Criteria for failure and worsening after surgery for lumbar spinal stenosis: a prospective national spine registry observational study.

Abstract Background context Criteria for success after surgical treatment of lumbar spinal stenosis (LSS) have been defined previously; however, there are no clear criteria for failure and worsening after surgery as assessed by patient-reported outcome measures (PROMs). Purpose We aimed to quantify changes in standard PROMs that most accurately identified failure and worsening after surgery for LSS. Study design /setting Retrospective analysis of prospective national spine registry data with 12-months follow-up. Patient sample We analyzed 10,822 patients aged 50 years and older operated in Norway during a decade, and 8,258 (76%) responded 12 months after surgery. Outcome measures (PROMs) We calculated final scores, absolute changes, and percentage changes for Oswestry Disability Index (ODI), Numeric Rating Scale (NRS) for back and leg pain (0-10), and EuroQol-5D (EQ-5D). These 12 PROM derivates were compared to the Global Perceived Effect (GPE), a 7-point Likert scale. Methods We used ODI, NRS back and leg pain, and EQ-5D 12 months after surgery to identify patients with failure (no effect) and worsening (clinical deterioration). The corresponding GPE at 12-months was graded as failure (GPE=4-7) and worsening (GPE=6-7) and used as an external criterion. To quantify the most accurate cut-off values corresponding to failure and worsening, we calculated areas under the curves (AUCs) of receiver operating characteristics (ROC) curves for the respective PROM derivates. Results Mean (95% CI) age was 68.3 (68.1 – 68.5) years, and 52% were females. There were 1,683 (20%) failures, and 476 (6%) patients were worse after surgery. The mean (95% CI) pre- and postoperative ODIs were 39.8 (39.5 – 40.2) and 23.7 (23.3 – 24.1), respectively. At 12 months, the mean difference (95% CI) in ODI was 16.1 (15.7 – 16.4), and the mean (95% CI) percentage improvement 38.8% (37.8 – 38.8). The PROM derivates identified failure and worsening accurately (AUC>0.80), except for the absolute change in EQ-5D. The ODI derivates were most accurate to identify both failure and worsening. We found that less than 20% improvement in ODI most accurately identified failure (AUC=0.89 [95% CI: 0.88 to 0.90]), and an ODI final score of 39 points or more most accurately identified worsening (AUC =0.91 [95% CI: 0.90 – 0.92]). Conclusions In this national register study, ODI derivates were most accurate to identify both failure and worsening after surgery for degenerative lumbar spinal stenosis. We recommend use of ODI percentage change and ODI final score for further studies of failure and worsening in elective spine surgery.