Muscular recovery around the hip joint after total hip arthroplasty.

A prospective study was conducted to quantitatively measure the relative muscle torque strengths in 20 consecutive women with unilateral osteoarthritic hips and 20 consecutive men with unilateral osteonecrotic hips before and after primary cementless total hip arthroplasty. Maximal isometric torque strengths in the muscles of flexion, extension, and abduction around the hip joint were measured preoperatively and postoperatively at six months and one year, using a Cybex 340 dynamometer. The results showed improved muscle function after total hip arthroplasty in both diseased and healthy hips. In the diseased hips, all muscle groups improved significantly, from 150 to 250% of the preoperative levels, at six months and one year postoperatively, except in the osteoarthritic women, in whom the improvement at six months was minimal. Preoperatively, all muscle groups in the diseased hips were weaker than those in the uninvolved hips, especially in the osteonecrotic men (51-79% of healthy side). In both groups, however, the torques strengths of the diseased hips had not caught up to the healthy hips in the one-year follow-up period (84-89% in the osteonecrotic male group, and 79-81% in the osteoarthritic female group). The authors recommended that muscle strengthening exercises for the hip should be continued for at least one year, and perhaps longer, after total hip arthroplasty.