Radiology of failed surface-replacement total-hip arthroplasty.

The radiographs, arthrograms, and bone scans in 23 patients with surgically confirmed failed total-surface hip replacement were reviewed. Guidelines for evaluation of the acetabular component are identical to those for conventional total arthroplasty. The femoral component of a surface-replacement total hip arthroplasty consists of a metallic cup affixed to a resurfaced femoral head with interposed methyl methacrylate. Because of bone-acrylic interface is obscured by the metallic cup, the radiographic features of loosening are limited to an abnormal alignment of the metallic cup in relation to the femoral neck or a change in the position of the cup in serial radiographs. These signs may be subtle. While the metallic cup may often prevent visualization of underlying isotope activity at the bone-acrylic interface, increased activity at the base of the cup when identified suggests loosening or infection.