Redefining Oswestry Disability Index success criteria to assess the effect of consecutive surgeries on lumbar spinal stenosis.

ABSTRACT

BACKGROUND: Register studies have shown that chances of success after surgery for lumbar spinal stenosis (LSS) decrease with increasing numbers of previous operations. However, these studies presumed that success criteria remain constant with each consecutive spinal surgery. PURPOSE: We aimed to redefine success criteria specific for each consecutive surgery. Also, we assessed if fusion could be an effective procedure for LSS patients with previous decompression(s). STUDY DESIGN: We retrospectively analyzed prospectively collected patient-reported outcome measures (PROMs) from surgically treated LSS patients enrolled in The NORspine Register. PATIENT SAMPLE Patients operated for lumbar spinal stenosis. OUTCOME MEASURES: PROMs Oswestry Disability Index (ODI) percentage (%) change and Global Perceived Effect (GPE). METHODS: We categorized the LSS cohort by number of previous spine surgeries (none to ≥3). ROC analyses gave the most accurate cut-offs for ODI% change that corresponded to success, anchored by GPE, i.e., "much improved" and "completely recovered". Areas under the ROC curves (AUCs) indicated how well ODI discriminated between success and nonsuccess for each consecutive surgery good (0.8-0.89) and excellent (0.9-0.99). We then calculated proportions of successfully treated patients by number of consecutive surgeries. We also analyzed whether fusion succeeded in patients with previous lumbar decompression(s). RESULTS: At 12 months, 8,919 (75%) responded; 6,961 (78%) had no previous LSS surgery, 1,338 (15%) had one, 417 (5%) had 2, and 203 (2%) had ≥3 previous surgeries. Preoperative ODI (95% CI) was 38.7 (38.2-39.1) for no previous surgery versus 49.4 (46.9-51.9) for patients with ≥3 previous surgeries. The postoperative ODIs (95% CI) were 21.9 (21.4-22.4) and 37.9 (34.9-40.8) for patients with no and ≥3 previous surgeries, respectively. For patients with no previous surgeries, ODI% change of 37.6% most accurately defined success (AUC [95% CI]=0.909 [0.903-0.916]), and 57.1% reported success. For patients with ≥3 previous surgeries, success was an ODI% change of 25.0% (AUC [95%CI]=0.930 [0.890-0.971]), and 46.3% reported success. Finally, 350 patients received fusion after previous decompression(s). ODI% change of 34.6% defined success (AUC [95% CI]=0.920 [0.890-0.949]). The proportion of successfully treated fusion patients was 47.7%, compared to 54.3% for the entire cohort. CONCLUSIONS: We redefined ODI success criteria for patients with consecutive lumbar spinal stenosis surgeries. Our register study found the detrimental effect of consecutive surgeries on success rates to be less pessimistic than previously reported; fusion may be an effective option for LSS patients with previous decompression.