Measuring viscoelastic properties of cortical bone with resonant ultrasound spectroscopy

Resonant Ultrasound Spectroscopy (RUS) allows to measure the elastic constants and mechanical damping of an anisotropic material from the resonant spectrum of a specimen. This method has been reported to fail to characterize bone because of its strong viscoelastic damping. However, our results reported at the last IUS symposium evidenced that the method could be modified and made successful in measuring elasticity of a bone-mimicking viscoelastic material. In this study, we applied the method to a specimen of human cortical bone and also explore the ability of RUS to provide quantitative information about damping properties of bone. The determined diagonal elastic constants were in good agreement with concurrent sound velocity measurements and the precision of the measurement is discussed. It was also possible to measure precisely the shear damping properties. This study demonstrates that RUS is suitable for an accurate measurement of cortical bone anisotropic elasticity and could also provide information about anisotropic viscous damping of bone.