Are bi-axial proximal sesamoid bone fractures in the British Thoroughbred racehorse a bone fatigue related fracture? A histological study.

The research article investigates if bone fatigue—in the form of microfractures and changes in the trabecular bone area—is associated with severe bi-axial proximal sesamoid bone fractures in the British Thoroughbred racehorse. However, the results indicate no significant difference in these factors in horses with and without the fractures, thus suggesting these fractures might not be due to bone fatigue.

Methods:

• The researchers examined proximal sesamoid bones (PSB) from 10 racehorses with bi-axial proximal sesamoid bone fractures and 10 control racehorses without musculoskeletal injury.
• They used the bulk basic fuchsin method for examination, further performing bone histomorphometric and microfracture analysis.
• The data from the case and control groups were statistically compared applying two-sample t-test, paired t-test, and Mann-Whitney U test methods.

Results:

• The results showed no significant difference in the microfracture density and the trabecular bone area between the bones from case and control horses.
• There was also no notable difference between fractured and non-fractured bones in the case horses.

Conclusions:

• The research found that the microfracture density was low in the PSB areas studied. This was consistent across both groups, indicating that the propagation of micro-cracks unlikely plays a role in predisposing horses to these fractures.
• There was no significant difference in the bone surface area between the two groups, which contradicts the expectation if modelling, adaptation, and an increased bone density were factors leading to the fractures.
• Consequently, the study concludes that bi-axial proximal sesamoid bone fractures in British racehorses do not seem to be associated with microfractures of the trabecular bone of the PSB.
• Given the results, the study suggests that PSB fractures could represent an acute single-event fracture. However, the exact cause of these fractures remains unknown, and further research is needed.