91. Reoperation rates following minimally invasive lumbar fusion compared to open fusion: a survivorship analysis with a minimum of five-year follow up

Abstract

<h3>BACKGROUND CONTEXT</h3> Both traditional open and less-invasive techniques such as minimally invasive (MIS) lumbar fusion have been shown to be effective for degenerative lumbar pathology. One of the critical measures of success following surgery is the reoperation rate, as well as the duration of reoperation from the index procedure. It is known that fusion of one or more segments alters the biomechanics of the adjacent level(s) and may cause accelerated degeneration of the adjacent segment(s). The clinical significance of muscle and musculotendinous preservation offered by MIS fusion and whether it offsets some of the altered biomechanics of fusion, and thus the reoperation rates for adjacent segment degeneration, are unclear. Current studies suggest that MIS fusion may demonstrate a lower long-term reoperation rate. However, evidence in this regard is very limited and conflicting. <h3>PURPOSE</h3> The primary objective of this study is to assess the long-term reoperation rate of 1- to 2-level MIS vs open lumbar instrumented fusion with a minimum of 5-year follow-up. <h3>STUDY DESIGN/SETTING</h3> Obervational study. <h3>PATIENT SAMPLE</h3> Adults with degenerative lumbar disease who underwent 1- to 2-level open and MIS fusion at our institution from January 2006 to December 2016. <h3>OUTCOME MEASURES</h3> Rate of reoperation for MIS vs open lumbar fusion. <h3>METHODS</h3> Retrospective study of all consecutive cases of operatively managed patients with lumbar degenerative disease who underwent 1- to 2-level lumbar fusion between January 2006 to December 2016 performed by two experienced surgeons from a single academic center. One surgeon exclusively uses an MIS tubular retractor fusion technique for all scheduled 1- to 2-level fusions, and the other surgeon only utilizes a midline open posterior approach. The patients were divided into an MIS fusion group and an open surgery group based on the surgical technique performed. The two groups were compared for baseline demographic features, surgical variables and diagnosis at index surgery. Reoperation rates defined as any operation on the same or adjacent levels were assessed. Levels of reoperation were assessed as (1) cranial, (2) caudal, (3) same level of index surgery and (4) both levels. Descriptive and comparative statistics were utilized for between-group comparison and Kaplan-Meier survivorship plots were generated. <h3>RESULTS</h3> A total of 370 patients were included, with range of follow-up (5-14 years). Fusion involved 1 level in 67.5 % of cases and 2 levels in 32.4 %. There was no significant difference between the two groups in age, sex (p = 0.34) or number of levels of fusion (p= 0.214). The overall rate of reoperation was 25.9 %, with incidence of 21.8 % in the MIS fusion group (n=42/192) and 30.3 % (n=54/178) in the open fusion group (p = 0.149). The mean time to reoperation was 4.45 years in the MIS group while in the open group it is 4.24 years. Adjacent segment degenerative pathology was the main reason for reoperation in both groups (69% [n=29/42] for MIS fusion and 76% [n=41/55] for open fusion [p=0.161]). Additionally, for MIS vs open fusions, instrumentation-related reoperations were 19% vs 3.7% (p=0.344); 9.5% vs 14.5% (p=0.376) for pseudoarthrosis; 2.4% vs 3.6% (p=0.468) for infection and 1 revision case for LIV fracture in open group. <h3>CONCLUSIONS</h3> While there seems to be a trend for a higher adjacent segment degeneration reoperation rate in open vs MIS fusion, this effect is offset by a higher rate of instrumentation-related re-operation in the MIS group. The overall reoperation rate did not statistically differ between MIS and open 1- to 2-level lumbar fusion at minimum of 5-year follow-up. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.