PERIPROSTHETIC BONE-MINERAL DENSITY AFTER MUELLER AND ZWEYMUELLER TOTAL HIP ARTHROPLASTIES

To assess the adaptive bone changes in adult human hips after insertio n of cemented or uncemented acetabular and femoral components for tota l hip arthroplasty, a retrospective clinical study using dual energy x ray densitometry was conducted. A consecutive homogeneous group of 52 female patients with an average age of 61 years was operated on for un ilateral hip osteoarthritis. The types of prosthetic components used w ere the cemented Mueller and the uncemented Zweymueller socket and ste m. Periprosthetic bone mineral density was measured in 7 different zon es (Zones I to VII) in hips that were operated on and hips that were n ot, and the results were compared to quantify periprosthetic bone mine ral 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 i ncrease in bone mineral density only at the cranial zone of the acetab ulum. The stem of the Mueller prosthesis induced bone mass reduction i n the lesser trochanter area and in the distal lateral fixation cortex . The Zweymueller stem produced significant bone resorption in the are a of the lesser trochanter, and in the medial and lateral distal corte x of the femur. The Mueller and Zweymueller stems induced bone mass in crease in the greater trochanter area. These findings were unaffected by the age of the patients. Further improvement in densitometry techno logy may be of major clinical relevance for early detection of aseptic loosening in total hip arthroplasty.