Poster Presentation 50th International Society for the Study of the Lumbar Spine Annual Meeting 2024

Introduction. Less invasive decompression procedure for lumbar stenosis (LSS) expected good long-term outcome by the preservation of the lumbar posterior element, however, there have been no clear evidence of the advantage of less invasive procedures in the long-term results compared with conventional methods. Hence, the effectiveness of less-invasive decompression surgery should be investigated by focusing on specific pathologies rather than comprehensive LSS. We focused on diffuse idiopathic skeletal hyperostosis (DISH), especially DISH extended to the lumbar segment (L-DISH), because previous reports demonstrated that clinical outcomes after decompression procedures were worse for LSS with L-DISH than for LSS without L-DISH. No studies have compared the effect of less invasive surgery versus conventional decompression techniques for LSS with DISH. The purpose of this study was to compare the long-term risk of reoperation after decompression surgery focusing on LSS with L-DISH.

Methods. This study compared open procedure cohort (open conventional fenestration) and less invasive procedure cohort (bilateral decompression via a unilateral approach) with ≥5 years of follow-up. Reoperation due to other than postoperative hematoma, infection, and insufficient decompression was investigated in revision surgeries at the index level and surgeries at other lumbar levels. Patients’ demographics and radiological parameters including CT and MRI were investigated as potential confounders for reoperation. First, stratified analysis by L-DISH was performed to investigate differences in reoperation between the two cohorts. Subsequently, patients with L-DISH were propensity score-matched for age and sex. Survival curves and a Cox proportional hazards model were used to compare reoperation in the propensity score-matched cohorts.

Results. There were 57 patients with L-DISH among 489 patients in the open procedure cohort and 41 patients with L-DISH among 297 patients in the less-invasive procedure cohort. The reoperation rates in L-DISH were higher in the open than less-invasive procedure cohort for overall reoperations (25% and 7%, p=0.026) and reoperations at index levels (18% and 5%, p=0.059). After propensity score matching in L-DISH, no significant difference was observed in patients’ demographic or radiological parameters, other than the surgical period. Propensity score-matched analysis in L-DISH demonstrated that open procedures were significantly associated with increased overall reoperations (hazard ratio [HR], 6.18; 95% confidence interval [CI], 1.37–27.93) and reoperations at index levels (HR, 4.80; 95% CI, 1.04–22.23); there was no difference in reoperation at other lumbar levels (Figure).

Discussion. Less-invasive procedures had a lower risk of reoperation, especially at index levels for LSS with L-DISH. Preserving midline-lumbar posterior elements could be desirable as a decompression procedure for LSS with L-DISH.