Biological response to wear debris generated in carbon based composites as potential bearing surfaces for artificial hip joints.

UHMWPE wear particles have been implicated in osteolysis, implant loosening, and long-term failure of total hip arthroplasties in vivo. This study examined four carbon-based composite materials as alternatives for UHMWPE in joint bearings. These materials were HMU-CVD, SMS-CVD, P25-CVD, and CFR-PEEK. New bearing materials should satisfy certain criteria: they should have good wear properties that at least match UHMWPE, and produce wear particles with low levels of biological activity. Of the four materials tested in multidirectional pin-on-plate tribological tests, SMS-CVD, P25-CVD, and CFR-PEEK showed lower volumetric wear factors than UHMWPE. P25-CVD had the lowest wear factor of 0.54 +/- 0.34 x 10(-7) mm(3)/Nm. Analysis of P25-CVD wear particles by transmission electron microscopy showed that the debris was very small, with the vast majority of particles being under 100 nm in size, which was similar in size to metal wear particles. The P25-CVD particles were isolated and cultured with L929 fibroblasts and U937 monocytic cells to assess their effect on cell viability. P25-CVD particles were significantly less cytotoxic (p < 0.01, ANOVA) to both cell types than CoCr metal wear particles. This work suggests that carbon-carbon composite materials may have potential for use in total hip replacement bearings. Of the materials tested P25-CVD had the lowest wear factor, and produced very small wear debris that had minimal cytotoxic effect on L929 and U937 cells in vitro. Therefore carbon-carbon composites, such as P25-CVD, may be important in the development of next-generation implants with lower wear rates and reduced cytotoxic potential. Copyright 2003 Wiley Periodicals, Inc.