Clinically significant improvement in health-related quality of life (EQ-5D-5 L) after endoscopic spine surgery

Purpose: This study aims to define the minimal clinically important difference (MCID) and substantial clinical benefit (SCB) for EQ-5D-5 L and identify factors associated with clinical benefit achievement after Full Endoscopic Spine Surgery (FESS). Methods: This is a retrospective analysis of a multicentric prospective study that included adults who underwent FESS for lumbar degenerative spine disease. Patients were monitored postoperatively via a smartphone application, PROMs including EQ-5D-5 L and Oswestry Disability Index (ODI), were collected preoperatively and one-year postoperatively. MCID and SCB thresholds of absolute changes were established using anchor- and distribution-based methods, which yielded consistent results with minimal quantitative differences. ODI was used as an anchor and ROC analysis determined optimal cutoffs. Multivariable logistic regression identified predictors of achieving MCID and SCB. Results: A total of 131 patients were analyzed, with 125 (95.4%) included for anchor-based analysis. Significant improvements were observed in ODI and EQ-5D-5 L scores at 1 year postoperatively. The MCID for EQ-5D, based on an 11-point ODI improvement, was defined as a 0.22 net improvement (AUC 0.88). The SCB, based on a 19-point ODI improvement, was defined as a net improvement of 0.3 (AUC 0.86). Distribution-based methods yielded comparable thresholds, with MCID defined as 0.15 and SCB as 0.32. Age, BMI, and baseline disease severity were the most influential factors in achieving postoperative clinical benefit. Conclusion: This study defines clinically meaningful thresholds for EQ-5D-5 L improvement following FESS, providing benchmarks for both clinical outcomes evaluation and research applications. Age, BMI, and baseline disease severity were found to influence the likelihood of achieving clinical benefit, offering insights for patient selection. Level of evidence: II.