Bone material ultrasound velocity is predictive of whole bone strength

In humans, bone strength is assessed indirectly by the noninvasive measurement of structure or mass. Recent clinical application of an ultrasonic critical-angle reflectometry technique (UCR) has demonstrated the measurement of the regional and directional distribution of mechanical stiffness. This study investigates the specific question: are these measurements of a local material level property predictive of the strength of whole bone? Maximum values of pressure wave velocity and breaking strength were recorded at two locations (midshaft and base of neck) on rat femurs from growing rats. The results demonstrate a strong empirical relationship between material-level ultrasound (US) velocity and whole bone mechanical strength. However, the US velocity at a specific bone site can be used to assess bone strength at that site only, explaining discrepancies in other published studies that negate a relationship between strength and US velocity. The results indicate an important role for US velocity measurement in clinical evaluation of bone health.