Impact of increased body mass index on outcomes of elective spinal surgery.

ABSTRACT

STUDY DESIGN: Observational retrospective cohort study of prospectively collected database. OBJECTIVE: To determine whether overweight body mass index (BMI) influences 30-day outcomes of elective spine surgery. SUMMARY OF BACKGROUND DATA Obesity is prevalent in the United States, but its impact on the outcome of elective spine surgery remains controversial. METHODS: We used National Surgical Quality Improvement Program, a prospective clinical database with proven validity and reproducibility consisting of 256 perioperative standardized variables from surgical patients at nearly 400 academic and nonacademic hospitals nationwide. We identified 49,314 patients who underwent elective fusion, laminectomy or both between 2006 and 2012. We divided patients according to BMI (kg/m2) as normal (18.5-24.9), preobese (25.0-29.9), obese I (30.0-34.9), obese II (35.0-39.9), and obese III (≥40). Relationship between increased BMI and outcome of surgery measured as prolonged hospitalization, complications, return to the operating room, discharged with continued care requirement, readmission, and death was determined using logistic regression before and after propensity score matching. RESULTS: All overweight patients (BMI ≥25 kg/m2) showed increased odds of an adverse outcome compared with normal patients in unmatched analyses, with maximal effect seen in obese III group. In the propensity-matched sample, obese III patients continued to show increased odds for complications (odds ratio, 1.6; 95% confidence interval, 1.1-2.3), readmission (odds ratio, 2.3; 95% confidence interval, 1.1-4.9), and return to the operating room (odds ratio, 1.8; 95% confidence interval, 1.1-3.1). CONCLUSION: Impact of obesity on elective spine surgery outcome is mediated, at least in part, by comorbidities in patients with BMI between 25.0 and 39.9 kg/m2. However, BMI itself is an independent risk factor for adverse outcomes in morbidly obese patients. LEVEL OF EVIDENCE 3.