Interrelationships between electrical, mechanical and hydration properties of cortical bone

Area of Science:

• Biomaterials Science
• Orthopedic Research
• Bioelectricity

Background:

• The relationship between cortical bone's electrical and mechanical characteristics, and the influence of its composition, remains incompletely understood.
• Investigating these interrelationships is crucial for developing advanced diagnostics and treatments for bone conditions.

Purpose of the Study:

• To explore the associations between electrical properties (impedance, dielectric constant, conductivity) and mechanical properties (toughness, strength, elastic modulus) of cortical bone.
• To elucidate the roles of unbound and bound water, organic matrix, and mineral phases in determining bone's electrical properties.

Main Methods:

• Bovine cortical bone samples (N=24) underwent three-point bending tests for mechanical evaluation.
• Sequential dehydration and demineralization were employed to isolate contributions of water and mineral content.
• Raman spectroscopy quantified water content, specifically collagen- and mineral-bound water.

Main Results:

• Statistically significant correlations were found between electrical and mechanical properties.
• Toughness and strength were negatively correlated with impedance and positively with conductivity and dielectric constant, particularly at 0.2, 0.5, and 1 MHz.
• Electrical properties were significantly altered by dehydration, highlighting the critical role of unbound and bound water. Bound water may independently influence electrical properties.

Conclusions:

• Electrical properties of cortical bone are significantly correlated with its mechanical properties, including toughness and strength.
• Water compartments, especially bound water, are key determinants of bone's electrical characteristics.
• Developing in vivo methods to measure electrical properties could enable assessment of bone strength and toughness.