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^®) or β-tricalcium phosphate granules (β-TCP) in experimental critical-size defects in dogs, which were created through medial and lateral femoral condyles. The defect was packed with Tetrabone^® (Tetrabone group) or β-TCP (β-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, β-TCP was gradually resorbed, while Tetrabone^® 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 β-TCP and Tetrabone groups (<i>P</i><0.01), and that of the β-TCP group was significantly higher compared with the Tetrabone group (<i>P</i><0.05). On histology, area of new bone tissue of the β-TCP group was significantly greater than those of the Tetrabone and control groups (<i>P</i><0.05), and new bone distribution of the Tetrabone group was significantly greater than those of the β-TCP and control groups (<i>P</i><0.05). These results indicate differences in biodegradability and connectivity of intergranule pore structure between study samples. In conclusion, Tetrabone^® may be superior for the repair of large bone defects in dogs.