at the treated level. The segments above and below the fusion must then compensate for that lost motion — absorbing additional stress with every movement. Over time this increased mechanical load accelerates the natural degenerative process at those adjacent levels, causing disc degeneration, facet arthritis, and potentially stenosis or instability that was not present before the fusion.

The risk of adjacent segment disease increases with the number of levels fused and the location of the fusion. Long fusion constructs — particularly those ending at L5 rather than the sacrum — are associated with higher rates of adjacent segment problems at the lumbosacral junction.

Symptoms

Adjacent segment disease typically presents as a return of back pain or leg symptoms years after a fusion that initially provided relief. The symptoms mirror the original problem — because the pathology is the same — but at a different level. Some patients describe it as the problem moving up or down from where they originally had it.

Treatment options

Treatment depends on the severity of the adjacent segment disease. Mild cases may respond to the same conservative measures used for primary disc degeneration — physical therapy, anti-inflammatory medication, and injections. When conservative care fails, extension of the fusion construct to include the affected adjacent level is typically the surgical solution.

Artificial disc replacement at the adjacent level — where anatomy and bone quality permit — is sometimes considered as a motion-preserving alternative to further fusion, though the biomechanical evidence for this approach continues to evolve.

If you have had prior spine surgery and are experiencing a return of symptoms, adjacent segment disease is one of the first things to evaluate. Dr. Enguidanos performs a thorough evaluation including current imaging to determine whether adjacent segment disease is the cause and what the appropriate treatment is.