The Effect of Body Mass Index on 30-day Complications After Revision Total Hip and Knee Arthroplasty.

Background: We aimed to explore the effect of body mass index (BMI) on 30-day complications after aseptic revision total knee arthroplasty (rTKA) and aseptic revision total hip arthroplasty (rTHA), considering BMI as both a categorical and continuous variable.

Methods: A total of 18,866 patients (9093 rTHA and 9773 rTKA) patients were included for analysis using the American College of Surgeons National Surgical Quality Improvement Project database. Thirty-day rates of readmissions, reoperations, and major and minor complications were compared between different weight categories (overweight: BMI >25 and ≤30 kg/m2; obese: BMI >30 and ≤40 kg/m2; morbidly obese: BMI >40 kg/m2) and the normal weight category (BMI >18.5 and ≤25 kg/m2) using multivariate regression models. Spline regression models were created to study BMI as a continuous variable.

Results: Both readmission rates and reoperation rates increased for rTKA as BMI increased (P < .005). There was a linear relationship between BMI and readmission rates for rTKA. Morbid obesity was associated with an increased reoperation rate for rTHA on univariate analysis (P = .022); however, multivariate analysis showed no statistically significant increase in readmission or reoperation rates as BMI increased for rTHA.

Conclusions: The relationship between BMI and complications after revision total joint arthroplasty is a J-shaped curve with the lowest rates of complications occurring around a BMI of 30 kg/m2. The relationship between BMI and perioperative complications is stronger for revision TKA as opposed to revision THA.