Minimally Invasive Surgery for Grade 1 Spondylolisthesis is Most Beneficial for Those with BMI Over 30: Two Years Follow up from the QOD

Introduction: Both minimally invasive (MIS) and open approaches may be effective for treatment of degenerative lumbar spondylolisthesis (DLS). However, comparative efficacy may be influenced by body mass index (BMI).

Methods: Retrospective analysis of the prospective Quality Outcomes Database registry including patients operated on for grade 1 DLS. BMI was split into four categories by CDC definitions. Outcomes were discharge location, Oswestry Disability Index (ODI), Numeric Rating Scale for leg and back pain, surgical complications, and reoperation.

Results: 608 patients with grade 1 DLS were identified (259 MIS, 349 open). 496 (82%) had 2-year follow-up (211 MIS, 285 open). BMI subgroups included 2 underweight, 105 healthy, 171 overweight, and 218 obese patients. 383 patients (77%) underwent single-segment arthrodesis while 113 (23%) underwent single-level decompression alone. Regardless of surgical technique or BMI, 2-year (2Y) ODI (mean difference [MD]: -24.0+/-0.052, p < 0.001), leg pain (MD: -3.87+/-0.008, p< 0.001) and back pain (MD: -3.35+/-0.009, p< 0.0001) improved from baseline. In BMI subgroup analyses, the proportion of patients achieving minimal clinically important difference in 2Y ODI was larger after MIS compared to open surgery only among obese patients (77.9% vs 64.4%, X²=3.887, p=0.049). Obese patients had less 2Y leg pain following MIS (median: -5, IQR: 5) than open (median: -3, IQR: 7) (U = 6240.5, p = 0.039), while 2Y back pain was equally decreased. 2Y reoperation rates trended higher for open compared to MIS only in obese patients (15.9% vs 7.0%; X²=3.05, p=0.081). Complication rates did not differ between approaches.

Conclusion : Regardless of approach, patients improved following surgery for grade 1 DLS. Our data suggest that for patients with BMI > 30, but not BMI < 30, an MIS approach can lead to better long-term outcomes and potentially lower reoperation rates compared to open surgery. Thus, MIS may be ideal for treatment of obese patients.