The purpose of this study was to evaluate the clinical and radiographic results of the primary total hip arthroplasty with uncemented AML (anatomic medullary locking) hip prosthesis for avascular necrosis of the femoral head.

Forty-nine patients (65 hips) had a primary total hip arthroplasty between May 1987 and March 1992. Average follow-up was 9.6 years. The mean age of the patients was 46.9 years. The canal fit of the stem at the proximal canal and isthmus level was obtained from postoperative radiograph. Components stability, stress shielding, polyethylene wear and periprosthetic osteolysis were evaluated from serial follow up radiographs.

The average Harris Hip Score was to 92.1 points at the last follow-up. Twelve hips (18.5%) had a good fit at both the proximal canal and isthmus level and 15 hips (23.1%) had a poor fit at both levels. All twelve hips that had a good fit at both the proximal canal and isthmus level had bone ingrowth. Thirty-three hips (56.3%) had femoral osteolysis. Twenty-one hips (32.3%) had acetabular osteolysis. Fourteen hips had acetabular and femoral osteolysis. The overall rate of revision was 16.7% (11 hips). Ten cases were revised because of excessive polyethylene wear and osteolysis. Revision of the femoral component for aseptic loosening was only one case.

The result of our study suggests that total hip arthroplasty using the AML hip prosthesis with an ACS (acetabular cup system) polyethylene liner should be monitored closely for catastrophic wear of the polyethylene liner. We recommend early revision arthroplasty in case of excessive wear of the ACS polyethylene liner.