The bubble sign: a new radiographic sign in total hip arthroplasty.

Abstract

The production of metallic debris from the wear of nonbearing surfaces of a total hip arthroplasty is encountered frequently. We describe a case of extreme generation of metallic debris that resulted in the radiographic outlining of the joint cavity. A 71-year-old woman with a total hip arthroplasty experienced dislodgment of the polyethylene liner from its acetabular shell, resulting in metal-on-metal articulation of the femoral head and the cup. This articulation created severe metallosis that could be seen on preoperative radiographs, producing the described bubble sign. At the time of revision surgery, copious metallic debris was seen macroscopically. This newly described radiographic sign should alert the arthroplasty surgeon to the extent of metallic wear.