Degenerative disc disease and isthmic spondylolisthesis have similar outcomes after L5-S1 anterior lumbar interbody fusion

Background and Objective: Anterior lumbar interbody fusion (ALIF) at L5-S1 is commonly performed for both isthmic spondylolisthesis (IS) and degenerative disc disease (DDD). However, the comparative clinical outcomes of ALIF in these two conditions remain unclear. This study aims to compare the clinical outcomes of L5-S1 ALIF for IS and DDD, focusing on patient-reported outcome measures and the achievement of minimum clinically important difference (MCID). Materials and Methods: This retrospective cohort study analyzed 93 consecutive patients who underwent L5-S1 ALIF with percutaneous posterior instrumentation for IS (n = 37) or stand-alone L5-S1 ALIF for DDD (n = 56). Patient-reported outcomes included Visual Analog Scale (VAS)-back, VAS-leg, Oswestry Disability Index (ODI), Short-Form Health Survey (SF-12), and Veterans RAND 12-item Health Survey (VR-12). Outcomes were assessed preoperatively and at the final postoperative follow-up. Changes between timepoints and the proportion of patients achieving MCID for VAS and ODI were compared between the IS and DDD groups. Results: The two groups were similar in age, sex, and ASA scores, although DDD patients had a slightly higher BMI (29.99 vs. 27.32, p = 0.012). Preoperative VAS-back, VAS-leg, and ODI scores did not differ between groups; however, DDD patients had significantly lower SF-12 and VR-12 scores (p = 0.024 for each). At final follow-up, clinical outcomes for VAS-back, VAS-leg, ODI, and VR-12 were comparable between the groups, though DDD patients had slightly worse SF-12 scores (-6.7, p = 0.021). Improvement from baseline to final follow-up was similar for both groups, and the proportion achieving MCID for VAS-back, VAS-leg, and ODI did not differ significantly. Conclusion: Despite inferior preoperative and final postoperative scores, patients with DDD experienced similar clinical improvement and outcomes after L5-S1 ALIF compared to patients with IS. Moreover, DDD patients were equally likely as IS patients to achieve MCID at final follow-up, suggesting that ALIF is an effective treatment option for both conditions.