JOINT MOTION OF BIPOLAR FEMORAL PROSTHESES

From 1982 to 1991, 251 bipolar hip arthroplasties were performed on 21 3 patients. Among them, 117 bipolar femoral prostheses were randomly s elected to examine the behavior of abduction motion under weight-beari ng loads. Roentgenographic motion study was performed at an average of 46.5 months after surgery (range, 2-110 months). One hundred one pros theses used in dysplastic osteoarthritic, rheumatoid, and revised fail ed total hip arthroplasy patients moved 18.2% at the outer bearing and 81.8% at the inner bearing, while 16 prostheses used in femoral neck fracture and osteonecrosis of the femoral head patients moved 49.7% at the inner bearing and 50.3% at the outer bearing. There was a statist ical difference in the motion pattern between the two groups. The abdu ction motion behavior of the bipolar femoral prostheses was not affect ed by the length of the follow-up period, the diameter of the outer he ads, or the position of the prostheses on immediate postoperative roen tgenograms.