Variations in the microstructural acousto-mechanical properties of cortical bone revealed by a quantitative acoustic microscopy study

A previously described Multi Layer Analysis (MLA) technique was used to examine the anisotropy, age and gender dependence of lamellar osteon ensembles of human cortical bone, obtained from 17 male and 9 female human cadaver femora. The samples were embedded in polymethylmethacrylate (PMMA) and cut in several directions with respect to the long axis of the femur. For each cut six measurements were made under standardized conditions using a scanning acoustic microscope at 900 MHz. The mean impedance of 998 MLA's was 3.38 Mrayl (std. 0.37 Mrayl), which is significantly lower than published low frequency values. The angular dependence of impedance exhibited a similar behavior as derived for the Young's modulus from an alternating lamellae model. Statistical analysis of age- and gender specific subgroups showed a general increase of impedance with age and a reversal for the oldest male age group only.