Predictors of clinical outcomes and muscle recovery after total hip replacement surgery: A prospective cohort study

Identifying predictors for functional recovery following total hip replacement (THR) is essential for optimizing postoperative care. We aimed to identify preoperative factors affecting muscle recovery and functional outcomes 1-year after THR. This prospective observational study enrolled 103 patients scheduled for unilateral THR. Demographic data, body composition (dual-energy X-ray absorptiometry), and physical functions (grip strength, knee extension strength, and gait speed) were assessed preoperatively. Patients were reevaluated 1-year after surgery using the same parameters and patient-reported outcome measures (PROMs: modified Harris hip score, Western Ontario and McMaster Universities osteoarthritis index, EuroQol-5D). Of the initial cohort, 57 patients completed the 1-year follow-up (dropout rate: 44.7%). Multivariable linear regression analysis was performed to identify independent predictors. Significant improvements in muscle strength, mass, and PROMs were observed 1-year postoperatively. Multivariable analysis revealed that leg mass, preoperative grip strength, and appendicular skeletal mass, adjusted by body mass index, were significant independent predictors of postoperative PROMs. However, indices adjusted by height squared did not demonstrate consistent associations. Preoperative gait speed was also strongly correlated with functional outcomes. Patients undergoing THR experienced significant improvement in their muscle strength, mass, and functional recovery 1-year after the surgery. Skeletal muscle indices adjusted for body mass index or weight, rather than height2, were more consistently associated with surgical outcomes. These findings highlight the importance of the "load-to-capacity" ratio in weight-bearing joints.