Determining the elastic modulus of mouse cortical bone using electronic speckle pattern interferometry (ESPI) and...

Area of Science:

• Biomechanical Engineering
• Materials Science
• Orthopedics

Background:

• Mouse models are crucial for understanding bone diseases and function.
• Accurate measurement of bone's elastic modulus is vital for assessing bone quality.
• Existing methods like whole bone bending and nanoindentation have limitations in measuring bulk elastic modulus in small mouse bones.

Purpose of the Study:

• To develop and validate a novel method for determining the bulk or effective elastic modulus of mouse cortical bone.
• To overcome the challenges posed by the small dimensions of mouse femurs in elastic modulus determination.

Main Methods:

• Utilized Electronic Speckle Pattern Interferometry (ESPI) to measure surface displacements of mouse femur segments under compression in water.
• Combined ESPI data with micro-computed tomography (micro-CT) for geometric information and cross-sectional area.
• Calculated effective stress and strain to determine the effective elastic modulus (E) from the stress-strain ratio.

Main Results:

• The novel ESPI-based method demonstrated accuracy and precision using a standard material.
• Measured mean elastic moduli for mouse femora: 10.4±0.9 GPa (8 months frozen), 8.6±1.4 GPa (2 weeks frozen), and 8.9±1.1 GPa (fresh).
• Obtained values are higher than three-point bending tests and lower than nanoindentation results, suggesting a more representative bulk measurement.

Conclusions:

• The developed ESPI method accurately and precisely measures the effective elastic modulus of mouse cortical bone.
• This technique offers a valuable tool for biomechanical studies of mouse bone, providing insights into bone quality and disease.
• The findings highlight the importance of choosing appropriate methods for measuring mechanical properties in small bone samples.