Veterinarians are commonly asked to evaluate horses for their clients and these "prepurchase" examinations often include radiographs.
A study completed by leading equine researchers and the Equine Orthopedic Research Laboratory at Colorado State has shed some
light on radiographic changes in Thoroughbred yearlings and correlated those changes to future athletic performance.
When the horse in question is young and has not been trained, raced or ridden extensively, then radiographic changes can
be very difficult to interpret. There may be no clinical history and there is usually very little performance history, so
the veterinarian must decide if the changes, usually subtle, seen in his/her films are significant.
Basis for decision
But what is this decision usually based on? Certainly past experience is important, but many times even this does not allow
for more than an "educated guess." Guess wrong, and say that the lucency that you see on this horse's films may indicate future
problems and your client passes on a great horse, or worse, ends up getting beat by this horse in some future event.
Guess wrong, and say that the small fragment in that joint is not of concern, and your client buys a horse that becomes lame,
may need future surgery or may never be a functional athlete. All in all, it is not a good position to be in and with the
increasingly litigious nature of the profession, many veterinarians find themselves less and less willing to evaluate young
Clients thinking about a horse for purchase often look to their veterinarian for help in evaluating radiographs. Information
that can help predict the relevance of X-ray changes will make such decisions easier.
Drs. Kane, McIIwraith, Park, Rantanen, Morehead and Bramlage may have provided a bit more information for veterinarians who
find themselves in this situation.
These researchers, along with the Equine Orthopedic Research Laboratory at Colorado State University, have completed a study
that looked at radiographic changes in Thoroughbred yearlings and then tried to correlate those changes to future athletic
This study took place over three years and looked at 1,200 horses. Because the evaluation of yearling Thoroughbreds occurs
each year at specific sales, this was a natural population to use for such a study.
Positive future athletic performance proved a bit harder to define and quantify but, for these Thoroughbred yearlings, the
ability of a horse to complete training and to actually start a race was taken as success.
The authors readily admit that this study may not be easily applied to the future success of horses used for different disciplines
because the stresses of racing are different from those of many other sports. It is the first such study of this scope however,
and much information can be learned that applies directly to racehorses, and indirectly to other equine athletes. This study
was jointly funded by the Keeneland Association, the Fasig-Tipton Sales Company, the Ocala Breeder Sales Company, the AAEP,
Barrett Equine Limited, the Jockey Club, and the Blood Horse Charitable Foundation.
Many other researchers have attempted to look for normal variations in radiographs in horses.
This study goes a step further by evaluation films, following these yearlings through their 3-year-old year and looking at
their performance. A questionnaire was also sent to the owners of these yearlings and information on training progress, problems
and surgical intervention was obtained. The results of the study hopefully give the practitioner some "black and white" information
as to the significance or lack of significance of certain abnormalities seen in the radiographs of thoroughbred yearlings.
As Dr. Al Kane stated, "One of the purposes of this study was to perhaps re-introduce the concept of 'incidental findings'
". Not all changes are significant and knowing which are and which are not can make all the difference.
This series of films contain minor changes of little significance to the athletic function of this horse. Other minor changes
in different locations, however, can be "red flags" and may mean a future of poor performance, possible surgery or lameness.
The most commonly affect area in these horses was the front fetlock. Abnormalities consisted of flat areas (51 percent) on
the distal articular surface or lucencies (17 percent) in the same area. Moderate to extreme palmar supracondylar lysis was
also noted in some horses and this finding was significantly associated with lowered racing performance. These horses were
one third less likely to start. Flat areas or light areas in the bone (lucencies) associated with the saggital ridge of the
distal cannon bone did not correlate to decreased racing performance or other medical problems. Enthesophytes or areas of
roughening on specific bones can be one of the more common incidental findings. Such areas on the front of the proximal sesamoid
bones were related to problems and these yearlings were one third less likely to start a race.
Vascular channels in these bones, however, were not associated with problems and 98 percent of yearlings had at least one
channel while 58 percent had more than two.