REOPERATION RATES FOR ADJACENT SEGMENT PATHOLOGY IN DEGENERATIVE LUMBAR FUSION SURGERY: A COMPARISON BETWEEN MINIMALLY INVASIVE AND OPEN SURGICAL APPROACHES

The primary objective of this study was to compare reoperation rates for adjacent segment pathology (ASP) between minimally invasive (MIS) versus open surgical approaches in degenerative lumbar fusion surgery. Secondary objectives were to compare MIS versus open post-operative changes in lumbosacral sagittal alignment parameters which may predispose to ASD and reoperation. Retrospective review of consecutive patients undergoing 1–3 level degenerative lumbar spinal fusions from 2007–2016. Patients were categorized into MIS versus open surgery groups. Both groups were compared for baseline demographic data, reoperation rates (for ASP versus other indication), time to reoperation, and pre- and post-operative radiographic sagittal alignment parameters including lumbar lordosis (L1-S1), distal lordosis (L4-S1), and adjacent disc lordosis. Binary logistic regression models were utilized for group comparison. 335 patients were included (mean follow-up: 64 months). 173 (52%) underwent MIS and 162 (48%) open approaches. The overall reoperation rate for all causes was 25.6% (n=86/335) with an incidence of 20.8% (n=36/173) in the MIS group and 30.8% (n=50/162) in the open group. The overall reoperation rate for ASP was 17% (n=57/335), with an incidence of 14% (n=24/173) for MIS and 20% (n=33/162) for the open group. Mean time to reoperation was 76 months (MIS) and 79 months (open). The lower reoperation for MIS was not statistically significant. At mean 64 months post-op, mean MIS vs open radiographic parameters were: L1-S1 (51o vs. 48o), L4-S1 (29o vs 27o), and adjacent disc lordosis (10o vs 10o), with no difference in the mean change from pre and post-op. Most reoperations following degenerative lumbar fusion surgery were due to adjacent segment pathology. Our study found no significant difference in reoperation rates for adjacent segment pathology when comparing MIS versus open approaches, Furthermore, there was no difference in post-operative lumbar sagittal alignment parameters between MIS and open approaches. Future studies will evaluate clinical outcome scores between the groups.