Do obese patients undergoing surgery for grade 1 spondylolisthesis have worse outcomes at 5 years' follow-up? A QOD study.

OBJECTIVE The long-term effects of increased body mass index (BMI) on surgical outcomes are unknown for patients who undergo surgery for low-grade lumbar spondylolisthesis. The goal of this study was to assess long-term outcomes in obese versus nonobese patients after surgery for grade 1 spondylolisthesis. METHODS Patients who underwent surgery for grade 1 spondylolisthesis at the Quality Outcomes Database's 12 highest enrolling sites (SpineCORe group) were identified. Long-term (5-year) outcomes were compared for patients with BMI ≥ 35 versus BMI < 35. RESULTS In total, 608 patients (57.6% female) were included. Follow-up was 81% (excluding patients who had died) at 5 years. The BMI ≥ 35 cohort (130 patients, 21.4%) was compared to the BMI < 35 cohort (478 patients, 78.6%). At baseline, patients with BMI ≥ 35 were more likely to be younger (58.5 ± 11.4 vs 63.2 ± 12.0 years old, p < 0.001), to present with both back and leg pain (53.8% vs 37.0%, p = 0.002), and to require ambulation assistance (20.8% vs 9.2%, p < 0.001). Furthermore, the cohort with BMI ≥ 35 had worse baseline patient-reported outcomes including visual analog scale (VAS) back (7.6 ± 2.3 vs 6.5 ± 2.8, p < 0.001) and leg (7.1 ± 2.6 vs 6.4 ± 2.9, p = 0.031) pain, disability measured by the Oswestry Disability Index (ODI) (53.7 ± 15.7 vs 44.8 ± 17.0, p < 0.001), and quality of life on EuroQol-5D (EQ-5D) questionnaire (0.47 ± 0.22 vs 0.56 ± 0.22, p < 0.001). Patients with BMI ≥ 35 were more likely to undergo fusion (85.4% vs 74.7%, p = 0.01). There were no significant differences in 30- and 90-day readmission rates (p > 0.05). Five years postoperatively, there were no differences in reoperation rates or the development of adjacent-segment disease for patients in either BMI < 35 or ≥ 35 cohorts who underwent fusion (p > 0.05). On multivariate analysis, BMI ≥ 35 was a significant risk factor for not achieving minimal clinically important differences (MCIDs) for VAS leg pain (OR 0.429, 95% CI 0.209-0.876, p = 0.020), but BMI ≥ 35 was not a predictor for achieving MCID for VAS back pain, ODI, or EQ-5D at 5 years postoperatively. CONCLUSIONS Both obese and nonobese patients benefit from surgery for grade 1 spondylolisthesis. At the 5-year time point, patients with BMI ≥ 35 have similarly low reoperation rates and achieve rates of satisfaction and MCID for back pain (but not leg pain), disability (ODI), and quality of life (EQ-5D) that are similar to those in patients with a BMI < 35.