[Transmission electron microscopy image of wear particles of joint endoprostheses and ultrastructural cell changes]

Wear particles from joint endoprostheses vary considerably in size, and may be detectable in tissue only by electron microscopy. Wear debris plays a central role in the non-infectious late loosening of prostheses, and it has been estimated that the submicron particles induce increased liberation of mediators of osteolysis by activated macrophages. From the types of prostheses currently in use, bone cement and polyethylene particles greatly predominate over metallic and ceramic particles. Since it had formerly not been possible to reliably identify wear particles in the transmission electron microscopy, and descriptions of them in the literature varied considerably, we analysed ultrathin sections obtained from periprosthetic tissue containing wear particles previously identified by laser microprobe mass analysis. Using this method, it proved possible to classify almost all the wear particles detected in the electron microscope, to determine their size range and to represent the cellular alterations caused by them.