Rising Body Mass Index Increased Early Complications, But Not Early Reoperations Following Aseptic Revision Total Knee Arthroplasty

BACKGROUND: Elevated body mass index (BMI) contributes to osteoarthritis and demand for total knee arthroplasty (TKA). Increased BMI is an established risk factor for complications following primary TKA. However, literature on BMI and outcomes of revision TKA (rTKA) is less conclusive. This study evaluated the association between BMI and outcomes in the early postoperative period following aseptic rTKA. We hypothesized that increasing BMI would be associated with a higher risk of short-term complications. METHODS: A retrospective review of 470 patients who underwent aseptic rTKA within one regional health system from 2017 to 2022 was performed. Revisions were due to infection (39.8%), instability (23.7%), arthrofibrosis (11.8%), and aseptic loosening (11.8%). Patient BMI was obtained from electronic medical records at the time of rTKA. The primary outcome was early reoperation, assessed at 30 and 90 days postoperatively. The secondary outcomes included readmission, major complications, and minor complications at 30 and 90 days postoperatively. Multivariate regression models considering BMI as a continuous variable were used to determine the impact of BMI on outcomes. RESULTS: Elevated BMI was associated with slightly increased risk of overall reoperation (odds ratio: 1.03, P = 0.036) and 30-day readmission (odds ratio: 1.05, P = 0.029). Rising BMI was also associated with greater length of stay (P = 0.005), supplemental oxygen requirement to at least postoperative day two (P = 0.016), and postoperative hypoxemia beyond 24 hours (P = 0.038). No associations were noted between BMI and 30- or 90-day reoperation, 90-day readmission, or other postoperative complications (all P > 0.05). CONCLUSIONS: This study suggests that failure rates and complications following rTKA remain high compared to primary procedures, with increased risk for overall re-reoperation and early readmission at 30 days. Otherwise, the complication profile was similar across the spectrum of BMI values. Further research is warranted to clarify the role of BMI in operative planning and prognosis.