Measurement and removal of adherent endotoxin from titanium particles and implant surfaces

Aseptic loosening is thought to be due primarily to osteolysis induced by c ytokines and prostaglandins that are produced in response to implant-derive d wear particles. Because endotoxin has many of the same effects as have be en reported for wear particles, we hypothesized that adherent endotoxin may be responsible for the biological responses induced by wear particles. We demonstrated the presence of significant levels of adherent endotoxin on co mmonly used preparations of titanium particles as well as on titanium and t itanium-alloy implant surfaces. In contrast, supernatants obtained by centr ifugation of particle suspensions contained approximately 1% as much endoto xin as did the particles. Therefore, it is erroneous to assume that particl es do not contain endotoxin on the basis of data that it cannot be detected in their supernatants or filtrates. These results emphasize the importance of considering the potential role of adherent endotoxin when examining the in vitro effects of wear particles and the in vivo performance of orthopae dic implants. We also developed a protocol that removed more than 99.94% of the adherent endotoxin from the titanium particles without detectably affe cting their size or shape. The removal of adherent endotoxin will allow com parison of the biological responses induced by particles with or without ad herent endotoxin.