Mechanical characterization via nanoindentation of the woven bone developed during bone transport.

Nanoindentation has been used successfully in the determination of the mechanical properties of bone. Its application in fracture healing provides information on the evolution of material properties of the woven bone during regeneration process. However, this technique has not been applied in assessing the mechanical properties of woven bone during distraction osteogenesis. Therefore, the aim of this work is to evaluate the spatial and temporal variations of the elastic modulus of the woven bone generated during the bone transport process. Callus samples were harvested from intervened animals at different time points during the bone transport process (35, 50, 79, 98, 161 and 525 days after surgery) for nanoindentation measurements. Results clearly showed that the mean elastic modulus of the woven bone increased during the bone transport process reaching 77% of value for cortical bone after 525 days (from 7GPa 35 days after surgery to 14GPa 525 days after surgery approximately). Woven bone generated during bone transport seems to present similar evolution of elastic modulus with time as values reported for fracture healing. Furthermore, different spatial variations of elastic modulus within the callus were found for different stages of the process.