Methods: We used 4 sizes of beta-TCP granules; 50-150 µm (P), 200-500 µm (S), 500-1000 µm (M), and 1000-2000 µm (L). Five bone defect models were prepared (inside diameter 4.5 mm, depth 8 mm) and each underwent bone defect filling with each granule size. Slice images were obtained using micro-CT and subjected to 3D image analysis, and the average size of the granule interspaces was determined.
Results: The average interspace size was 80.0±6.16, 159.5±6.45, and 207.5±8.70 µm in the S, M, and L types, respectively. That for the P type was too small to measure.
Conclusions: When bone defects are filled with granules, the interspaces are larger with larger sized granules. Since the interspaces of the P type were smaller than the resolution of micro-CT imaging, we thought that they were 20 µm or smaller. Past reports have shown that vascularization requires interspaces of 50 µm or more. Therefore, granules larger than the present P type beta-TCP granules are considered suitable for use in bone defects.