Impact of Body Mass Index on Long-term Reoperation Risk in Robotic-assisted Transforaminal Lumbar Interbody Fusion (TLIF)

Introduction: Elevated Body Mass Index (BMI) is often associated with increased surgical risks, yet its effect on long-term reoperation rates in robotic-assisted spine surgery is unclear. This study examines BMI's influence on long-term reoperation risk in patients undergoing robotic-assisted transforaminal lumbar interbody fusion (TLIF) across BMI categories.

Methods: We conducted a retrospective analysis of robotic-assisted TLIF cases, categorizing BMI into underweight, normal, overweight, and obese groups. The primary outcome was long-term reoperation, with secondary analyses of intraoperative complications, comorbidities, and demographic factors. Multiple predictive algorithms were used to evaluate reoperation risk. Synthetic Minority Over-sampling Technique (SMOTE) was applied to address class imbalance, and model performance was assessed via ROC curve analysis.

Results: The cohort comprised 223 patients (mean age 61.4 years) with a higher proportion of patients being white (77.6%; p=0.036) and female (56.1%; p< 0.01), predominantly in the overweight (31.8%; n=71) or obese (42.6%; n=95) BMI categories. Most patients (55.5%; n=122) had spondylolisthesis followed by stenosis (15.9%; n=35) with no differences across BMI groups (p=0.530). Almost all (99.1%) underwent a posterior approach. Overall, 28.7% (n=64) required revision surgery; however, reoperation rates did not significantly differ by BMI category, indicating consistent outcomes across BMI extremes (p=0.851). Obese patients showed higher rates of hypertension (69.5%; p< 0.01) and chronic kidney disease (9.5%; p=0.05). Both obese and underweight patients demonstrated higher rates of diabetes (p=0.038) and chronic pulmonary disease (p=0.05). No significant differences were observed for smoking history (p=0.378), Charlson Comorbidity Index (p=0.131), and operative complications across BMI groups. Among the models, Support Vector Machine (SVM) yielded the highest AUC of 0.71, reflecting moderate discriminative ability, with a favorable ROC curve profile. An optimal BMI cutoff point was determined at 38.70, offering a potential threshold for risk stratification.

Conclusion : These findings suggest that BMI does not significantly impact long-term reoperation risk in robotic-assisted TLIF, supporting its safe application across BMI categories. Elevated BMI alone may not necessitate additional precautions, though integrating other clinical predictors may improve postoperative outcome predictions in future research.