Jerry J. Broz
Dept. of Mech. Eng. and The Ctr. for Acoust. Mech. and Mater., Univ. of Colorado, Boulder, CO 80309
Steven J. Simske Alan R. Greenberg
Univ. of Colorado, Boulder, CO 80309
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(plus or minus)0.12 km/s and 1.49(plus or minus)0.06 km/s and 27.2(plus or
minus)2.5 GPa and 2.95(plus or minus)0.26 GPa, respectively [Broz et al., 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.