The Influence of Body Mass Index in Obese and Morbidly Obese Patients on Complications and 30-and 90-day Readmissions Following Lumbar Spine Fusion

Study Design. Retrospective cohort study using the 2013-2017 National Readmission Database. Objective. The aim of this study was to quantify the influence of body mass index (BMI) on complication and readmission rates following lumbar spine fusion. Summary of Background Data. Compared to controls, patients with BMI >35 had greater odds of readmission, infection, and wound complications following lumbar spine fusion. Methods. Patients who underwent elective lumbar spine fusion within the population-based sample were considered for inclusion. Exclusion criteria included nonelective lumbar spine fusions, malnourished, anorexic, or underweight patients, and surgical indications of trauma or neoplasm. Patients were grouped by BMI: 18.5 to 29.9 (controls), 30 to 34.9 (obesity I), 35 to 39.9 (obesity II), and >= 40 (obesity III). Multivariate regression was performed to analyze differences in complications and readmissions between groups. Predictive modeling was conducted to estimate the impact of BMI on 30- and 90-day infection, wound complication, and readmissions rates. Results. A total of 86,697 patients were included for analysis, with an average age of 58.9 years and 58.9% being female. The obesity II group had significantly higher odds of infection (odds ratio [OR]: 1.82, 95% confidence interval [CI]: 1.28-2.62, P = 0.001), wound dehiscence (OR: 3.08, 95% CI: 1.70-6.18, P = 0.0006), and 30-day readmission (OR: 1.32, 95% CI: 1.11-1.58, P = 0.002), whereas the obesity III group had significantly higher odds of acute renal failure (OR: 2.14, 95% CI: 1.20- 4.06, P = 0.014), infection (OR: 2.43, 95% CI: 1.72- 3.48, P<0.0001), wound dehiscence (OR: 3.76, 95% CI: 2.08-7.51, P<0.0001), 30-day readmission (OR: 1.62, 95% CI: 1.36-1.93, P<0.0001), and 90-day readmission (OR: 1.53, 95% CI: 1.31-1.79, P<0.0001) compared with controls. Predictive modeling showed cumulative increases of 6.44% in infection, 3.69% in wound dehiscence, and 1.35% in readmission within 90-days for each successive BMI cohort. Conclusion. Progressively higher risks for infection, wound complications, and hospital readmission were found with each progressive BMI level.