Abstract
Dual-mobility bearings are being increasingly utilized in total hip arthroplasty. Contemporary modular designs often feature inner cobalt-chromium liners that are seated in outer titanium acetabular shells. However, mating of these 2 dissimilar metals may lead to complications. We present a case report of a patient who was found to have osteolysis and acetabular protrusio due to an adverse local tissue reaction from corrosion between a cobalt-chromium liner and titanium acetabular shell that appeared to be well-seated clinically and radiographically. This case suggests that implant failure and associated adverse local tissue reactions may occur even in seemingly well-seated modular dual-mobility implants.