An interesting observation about my original THR: Because I have a ceramic-on-metal prosthesis in the THR that has become loose, I was tested for metal ion levels -- cobalt, chromium, aluminum, and titanium. All metal levels were measured as low and in the case of titanium, undetectable. That means that metallosis did not cause the loosening. The original concept of using the ceramic and metal combo 10 years ago was that it would wear as well or better than MOM or ceramic-on-plastic, but shed an order of magnitude fewer metal ions into surrounding tissue. That concept seems to be holding true in my case. Too bad the prosthesis loosened for other reasons.