OSSEOINTEGRATION OF SURFACE-BLASTED IMPLANTS MADE OF TITANIUM-ALLOY AND COBALT-CHROMIUM ALLOY IN A RABBIT INTRAMEDULLARY MODEL

The purpose of this study was to compare the osseointegration of surfa ce-blasted Ti6Al4V and CoCr implants in vivo. Ti6Al4V and CoCr rods bl asted with 710 mu m Al2O3 particles were bilaterally press-fit into th e medullary space of distal femora of 24 rabbits. Evaluation was made radiographically, histologically, histomorphometrically (3, 6, and 12 weeks after implantation), and mechanically (12 weeks). Both Ti6Al4V a nd CoCr implants demonstrated good biocompatibility radiographically a nd histologically. Toluidine blue-stained sections revealed an osteoco nductive effect of the blasted surface, and fluorochrome labeling anal ysis showed active bone formation at the bone-implant interface at as late as 12 weeks for both specimens. CoCr showed significantly lower i nterfacial shear strength than Ti6Al4V although the bone contact area with the implant surface was comparable and no intervening soft tissue at the bone-implant interface could be seen for either implant by sca nning electron microscopy backscatter analysis. Unmineralized tissue ( cartilage and osteoid) was observed more frequently on the CoCr surfac e than on the TiGAl4V surface. These data show less osseointegration o f CoCr implants with this blasted surface for this short period, possi bly due to a slight difference in surface roughness and some negative effects of CoCr on bone attachment. (C) 1998 John Wiley & Sons, Inc.