Endoprostheses for osteonecrosis of the femoral head. A comparison of four models in young patients.

Eighty-eight hip arthroplasties were carried out in 75 patients, all aged 50 years or less, with osteonecrosis. All the operations were carried out by one surgeon. Four different methods were used: a standard cemented arthroplasty; a cemented THARIES surface replacement; an uncemented surface replacement; a cemented titanium femoral surface hemiarthroplasty. Comparable clinical improvement occurred in all 4 groups initially. Aseptic loosening, with intersurface degradation and osteolytic lesions, was the most common cause of failure in the 3 types which had a polythene bearing. Polyethylene is the major contributor to bone loss around the endoprosthesis and loosening. Fixation of the surface hemiarthroplasty remained intact in every patient and failure was secondary to wear of the acetabular cartilage. We recommend surface hemiarthroplasty as an interim solution for young patients with stage III or early stage IV osteonecrosis because this procedure conserves bone stock, there is little osteolysis and it can easily be revised.