The appliance of science

How can science help reduce the risk of fractures in racing, and in turn societal concerns about horses in sport?

- Christopher M Riggs

How can science help reduce the risk of fractures in racing, and in turn societal concerns about horses in sport? Christopher M Riggs FRCVS explains

WORK behind the scenes, in research laboratories globally over the past 50 years, has made a big impact on our understanding of why horses sustain fractures when racing and, more recently, ways to prevent them. It is a good example of how science can contribute to horse sports and how investment in research is critical if we are serious about addressing some of the concerns society has about the welfare of horses in sport.

Most fractures that occur in horses during racing happen in the absence of any obvious incident; one second the horse is galloping, the next it is hobbling to a stop. While it is tempting to think that the horse must have taken a misstep on uneven ground, we now know that these fractures are the end stage of a process that started weeks earlier. This last race just happened to be the one that “broke the camel's back”.

Bone plays many vital roles, the most obvious being to provide rigid support to the body and to facilitate muscular action to create movement. Individual bones, especially those of the limbs, are subject to loads with every step. Each load will bend the bones, deforming them by small amounts. Microscopic damage is caused to a bone's structure each time it is deformed. Accumulation of this damage is referred to as material fatigue. If the material fatigue accumulates above a threshold level, then a bone may be weakened to a point where it will fail at loads within the range of those experienced in normal life.

Studies in engineering labs, where bone is treated as a structural material, and standardised bone specimens are machined and tested in materials testing machines, have demonstrated that the rate of microscopic damage increases rapidly as the magnitude of the load increases (see figure 1, right).