Evaluation of cytotoxicity of UHMWPE wear debris

We established a novel method to investigate the phagocytosis of ultra high molecular weight polyethylene using pri- mary macrophage cells by an inverted cell culture method. Abundant wear debris derived from implant materials are generated in aseptic loosening and are deposited in periprosthetic tissues in which they are phagocytised by mono- and multi-nucleated macrophage like cells. Ultra-high-molecular-weight-polyethylene wear debris generated from different sources namely, from laboratory test wear machine, in vivo methods and from knee and hip simulator were mainly used in this investigation. The cytotoxicity index of the different UHMWPE particles obtained from various sources were compared with that of the PE beads and the control without particles by Alamar Blue and Neutral Red assays. The results showed that the cytotoxicity index was significantly lower for the wear debris from the in vivo experiments than that for other particles. SEM analysis were also done to understand the morphology of the wear debris and polyethylene beads and to confirm the phagocytosis process. The mean diameter of the wear debris obtained from the in vivo experiments as estimated from the imaging analysis of the SEM pho- tographs was found to be the least. The inverted cell culture method may be regarded as one of the good methods to study the phagocytosis of UHMWPE by macrophage cells.