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

Abstract

Purpose: Developmental spinal stenosis (DSS) is manifested as pre-existing narrowing of the bony spinal canal and may run risk of multi-level stenosis and need for reoperation after decompression surgery. 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 effects of DSS on reoperation rates at the adjacent level after decompression surgery for lumbar spinal stenosis. Materials and Methods: Consecutive patients with decompression-only surgery for lumbar spinal stenosis and minimum 5-year follow-up were recruited. Adult deformities, previous spinal surgery, and spondylolisthesis were excluded. Presented symptoms and levels operated on initially and at reoperation were studied. Magnetic resonance imaging measurements included the anteroposterior bony spinal canal diameter, degree of disc degeneration (disc intensity, herniations, 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 (CIs) 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±4.8 years since the index surgery. Gender and disc degeneration parameters were not factors contributing to reoperation. 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 to 14.01; p=0.035). Conclusion: 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 surgery.