Major Thoroughbred study seeks to uncover true impact of leg issues seen in imaging

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Racehorses emerge from the starting gates at Suffolk Downs, East Boston, Massachusetts. Photo: Anthony92931 (Own work) CC BY-SA 3.0 via Wikimedia Commons
Racehorses emerge from the starting gates at Suffolk Downs, East Boston, Massachusetts. Photo: Anthony92931 (Own work) CC BY-SA 3.0 via Wikimedia Commons

Researchers seeking to uncover critically sought-after information around the significance of sesamoiditis and stifle lesions in the legs of young Thoroughbreds will be following a group of racehorses until the end of their three-year-old seasons.

The crucial earlier phases of the study have already been completed.

The x-ray/ultrasound-based study is exploring two of the most often discussed controversial issues affecting the Thoroughbred: radiographic findings in the proximal sesamoid bones of the fetlock with associated suspensory branch changes; and radiographic findings in the medial femoral condyle of the stifle.

The work is being led by Colorado State University’s Orthopaedic Research Center veterinarians, Drs Wayne McIlwraith, Frances Peat, and Chris Kawcak; and Dr Jeff Berk, from Lexington.

The study began at the 2016 Keeneland September yearling sale and involved 2795 yearlings. It continued through the two-year-old sales in 2017.

Researchers were able to follow 78% of all eligible two-year-olds that had consignor permission for radiographic inclusion in the study as yearlings because of the understanding within the industry of the need for this research.

Studies of this size require a lot of funding.

Three major industry organizations have stepped up to date. The Keeneland Association has committed $US100,000 toward completion of the work. Fasig-Tipton Company has also made a $US50,000 commitment, and the Grayson-Jockey Club Research Foundation has approved a $US143,624 grant.

The study team is now in the final phase of collecting funding contributions from private donors who believe in the value of the study.

Since repositories were introduced to US Thoroughbred auction houses in the 1990s, some uniformity in radiology has developed, particularly for osteochondritis dissecans lesions.

However, some radiographic changes remain a persistent source of controversy for sellers, buyers, trainers, and veterinarians. That is why sesamoiditis, and lucencies or subchondral cystic lesions of the medial femoral condyle, are the focus of this study.

The first study phase at the 2016 Keeneland September yearling sale resulted in excellent collaboration from the sales company and consignors. Consignors presenting yearlings at this sale were asked permission to include the yearlings in the radiographic and/or ultrasonographic portions of this study.

Radiographic permission was granted by 71 consignors, resulting in a total of 2795 yearlings, or 74% of all yearlings presented for sale that had radiographs available.

Of these 2795 yearlings, suspensory branch ultrasonography on 704 horses was performed on farms before they were shipped to Keeneland.

The radiographs have since been evaluated for changes in the sesamoid bones and the medial femoral condyles of the stifles. The ultrasound images will be evaluated for abnormalities involving the suspensory ligament branches at their insertion onto the sesamoid bones.

The second phase of the project followed horses that had radiographs included in the study as Keeneland September yearlings, to five of the major two-year-old sales in 2017: the Fasig-Tipton Gulfstream Sale, OBS Select Sale, OBS Spring Sale, Fasig-Tipton Midlantic Sale and the OBS June Sale.

Permission for inclusion in the second phase of the study was granted by 45 two-year-old consignors, for 78% of eligible horses. This amounted to 473 two-year-olds on which to evaluate radiographs, and 415 of these horses also had suspensory branch ultrasounds performed for the study.

Researchers will again evaluate the sesamoid bone/suspensory branch complex and the radiographic stifle lucencies in this group of horses.

The third phase will follow the racing performance of these horses, finishing at the end of their three-year-old season.

Paired radiographs and ultrasound images will enable researchers to identify the progression, regression, or static nature of certain radiographic and ultrasonographic findings under the conditions in which these sale horses are managed.

“This study is badly needed,” said Berk, whose equine veterinary career exclusively involves sales work.

“Critical decisions have to be made at the sale that affect both consignors and potential buyers that preclude sales of horses when the decision is sometimes based on no evidence of a given lesion leading to unsoundness.”

McIlwraith added that modern medicine decisions were supposed to be based on evidence – “and these two problems are excellent examples of decisions being made without adequate data”.

“No evidence-based work has been published that pairs yearling and two-year-old sale radiographs for individual horses,” he said.

The study will be the largest of its kind and is expected to yield information that will be useful to those involved in the selection process of sales horses. It will aid veterinarians in providing their buying and selling clients with a more accurate assessment of the significance of these findings.

It will also help those in the Thoroughbred industry gain an understanding that not all radiographic findings are contributory factors to any given horse’s suitability for racing.

The study has, according to the researchers, gained considerable traction, with all those involved in the sales process standing to benefit from the much-needed and now highly anticipated findings

The contributions from Keeneland Association, Fasig-Tipton Company and the Grayson-Jockey Club Research Foundation total $US293,624, with the overall budget for the project to bring it to completion estimated at $425,000.

The researchers are now looking to individuals, farms or organizations to contribute to the remaining $US135,000.

Parties interested in making a contribution through Colorado State University may contact wayne.mcilwraith@colostate.edu.

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