Veterinarians Launch Four-Year Study To Track Progress, Relevance Of Yearling Radiographic Abnormalities

by | 11.18.2016 | 1:52pm
A veterinarian examines a radiograph

A large study led by Drs. Wayne McIlwraith, Frances Peat and Chris Kawcak from the Orthopaedic Research Center at Colorado State University, working with Dr. Jeff Berk from Lexington, Ky., was commenced at the Keeneland September Yearling Sale this year. This study will look at two issues that are typically the most-discussed findings by buyers, sellers, and veterinarians alike: 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.

Since repositories were introduced to Thoroughbred auction houses in the 1990s, a degree of uniformity in radiology, particularly for OCD lesions has developed. 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 (SCLs) of the medial femoral condyle are the focus of the study. An initial study prior to both digital radiographs and the advent of the repository was performed 15 years ago by Drs. McIlwraith, Kane, Park, Rantanen, Morehead, and Bramlage. A Second study prior to digital radiographs was performed by Drs. Spike-Pierce and Bramlage. These studies led to more questions about sesamoiditis, and could not address the stifle lesion question at all because of the lack of digital radiographs.

Since then, there has been investigation of sesamoiditis relative to development of suspensory ligament branch injury by Drs. McLellan and Plevin in Florida. A study that specifically investigates sales horses and follows them at the yearling and 2-year-old sales with radiographic and ultrasonographic examination (as appropriate) has never been performed.

The first phase of the study was conducted at the 2016 Keeneland September Yearling Sale with 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 2,795 yearlings, or 74 percent of all yearlings presented for sale which had radiographs available. Of these 2,795 yearlings, suspensory branch ultrasonography on 704 horses was performed on farms before they shipped to Keeneland. The radiographs have been evaluated for changes in the sesamoid bones and the medial femoral condyles of the stifles, and the ultrasound images will be evaluated for abnormalities involving the suspensory ligament branches at their insertion into the sesamoid bones.

The second phase of the project will follow these horses through the 2-year-old in training sales in 2017, again evaluating the sesamoid bone/suspensory branch complex and the stifle lucencies. The third phase will follow this group to the races, culminating at the end of their 3-year-old year.

The study will be the largest of its kind and will yield information that will be extremely 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. With the cooperation of the sales companies, consignors, owners, and veterinarians, this study stands to significantly benefit all involved in the sales process.

“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.”

“Modern medicine decisions are supposed to be evidence based, and these two problems are excellent examples of decisions being made without adequate data,” said McIlwraith. “No evidence-based work has been published that pairs yearling and 20year0old sale radiographs for individual horses.”

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

The sheer size of the study, which is necessary to assure its statistical significance, plus the requirement to employ individual veterinarians with skills in performing both the ultrasonographic and radiographic reading, will result in crucial information for the industry, but also a large expense.

The amount for Year 1 of the project (in the process of completion) is $175,000 and the overall pricetag for the four-year study is estimated to be approximately $445,000. Bridge funding has been obtained for the first years' expenses from discretionary dollar sat Colorado State, but it is the hope of researchers that individuals from the industry will contribute to costs. A research grant has already been written for funding the second and third years.

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