FP9.6 Body Mass Index and Age Predict Conversion to Total Hip Arthroplasty After Primary Hip Arthroscopy for Femoroacetabular Impingement Syndrome: A 15-Year Survival Analysis

Abstract

Abstract ICLB09 - The Revision Playbook: Advanced Execution and Technical Rescues in Failed Preservation, Session Room 6 (BMCC Level 3), October 9, 2026, 10:30 - 12:30 Background/Objective Long-term predictors of conversion to total hip arthroplasty (THA) after primary hip arthroscopy (HA) for femoroacetabular impingement syndrome (FAIS) remain incompletely characterized, particularly beyond 10 years. Existing evidence has also been limited in clarifying the relative contributions of modifiable risk factors (eg, BMI) versus nonmodifiable factors (eg, age and sex) at extended follow-up. Therefore, we aimed to determine whether BMI, sex, Tönnis grade, and age at surgery independently predict 15-year THA conversion and THA-free survivorship after primary HA. Methods Patients undergoing primary hip arthroscopy at a single academic institution were prospectively collected and retrospectively reviewed. Exclusion criteria were revision surgery, inflammatory arthropathy, age <15 years, BMI <18.5 kg/m¬2 and Tönnis >1. Time-to-event was defined from index arthroscopy to THA conversion (event) or latest follow-up (censor). Multivariable Cox proportional hazards regression included BMI, sex, Tönnis grade, and age at surgery. Kaplan-Meier analysis estimated THA-free survivorship at 5, 10, and 15 years. Univariable Cox proportional hazards models assessed age, sex, BMI as well as preoperative Tönnis grade, anterior-center edge angle (ACEA), lateral-center edge angle (LCEA), and alpha angle as predictors of THA. A multivariable model included all covariates simultaneously to explore impact on THA conversion. Results The analytic cohort included 338 hips with 76 THA conversions. Kaplan-Meier THA-free survivorship was 81.9% at 5 years (n at risk=228; 59 conversions; 51 censored), 78.3% at 10 years (n at risk=217; 10 conversions; 1 censored), and 75.3% at 15 years (n at risk=120; 7 conversions; 210 censored). Seven THA conversions occurred between 10 and 15 years. In multivariable Cox analysis (n=338; 76 events), BMI was independently associated with increased THA risk (HR 1.06 per kg/m2, 95% CI 1.02-1.11, p=0.002), and age was independently associated with increased risk (HR 1.06 per year, 95% CI 1.04-1.08, p<0.001). Sex was not independently associated with THA conversion (male vs female: HR 0.80, 95% CI 0.48-1.32, p=0.384). Conclusion In this 15-year primary hip arthroscopy cohort for FAIS, higher BMI and older age were significant independent predictors of THA conversion, while sex and Tönnis grade were not significant predictors. Kaplan-Meier survivorship curves showed a clinically meaningful decline in long-term hip survivorship at 5, 10, and 15 years with higher BMI and older age. These findings may help preoperative counseling and risk stratification for patients considering hip arthroscopy.