The relationship between elastic properties and microstructure of bovine cortical bone.

The relationship between the structure of bone on the microscopic level and its mechanical properties was investigated by comparing bovine cortical bone of two microstructural types. Measurements of elastic properties were made in three orthogonal directions on specimens of plexiform and Haversian bone, taken from the same level of the same bone, using extensional wave ultrasonic techniques. Differences in Young's modulus of elasticity measured in the three directions correspond to observed structural differences; plexiform bone is anisotropic, while Haversian bone appears to be transversely isotropic. The pattern of distribution of the two structural types within different aspects of the same bovine femur suggests that the level of osteonal remodeling is related to the pattern of mechanical stress, especially due to muscular activity, in the bone. This may occur because Haversian remodeling is stimulated by microcracks in regions of high stress and/or repeated stress cycles, thus replacing fatigue-damaged bone and preventing failure.