Use of large-head metal-on-metal (MoM) bearing surfaces in total hip arthroplasty (THA) has created new and unique modes of failure for this type of articulation. These unique modes are in addition to the traditional modes of failure seen in conventional THA, which include instability, osteolysis, infection, iliopsoas tendinitis, aseptic loosening, and periprosthetic fracture. Ion levels and cross-sectional imaging are helpful when evaluating a MoM patient in the identification of adverse local tissue reactions. Unique modes of failure in MoM THA include tissue necrosis, metallosis-induced osteolysis, skin hypersensitivity reactions, and rarely systemic cobaltism. This article outlines the evaluation and treatment of modes of failure in MoM THA.
Key points
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When evaluating any patient with a painful total hip arthroplasty, a systematic approach is mandatory regardless of bearing type.
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In metal-on-metal hips, bearing malfunction can occur without the presence of symptoms.
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Metal corrosion and adverse local tissue reaction may occur because of problems with the articulation or any modular junction of the implant.
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Ion levels and cross-sectional imaging techniques (MRI, ultrasound) are beneficial in evaluating a metal-on-metal THA.
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Stratifying the MoM patient into low, moderate, or high risk can help the diagnostic and treatment algorithm.
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