What Have We Learned From Over 1,000 PET Scans Of Racehorse Fetlocks? - Horse Racing News | Paulick Report
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What Have We Learned From Over 1,000 PET Scans Of Racehorse Fetlocks?

One of the overarching themes from the 10th Welfare and Safety of the Racehorse Summit at the Keeneland sales pavilion on Wednesday, June 22, was that prevention and early monitoring are going to be the key to reducing racetrack fatalities and injuries in the future.

“If you're only looking at horses on race day, you are missing the boat at this point,” said Dr. Mary Scollay, executive director and chief operating officer of the Racing Medication & Testing Consortium. “We know these are cumulative injuries; anybody who says the horse took a bad step is in for a really wicked glance from me. If we're not looking at these horses at other times, we are missing an opportunity to help protect them.”

Dr. Mathieu Spriet, an associate professor of surgical and radiological sciences at the University of California, Davis, gave a fascinating presentation during the summit discussing the results of over 1,000 PET scans of racehorse fetlocks.

A positron emission tomography (PET) scan is an imaging test that can help reveal abnormal metabolic activity in the bones of a racehorse's fetlock. Across multiple studies, Spriet was able to demonstrate not only that the PET findings can be more helpful and accurate than other methodologies at identifying potential issues, but he was also able to create a grading system for the lesions found on PET scans that can fairly reliably indicate the necessary healing/layup time.

The Stronach Group installed the first equine PET scan machine which did not require a horse to undergo general anesthesia at Santa Anita in 2019, and there have been four more of the machines installed across the United States. By the end of this year, Spriet said, that number will double.

By pairing the PET scans with other imaging methods, like CT scans (basically a three-dimensional x-ray), Spriet was able to improve his ability to identify at-risk horses.

One of the studies commissioned using the PET scanners was a 72-horse study of horses not showing clinical signs of lameness. Horses were selected at three different locations: Golden Gate Fields (specifically, only horses both training and racing on the Tapeta synthetic surface), Santa Anita, and Fair Hill Training Center. Each horse had all four fetlocks scanned within a week of finishing in the top half of a race.

Three of the 72 showed findings severe enough to require a layoff, while another 15 percent demonstrated findings which convinced Spriet to recommend that trainers modify the horse's training. Interestingly, the horses at Golden Gate showed less evidence of lesions than those racing at Santa Anita or from Fair Hill.

In total, the non-clinical horses demonstrated far fewer PET scan findings than their clinically lame counterparts.

In an additional study of 2-year-olds at Golden Gate, which included six normal and six clinically lame horses, the normal horses again showed less severe findings than their clinical counterparts.

While these findings have improved Spriet's confidence in the technology's ability to one day be used as a preventative, he cautioned that the current best use of PET scanners is in longitudinal studies, i.e. over time, in terms of monitoring horses' healing from bone lesions.

In examining longitudinal cases, in which a horse was scanned multiple times over a period of several months, Spriet determined that the most important time to scan a horse to check for recurrence of an issue is three to four months after beginning training, around its first five-furlong workout.

Those cases allowed Spriet to create a grading system for the initial size and severity of the remodeling, which indicates the approximate amount of time a horse will need to be laid off to recover.

From the total of more than 1,000 fetlock PET scans, Spriet was able to determine the most common locations of issues which may be related to later breakdowns. However, he cautioned that approximately 20 percent of horses with no clinical abnormalities will show abnormalities on a PET scan, so the intensity of the uptake is also an important factor when assessing for racing soundness.

“We have some very specific localization of findings,” Spriet said. “When we see uptake in sites related to breakdown we have concerns, and the intensity of the uptake will dictate the management of the horse.”

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