OSTEOLYSIS MODEL WITH CONTINUOUS-INFUSION OF POLYETHYLENE PARTICLES

Several in vivo studies have investigated bone to implant interface ti ssues after a single injection of wear particles into animal joints. H owever, in the clinical setting, wear debris are generated continuousl y rather than periodically. Histomorphologic findings and the gene exp ression of bone resorbing cytokines in reactive membranes were analyze d in response to continuous infusion of polyethylene particles with an osmotic pump, In this model, it took only 6 weeks for proliferative f ibrous tissue to form, which penetrated the subchondral bone to commun icate with the bone marrow. In addition, tartrate resistant acid phosp hatase positive osteoclastlike cells were found in empty lacunae, Acco rding to the analysis of gene expression, only tumor necrosis factor a lpha messenger ribonucleic acid was expressed specifically in the fibr ous tissue of rats infused with particles from 4 weeks after surgery. This finding suggests that tumor necrosis factor alpha may play a majo r role in fibrous tissue formation and osteoclastic bone resorption ca used by wear debris around implants, In addition, this in vivo model s eems useful for investigating the mechanism of membrane formation and associated bone resorption around implants in a situation more similar to human prostheses than in conventional models.