Implantation of Tetrapod-Shaped Granular Artificial Bones or β-Tricalcium Phosphate Granules in a Canine Large Bone-Defect Model

We investigated biodegradability and new bone formation after implantation of tetrapod-shaped granular artificial bone (Tetrabone (R)) or beta-tricalcium phosphate granules (beta-TCP) in experimental critical-size defects in dogs, which were created through medial and lateral femoral condyles. The defect was packed with Tetrabone (R) (Tetrabone group) or beta-TCP (beta-TCP group) or received no implant (control group). Computed tomography (CT) was performed at 0, 4 and 8 weeks after implantation. Micro-CT and histological analysis were conducted to measure the non-osseous tissue rate and the area and distribution of new bone tissue in the defect at 8 weeks after implantation. On CT, beta-TCP was gradually resorbed, while Tetrabone (R) showed minimal resorption at 8 weeks after implantation. On micro-CT, non-osseous tissue rate of the control group was significantly higher compared with the beta-TCP and Tetrabone groups (P<0.01), and that of the beta-TCP group was significantly higher compared with the Tetrabone group (P<0.05). On histology, area of new bone tissue of the beta-TCP group was significantly greater than those of the Tetrabone and control groups (P<0.05), and new bone distribution of the Tetrabone group was significantly greater than those of the beta-TCP and control groups (P<0.05). These results indicate differences in biodegradability and connectivity of intergranule pore structure between study samples. In conclusion, Tetrabone (R) may be superior for the repair of large bone defects in dogs.