Risk Factors for Operative Adjacent Segment Disease Following Laminectomy Without Fusion for Lumbar Spinal Stenosis.

Abstract

Adjacent segment disease (ASD) generally refers to the development of symptomatic degenerative changes at a level neighboring a fusion. ASD is often attributed to alteration in the native biomechanics of the spine secondary to elimination of a motion segment and is widely cited as a risk of lumbar fusion operations. However, the development of ASD may also represent a product of the normal aging process. We sought to identify the incidence of ASD following decompressive nonfusion procedures in lumbar stenosis. We retrospectively identified all adult patients undergoing open laminectomy for lumbar stenosis over a 6-year period at an academic center. Patients undergoing fusion, diskectomy, >4 level procedures, or those with a fusion adjacent to the operative segment were excluded. The primary end point was the incidence of clinical and radiographic ASD requiring reoperation at a level immediately rostral or caudal to the operative segment. A secondary end point was identification of clinical and radiographic risk factors for the development of ASD, based on a multivariate Cox proportional hazards model. We identified 658 patients meeting all inclusion and exclusion criteria for analysis. Over a mean clinical follow-up period of 32 months, 62 (9.4%) patients underwent reoperation for ASD. The ASD reoperation occurred at a mean of 29.8 months after initial laminectomy. Factors associated with development of ASD on multivariate analysis were a history of cervical/thoracic spine surgery, lumbar spine surgery, or joint arthroplasty (shoulder, knee, and/or hip) prior to the index laminectomy. In this cohort analysis of patients undergoing laminectomy without fusion, we found an incidence of ASD of nearly 10%. This provides evidence that the normal degenerative process-together with impact from prior surgery-likely contributes to the development of ASD, although the specific amount by which fusion accelerates this process is yet to be quantified.