Viscoelastic dissipation in compact bone: implications for stress-induced fluid flow in bone

Area of Science:

• Biomechanics
• Materials Science
• Orthopedics

Background:

• Human compact bone exhibits viscoelastic properties crucial for load-bearing and shock absorption.
• Understanding these properties is essential for diagnosing bone conditions and designing orthopedic implants.

Purpose of the Study:

• To investigate the viscoelastic properties of wet and dry human compact bone.
• To determine the effect of hydration on bone's damping capacity across a wide frequency range.
• To assess bone's efficacy as a shock absorber based on its viscoelastic behavior.

Main Methods:

• Mechanical testing of human tibia specimens in torsion and bending.
• Measurements conducted in longitudinal and transverse directions.
• Analysis of viscoelastic damping (tan delta) across frequencies from 5 mHz to over 50 kHz.

Main Results:

• Wet bone demonstrated significantly higher viscoelastic damping (tan delta) than dry bone.
• A consistent relative minimum in damping was observed between 1 Hz and 100 Hz for both conditions.
• No distinct damping peak attributable to fluid flow was identified within the tested frequency spectrum.

Conclusions:

• Bone's viscoelastic damping profile, particularly the minimum during normal activity frequencies, challenges its optimal design as a shock absorber.
• Hydration plays a significant role in modulating the damping characteristics of human compact bone.
• Further research is needed to fully elucidate the mechanisms of damping in bone, potentially involving fluid flow at different scales or other factors.