Periprosthetic bone mineral density after Mueller and Zweymueller total hip arthroplasties.

To assess the adaptive bone changes in adult human hips after insertion of cemented or uncemented acetabular and femoral components for total hip arthroplasty, a retrospective clinical study using dual energy xray densitometry was conducted. A consecutive homogeneous group of 52 female patients with an average age of 61 years was operated on for unilateral hip osteoarthritis. The types of prosthetic components used were the cemented Mueller and the uncemented Zweymueller socket and stem. Periprosthetic bone mineral density was measured in 7 different zones (Zones I to VII) in hips that were operated on and hips that were not, and the results were compared to quantify periprosthetic bone mineral changes over time. The Zweymueller socket induced bone resorption at the medial and caudal zone of the acetabulum, whereas implantation of the Mueller polyethylene socket was associated with a significant increase in bone mineral density only at the cranial zone of the acetabulum. The stem of the Mueller prosthesis induced bone mass reduction in the lesser trochanter area and in the distal lateral fixation cortex. The Zweymueller stem produced significant bone resorption in the area of the lesser trochanter, and in the medial and lateral distal cortex of the femur. The Mueller and Zweymueller stems induced bone mass increase in the greater trochanter area. These findings were unaffected by the age of the patients. Further improvement in densitometry technology may be of major clinical relevance for early detection of aseptic loosening in total hip arthroplasty.