Migration of polyethylene particles around stable implants in an animal model

The aim of this study was to test the hypothesis that a tight seal between bone and implant will eliminate the avenue of particle migration around sta ble implants. Three types of implants were used in rabbits (polished press- fit Ti-6Al-4V or plasma-sprayed hydroxyapatite [HA]coated Ti-6Al-4V) or dou ghy stage polymethyl methacrylate (PMMA). Implants were placed in the condy lar notch. Each animal received an intra-articular injection of high densit y polyethylene (PE) particles (10(8) in 0.4 mt; mean size 4.7 mu m) at 4 an d 6 weeks postoperatively. Eight weeks postoperatively, peri-implant tissue s were examined for PE particles and osteolysis. In all cases, intracellula r PE particles were seen at the bone-implant interface and within marrow. N o osteolysis was observed. Bone apposition was determined by computerized i mage analysis. There was no significant difference in the percentage of bon e apposition (+/- SD) among the three groups of implants: Ti-6Al-4V (68% +/ - 19%), HA-coated Ti-6Al-4V (70% +/- 10%), and PMMA (59% +/- 12%). These re sults indicate that a polished Ti-6Al-4V surface is as effective as PMMA or HA coating in Limiting migration of PE particles around stable osseointegr ated implants in rabbits.