It is a fact that implants containing a metal-metal bearing result in higher metal ion levels in your body. To a lesser extent this is true of any metal implant including all total joint replacements , even those with ceramic or plastic bearings. There is speculation put forth primarily by proponents of bearing surfaces other than metal-on-metal that elevated levels of metal irons are harmful. There is no credible evidence that this is actually the case. Cobalt and chromium ions are native to your body and are commonly taken as supplements in most multivitamin preparations. Some people also take additional mineral supplements with the belief that there is an added effect. Polyethylene and ceramic are completely foreign to our body. Multiple studies have shown that they are found throughout the body in the lymph system as well as in the liver. One could certainly speculate about harmful effects of these materials. The truth is that there is no credible evidence that any of these foreign particles cause long term problems in our bodies. Of course , we would prefer to have no foreign particles present if we had a choice. The best long term study available on metal-metal bearings and possible cancer risks is by the Dr.Visuri published in the journal Clinical Orthopedics and Related Research in 1994. It indicates no increased cancer risk with metal-metal implants in 450 patients over 15 years.