Histological Findings in Six Failed Metal-on-Metal Implants

Although joint replacement surgery to relieve pain due to osteoarthritis is generally a successful operation, adverse local tissue reactions can occur in hip arthroplasty in patients who receive metal-on-metal (MoM) implants and lead to early failure. This has led to revisions, lawsuits, and manufacturing recalls. An understanding of the pathological process initiated by metal wear debris is essential in clinical surveillance of cases. We retrospectively reviewed six cases of patients who underwent MoM hip arthroplasties and required early revision. Tissue removed at revision surgery was analyzed histologically by two independent reviewers. All six patients (four males, two females) underwent revision hip arthroplasty after early failure. Revision occurred between 18 and 56 months after the index procedure. Four patients received MoM implants from Depuy, one from Stryker, and one from Wright Medical. A consistent array of pathological findings was associated with these failed MoM implants. Beginning with the development of metal debris, a histiocytic response and proliferation occurred with subsequent corrosion product formation. Membranes were formed, many with cellular infiltrates and pseudosynovial linings and often with ulceration and bleeding. The tissue also demonstrated lymphocytosis and perivascular infiltrates with atypical changes of the endothelial lining cells. Our findings document a predictable cascade of harmful local tissue changes initiated by metal debris in failed MoM hip arthroplasties.