Anisotropic properties of trabecular bone. Conductometric and ultrasonic studies

Bones are materials characterized by anisotropic mechanical and structural properties. The main directions of anisotropy of such materials are related to mechanical loads to which they are subjected in physiological conditions. Studies of mechanical properties show that bones are mostly orthotropic or transversally isotropic materials. The aim of the present paper is to investigate parameters of anisotropic structure of trabecular bone such as formation factor and tortuosity using measurements of electric impedance. Moreover, the qualitative correlation between the measured parameters of structure and velocity of propagation of ultrasonic waves in these materials is established. To determine the impedance of the materials the two-electrode method with RLC bridge or direct technique are used. The cubic specimens (1 cm x 1 cm x 1 cm) of trabecular bovine bone were cut from the distal epiphysis of fresh bovine femora and measurements of impedance were made both for material containing bone marrow and physiological fluid. The results show a good correlation between tortuosity measured by electric spectroscopy and velocity of longitudinal waves.