The Effect of Age-adjusted Sagittal Alignment on the Result of Posterior Decompression Surgery for Lumbar Spinal Canal Stenosis

Abstract

Study Design. Retrospective case series. Objective. The aim of this study was to compare the outcomes of posterior decompression surgery for lumbar spinal canal stenosis (LSS) in patients with preoperative sagittal malalignment to those without, after adjusting for age and sex. Summary of Background Data. Sagittal balance is an important factor in spine surgery and is thought to affect postoperative outcomes following LSS. However, the relationship between sagittal malalignment and postoperative outcomes has not been thoroughly examined. Methods. We included 533 patients who underwent surgical treatment for LSS and also achieved two-year follow-up. Patients were categorized into either a malalignment (MA+) group (69 patients) or a matched-alignment (MA-) group (348 patients) based on age-adjusted preoperative sagittal alignment. We compared the baseline and two-year postoperative health-related quality of life (HRQOL) using the Visual Analog Scale and Japanese Orthopaedic Association Back Pain Evaluation Questionnaire (JOABPEQ) scores. We also calculated clinical efficacy using the minimal clinically important difference (MCID) based on JOABPEQ scores, and age- and sex-adjusted JOABPEQ scores two years after surgery. Differences between groups were examined using the Mann‒Whitney U test and χ2 analysis, where applicable. Results. Both groups showed an improved HRQOL after decompression surgery. Similar proportions of patients showed substantial improvement, as estimated by the MCID, in four out of five subdomains of the JOABPEQ. A significantly smaller proportion of patients in the MA+ group showed substantial improvement in lumbar function. The age- and sex-adjusted HRQOL scores two years after surgery were lower in the MA+ group, particularly in the lumbar function and social life function subdomains of the JOABPEQ. Conclusion. The effects of posterior decompression surgery alone can still be observed at least two years postoperatively for patients with LSS and concomitant sagittal malalignment. Patients with sagittal malalignment may experience lower HRQOL than those without this type of malalignment.