Obesity Class Does Not Associate With Incidence, Timing, or Invasiveness of Reoperations After Total Hip Arthroplasty.

Background: Body mass index (BMI) cut-off values have been proposed to determine eligibility for elective total hip arthroplasty (THA) in obese patients. However, the relationship between the severity of obesity and reoperations remains poorly understood. We evaluated whether the World Health Organization (WHO) obesity class is independently associated with the risk, invasiveness, or timing of reoperations after THA in obese patients.

Methods: There were 7,022 patients who had a BMI ≥ 30 who underwent elective, unilateral THA for primary osteoarthritis between 2016 and 2022 at a tertiary care institution. The patients were grouped according to the WHO obesity classification: class 1 (60.7%, n = 4,265); 2 (26.2%, n = 1,840); and 3 (13.1%, n = 917). A chart review was conducted to identify individuals who underwent any closed or open reoperation requiring anesthesia, and to determine characteristics, including invasiveness and timing. Kaplan-Meier survival analysis was used to estimate the probability of survival over time. The reoperation was defined as the event of interest. The Cox proportional hazards regression model was used to analyze the impact of obesity class on time to reoperation, adjusting for age, sex, race, and Charlson Comorbidity Index.

Results: There were 67 patients (1.0%) who required at least one reoperation, with 17 undergoing two or more. The reoperation rates for class 1, 2, and 3 were 1% (n = 44), 0.9% (n = 17), and 0.7% (n = 6), respectively (P = 0.77). There were five minor procedures (7.5%), 27 open procedures with or without liner exchange (40.3%), and 35 revisions with acetabular and/or femoral component exchange (52.2%) performed. Survival analysis did not show a statistically significant difference between groups.

Conclusions: In this cohort of obese patients who underwent THA, the WHO obesity class was not associated with risk, invasiveness, or timing of reoperations. Policies that preclude patients fromreceiving THA based solely on BMI may have limited efficacy in reducing reoperations following THA.