Effect of particles and interface conditions on fibrous tissue interposition between bone and implant. A particle challenge model in rabbit

Interposed fibrous tissue at bone-implant interfaces was quantitatively mea sured in the presence or absence of polyethylene (PE) or alumina particles. Three different conditions of the interface were designed by implanting a pre-polymerized polymethylmethacrylate (PMMA) plug (plug group), a doughy P MMA (injection group) and a hydroxyapatite (HA) plug (HA group) in the hole drilled at the intercondylar notch of rabbit knees. PE (170 +/- 18 mu m) o r alumina particles (88 +/- 26 mu m) were repeatedly administered into the knee joints at one month intervals (six times). All animals were sacrificed seven months after the implantation. The bone-implant interface was histom orphometrically examined using undecalcified ground sections. In the plug g roup, the PE particles significantly increased the extent of the interposed fibrous tissue (p < 0.05), while the alumina particles showed no effect. I n contrast, both particles showed no significant effects in the injection a nd the HA groups. These results indicate that both particle characteristics and conditions of the bone-implant interface affected particle-induced fib rous tissue interposition. The loose PMMA plug with PE particles induced th e greatest amount of fibrous tissue interposition. (C) 2000 Kluwer Academic Publishers.