Usefulness of Quantitative Ultrasound in Evaluating Structural and Mechanical Properties of Bone: Comparison of Ultrasound, Dual-energy X-ray Absorptiometry, Micro-computed Tomography, and Mechanical Testing of Human Phalanges in Vitro

Introduction: Ultrasound studies evaluating bone tissue generally concentrate on two parameters--velocity and attenuation. This study aimed to determine whether ultrasound signal analysis techniques could provide additional information on the structural and mechanical characteristics of bone.

Materials And Methods: In vitro measurements were made on 26 left index fingers from human cadavers. Ultrasound measurements at the distal metaphysis and epiphysis; dual-energy X-ray absorptiometry of the whole phalanx; micro-computed tomography at the distal quarter of the phalanx (that is, the distal epiphysis and metaphysis), and mechanical three-point bending tests were performed. Univariate and multivariate linear regression techniques were used to analyze the results.

Results: The ultrasound parameters, speed of sound and ultrasound peak amplitude correlated significantly with the three micro-computed tomography measures used to describe the characteristics of mineralized material (r=0.69-0.79, p<0.05). Low frequency ultrasound correlated significantly with micro-computed tomography parameters describing inter-trabecular or marrow spaces (r=0.68-0.78, p<0.05). Comparison of ultrasound parameters with geometric characteristics showed that while speed of sound and ultrasound peak amplitude were related to the cortical area, moment of inertia, and mechanical load (r=0.57-0.83, p< 0.05), the amplitude of the fastest part of the ultrasound signal and full width at 80% maximum of the low frequency peak were related to the relative area of the medullary canal (r=0.40-0.43, p<0.05).

Discussion: Quantitative ultrasound may provide information on structural, material and mechanical characteristics of bone to the same extent and even better than DXA Bone Mineral Density. These results have been obtained by a complete and exhaustive use of QUS technology in situ but under clinical conditions. The ultrasound parameters, correctly used and combined, seem to be effective tools for investigating bone tissue.