Relationship between ultrasonic parameters and apparent trabecular bone elastic modulus: a numerical approach

Area of Science:

• Biomechanics
• Biomaterials Science
• Medical Imaging

Background:

• The physical principles of quantitative ultrasound (QUS) in trabecular bone are not fully understood.
• Translating QUS results into reliable bone strength predictions remains a challenge.
• Ultrasound's mechanical wave properties suggest its potential for assessing apparent bone elasticity.

Purpose of the Study:

• To determine the sensitivity of QUS parameters to changes in apparent bone elasticity, a proxy for bone strength.
• To evaluate the predictive power of QUS for bone strength using advanced simulation techniques.

Main Methods:

• Reconstruction of 3-D geometry for 34 human trabecular bone samples using synchrotron micro-computed tomography.
• Finite-difference time-domain (FDTD) simulations coupled with 3-D micro-structural models to compute apparent Young's modulus (E).
• Voxel-based micro-finite element analysis performed in three perpendicular directions for each sample.

Main Results:

• In the antero-posterior direction, speed of sound and normalized broadband ultrasonic attenuation predicted E with high accuracy (0.9 and 0.87, respectively).
• QUS predictive power for bone strength surpassed that of bone density alone or with micro-architectural parameters.
• Predictive power decreased when testing was parallel to trabecular orientation, attributed to dual longitudinal wave modes.

Conclusions:

• Quantitative ultrasound techniques show significant potential for assessing trabecular bone strength.
• QUS parameters, particularly speed of sound and normalized broadband ultrasonic attenuation, are sensitive indicators of apparent bone elasticity.
• Results validated using two distinct simulation tools underscore the reliability of QUS for bone health assessment.