Lumbar Instability Adjacent to a Previous Fusion

Disc degeneration that occurs at the level adjacent to a previous fusion is known as adjacent segment degeneration (ASD). Altered biomechanical forces at the adjacent level motion segments may predispose to subsequent degeneration and pain, which may require further surgery consisting of decompression with or without an extension of the fusion. The rapid rise in the rates of lumbar spinal fusion over recent years suggests that ASD may become even more prevalent with time. Adjacent segment degeneration has served as the impetus for the development of motion-preserving alternatives for the treatment of degenerative disc disease, most notably total disc replacement (TDR). This article will highlight the diagnosis, etiology, risk factors, and treatment for lumbar instability adjacent to a previous fusion and discusses the potential role for total disc replacement in the prevention of ASD.