Roentgenographic evaluation of a conical threaded acetabular cup

A radiographic analysis was done of 83 primary hip arthroplasties performed in 70 patients. The arthroplasty consisted of a truncated acetabular cup and a cemented titanium femoral stem. The patients were evaluated at an average of 3.3 years postoperatively (range 2 to 5 years). Using the method of DeLee and Charnley, the acetabulum was divided into three zones. Specific attention was focused on the percentage of fill in the threads of zones 1 and 3 and the measurement of radiolucency in zone 2. Over time, a large percentage of the acetabulae showed both a decrease in bone fill in zone 3 and an increase in radiolucency in zone 2. By the third postoperative year, 16% (11 of 70) of the acetabulae had migrated. Although all the hips had been rated good or excellent on the Charnley hip score, ie, receiving a 5 or better, 11 had migrated and 3 had been revised, indicating an unacceptable failure rate of the acetabular component.