The impact of body mass index classification on operative characteristics and perioperative outcomes in lumbar microdiscectomy.
INTRODUCTION: Body mass index (BMI) stratification helps classify obesity severity. In patients undergoing microdiscectomy for symptomatic lumbar disc herniation, the effect of obesity on perioperative risk remains incompletely understood. This retrospective single-institution study evaluated whether BMI class influences perioperative risk in a large surgical cohort. METHODS: Adults older than 18 years who underwent primary, elective single-level lumbar microdiscectomy between June 2018 and March 2025 with at least 3 months of follow-up were included. Patients were grouped by BMI: without obesity (WO, BMI < 30), class I (CI, 30-34.9), class II (CII, 35-39.9), and class III (CIII, ≥40). Outcomes were analyzed separately for open microdiscectomy (OM), tubular microdiscectomy (TM), and endoscopic discectomy (ED). Continuous variables were compared using Kruskal-Wallis testing with Dunn post hoc analysis; categorical variables were compared with chi-square tests. Significance was set at p < 0.05. RESULTS: A total of 757 patients were included (OM 422, TM 190, ED 145). Higher obesity classes underwent ED more frequently (p = 0.038). In the OM cohort (WO 258, CI 97, CII 50, CIII 17), CI had a higher proportion of males and CII a lower proportion (p = 0.007). Operative time, length of stay, and estimated blood loss were greatest in CII and CIII patients (all p < 0.001). CII patients also had more emergency department visits within 1 year than other classes (p = 0.026). No differences were found in age, smoking status, disc herniation type, dural tears, intraoperative or postoperative complications, or revision presence/time. In the TM cohort (WO 117, CI 47, CII 21, CIII 5), WO patients were oldest and CIII youngest (p < 0.001), with no other significant differences. In the ED cohort (WO 79, CI 31, CII 20, CIII 15), WO patients were oldest and CIII youngest (p = 0.004). CIII patients had higher estimated blood loss (p = 0.028) and shorter time to revision (p < 0.001), while other variables were similar. CONCLUSIONS: ED was used more often in higher obesity classes. In OM, CII and CIII obesity were associated with longer operative time, longer hospital stay, and greater blood loss, likely due to increased exposure requirements. TM and ED showed few obesity-related differences in complications, suggesting minimally invasive approaches may mitigate obesity-related perioperative risk. However, the retrospective design and small number of CIII patients warrant further study.