Estimation of local anisotropy of plexiform bone: Comparison between depth sensing micro-indentation and Reference...

Area of Science:

• Biomaterials Science
• Orthopedic Research
• Mechanical Engineering

Background:

• Reference Point Indentation (RPI) is a novel technique for in vivo bone property assessment.
• Understanding bone's anisotropic mechanical behavior is crucial for tissue-level analysis.

Purpose of the Study:

• To compare the local anisotropic behavior of bovine plexiform bone using micro-indentation and RPI.
• To evaluate the correlation between RPI measurements and micro-indentation data.

Main Methods:

• Bovine femur specimens were prepared and subjected to micro-indentation and RPI tests along axial, radial, and circumferential directions.
• Depth-sensing micro-indentations (2.5µm) and RPI indentations (~50µm) were performed.
• Indentation modulus (Eind), unloading slope (US1), and Indentation Distance Increase (IDI) were measured.

Main Results:

• Indentation modulus (Eind) was highest in the axial direction, significantly lower in radial and circumferential directions, indicating anisotropy.
• RPI measurements generally showed directional dependence, except for IDI.
• Unloading slope (US1) from RPI mirrored the anisotropy observed in Eind, correlating significantly with it.
• IDI showed no significant correlation with any micro-indentation measurements.

Conclusions:

• Certain RPI measurements can reflect local bone anisotropy, unlike IDI.
• A linear relationship exists between most RPI and micro-indentation mechanical properties, excluding IDI.
• RPI shows promise for assessing bone mechanical anisotropy, but IDI requires further investigation or is not suitable for this purpose.