Quantitative ultrasound does not reflect mechanically induced damage in human cancellous bone

This study investigated the ability of quantitative ultrasound (QUS) to det ect reductions in the elastic modulus of cancellous bone caused by mechanic al damage. Ultrasonic velocity and attenuation were measured using an in-ho use parametric imaging system in 46 cancellous bone cores from the human ca lcaneus, Each core was subjected to a mechanical testing regime to (a) dete rmine the predamage elastic modulus, (b) induce damage by applying specifie d strains in excess of the yield strain, and (c) measure the postdamage ela stic modulus, The specimens were divided into four groups: a control group subjected to a nominally nondestructive 0.7% maximum strain (epsilon (m)) a nd three damage groups subjected to increasing strain levels (epsilon (m) = 1.5, 3.0, and 4.5%), QUS measurements before and after the mechanical test ing showed no significant differences between the control group and damage groups, despite highly significant (p < 0.001) reductions in the elastic mo dulus of up to 72%, These results indicate that current QUS techniques do n ot intrinsically reflect the elastic properties of cancellous bone. This is consistent with ultrasonic properties being determined by other factors (a pparent density and/or architecture), which normally are associated strongl y with elastic properties, but only when bone is mechanically intact. Clini cally, this implies that ultrasound cannot be expected to detect bone fragi lity in the absence of major changes in bone density and/or trabecular arch itecture.