Acoustic characterization of chemically altered cortical bone

A novel combination of microscopic evaluation techniques is utilized to evaluate localized compositional and material properties of bovine femoral cortical bone. Cortical bone sections were selectively demineralized by timed immersion in supersaturated (ethylenedinitrilo)‐tetraacetic acid. Optical microscopy of the sections indicated that a collagen layer of varying thickness surrounded a core of mineralized tissue. The treated sections were characterized with a scanning acoustic microscope (SAM) using a 50‐MHz transducer. Based on the acoustic signals reflected from both the surface of the collagen layer and the mineralized tissue layer below, the sonic wave velocities and elastic stiffnesses of the mineralized tissue and collagen were 3.65±0.12 km/s and 1.49±0.06 km/s and 27.2±2.5 GPa and 2.95±0.26 GPa, respectively [Broz etal., 12th South. Biomed. Conf., Tulane Univ. (1993)]. Following the acoustic evaluation, microhardness and elemental composition maps were obtained for the sections using a diamond pyramid indenter and a Jeol JXA‐8600 Superprobe, respectively. The size and location of the demineralized regions as determined by the microhardness testing and wave dispersive analysis were in good agreement with the acoustic micrograph data. The combination of acoustic, chemical, and mechanical microscopic techniques provides important insights into the site‐specific phasic properties of cortical bone.