The Growing Impact of Severe Obesity on 90-Day Outcomes After Elective Primary Total Hip Arthroplasty: A National Propensity-Matched Study

Background: Severe obesity is increasingly prevalent among patients undergoing total hip arthroplasty (THA), yet contemporary national data evaluating its impact on early complications and revision risk remain limited.We evaluated temporal trends and 90-day outcomes associated with severe obesity after elective primary THA.Methods: We performed a retrospective cohort study using the Nationwide Readmissions Database (2020)(2021)(2022).Elective primary THAs performed on hospital day 0 were identified.Severe obesity was defined by ICD-10-CM codes E66.01 or E66.2.To ensure complete follow-up, 90-day analyses included procedures performed between January and September.Propensity score matching (1:1, nearest neighbor without replacement) adjusted for demographics, payer, hospital characteristics, and major comorbidities.The primary outcome was all-cause 90-day readmission.Secondary outcomes included reoperation, true component-level revision, and resource utilization.Results: Among 366,374 weighted elective THAs, 28,798 (7.9%) involved severe obesity.Prevalence increased from 7.4% in 2020 to 8.7% in 2022 (P < .001).After matching (55,976 patients), severe obesity was associated with higher rates of acute kidney injury (3.8% vs 2.0%) and blood loss anemia (17.2% vs 12.8%) (both P < .001),longer length of stay, and greater charges.Ninety-day readmission occurred in 6.7% vs 5.8% (Odds Ratio OR: 1.32; 95% Confidence Intervals CI: 1.23-1.41).Severe obesity was associated with higher odds of any procedure (OR: 1.45), hip-related reoperation (OR: 1.57), and component-level revision (OR: 1.53) (all P < .001).Conclusions: Severe obesity is increasingly prevalent and independently associated with higher early complications, readmission, reoperation, and revision following elective primary THA.Level of Evidence: Level III.