Mechanical properties of subchondral bone in the distal aspect of third metacarpal bones from Thoroughbred racehorses.

The study investigates the mechanical properties of a specific part of a horse’s bone, known as the subchondral bone (SCB) in the third metacarpal bone (MC3). The results reveal variations in these properties which could contribute to certain types of bone fractures in racehorses. These properties can also be predicted using a technique called micro-computed tomography.

Study Design and Methods

• The researchers studied 12 pairs of MC3s, a specific part of the bone structure in Thoroughbred racehorses. These samples were obtained from horses that had been euthanized for various reasons.
• These specimens were split into two groups based on whether they had mild or severe changes in the SCB, as determined by micro-computed tomography (CT).
• The researchers extracted samples from the SCB plate and trabecular bone, specific parts of the bone structure, from the distopalmar aspect (the back part) of the condyles (rounded end parts of the bone) and the sagittal ridge.
• They then tested these samples in compression, calculating their elastic modulus, yield stress, yield strain, and toughness, which are measures of a material’s ability to withstand forces without deforming or breaking.
• Measurements related to bone mineral density, bone volume fraction, thickness, separation, and connectivity of the trabecular bone were also calculated.

Results of the study

• No significant differences were observed between the left and right forelimbs of the horses.
• The researchers found that samples taken from the condyles had higher values for elasticity, yield stress, and toughness compared to those taken from the sagittal ridge.
• They noted that in cases where severe changes had occurred in the SCB due to disease, the SCB plate was weaker and the trabecular bone was stronger in comparison with specimens showing mild changes.
• A significant correlation was observed between the microstructural and the mechanical properties of the bone material.

Conclusions drawn from Research

• The researchers identified a significant gradient (variation) in the mechanical properties of SCB taken from horses, a factor which could contribute to condylar fractures (fractures of the rounded ends of bones).
• They also concluded that the mechanical properties of the SCB from the distal (further away from the center of the body) aspect of the MC3 could be predicted using micro-computed tomography.