Some new developments in the rheology of bone

Area of Science:

• Biomechanics
• Materials Science
• Biophysics

Background:

• Bone exhibits viscoelastic and thermorheologically complex behavior.
• Multiple mechanisms contribute to bone's viscoelastic response.
• Understanding these mechanisms is crucial for bone mechanics research.

Purpose of the Study:

• To calculate the contribution of fluid flow to bone's viscoelastic behavior.
• To estimate relaxation time and strength based on porous material models.
• To predict the frequency range of fluid flow-induced relaxation in bone.

Main Methods:

• Utilized Biot's model for fluid flow relaxation in porous materials.
• Employed simple composite models to estimate relaxation strength.
• Measured ultrasonic wave propagation and attenuation in wet bone (0.5 MHz–15 MHz).
• Measured mechanical damping (100 Hz–1 kHz) across various fluid viscosities.

Main Results:

• Calculations predict fluid flow relaxation can occur at high frequencies (>10 kHz) in vitro.
• Experimental data spans low-frequency damping and high-frequency ultrasonic measurements.
• Observed mechanical damping varied with fluid viscosity.

Conclusions:

• Fluid flow is a significant contributor to bone's viscoelasticity.
• High-frequency relaxation due to fluid flow is predicted.
• Additional experiments are necessary to bridge low and high-frequency measurement gaps for a complete understanding of bone rheology.