Dependence of local wave velocity in bovine cortical bone on the decalcification

Bone is a composite material, mainly composed of HAp crystallites and type I collagen. It is known that the amount and orientation of HAp crystallites contribute to the “bone quality”, which affects the bone elasticity. In this study, using a micro-Brillouin scattering technique which is able to evaluate wave velocity in the minute area, the effect of HAp amount on the velocity was measured. 36-plate-specimens in the plane of bone axis and radial directions were obtained from the middle part of a bovine femur. Wave velocity and HAp amounts were evaluated by the micro-Brillouin and XRD techniques, respectively. The specimens were then decalcified using ethylenediaminetetraacetic acid and measured again. Before decalcification, the average velocity was 5.06×103 m/s, and showed a moderate correlation with the HAp amounts (R2}=0.56). After decalcification, the average velocity dramatically decreased to the value of 3.28×103 m/s, showing a strong dependence on the HAp amounts. In addition, the wave velocities except for the lateral part shows the moderate correlation (R2}=0.30) before and after decalcification, which implies the possible effects of collagen on the wave velocities.