The influence of developmental spinal stenosis on reoperation risk at the adjacent segment after decompression surgery for lumbar spinal stenosis

Abstract

Introduction: Developmental spinal stenosis (DSS) is manifested as pre-existing narrowing of the bony spinal canal. With a narrowed spinal canal, neural tissues may be more prone to compression and development of symptoms. Multilevel involvement is commonly observed and there is a possible risk of reoperation due to the predilection for symptomatic stenosis. Reoperation at the adjacent level may be attributed to adjacent level degeneration but the influence of DSS on reoperation rate is unknown. The aim of study is to determine the risk of reoperation at the adjacent level after decompression surgery for lumbar spinal stenosis with particular emphasis on the influence of DSS. Methods: This was a retrospective study of consecutive patients with decompression-only surgery for lumbar spinal stenosis and minimum 5-years follow-up. Adult deformities, previous spinal surgery, and spondylolisthesis were excluded. Presenting symptoms, levels operated on initially and at reoperation were studied. MRI measurements included the anteroposterior bony spinal canal diameter, degree of disc degeneration (Pfirrmann grading, Schenidermann classification, anterior or posterior disc bulging and herniation, disc height) and ligamentum flavum thickness. DSS was defined by respective bony spinal canal diameter measurements. Risk factors for reoperation at the adjacent level were determined and included into a multivariate stepwise logistic regression for prediction modeling. Odds ratios (ORs) with 95% confidence intervals were calculated. Results: A total of 235 subjects were analyzed and 21.7% required reoperation at adjacent segments. The mean duration of follow-up was 10.1 (± SD of 4.8) years since the index surgery. No associations were found between reoperation and gender, nor with disc height and disc degeneration at adjacent segment. Reoperation at the adjacent segment was associated with DSS (p=0.026), the number of operated levels (p=0.008) and age at surgery (p=0.013). Multivariate regression model (p<0.001) controlled for other confounders showed that DSS was a significant predictor of reoperation at an adjacent segment, with an adjusted OR of 3.93 (95% CI: 1.10, 14.01, p=0.035). Discussion: This is a novel outlook on the effects of DSS on the risk of reoperation at the adjacent segment after lumbar spinal stenosis decompression surgery. Adjacent nonoperated DSS levels are 3.9 times more likely of undergoing future surgery. This is a poor prognostic marker that can be identified during the index decompression surgery. Nonoperated DSS levels are high risk for surgery after lumbar spinal stenosis decompression surgery. Adjacent levels should be screened for DSS prior to the index operation for risk assessment. There are significant implications on the approach to designing patient specific management strategies.