The challenge of catastrophic bone fractures in endurance

The sport of endurance has suffered irreparable harm in recent years over catastrophic leg injuries to horses.

The images we have seen out of the Middle East over the years have been harrowing.

Followers of the sport don’t need me to tell them that the United Arab Emirates has been a hot-spot for such catastrophic failures, no doubt due to the fast desert courses and the speeds that result. The big prizes on offer and the use of jockey-style riders are hardly conducive to horse welfare, either.

I have advocated before for the grading of endurance courses, in which races on tracks that are assessed as “fast” are run under more stringent parameters. However, even that would be only part of the solution.

These leg fractures may be catastrophic, but research suggests there is a common background that sets horses on a path to these leg breaks.

In short, we could say it is overtraining, but that is the simplistic answer. Two horses can undergo identical training, in which one remains sound and the other suffers a leg break.

It is clear that it is an accumulation of microdamage – tiny fractures, if you will – in the leg bones that absorb the most stress. These minute fractures can heal, but if the training regime generates the fractures at a faster rate than the horse’s body can heal them, then the bones inevitably weaken and the chances of fracture increases.

Much of the research in this field centers on the racing industry, but there is little doubt that the findings will apply equally to endurance.

So, the challenge for scientists and horse owners are manifold.

We need to know why some horses are more prone to these micro-fractures than others. Certainly, training (and recovery time) plays a role, but there may well be a genetic component. Perhaps diet is a contributing factor. At present, there are more questions than answers. We also need to be able to identify these at-risk horses early and either adjust their training programs accordingly, or find them a discipline that carries less risk.

This field has been the subject of some excellent research at Australia’s University of Melbourne, albeit focused on racehorses.

The study team has identified how bone microdamage accumulates and is repaired during the racehorse training cycle, and are now focused on how to prevent the life-threatening leg injuries that can arise.

It is important to remember that bone injuries are not only a cause of horse fatalities. They are also a common factor in lameness and can force the premature retirement of horses.

Professor Chris Whitton, who heads the University of Melbourne’s Equine Centre in Werribee, says: “Understanding the bone’s response to exercise and over-stress is critical to preventing injuries and fatalities and ensuring the long-term sustainability of the industry.”

Whitton says much more knowledge is needed on how to manage racehorses in order to work with the natural bone adaptation and damage-repair processes.

“At the moment, bone injuries are regarded as an inevitable consequence of training, but this needn’t be the case,” he says. “If we can unravel the intricacies of the bone’s response to stress and exercise; and detect bone damage early, it will go a long way to preventing long-term injury and fatalities.”

And so the work continues, with efforts going toward developing best-practice strategies to prevent bone and joint injuries in racehorses. It involves a collaboration between veterinarians, biomechanical engineers, epidemiologists and bone biology researchers.

The research project will continue to examine pressure and loads in the lower limbs; investigate the processes surrounding bone fatigue; seek to understand bone modelling and re-modelling in horses both in training and at rest; and analyse how distances and speeds affect bone fatigue.

The findings are sure to have value to the sport of endurance.

The results may well prove to have profound consequences for the future of endurance. It is possible it will result in changes to the way these horses train, and a reassessment of what we can reasonably expect from these animals in terms of distance and speed in an endurance contest.

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