Preoperative Hip Abductor Muscle Strength Predicts Patient-Reported Functional Outcomes Following Total Hip Arthroplasty.

BACKGROUND: Total hip arthroplasty (THA) is a widely performed and effective intervention for the management of hip osteoarthritis. Despite its overall success, substantial variability persists in postoperative functional recovery. Hip abductor weakness has been associated with altered gait patterns, impaired balance, and reduced hip function following THA. These deficits are reflected in commonly used patient-reported outcome measures, including the Hip Disability and Osteoarthritis Outcome Score for Joint Replacement (HOOS-JR) and Veterans RAND 12-Item Health Survey (VR-12). However, the extent to which preoperative hip abductor muscle strength predicts 12-month postoperative outcomes remains poorly characterized.

METHODS: A prospective analysis was conducted on 184 patients who underwent primary THA at our institution between 2022 and 2023; 163 completed one-year follow-up and were included in the final analyses. Adjusted linear mixed-effects models were used to evaluate the predictive value of preoperative hip abductor muscle strength on 12-month HOOS-JR and VR-12.

RESULTS: The mean preoperative hip abductor muscle strength was 8.8 ± 3.8 kg. Greater preoperative ipsilateral hip abductor muscle strength was independently associated with higher HOOS-JR scores at 12 months following THA (β = 3.58, 95% confidence interval (CI) 0.48 to 6.68; P = 0.024), increased odds of achieving minimal clinically important difference (MCID) (odds ratio (OR) 9.0 per 5-kg increase; P = 0.044), and lower odds of failing to reach patient-acceptable symptom state (PASS) (OR 0.79 per 0.01-unit increase, 95% CI 0.59 to 1.00; P = 0.048). Similarly, greater preoperative ipsilateral hip abductor strength was independently associated with higher VR-12 scores at 12 months (β = 3.66, 95% CI 1.60 to 5.73; P = 0.006).

CONCLUSION: Preoperative hip abductor muscle strength was an independent predictor of patient-reported functional recovery after THA, supporting abductor muscle strength as a clinically relevant marker for risk stratification. Future studies should determine whether targeted strengthening can improve outcomes.