Clinical experience in threaded-in cup acetabuloplasty.

By utilizing torque and compression to gain purchase of the acetabular cup into the bony margin of the acetabulum, the concept of threaded-in acetabular implant is attractive. However, controversies about long term fixation have recently arisen. From July 1985 to June 1989, 37 cases (42 hips) were treated with Mecron hemispheric self-tapering threaded-in acetabular cup. With a minimum postoperative period of 2 years, 29 cases (32 hips) were followed up clinically and roentgenographically for an average of 39 months. Among these THRs, 15 operations (47%) were performed primarily and 17 operations (53%) were performed as revisional arthroplasty. Of the 15 primary THRs, 10 hips were operations for osteonecrosis of the femoral head. The success rate in the primary group was 87%, and 59% in the revisional group. In our experience, the Mecron threaded-in cup has been associated with a relatively high rate of failure. However, the high percentage of revisional surgeries and osteonecrotic cases in this study may be factors determining the poor results.