Metal-on-Metal Bearings in Total Hip Arthroplasty.

The demand for total hip arthroplasty is increasing, as are patients' expectations to return to high activity levels. Metal-on-metal bearings are being used in an effort to maximize the longevity of primary hip replacements. Acetabular component inclination has been a recognized aspect of surgical technique for more than 20 years; it now is considered critical, especially in hip resurfacing or implantation of a stem-type device with a larger diameter femoral head and a monoblock acetabular component. It is important to understand the indications for using metal-on-metal bearings as well as the key clinical factors for avoiding early implant failure.