The Design,Fabrication And Clinical Application Of Metal On Metal Surface Replacement Hip Prosthesis For Avascular Necrosis Of The Femoral Head

Objective (l)Cases of fracture of femoral neck treated with artificial femoral head replacement were studied retrospectively to measure the acetabular wear by the metallic femoral head. (2) To introduce the methods of design and fabrication of surface arthroplasty prosthesis and operative instruments of hip joint and to present the preliminary clinical application (3) To evaluate the clinical results of resurfacing arthroplasty in the treatment of avascular necrosis of femoral head of the hip using the prosthesis designed by McMinn .(4)To study the pathological changes of the femoral heads suffering from osteonecrosis and osteoarthritis. Methods (l)To measure the acetabular wear with special computer soft ware program for 84 cases of femoral head replacement arthroplasties 1-6 years after the operation and to analyze the radiological acetabular wear with the clinical results. (2) To introduce the method of design and fabrication of the hip resurfacing prosthesisand operative instruments,and to present the method of operation and the early clinical results in 7 patients 8 hips 2-14 months after operation. (3) Twenty-seven hips in 21 patients with femoral head osteonecrosis were treated with McMinn's surface replacement arthroplasty and were reviewed 1-6 years after the operation. (4) Specimens of the 10 femoral heads from patients suffering from osteonecrosis and osteoarthritis were studied histologically to observe the pathological changes of avascular necrosis of bone and the apoptosis of cartilage cells.Results (l)Hip pain occurred in 78% of 84 cases on an average of 3.8 years after the femoral head replacements and the factors influencing the clinical results were analyzed. (2)The newly designed surface replacement arthroplasty prosthesis were used in 7 patients 8 hips with early satisfactory clinical results. According to the method proposed by Merle d'Aubigne to assess the results of treatment,the average pre-operative score of 7 was increased to 15 post-operation. (3)The average Merle d'Aubigne score of patients with femoral headosteonecrosis after McMinn hip resurfacing operation was improved from 8 to 16. (4) Different histological changes were found in the femoral heads suffering from avascular necrosis and osteoarthritis although there were changes compatible with necrosis of bone in bothkinds of patients. There may be different mechanisms in the control of chondrocyte apoptosis between cases of avascular necrosis caused by steroids and other etiological factors.Conclusions We propose that total hip arthroplasty may be superior to femoral head replacement for patients with femoral neck fracture both in relatively young patients and in old aged. Hip resurfacing arthoplasty using metal on metal components offers a feasible treatment alternative for the relatively young patient with osteonecrosis of femoral head and osteoarthritis. The satisfactory mid-term results from the contemporary metal on metal articulation investigated in this study are encouraging and warrant continued study. Perhaps there is a different mechanisms in the control of chondrocyte apoptosis among cases of osteonecrosis caused by different causes. The pathogenesis of osteonecrosis in patients with a history of steriods treatment may not be the same as those caused by alcoholism.