Aim: This study was designed to assess the regenerative process in models of leg lower bone defects in the rats, assessed with the use of in vivo micro-X-ray CT (M-CT: Rigaku Co., Tokyo, Japan).

Material and methods : In group A, a partial defect was made in the tibia, and the fibula was totally excised; however, the blood supply to the periosteum was maintained. In addition, an external fixation device was applied to the tibial defect. In group B, only the fibula was removed, and the tibia was left intact. Immediately after operation and on postoperative days 3, 5, 7, and 14, the bone defect region underwent radiographic analysis by M- CT . New bone formation was estimated qualitatively and quantitatively with the use of image reconstruction software i-VIEW (Morita Co., Tokyo, Japan) and analysis software 3-by-4 viewer 2011 (Kitasenju Radist Dent, Tokyo, Japan)

Results: Both groups showed initial signs of bone formation on the fibula at 5 days, which continued to increase until 14 days. Bone formation was greater in group A than in group B.

Conclusions: Detailed observations by M-CT showed that the vascularized periosteum had high osteogenic activity. Our results suggest that the osteogenic activity of the periosteum depends not only on the blood circulation, but also on the conditions of the bone defect. This model is useful for evaluating osteogenic capacity, biocompatibility and osteoinductive ability of artificial bones. M-CT can demonstrate bone regenerative course of one and same animal and is more effective in evaluation of regenerative process.

Conflict of interest: This bone defect model is useful for evaluating osteogenic capacity, biocompatibility and osteoinductive ability of artificial bones. Micro-X-ray CT can demonstrate bone regenerative course of one and same animal and is effective in evaluation of regenerative process in bone defect.