Metal-on-metal hip implants: Progress and problems

Abstract

Once perceived as the future of hip arthroplasty, metal-on-metal (MoM) prostheses have since infamously fallen out of favor. The in vitro advantages of MoM implants, which included improved wear properties, reduced osteolysis, and allowed for the use of larger femoral heads to improve stability, have since been far outweighed by the local and systemic reactions associated with metal-on-metal implants. These adverse reactions stem from local release of chromium and cobalt ions, which result in immune responses locally and the formation of effusions and large solid masses known as pseudotumors or systemic effects on various organ systems. With over 1 million MoM prostheses in circulation worldwide, the revision burden of these devices is expected to increase, and a thorough understanding of the clinical manifestations of adverse reactions and revision strategies is essential for revision arthroplasty surgeons.