Objective Lameness Measurement in U.S. Horse Racing – For the Welfare of the Equine Athlete
By Kevin G. Keegan, DVM, MS, DACVS | Laurie Tyrrell-Schroeder, DVM | Andy Wolter, CEO Equinosis, LLC | Deborah Sieber, BVetMed
In the Spring 2019 and May e-edition of Eye on Objectivity, Drs. Bronte Forbes, Kevin Keegan, and Joanne Kramer wrote about the potential of objective measurements to help identify pre-existing conditions as a risk factor for catastrophic breakdown in horse racing. In this issue, we offer what, based on lessons learned at the Hong Kong Jockey Club and Singapore Turf Club, can be done now to immediately improve the welfare of racehorses in the USA.
Objective lameness measurements seem to draw immediate criticism from some associated with horse racing – both veterinarians and horsemen alike. With an incomplete understanding of the technology and how it is being applied successfully at racetracks in Singapore and Hong Kong, some conclude that inertial sensors are “too sensitive for racing Thoroughbreds”.
Some regulatory veterinarians claim that an absolute threshold of asymmetry is required to denote “fit” from “unfit” to compete and that, since this threshold is not currently known, objectively measuring for lameness may open a pandora’s box. On the other hand, horsemen fear the added sensitivity of a threshold set too low – which they feel can only restrict their horse’s competitive career. However, both of these perspectives subordinate the care and welfare of the equine athletes and grossly mischaracterize how objective measurement of lameness in horses is used by knowledgeable veterinarians to support their clinical opinions and prevent bias.
Regulation based on pre-race, objective lameness measurement of equine athletes may eventually be adopted, but not until more data is collected and definitively associated with professional opinion and post-race outcomes. A reasonable place to start would be to first study objective lameness data from horses already placed on the vet’s list. How is the measured data different from horses cleared to race? Is there a difference in the reference ranges of measures of lameness between these two groups of racehorses? This information, used as the justification to perform a more in-depth veterinary examination to establish a diagnosis, we think, would be more successful at identifying horses at risk of catastrophic breakdown.
For those unfamiliar with the current Lameness Locator reference ranges, these are purposely set lower limits of asymmetry intended to guide the veterinarian to first investigate the cause of lameness in the limb most likely affected. There were determined empirically on a heterogenous population of non-racehorses as the 95% confidence interval of inertial sensor measures found in horses with a mean AAEP score of 0, given by three experienced veterinarians. The principle utility is in cases presented for lameness or poor performance, in other words in horses already suspected to have lameness. Used as the reference range for screening racehorses for the likelihood of further injury if allowed to race, they will almost certainly be too low. More relevant reference ranges for this specific purpose will need to be determined and this can only be accomplished with further study.
Objective measurements, whether they are used in performance or pleasure horses, and if they are used and interpreted skillfully, simply protects against bias and minimizes mistakes. Veterinarians at the Singapore Turf Club and Hong Kong Jockey Club have been using inertial sensors to evaluate racehorses for a few years already. They have integrated lameness measurement into their clinical care (both clubs are responsible for the care of the athletes competing at their tracks) and are now looking for ways to more fully implement objective measurements to screen for pre-existing injury and to more fully assess recovery. The horsemen under their direction accept and understand the utility of this technology when used properly. They trust the data, viewing it more as an aid to return their horse to racing as soon as possible, rather than as just another regulatory obstacle. A similar initiative, to use inertial sensors to evaluate racehorses, is being investigated in the United States.
With input from many customers and colleagues involved with racing, and the collaboration of key stakeholders, we believe that pilot studies can be successfully completed, 1) to evaluate the difference of objective measurements from horses deemed fit and unfit to compete, and 2) to evaluate the change in objective measurements in horses placed on the vet’s list. These longitudinal studies could establish the natural variability of objective measurements in a homogeneous group of Thoroughbreds in competition that would have to be taken into consideration in assessing any differences between groups or changes over time. Such longitudinal studies would be a first step into further understanding how pre-existing injury, thought to be a major factor contributing to catastrophic musculoskeletal injury, may be better detected and assessed. Better detection and assessment of injury, regardless of its association with catastrophic musculoskeletal injury, is important for the welfare of the horse.