Abstract
The relationship between the mechanical properties and hierarchical structure in the bone tissue is essential to understand the factors determining the bone strength during aging and/or osteoporosis. This study aimed to investigate the distribution of elastic modulus at the microstructural level, i.e., osteon scale, in the cortical bone. In the experiments, block-like specimens were taken from the ocrtex in a bovine femoral diaphysis and the transverse cross-section of the diaphysis was polished. The microindentation tests were conducted by using a spherical shape head indentor at four kinds of microstructure from the outer to the inner surface: osteon and interstitial region in the osteonal bone and lamellar and interstitial regions in the plexiform bone. To evaluate the distribution of elasticic modulus, the contact stiffness was calculated from the force-depth relationship during unloading. As a result, in the posterior specimen, the contact stiffness of plexiform bone obserbed in the outer region was larger than that of osteonal bone in the inner rregion. In the anterior specimen, the valiation of contact stiffness was larger than that of the posterior specimen and there was no significant difference among the four kinds of microstructure. A further study of the radial distribution of the microstructure in the diaphysis and the effects on the elastic modulus is needed for further elucidating the difference of elastic modulus at those microstructures.
