Predictors of physical activity recovery after total hip arthroplasty: a prospective observational study.

PURPOSE: Little is known about the changes and the factors in physical activity as following total hip arthroplasty (THA). There are potential discrepancies between subjective and objective measurements of physical activity. Thus, our porpose is to compare objective and subjective measurements of activity levels in patients undergoing THA preoperatively, three months and one year following surgery, and investigated the factors that predicts the objective activity level after THA. METHODS: This prospective observational study included 42 patients with unilateral symptomatic hip osteoarthritis who underwent THA. The objective activity level (step counts, sit-to-stands, and upright time) by using a tri-axial accelerometer, PRO (Oxford hip score; OHS and University of California, Los Angeles activity score; UCLA score), and muscle volume around the hip joint by using preoperative computed tomography were measured. RESULTS: The number of steps, OHS, and UCLA score before, at three months, and one year after THA averaged 5092, 6532, and 6545 steps, 30.3, 43.0, and 44.2 points, and 3.4, 4.8, and 4.6 points, respectively, with significant postoperative increases (P < 0.05). No significant difference was found between three months and one year postoperatively. In multivariate analysis, younger age and higher preoperative contralateral gluteal medius volume were the predictors of higher postoperative step counts (P < 0.05). CONCLUSIONS: Physical activity, including step counts, OHS, and UCLA score increased significantly until three months after unilateral THA. Early surgical intervention before contralateral muscle declines and preoperative rehabilitation including contralateral side may additionally improve postoperative activity levels.