Comparison of damage accumulation measures in human cortical bone

Area of Science:

• Biomechanics
• Materials Science
• Orthopedics

Background:

• Traditional metrics like elastic modulus, strength, and energy dissipation offer limited insight into bone damage.
• Cortical bone's complex mechanical nature necessitates alternative damage assessment methods.

Purpose of the Study:

• Investigate alternative measures for monitoring the damage process in human cortical bone under torsion.
• Compare the sensitivity of yield, relaxation, and failure properties against traditional metrics.

Main Methods:

• Machined human cortical bone specimens (n=72) were subjected to torsional relaxation cycles.
• Damage was induced during a single relaxation cycle.
• Effects on elastic, yield, viscous, and failure properties were assessed pre- and post-damage.

Main Results:

• Degradation of torsion properties showed a significant twist magnitude effect.
• Yield stress/strain and relaxation properties degraded 5-10 times more than strength and modulus.
• Relaxation and yield properties demonstrated higher sensitivity to shear damage accumulation.

Conclusions:

• Relaxation and yield properties are more sensitive indicators of shear damage in cortical bone than strength or modulus.
• An interaction between damage and viscous behavior provides new insights into bone mechanics.
• These findings suggest improved methods for assessing bone health and damage.