The impact of body mass index on hospital stay and complications after spinal fusion

Background: Obesity is a dominant public health concern and risk factor for disability, with few studies examining its impact in spinal surgery. Patients with a higher body mass index (BMI) have lower functional status, increased pain, and worse physical condition than those with ideal weight. Objective: To determine associations between BMI categories on adverse patient outcomes after long-segment spinal fusions. Methods: Consecutive, open, elective fusions (interbody and/or posterolateral arthrodesis) of more than 5 levels from 2007 to 2010 were retrospectively analyzed with follow-up of more than 1 year. Bivariate analyses examined outcome variables based on BMI categories. Linear regression analysis evaluated BMI, hospital stay, and complications at 1 and 2 years, controlling for confounders. Mean and median follow-up lengths were 2.1 and 2.0 years, respectively. Results: A total of 189 surgeries on 112 patients, with a mean age of 59.5 years and a mean BMI of 29.8 kg/m², were analyzed. Morbidly obese patients had longer hospitalizations, worse Oswestry Disability Index (ODI), and more complications at 1 and 2 years than ideal weight patients. Multivariate linear regression modeling revealed sex, cardiac medications, cerebrospinal fluid leak, and BMI category of ideal vs nonideal influenced hospitalization length. Multivariate analysis showed BMI greater than 30 kg/m², preoperative ODI, and pedicle subtraction osteotomy influenced all complications at 1 year. Mean complications at 2 years for the morbidly obese were 3 times more than those underweight and 8 times more than those with ideal weight. Controlling for age, sex, and length of stay, obese and morbidly obese patients had more complications at 2 years; morbidly obese patients had a worse 2-year ODI. Conclusion: BMI is an independent predictor of hospitalization length and all complications at 1 and 2 years in patients receiving long-segment fusions.