I’ve blogged before on known knee replacement wear particles as a significant complication of replacement. Wear particles are microscopic pieces of metal, ceramic, or plastic that break off of from the knee replacement or hip prosthesis and irritate the local tissues and/or enter the bloodstream. In addition, at least one large study has associated a knee replacement with more serious adverse health consequences. These issues are more significant now that new partial or resurfacing knee replacements are becoming popular, as these new devices need to be metal to withstand the additional stresses placed on smaller parts. The research concerning what happens to your body with all that metal seems to point in the same direction, patients who receive knee replacements have higher levels of various metals in their blood stream. For example, researchers from Austria recently demonstrated that the size of the prosthesis was directly correlated with the blood concentration of metal ions (the larger the knee replacement device, the more metal ions that were found in the bloodstream). One group in Italy actually found more of these metal ions in knee replacement patients who had a loose prosthesis. Why? In some patients the knee replacement device may not be seated tightly or may not be bind to the surrounding bone, which would cause more wear between the bone and the metal prosthesis thus leading to more metal particles. Another group in Germany recently found that metal ions in the blood increased precipitously after a knee prosthesis was implanted. A different German group also found higher serum levels of chromium and cobalt in knee replacement patients than patients without knee replacements. The upshot of all of this research? While the trend toward computer assisted mini-knee replacements, partial knee replacements, or knee resurfacing may represent smaller surgeries, the increased use of metal in these devices likely means more of these metal ions. There seems to be no getting around the fact that metal knee replacement devices produce wear particles that lead to metal ions in the blood. While we don’t know the long-term implications of these higher serum metal concentrations in knee replacement patients, I’m guessing it’s not a good thing.