Early failure with massive metallosis and posteromedial wear following atraumatic anterior cruciate ligament rupture after medial unicompartmental knee arthroplasty

Severe metallosis following medial unicompartmental knee arthroplasty (UKA) is relatively rare. It is usually due to long-standing wear of the polyethylene component, resulting in frictional wear between the femoral and tibial metallic components. Biomechanical and cadaveric studies have shown the effects of anterior cruciate ligament (ACL) transection following medial UKA. We describe a case of a 58-year-old male who developed attritional rupture of the ACL 16 months following medial UKA leading on to early accelerated failure over the next 8 months. The patient underwent revision to total knee arthroplasty with good outcome. The clinical effect of spontaneous ACL transection on medial UKA causing abnormal posteromedial wear of polyethylene component and tibial tray, massive metallosis, and worsening of mechanical axis can be demonstrated in this case report.