Response to "Clinical Evaluation of Bone Strength and Fracture Risk".

We read with great interest the recent review by de Bakker et al that summarized the state of several existing and emerging technologies for estimating bone strength and fracture risk in vivo. Much of their review focused on how well the measurements of selected technologies predicted experimental measurements of bone strength by ex vivo quasistatic mechanical testing (QMT) and on how well they tracked changes in mechanical properties of bone. The authors noted that the association of many common skeletal health measurements (e.g., DXA measures of trabecular bone score and areal and volumetric BMD) are only moderately associated with bone strength. The authors did not include mechanical response tissue analysis (MRTA) in their review. MRTA is a dynamic mechanical bending test that uses a vibration analysis technique to make immediate, direct, functional measurements of the mechanical properties (mass, stiffness, and damping) of long bones in humans in vivo. In this article we note our interest in the ability of MRTA to detect large changes in bone stiffness that go undetected by DXA. We also highlight results of our proprietary improvements to MRTA technology that have resulted in unmatched accuracy in QMT-validated measurements of the bending stiffness and estimates of the bending strength (both R2 = 0.99) of human ulna bones. To distinguish our improved technique from the legacy MRTA technology, we refer to it as Cortical Bone Mechanics Technology (CBMT). Further research will determine whether such CBMT measurements are clinically useful.