The compressive behavior of bone as a two-phase porous structure

Area of Science:

• Biomechanics
• Biomaterials science
• Orthopedic research

Background:

• Trabecular bone mechanical properties are crucial for skeletal integrity.
• The influence of bone marrow on these properties, especially under dynamic loading, requires further elucidation.

Purpose of the Study:

• To investigate the effect of bone marrow on the mechanical behavior of human and bovine trabecular bone.
• To determine the relationship between apparent density, strain rate, and the mechanical properties of defatted trabecular bone.

Main Methods:

• Compression testing of trabecular bone specimens (human and bovine) with and without marrow.
• Testing conducted across a range of strain rates (0.001 to 10.0 s⁻¹).
• Utilized a porous platen to allow controlled marrow egress during testing.

Main Results:

• Marrow presence significantly increased strength, modulus, and energy absorption only at the highest strain rate (10.0 s⁻¹).
• Marrow's enhancement at high strain rates is attributed to restricted viscous flow, not pore flow.
• For defatted bone, strength correlated with apparent density squared; modulus correlated with apparent density cubed.
• Both strength and modulus showed a power-law relationship with strain rate (exponent ≈ 0.06).

Conclusions:

• Bone marrow can enhance trabecular bone mechanical properties under rapid loading conditions.
• Established power-law relationships between density, strain rate, and mechanical properties allow for predictive modeling.
• Findings are applicable to all skeletal bone, aiding in the prediction of bone strength and stiffness from in vivo density measurements.