Sex specific associations between biomechanical recovery and clinical recovery after total hip arthroplasty

BACKGROUND: There are sex-specific gait differences in men and women before and after total hip arthroplasty (THA) but we do not know their impact on clinical outcomes. The objective of this study was to identify sex-specific associations between pre- and postoperative changes in pain and function and (i) gait mechanics, (ii) passive range of motion, and (iii) abductor strength. METHODS: Pre- and one-year postoperative data were identified from a data repository (n = 124; 64 Women; Age 61 (SD 10); BMI 29 (SD 5)). We used linear regression analysis to identify sex-specific associations between Harris Hip Score pain and function subscores, and sagittal plane hip kinematics and 3D hip kinetics during gait, hip abductor strength, and passive hip range of motion (RoM). FINDINGS: Combinations of biomechanical variables predicted up to 24% of the variation in pain improvement and up to 27% of the variation in functional improvement. In men, increased peak external rotation moments were associated with pain improvement. Passive flexion RoM and peak extension moments were associated with functional improvement. In women, increased passive adduction RoM and peak external rotation moments were associated with pain improvement. Peak adduction moments and passive flexion RoM were associated with functional improvement. INTERPRETATIONS: The different associations between improvement in clinical outcomes and improvement in gait, passive RoM, and abductor strength suggest that the biomechanical path to recovery may be different in men and women.