Degenerative spondylolisthesis versus spinal stenosis: Does a slip matter? Comparison of baseline characteristics and outcomes (SPORT)

Study Design: As-treated analysis of the Spine Patient Outcomes Research Trial. Objective: To compare baseline characteristics and surgical and nonoperative outcomes between degenerative spondylolisthesis (DS) and spinal stenosis (SPS) patients. Summary of Background Data: DS and SPS patients are often combined in clinical studies despite differences in underlying pathology and treatment. Methods: The DS cohort included 601 patients (369 [61%] underwent surgery), and the SPS cohort included 634 patients (394 [62%] underwent surgery). Baseline characteristics were compared between the 2 groups. Changes from baseline for surgical and nonoperative outcomes were compared at 1 and 2 years using longitudinal regression models. Primary outcome measures included the SF-36 bodily pain and physical function scores and the Oswestry Disability Index. Results: The DS patients included more females (69% vs. 39%, P < 0.001), were older (66.1 year vs. 64.6 years, P = 0.021), and were less likely to have multilevel stenosis (35% vs. 61%, P < 0.001) compared with the SPS patients. There were no significant baseline differences on any of the main outcome measures. DS patients undergoing surgery were much more likely to be fused than SPS patients (94% vs. 11%, P < 0.001) and improved more with surgery than SPS patients on all primary outcome measures (DS vs. SPS): physical function (+30.4 vs. +25.3, P= 0.004 at 1 year; + 28.3 vs. +21.4, P < 0.001 at 2 years), bodily pain (+32.3 vs. +27.5, P = 0.006 at 1 year; +31.1 vs. +26.1, P = 0.003 at 2 years), and Oswestry Disability Index (-25.9 vs. -21.0, P < 0.001 at 1 year; -24.7 vs. -20.2, P < 0.001 at 2 years). Patients treated nonoperatively improved less than those treated surgically, and there were no significant differences in nonoperative outcomes between the 2 cohorts. Conclusion: Overall, DS and SPS patients had similar baseline characteristics. However, DS patients improved more with surgery than SPS patients. Future studies should probably not combine these heterogeneous patient populations.