Impact of pore size on the vascularization and osseointegration of ceramic bone substitutes in vivo

The repair of bone defects with biomaterials depends on a sufficient vascularization of the implantation site. We analyzed the effect of pore size on the vascularization and osseointegration of biphasic calcium phosphate particles, which were implanted into critical‐sized cranial defects in Balb/c mice. Dense particles and particles with pore sizes in the ranges 40–70, 70–140, 140–210, and 210–280 μm were tested (n = 6 animals per group). Angiogenesis, vascularization, and leukocyte–endothelium interactions were monitored for 28 days by intravital microscopy. The formation of new bone and the bone–interface contact (BIC) were determined histomorphometrically. Twenty‐eight days after implantation, the functional capillary density was significantly higher with ceramic particles whose pore sizes exceeded 140 μm [140–210 μm: 6.6 (±0.8) mm/mm2; 210–280 μm: 7.3 (±0.6) mm/mm2] than with those whose pore sizes were lesser than 140 μm [40–70 μm: 5.3 (±0.4) mm/mm2; 70–140 μm: 5.6 (±0.3) mm/mm2] or with dense particles [5.7 (±0.8) mm/mm2]. The volume of newly‐formed bone deposited within the implants increased as the pore size increased [40–70 μm: 0.07 (±0.02) mm3; 70–140 μm: 0.10 (±0.06) mm3; 140–210 μm: 0.13 (±0.05) mm3; 210–280 μm: 0.15 (±0.06) mm3]. Similar results were observed for the BIC. The data demonstrates pore size to be a critical parameter governing the dynamic processes of vascularization and osseointegration of bone substitutes. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008