Angiogenesis and new bone formation in novel unidirectional porous beta-tricalcium phosphate: a histological study

Affinos (R) (Kuraray Co., Ltd., Tokyo, Japan) is a beta-tricalcium phosphate (TCP) artificial bone comprising a novel unidirectional porous structure with 57% porosity. This study examined angiogenesis and bone formation over time with unidirectional porous beta-TCP (UDPTCP). Ten Japanese White rabbits were used in this study. A 5x8-mm rectangular area of periosteum was resected, followed by preparation of a cortical bone defect using a high-speed bur. UDPTCP was embedded in the defect in the direction of the pores, parallel to the axis of the tibia. Tissue samples were harvested at 2 weeks (n=3) and 6 weeks (n=7) after implantation. Just before euthanasia, the vasculature of the lower limb was perfused with saline from the femoral artery and filled with MICROFIL (R) (Flow Tech, Inc., Carver, MA) to create a vascular cast. The tibia was cut longitudinally at the center of the material. Decalcified sagittal sections treated with hematoxylin and eosin staining, undecalcified sagittal sections treated with Villanueva-Goldner staining, and axial unstained sections were used for histological evaluation. The lengths of the largest vessels and newly formed bone at the material border were measured in a sagittal section. Both lengths were significantly larger at 6 weeks than at 2 weeks. In the axial sections at 2 weeks, newly formed vessels filled with blue dye grew along the pores of the UDPTCP. Mature bone tissue with a lamellar structure was observed at 6 weeks. Our histological findings demonstrated that angiogenesis and bone formation occur over time in UDPTCP.