Spine

Adjacent segment disease (ASD)

Also called: adjacent segment degeneration, ASD after lumbar fusion

Adjacent segment disease is symptomatic degeneration at the spinal level next to a fusion. It is distinguished from adjacent segment degeneration, which is seen on imaging without symptoms.

After a spinal fusion, the motion segments above and below the fused levels take on more stress. Over time they can degenerate. When the change is seen only on imaging it is called adjacent segment degeneration; when it causes symptoms such as pain, stenosis or instability, it is called adjacent segment disease (ASD).

Reported risk factors include older age, pre-existing degeneration at the adjacent level, the number of levels fused, sagittal malalignment such as a high PI-LL mismatch, and disruption of the adjacent facet or ligaments during surgery.

ASD can appear years after surgery and some patients are never followed long enough to show it, so it is studied with survival methods and reported as ASD-free survival over time.

Tools that use this

Adjacent Segment Disease Prediction StudioTime-to-event risk of adjacent segment disease after lumbar fusion at 1, 2, 3 and 5 years, from sagittal alignment, levels fused and surgical technique.

Related terms

Educational reference. Not medical advice and not for clinical decision-making.