Management of painful metal-on-metal hip replacement: current evidence of diagnosis and treatment

The evolution of metal-on-metal (MoM) total hip replacement exemplifies the tension between biomaterial innovation and long-term patient safety, highlighting the critical role of robust post-market surveillance. First-generation MoM implants, introduced in the 1960s, were designed to mitigate polyethylene wear but exhibited inconsistent fixation, variable tribological properties, and poorly characterized local tissue reactions, ultimately resulting in their decline. A resurgence of interest in the 1990s, driven by advances in metallurgy and precision engineering, promoted large-diameter femoral heads to enhance stability and reduce dislocation risk, leading to widespread use, particularly among young and active patients. However, registry data and multicentre analyses soon revealed inferior survivorship compared with metal-on-polyethylene and ceramic alternatives, primarily due to adverse reactions to metal debris. These encompass a spectrum of local tissue responses – including pseudotumour formation, aseptic lymphocytic vasculitis–associated lesions, and soft-tissue necrosis – often complicating both diagnosis and surgical management. Although concerns regarding systemic cobalt and chromium toxicity have been raised, large-scale cohort studies have not demonstrated population-level risks, underscoring the importance of individualized monitoring. Current diagnostic algorithms integrate clinical evaluation, serum ion measurements, and cross-sectional imaging such as metal artifact reduction sequence magnetic resonance imaging (MARS MRI), while surgical management emphasizes comprehensive debridement and revision to biologically favorable bearings, notably ceramic-on-highly cross-linked polyethylene. The decline of MoM implants has reshaped contemporary replacement practice by reinforcing preclinical testing standards, international registry collaboration, and vigilance in the clinical adoption of novel biomaterials.