Methods: Under approval of the GA Tech IACUC, a 1.5 by 2.5 mm defect was created in 21 day old C57Bl/6J male mice removing the posterior frontal suture. On post-operative days 1, 2
Results: The defect distance decreased on post-op days 3-6, followed by an increase in bone volume on post-op days 14 - 21. Expression of mRNAs for markers of chondrogenesis (Sox9,ColII, ColX, and Comp) all increased on post-op days 3-5. This was followed by an increase in Bmp4 on day 5 then Bmp2 on day 7. The increase in bone volume on day 14 was associated with an increase in expression of osteocalcin, Vitamin D receptor, and TGFB2.
Conclusion: The results from this study show that the rapid re-synostosis of the defect occurs through a biphasic process with a thin bridge of bone forming 3 days post-op and then a large increase in bone volume by 14 days post-op. Following the bridging there was an increase in expression of markers associated with cartilage development, which suggests that this re-synostosis occurs through endochondral ossification.
Keywords: Bone, Bone repair, Children, Digital image analysis and Regeneration