Joint function after total hip arthroplasty: a four-year follow-up of 72 cases with Charnley and Müller replacements.

To help determine the duration of benefits in functional performance resulting from total hip arthroplasty (THA), multiple kinesiologic measurements were made before surgery and two and four years after 32 Charnley and 40 Müller THA procedures were done in 58 patients. There were no complications of loosening or infection, nor was there additional disability in other joints of the lower extremities. Measurements of functional performance included range of hip motion, hip abductor and adductor muscle strength, weight distribution between the feet during standing, forces applied to canes or crutches, and multiple components of free-speed and fast-walking performance. The average measurements showed significant improvement in almost all components of function from the time preceding surgery to two years afterward. The two-year level of function was then maintained without significant improvement or decline in function four years postoperation.