Abstract: Objective To establish a rabbit model of midsagittal sutural distraction osteogenesis for future experiments, to evaluate this rabbit model's feasibility and to explore the role of rhBMP-2 in subperiosteum to distraction osteogenesis. Methods Nickel-titanium open coil springs (50 g) and 3 mm long miniscrew implants (MSIs) were used for skeletal anchorage to establish a rabbit model of midsagittal sutural distraction osteogenesis. Fourteen New Zealand white rabbits, 11 weeks, were randomized into experimental group (traction+rhBMP-2, n=7) and control group (simple traction, n=7). Controlled extraoral forces were used to expand rabbit midsagittal sutures ( n=14) for 29 days, X ray and Micro-CT were used to evaluate the open joint and measure the distance between MSI of each group on day 0, 5, 11, 17, 23, and 29;Tetracycline was injected on day 7, 27 and calcein was injected on day 17, as a biomarker for fluorescence tissue section postoperatively. The feasibility of this sagittal suture distraction osteogenesis rabbit model was explored by observing the tolerance of the rabbit distraction osteogenesis system, comparing each joint open distance and the sagittal suture tissue morphology. Results The total successful rate of the rabbit model of midsagittal sutural distraction osteogenesis was 86%. Controlled extraoral forces were successfully used on the sutural distraction model. The open distance of sagittal suture (D29) in control group was greater than in experimental group. The open distance of sagittal suture was increased with the duration of traction in the two groups, but the sutural separation rate presented a trend of fast before they are slow. New bone formation was observed in both experimental group and control group by histomorphormetric analyses, which demonstrated that the distraction osteogenesis model can not only distract the suture effectively, but also induce the osteogenesis between the suture. But the new bone formation in experimental group was faster. Conclusion The rabbit model of midsagittal sutural distraction osteogenesis can be rapidly established by nickel-titanium open coil springs and 3 mm long miniscrew implants (MSI). Local application of rhBMP-2 can promote the osteogenesis but lead to the suture fusion during the process of distraction.

Key words: Animal model, Miniscrew implants, Recombinant human bone morphogenetic protein-2, Suture distraction osteogenesis