Severe Metallosis Owing to Intraprosthetic Dislocation in a Failed Dual-mobility Cup Primary Total Hip Arthroplasty

We report a case of extensive metallosis owing to an intraprosthetic dislocation of a dual-mobility cup after a primary total hip arthroplasty. A 70-year-old man was referred to us from another center with a painful right hip 3 years after the arthroplasty. Initial investigations were suspicious of osteolysis secondary to metallosis with the characteristic "bubble sign" visualized on plain radiographs. At the revision procedure, widespread black staining of soft tissues and bone was noted. The polyethylene liner had dislodged leading to erosion of the metal socket by the prosthetic head. Histopathology examination of periprosthetic tissue confirmed metallosis. To our knowledge, this is the first reported case of severe metallosis owing to a known complication of dual-mobility sockets.