Comparative investigations of regional lymph nodes and pseudocapsules after implantation of joint endoprostheses.

Morphological alterations of pseudocapsules and regional lymph nodes were studied by light and electron microscopy and by Laser Microprobe Mass Analysis (LAMMA). The tissue specimens originated from 32 autopsies of patients with hip joint endoprostheses (time in situ: 3 weeks - 15 years, average: 6 years) and two cases with knee joint endoprostheses. Characteristic changes of the lymph nodes as well as of the pseudocapsules consisted in an infiltration by monocytic histiocytes with various intracytoplasmatic wear particles. The foreign material consisted mainly of the components of bone cement: polymethylmethacrylate (PMMA) and zirconium oxide, to a lesser degree of polyethylene from the articulating surfaces. In two cases with special types of prostheses ceramic or metallic wear particles could be detected too. Most of the wear particles were found in the ipsilateral parailiac lymph nodes and in the paraaortic lymph nodes bilaterally. In the cases with mostly stable prostheses small amounts of wear particles were found in the lymph nodes as soon as 1.5 years after insertion and their number increased in all groups of lymph nodes after longer duration of the implant. The phagocytosing histiocytes showed degenerative changes. At present it is not clear, if the cell damage is caused by the amount of phagocytosed wear particles alone or if specific toxic effects of certain substances are of importance.