[Histological and mechanical observations of interconnection between sintered porous hydroxyapatite and Achilles...

Sintered porous hydroxyapatite blocks (3 x 3 x 4 and 5 x 5 x 5) were implanted into the calcaneal tendons of 64 Wistar rats to observe tissue reaction and interconnection. Histological observations and measurements of mechanical strength of the interconnection were performed at 1 to 24 weeks after the implantation surgery. The implants were found to be surrounded by connective tissue consisting of small, round cells which infiltrated into micropores of the hydroxyapatite blocks. Neither calcifications nor inflammatory reactions were observed. The mechanical strength at the interconnection increased significantly from 1 week to 8 weeks after the implantation, which then reached the peak of 1.3 +/- 0.3 kg/cm2 at 8 weeks.