Bending properties of cortical bone of the horse

Bending properties of samples of cortical bone taken from the cranial, caudal, medial, and lateral quadrants of the midshaft of the radius, femur, and metacarpus of 12 ponies, 18 months old, were determined by 4-point loading at a rate of 10 mm/minute. The elastic modulus for all samples was between 16.2 and 20.2 GN/m2, and the ultimate breaking strength, between 204 and 255 MN/m2. There was greater variation in these properties between bone quadrants than between bones. Samples from the cranial and medial quadrants of both femur and radius were stiffer and had greater ultimate breaking strength than caudal or lateral samples. All samples of radius deformed more and absorbed more energy before reaching the greatest load than did samples of femur. The elastic modulus and the ultimate breaking strength of radius within any quadrant were highly correlated to specific gravity. However, at any specific gravity, caudal and lateral samples were not as strong as cranial and medial samples. Samples taken from exercised ponies, male ponies, or those fed diets containing 0.7% Ca,0.6% P or 2.7% Ca,1.1% P tended to be stiffer and have a greater ultimate breaking strength than samples taken from unexercised ponies, females, or those fed diets containing 0.7% Ca,1.4% P.