P3F-7 Impact of Microstructure on Elastic Behavior of Cortical Bone

The axial transmission technique dedicated to clinical assessment of cortical bone involves propagation of various propagation modes such as Lamb type modes or lateral wave. As revealed by in vitro experiments, velocities of these elastic waves reflect a combination of bone properties, which themselves are highly related to bone strength: cortical thickness, porosity, elastic impedance and mineral content of the bone tissue. Assuming that bone properties could be evaluated from measured velocities, we investigated the sensitivity of elastic waves to these different bone properties, particularly to porosity, on the basis of finite difference time domain simulation approach. Results exhibit quadratic variations of the compression and shear velocity with porosity. For a typical transversely isotropic bone matrix, an increase of the porosity from 0% to 10% leads to a 4%-decrease of the compression velocity along the axial direction and an 11%-decrease of the compression velocity along the transverse direction, resulting in an increase of anisotropy (ratio c₃₃/c₁₁ of 17%. The impact of porosity on a specific propagation mode (S₀ Lamb-mode type) used in axial transmission was derived