Femoral bone loss following hip replacement. A comparative study.

Fifty femoral stems of 5 different types were compared with respect to bone retention in the proximal femur at least 3 years after implantation. Dual energy x-ray absorptiometry scans were used to compare bone mineral density in the medial neck of the replaced hip with that of the other hip where surgery had not been performed. Bone mineral density declined on average of 57% with the cemented straight stem Mueller prosthesis and 34% for the uncemented Anatomic Medullary Locking prosthesis. For the cemented Harris Precoat prosthesis, the decline in bone mineral density was 43%. Two uncemented implants with horizontal platform-type collars showed an average decline in bone mineral density of 8% and 14%. Clinically, all the stems functioned well, and excellent implant insertion technique had been used. The decline in bone mineral density was evident on plain radiographs. The decrease in bone mineral density paralleled the known decrease in the medial neck strain. This study suggests that more proximal bone will be maintained by implants that load the proximal femur in as physiologic a fashion as possible.