FP12.1 Impact of Borderline Hip Dysplasia on 1-Year THA Outcomes: Lower Satisfaction and PROMIS Physical Function in Young Non-arthritic Patients Versus Arthritic Controls

Abstract

Abstract ICLA12 - The Chondral Masterclass: Advanced Scaffolds, Orthobiologic Realities, and Young THA, Auditorium B (BMCC Level 1), October 9, 2026, 10:30 - 12:30 Purpose To compare one-year patient-reported outcomes and satisfaction following total hip arthroplasty (THA) in young adults (<50 years) with non-arthritic hips (NAH) versus arthritic hips (AH). Hypothesis Patients with more severe radiographic arthritis will demonstrate greater improvement in outcome scores and report higher satisfaction at one year after THA. Methods We performed a retrospective, multicenter database study including primary THA patients under age 50 who underwent surgery between 2021 and 2025 and had complete one-year outcome data. Demographic and radiographic variables collected included age, sex, Tönnis grade, lateral center-edge angle (LCEA), and acetabular index (AI). Patient-reported outcome measures evaluated preoperatively and at one year included PROMIS Physical Function (PF), the International Hip Outcome Tool-12 (iHOT-12), and a 0–10 satisfaction score. The study was powered a priori to detect a clinically meaningful change in PROMIS PF, requiring a minimum of 17 patients per group; statistical significance was set at p ≤ 0.05. Between-group comparisons used appropriate parametric or nonparametric tests based on distribution; paired analyses evaluated within-group changes from baseline to one year. Results The NAH cohort comprised 96 patients (mean age 46.1 years; 83% female), with Tönnis grades distributed as 43% grade 0 and 57% grade 1. Mean LCEA and AI were 23.6° and 7.5°, respectively. The AH cohort included 98 patients (mean age 47.6 years; 54% female) with 54% Tönnis grade 2 and 46% Tönnis grade 3; mean LCEA and AI were 22.5° and 11.26°. Preoperative PROMIS PF averaged 37.8 (NAH) and 39.1 (AH), improving to 50.4 and 53.24 at one year, respectively; the between-group difference in PROMIS PF improvement reached the threshold for statistical significance (p = 0.05). iHOT-12 scores showed large, clinically meaningful within-group improvements in both cohorts: NAH from 35.8 to 73.9 and AH from 35.4 to 70.9 at one year, with no significant difference between groups (p = 0.60). Satisfaction scores were high in both groups, with mean values of 8.9 (NAH) and 9.5 (AH); AH patients reported significantly higher satisfaction (p = 0.025). Conclusion In young adults undergoing THA, both NAH and AH patients experience substantial and clinically meaningful improvements in hip-specific function at one year, as reflected by large increases in iHOT-12 and PROMIS PF scores. While iHOT-12 outcomes were comparable between groups, patients with more advanced radiographic arthritis reported greater gains in general physical function (PROMIS PF) and higher satisfaction at one year. These findings suggest that THA provides significant benefit across a spectrum of preoperative hip pathology in the young adult population, with particularly strong perceived functional and satisfaction gains among those with more severe arthritis. Further prospective studies are warranted to explore longer-term outcomes, predictors of differential response, and the impact of baseline radiographic severity on recovery trajectories.