Preventing Injuries in Thoroughbred Racehorses

Fractures are to blame for more than 80% of catastrophic injuries in Thoroughbred racehorses.

Photo: Photos.com

The big names are recognizable: Barbaro, Eight Belles, St Nicholas Abbey. But hundreds of other racehorses have suffered racing or training injuries that ultimately proved fatal, as well. And while everyone would like to see the number of catastrophic injuries that occur on racetracks reduced, finding ways to actually accomplish that is easier said than done.

Christopher Riggs, BVSc, PhD, DEO, Dipl. ECVS, MRCVS, head of Veterinary Clinical Services at the Hong Kong Jockey Club, shared some suggestions on how we can work to prevent racehorse injuries at the 2014 British Equine Veterinary Association Congress, held Sept. 10-13 in Birmingham, U.K.

Riggs said fractures are to blame for more than 80% of catastrophic injuries in Thoroughbred racehorses.

"The prevalence of such incidents varies greatly between racing jurisdictions and race types, but typically ranges between 6.6 fractures per 1,000 starters in jump races and 0.9 fractures per 1,000 starters in flat racing," he said. "The loss of these horses is a significant ongoing issue for the industry, both financially and in terms of human and equine welfare."

Researchers and veterinarians know that the majority of catastrophic fractures occur due to bone fatigue and excessive loading. So, Riggs said, "through an understanding of the processes involved in fatigue damage of bone, it should be possible to implement strategies to reduce the accumulation of fatigue damage and to facilitate its repair. In addition, the progressive nature of fatigue damage means that, if we can identify the injuries early enough, we can intervene while the damage is still reversible."

Riggs offered the following suggestions on how veterinarians and trainers could work to prevent future injuries.

Eliminate the Cause

"Fatigue is a consequence of cyclical loading," such as repetitive galloping, Riggs said. And fatigue life is related to the magnitude of strain placed on the structure from each load cycle—essentially, how much strain a bone endures with each galloping stride.

"Strain will depend on the stress applied, which, in turn, will depend on the magnitude and direction of the load and the mass and structure of the bone," he said. And the number of load cycles and the magnitude and direction of load the bone is placed under depends on the horse's training schedule.

Basically, the amount of fatigue a bone suffers and its fatigue life depend on how frequently and how hard the horse works.

To reduce fatigue, Riggs recommended trainers develop a training schedule that effectively helps the horse's bone adapt without causing increased strain, such as workouts with regular, short, high-speed bursts rather than longer high-speed works on a less frequent basis.

A typical stress fracture of the scapula, the horse sustained this severe fracture while racing, without any associated trip or fall.  There's an area of smoothed, porous bone at the bottom of the scapula spine (towards the top of the image above, as the bone is upside down) and enlarged in the image below, which indicates an area of bone surface activity consistent with a stress fracture. The catastrophic fracture originated from this location.

Photo: Christopher Riggs, BVSc, PhD, DEO, Dipl. ECVS , MRCVS

Photo: Christopher Riggs, BVSc, PhD, DEO, Dipl. ECVS , MRCVS

He also encouraged trainers to monitor and attend to small issues that could impact the amount of fatigue a horse's skeleton suffers, such as hoof balance.

Choosing Screening Tools

Riggs said many horses that suffer catastrophic injuries don't show signs of injury prior to a breakdown: "They are not lame in the days preceding the race, cause the trainer no concern, and appear normal on pre-race veterinary inspection."

However, at necropsy, these horses generally show "grossly identifiable, well-established pathology that precipitated the final catastrophic injury."

So, Riggs said that screening for at-risk horses is a critical part of preventing catastrophic fractures. It also underscores the need for a better screening protocol: "A simple, cheap, effective technique for screening horses in training for evidence of early fatigue damage would allow 'silent' cases to be identified," Riggs said.

That said, using a single technique—such as radiographs or nuclear scintigraphy—to screen each of the thousands of horses that enter the starting gate each year isn't feasible. Instead, Riggs suggested using a combination of available techniques.

"For instance, epidemiological studies identify subpopulations that are at greater risk of certain injuries," he said. "Then, serum or urine samples from this group could be used to identify those with evidence of metabolic changes associated with skeletal pathology, and then diagnostic imaging could be used to screen for structural change."

After deciding which screening tools to use, it's time to put them into practice, Riggs said. Certain groups of racehorses that appear to be at more risk of suffering catastrophic fractures than others include:

  • Horses resuming high-speed work after a period of rest; and
  • Horses that have accumulated high “miles on the clock” (i.e., they have more than a threshold number of starts, or they have galloped beyond a certain number of kilometers in their training and racing).

Riggs said research has shown that horses appear to be at higher risk of injury if they have started more than 30 times and have accumulated more than178 kilometers (110 miles) in their training and racing careers. Veterinarians should identify horses that fall in this "high-risk" group and use diagnostic imaging to examine them more closely for subtle signs of lameness or injury, he said.

"Nuclear scintigraphy is highly sensitive at detecting fatigue-related bone injury and early stress fractures," Riggs said. "And MRI can resolve structural detail indicative of fatigue damage that is not detectable by other modalities."

Additionally, he said, veterinarians can use specialized radiographic techniques, such as obtaining more technical views of the structure in question, to pinpoint injuries that might be missed on traditional views. Having these modalities available to evaluate at-risk horses for signs of injury or illness could help prevent catastrophic breakdowns from occurring.

Riggs also said veterinarians should use caution when administering anti-inflammatory drugs and analgesic (pain-killing) treatment, as these can mask some clinical signs of lameness or injury.

"Horses presented with mild clinical signs for 'routine" intra-articular medication sometimes harbor incomplete fractures," he explained. "Clinicians should ideally ensure that there is no significant underlying lesion before they administer such potent agents as intra-articular corticosteroids to any horse."

Educate Owners and Trainers

Finally, Riggs said, veterinarians must educate owners and trainers on the signs of injury and lameness and encourage them to take even subtle signs of a problem seriously. Encourage the use of diagnostic tools, he told veterinary attendees, and avoid owner or trainer pressure to simply mask clinical signs rather than getting to the bottom of the issue.

"Preventing injury requires a commitment from all involved," he said.

Take-Home Message

We can't eliminate injury risk from any sport, including horse racing. However, with careful planning, management, and screening, veterinarians and trainers might be able to reduce racehorses' risk of sustaining catastrophic fractures.

About the Author

Erica Larson, News Editor

Erica Larson, news editor, holds a degree in journalism with an external specialty in equine science from Michigan State University in East Lansing. A Massachusetts native, she grew up in the saddle and has dabbled in a variety of disciplines including foxhunting, saddle seat, and mounted games. Currently, Erica competes in eventing with her OTTB, Dorado.

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