Differential healing response of bone adjacent to porous implants coated with hydroxyapatite and 45S5 bioactive glass

This study tested the hypothesis that the rate and the extent of bone forma tion adjacent to porous, coated Ti-6Al-4V implants are differentially affec ted by the type of bioactive ceramic coating. Forty-eight rabbits received cylindrical Ti-6Al-4V intramedullary distal femoral implants bilaterally. I mplants for the right limbs were coated with 45S5 Bioglass (R) (45S5). Impl ants used for the left limbs either were coated with tricalcium phosphate/h ydroxyapatite (HA) or were left uncoated as controls (CTL). The 45S5-coated implants histologically and biomechanically were compared to HA-coated and CTL implants at 4, 8, 12, and 16 weeks. After 12 and 16 weeks of healing, more bone and thicker trabeculae were measured histomorphometrically within the im-plant pores for the 45S5-coated implants compared to the HA-coated and CTL implants (p < 0.05). With time the HA-coated and CTL groups exhibit ed a significant decline in percent of bone and of trabecular thickness (p < 0.05) while the 45S5-coated implants did not. Biomechanical analyses indi cated similar shear strengths for all treatment groups. in summary, 45S5-co ated implants exhibited greater bone ingrowth compared to HA-coated and CTL implants, and they maintained their mechanical integrity over time. (C) 20 01 John Wiley & Sons, Inc. J Biomed Mater Res 55: 603-612, 2001.