Disuse osteoporosis in patients with total hip prostheses.

Aseptic loosening of total hip arthroplasty is still a serious problem. Bone quality might be one of the major factors influencing loosening. In a previous study, bone loss during the reparation phase was evaluated with modified computed tomography at the site of the implant. The present study documents the degree of disuse osteoporosis prior to and after surgery. Bone density of both tibiae of patients with unilateral artificial hip joints was evaluated longitudinally. Preoperatively a significant right-left difference was found, that has to be attributed to the preoperative unloading of the diseased leg. After surgery a slight but significant bone loss was found in both legs attributable to the immobilization following surgery and the reduced activity in the first 6 months. In successfully operated cases this loss is temporary. In one patient bone loss continued; after 1 year there are now clinical signs of implant loosening. Although the spectrum of physical activity in our group was wide, no correlation between activity and bone loss has been found so far.