Fig. 1

A Schematic drawing of an implant and tube (blue arrowheads) inserted into a rabbit tibia. The tibia was drilled bicortically, the tube was inserted into the upper cortical bone, and the implant was inserted through the tube into the lower cortical bone. The gap (pink area) between the implant and the tube allowed blood flow from the lower cortical bone. Numbers indicate dimensions in millimetres. B Two implants were inserted into each tibia. An implant (yellow arrowhead) is shown on the left without a Ti tube, while on the right, a Ti tube (black arrowheads) is shown around the implant. Scale bar = 5 mm. C Schematic diagram comparing the response of bone to implants in Ti tubes with that to Ti tubes alone. The experimental groups were arranged in a 2 × 2 Latin square. D Schematic diagram of the comparison of the response of bone to implants with or without Ti tubes. The groups were arranged in a 2 × 2 Latin square. E Evaluation of the effects of blood-borne substances on bone formation. A split-plot design was used for this experiment. RhBMP-2 was used in the Ti tube + implant + rhBMP-2 group to represent cytokines derived from existing bone. PRP from each rabbit was applied to the Ti tube + implant + PRP group to test the effects of blood-borne factors on bone formation. R right tibia, L left tibia, Ti titanium, rhBMP-2 recombinant human bone morphogenetic protein-2, PRP platelet-rich plasma