Osteon interfacial strength and histomorphometry of equine cortical bone

Area of Science:

• Biomechanical Engineering
• Orthopedic Research
• Veterinary Science

Background:

• The mechanical properties of cortical bone are crucial for understanding bone fragility and damage.
• Secondary osteons, the basic structural units of cortical bone, play a significant role in bone's fatigue life and fracture toughness.
• Osteon interfacial strength is a key factor in bone's response to mechanical stress, yet it remains incompletely understood.

Purpose of the Study:

• To evaluate the interfacial strength of secondary osteons in the Thoroughbred equine third metacarpal bone.
• To investigate regional and osteon-type dependent variations in interfacial strength.
• To correlate interfacial properties with bone fragility and damage accumulation mechanisms.

Main Methods:

• Fiber pushout tests were performed on machined bone blocks from different anatomic regions.
• Osteon types were classified under polarized light based on their appearance.
• Shear strength was estimated using shear lag theory, and histomorphometry was employed for regional analysis.

Main Results:

• Interfacial strength varied significantly among osteon types, with bright field osteons exhibiting the highest strength (40.3 MPa) and dark field osteons the lowest (22.8 MPa).
• The dorsal region demonstrated superior shear strength and toughness compared to other regions.
• Regional and osteon type dependencies were observed, with palmar regions and alternating osteon types showing reduced strength.

Conclusions:

• Osteon interfacial strength is a critical determinant of cortical bone's mechanical behavior.
• Regional and osteon type variations in interfacial strength contribute to differences in bone fragility and damage accumulation.
• These findings enhance the understanding of biomechanical properties in equine cortical bone, with implications for fracture mechanics.