Triple-Taper Stems in Obese Total Hip Arthroplasty Patients: Complication and Revision Rates from a U.S. Registry.

Abstract

Obesity is a known risk factor for complications and revision following total hip arthroplasty (THA). A triple-taper femoral stem design may improve metaphyseal engagement and rotational stability. This study investigated outcomes in obese patients undergoing cementless primary THA by stem design. We conducted a retrospective cohort study of 25,112 obese patients undergoing unilateral, cementless THA for osteoarthritis between 2018 and 2024. Use of triple-taper increased over the study period (25.4% in 2018 versus 58.3% in 2024). Patients were categorized by stem type per the Khanuja-Mont 2011 classification: Type 1 (single taper), Type 2 (dual taper), and Type 3C (triple-taper) and stratified by obesity class (Class I: body mass index (BMI) 30.0 to 34.9; Classes II to IV: BMI ≥ 35.0). Multivariable Cox proportional hazard models assessed cause-specific revision risk, adjusting for confounders and surgeon clustering. At five years, cumulative aseptic revision probability was lowest for Type 3C stems. Among Class I obesity patients, Type 3C stems were associated with lower aseptic revision risk compared to Type 1 (hazard ratio (HR) = 0.47, 95% confidence interval (CI) = 0.31 to 0.71, P = 0.0004) and Type 2 stems (HR = 0.39, 95% CI = 0.17 to 0.91, P = 0.029). Similar findings were observed for Class II to IV obesity. Type 3C stems were also associated with lower periprosthetic fracture risk. The triple-taper stems are increasingly utilized in obese THA patients and are associated with a reduced aseptic revision and (periprosthetic fracture (PPF) risks compared to Type 1 and 2 stems, supporting the notion that these stems confer a clinically relevant biomechanical advantage.