Body Mass Index as a Risk Factor for Readmission Rates in Direct Anterior Approach Total Hip Arthroplasty.

Multiple studies have examined the relationship between obesity and increased risk of perioperative complications in patients undergoing total hip arthroplasty (THA). The purpose of this study was to compare the rate of perioperative complications stratified by body mass index (BMI) in patients undergoing THA through a direct anterior (DA) approach. A retrospective review at a single high-volume orthopaedic specialty hospital identified all DA THAs performed between January 2019 and August 2022. Patients were stratified by BMI into the following cohorts: underweight (BMI<18.5), normal (BMI = 18.5-25), overweight (BMI = 25-30), obese class I (BMI = 30-35), obese class II (BMI = 35-39.9), and obese class III (BMI ≥ 40). Primary outcomes collected included 30-day and 90-day readmissions, emergency department visits, intraoperative fracture, and 90-day infection requiring return to the operating room. There were 4767 patients with a mean BMI of 28 kg/m2 (15.5-54.5) and a mean age of 67 years (18-100 years). Thirty-day readmission rates in the obese class III (6.2%) were significantly higher when compared individually to all other cohorts (P < .001). Additionally, logistic regression found that underweight patients had an increased likelihood of an intraoperative fracture (odds ratio [OR]: 13.120, 95% confidence interval [CI]: 1.172-146.930, P < .001), and both obese classes I and III were more likely to have a 90-day infection that required a return to the operating room (OR: 8.508, 95% CI: 1.023-70.779, P < .001 and OR: 29.853, 95% CI: 2.683-332.187, P < .001, respectively). Obese class III patients have a higher rate of 30-day readmission following DA THA than all other BMI cohorts and are at increased risk of infection requiring return to the operating room when compared to patients with normal BMI. Surgeons should counsel patients regarding the increased potential complication risks related to BMI.