Histiocyte reaction in rabbit femurs to UHMWPE, metal, and ceramic particles in different sizes.

To assess the histologic reaction caused by biomaterial particles in different sizes around the bone-implant interface, we examined ultra-high molecular weight polyethylene (UHMWPE, average diameter of 11 microm), UHMWPE (99 microm), cobalt-chromium alloy (Co-Cr, 3.9 microm), stainless steel (SUS316L, 3.9 microm), alumina ceramics (3.9 microm), titanium alloy (Ti, 3.5 microm), Co-Cr (0.03 microm), and Ti (0.03 microm). After the longitudinal groove on a polymethylmethacrylate plug was filled with one type of the particles, the plug was inserted into the medullar canal of the distal end of rabbit femurs, and tissue block was resected 4 and 12 weeks after the insertion. Histiocytes were markedly accumulated around the particles of UHMWPE (11 microm), Co-Cr (3.9 microm), SUS316L (3.9 microm), Co-Cr (0.03 microm), and titanium alloy (0.03 microm). Around the UHMWPE particles (99 microm), a slight histiocytic reaction and bone formation were observed. Particles of alumina ceramics (3.9 microm) and titanium alloy (3.5 microm) which were in phagocytosable sizes also had few histiocytic reactions. Statistically, the material difference was more strongly related to the histiocyte reaction than to the particle size and calculated total surface area of particles. Our findings demonstrate that particles of different biomaterials and in different sizes induce different foreign-body histological reactions.