Not One Size Fits All: Paper Outlines Findings From Newmarket Fetlock Injury Symposium

While the racing industry has made important strides forward in detecting horses at risk of suffering catastrophic injuries before they occur, that system is far from perfect. But better use and understanding of the various diagnostic tools at our disposal could help to plug those existing gaps–that's the main takeaway from a recent article published in the Equine Veterinary Journal.

The seven-page paper provides a summary of the findings that came from a symposium held this past March at Newmarket, during which various veterinarians and experts shared their research into fracture risk assessment of the fetlock–the most common catastrophic injury site in racehorses.

For so long, the industry has been looking for “that one” diagnostic imaging technology “that solves all our problems,” Ryan Carpenter, a Santa Anita-based private veterinarian who gave a presentation at the symposium, told TDN. “The reality is, we're not there yet,” he added.

“More importantly, we have to acknowledge that there are strengths and weaknesses to the whole modalities. It's not a one size fits all,” Carpenter said. “But I think when you use them in conjunction with one another, and you recognize their strengths and weaknesses, I think you can make some serious headway.”

Many of the pre-existing injuries that end up proving catastrophic are extremely subtle and therefore difficult to detect. Indeed, this study found that 90% of horses fatally injured in Hong Kong displayed no noticeable clinical signs of injury during a pre-race veterinary inspection.

Experts have identified a range of race, horse and management-related factors that can be used to identify horses at serious risk of suffering catastrophic injuries on the track.

But as the paper points out, the statistical models these factors can be plugged into still aren't especially effective at predicting catastrophic injuries, partly because of the low prevalence of these sorts of injuries anyway, and the dearth of relevant data.

Indeed, one study which encompasses some 2,000,000 starts and 4,000,000 workouts had a 65% success rate at predicting which one of only two horses was about to sustain a fracture–odds only marginally higher than that of a coin toss.

Which is where imaging can come in.

The paper finds a direct relationship between “serial testing”–what is a more systematic way of monitoring problem areas–and a higher probability of targeting pathology at the site of a potentially catastrophic injury.

Let's zero in on radiography, what the paper says remains the most “important imaging modality in fetlock bone risk assessment,” but is nevertheless a “relatively untapped resource that through education of primary care vets could immediately have a profound impact on injury mitigation.”

What does the paper mean by “untapped”? This study on the effect of intraarticular joint injections on the risk of subsequent fracture found that prior imaging on the injected site had been done in less than 8% of cases.

Under the serial testing model, however, a clinical examination that identifies a problem area in the fetlock joint would lead to a second diagnostic test, like a radiograph, to get a better understanding of the issues at play.

If the veterinarian suspects further issues brewing in the fetlock than is visible on the radiograph, they have the option of ordering additional tests using a more sensitive imaging modality, like a positron emission tomography (PET) or an magnetic resonance imaging (MRI) scan.

And why isn't that done more often as it is? “I think a lot of people are,” said Carpenter. “But I think some people aren't.”

These are “multifactorial issues,” he added, stressing the need for trainers and their staff to flag sore horses in the first place, at the same time pinpointing the pressure put on trainers from owners and the racing office. “There's a lot of these other factors that come into play that may or may not lead to good decisions.”

Nevertheless, as the paper points out, “there is no diagnostic test with 100% accuracy,” nor any one clear consensus of how the images are interpreted. To help in that regard, the paper has broken down into a table the pluses and minuses of each available imaging technology.

“Our goal was to basically condense a lot of information into a very useable reference,” said Carpenter.

Each technology–radiography, nuclear scintigraphy, computed tomography (CT), MRI and PET–is rated within the confines of these four categories: strengths, clinical information obtained, practical and technical limitations, and current knowledge gaps.

For nuclear scintigraphy, for example, large areas can be imaged but with low specificity. CT can be done quickly with high spatial resolution images, but there's currently a knowledge gap in differentiating between active abnormalities in the bone and “static” long-term changes.

But knowledge is only useful when placed into the right hands, and the racing industry, the paper says, would be wise to take some lessons from human medicine, particularly when it comes to regulatory transparency and the sharing of relevant information. From a bird's-eye viewpoint, the globalization of horse racing could be a more streamlined affair.

“Whilst veterinary assessment and regulatory pathways are in place in many racing jurisdictions globally, transparency about the process and standardization across countries is lacking,” the paper says.

But individual practitioners too must be more willing to share veterinary information that could have a bearing on that horse's fate on the track, the paper similarly stresses. “Equally, owners, trainers and other stakeholders must understand their obligation to comply with the risk assessment process if they wish to enter a horse in a race.”

The paper also pinpoints several “actionable items” resulting from the symposium. These include:

• A best practice guide on fetlock radiography.
• The creation of trainer manuals to help them both identify the warning signs of serious fatigue injury and understand how these injuries progress.
• The creation of an international, anonymized data repository, into which goes information like racehorse clinical and imaging data, and exercise and racing history.

This repository would then be used as a research tool.

“I don't think anybody expected this symposium to solve all our problems, but what it did was lay a very nice foundation for the work that will come from this,” said Carpenter. “I think you're going to look back in three to five years at a lot of good things that came out of this starting point and have a significant impact on this industry.”