Metal-on-metal total hip arthroplasty.

Although metal-on-metal total hip arthroplasty (MOM THA) has been used for over 3 decades, substantial improvements in manufacturing and design have led to improved durability with modern implants. Reported advantages of the use of MOM THA include very low wear and subsequent osteolysis, increased range of motion to impingement secondary to the availability of larger diameter femoral heads, and the potential to monitor implant performance by serial assessment of metal ion levels. Clinical results of both first-generation and second-generation MOM THA have revealed good survivorship and a low incidence of osteolysis. Although the advantages of low wear and increased range of motion have made MOM THA an attractive bearing surface option, more widespread use of MOM bearing surfaces has been tempered with concern for increased metal ion levels and hypersensitivity reactions.