Tissue reaction after implantation of sintered porous hydroxyapatite in the distal metaphysis or epiphysis of the femur of rabbits

The present investigator implanted sintered porous hydroxyapatite rod (phi 3 mm x 10 mm) in the distal metaphysis or epiphysis of the right femur of 40 Japanese white rabbits and studied tissue reaction around hydroxyapatite (abbreviated as HAp) with radiograms and microphotographs. As control, stainless-molybdenum alloyed (abbreviated as SMO) rod was used. In the groups with metaphyseal implantation of HAp or SMO, the distance between the center of implant and the distal femoral epiphyseal line increased during 12 weeks after operation. New bone was directly bonded to implanted material only after implantation of HAp. Ratio of length of HAp bone interface and length of HAp circumference was greater in the groups with implantation in the metaphysis 2 weeks after operation than those in the epiphysis. On the other hand, it was greater in groups with implantation in the epiphysis than those in the metaphysis 12 weeks after operation. In the groups with metaphyseal implantation of HAp, the ratio in groups 2 weeks after operation was greater than that in 12 weeks and there was a firm interrelationship between the ratio and the distance between the center of implant and the distal femoral epiphyseal line.