Osteogenic response of the rabbit femur to a hydroxyapatite thermal decomposition product–fibrin glue mixture

The effect of fibrin glue on the hardening process of hydroxyapatite thermal decomposition product (HATDP) was investigated in vitro. To study, in vivo, the effect of fibrin glue on osteogenesis, a mixture of HATDP with fibrin glue was injected into the left femurs of 20 rabbits, and HATDP without fibrin glue was injected into the right femurs. New bone formation was observed in the area of direct contact with the fibrin-containing mixture in the metaphysis at 2 weeks after injection in two of four femurs, but not in the fibrin-free group. At 4 weeks after injection, new bone formed a bridge between the mixture and the cortical bone in three of the four specimens. A parameter of osteogenesis (the affinity index) was calculated at 4, 12 and 24 weeks after injection. It was respectively 0.14±0.02, 0.49±0.12 and 0.44±0.05 for the fibrin-containing mixture, and 0.14±0.062, 0.44±0.15 and 0.49±0.04 for the control. A comparable but significant increase in the average affinity index was noted over 12 weeks in both the fibrin-containing and the fibrin-free HATDP. These findings indicate that fibrin glue accelerated the hardening of HATDP but did not inhibit the process of osteogenesis.