Characterizing bone strain distributions in vivo using three triple rosette strain gages

Area of Science:

• Biomechanics
• Equine Orthopedics
• Computational Modeling

Background:

• Understanding equine limb loading is crucial for diagnosing and preventing injuries.
• The third metacarpal bone (cannon bone) is a primary weight-bearing structure in horses.

Purpose of the Study:

• To characterize site-specific strains on the equine third metacarpal during locomotion.
• To determine the distribution of normal and shear strains and strain energy density (SED).

Main Methods:

• Attachment of triple-element rosette strain gages to the equine third metacarpal midshaft.
• Analysis using combined beam theory and finite element modeling.
• Measurement during a medium-speed trot (3.6 m/s).

Main Results:

• Non-uniform strain distributions were observed across the bone's cross-section.
• Maximum compression (-2400 µε), tension (810 µε), shear (1500 µε), and SED (54 kPa) were not at gage sites.
• Complex loading including bending, axial compression, end shear, and torsion was identified.

Conclusions:

• A minimum of three rosette gages are needed to accurately capture peak strains and their locations.
• The equine third metacarpal experiences complex and varied strain stimuli across its cross-section during trotting.
• This complex loading pattern is consistent throughout the stance phase.