Racing's Future Without Fatal Fractures: Science Fiction?

Racing's Future Without Fatal Fractures: Science Fiction?

Clinical science has made significant strides over the past 30 years to help us understand why catastrophic injuries occur. This has led to techniques and practices that enable veterinarians to identify many at-risk horses.

Photo: Courtesy University of Pennsylvania School of Veterinary Medicine

By Christopher M. Riggs, BVSc, PhD, DEO, Dipl. ECVS, MRCVS, The Hong Kong Jockey Club Department of Veterinary Clinical Services Equine Hospital, Sha Tin Racecourse, New Territories, Hong Kong

More than 80% of life-threatening injuries Thoroughbreds sustain at racetracks are the result of limb fractures. Losing horses this way is a significant issue for racing in terms of horse welfare and owner finances.

Most fractures happen during galloping without any apparent inciting event. Many scientific studies over the past 25 years have shown that these injuries are the consequence of repetitive stress injuries to the skeleton due to the repeated large loads associated with high-speed work.

Bone tissue can detect the type of loads and forces placed on it and respond through a biological process called bone adaptation. This process strengthens the bone so it is better able to withstand the new loads and forces. However, adaptation is not instant, and as part of the process, some areas of bone will become weaker before they become stronger. If the horse continues to do repeated high-intensity exercise during this phase, microdamage accumulates and can lead to small, incomplete stress fractures, also called “bone fatigue.”

If the horse shows signs of lameness during this phase, the horse’s veterinarian and trainer can take steps to reduce the bone fatigue and allow the bone to repair itself. The outlook for these horses is usually excellent.

Unfortunately, a significant proportion of horses that suffer bone fatigue injury show no warning signs, and the first indication of a problem is a life-threatening breakdown during a race or training gallop.

How can we reduce the number of horses that suffer catastrophic fractures?

1: Tailored training schedules

We can use the scientific knowledge of how bone responds to exercise to design training schedules that stimulate bone development, reduce the amount of microdamage, and allow time for bone healing. Each horse’s training schedule should be tailored to consider risk factors for bone damage such as previous training history, prolonged rest periods, and fitness, as well as the condition of the horse’s feet and shoeing.

2: Identify more horses with bone fatigue and early microdamage

There is currently no cheap, simple, and effective screening tool that could be deployed across the racehorse population to detect early fatigue damage. However, epidemiological studies of Thoroughbred populations have shown that certain groups of horses (for example, those coming back into fast work after a period of rest) are at increased risk of some injuries. There are also some tests for metabolic markers in blood or urine that could help identify horses in high risk groups with active fatigue damage. Research is ongoing to find more accurate and effective screening tools.

3: Stop incomplete stress fractures from progressing to catastrophic fractures

Clinical signs warning of an underlying stress fracture must be taken seriously and investigated. Avoiding the overuse of pain killers and anti-inflammatory drugs will make it easier for trainers and veterinarians to detect subtle signs, if present.

Additionally, appropriately trained veterinary surgeons in racehorse practice can make the most of already available diagnostic techniques to closely monitor horses in high-risk groups. By applying the latest knowledge, such as specific radiographic views of the legs, vets can use standard, portable equipment to detect more early fatigue-related injuries. MRI and radioactive bone scanning are also useful techniques for gathering more information in specific cases, although neither is suitable for general screening of large numbers of horses.

Seeing a horse breakdown on the track is an utterly miserable experience. Thankfully, it does not happen often, although when it does the impact is great. Clinical science has made significant strides over the past 30 years to help us understand why these injuries occur. This has led to techniques and practices that enable veterinarians to identify many at-risk horses. We can then intervene to enforce a rehabilitation program that allows the bone to heal and these horses to recover.

However, a proportion of injuries that predispose horses to catastrophic fracture remain elusive and undetectable by conventional means. Those of us caring for Thoroughbred racehorses need that last big step to develop a practical screening tool to identify these hidden injuries and save these horses, as well.

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