The Horse

NOV 2018

The Horse:Your Guide To Equine Health Care provides monthly equine health care information to horse owners, breeders, veterinarians, barn/farm managers, trainer/riding instructors, and others involved in the hands-on care of the horse.

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TheHorse.com | The Horse November 2018 63 move asymmetrically, or by having a rider on board. Her recent studies on rider influence show that the rising or posting trot causes considerable asymmetry in a horse. And that rider effect, combined with circling, can multiply or cancel out asymmetry, depending on which diagonal the rider is posting on and which direc- tion the horse is turning. Other factors, such as terrain, environ- ment, the horse's mental status, and even day-to-day variations, could affect sym- metry readings, says van Weeren. It's not even accurate to say all lame horses are asymmetrical, he adds. A horse that's lame on both forelimbs or both hind limbs, for example, might move symmetrically despite significant pain. "We have to keep in mind that 'lameness' is a clinical term, but 'asymmetry' is not," van Weeren says. Allowing for some level of asymmetry makes sense, because that's just part of our physical individuality, regardless of species, says Sue Dyson, MA, VetMB, PhD, DEO, Dipl. ECVSMR, FRCVS, head of Clinical Orthopaedics at the Animal Health Trust Centre for Equine Studies, in Newmarket, England. In most cases slight asymmetry is normal, isn't painful, and doesn't affect performance. "You don't have perfectly symmetrical people," Dyson says. "So why would you have perfectly symmetrical horses?" Developing Technology and Ideas The current "gold standard" in objec- tive asymmetry exams measuring move- ment is optical motion capture (OMC), says Filipe Serra Braganca, DVM, a PhD candidate in equine musculoskeletal biol- ogy in the Faculty of Veterinary Medi- cine's Department of Equine Sciences at Utrecht. With this technology, scientists place markers all over the horse's body, and a high-speed camera system detects their movement. He says one drawback to this method, though, is it can give inaccurate mea- surements when, for example, horse or handler limbs block the cameras' field of view or cause errors in depth perception. This, in addition to expense and impracti- cality, has pushed scientists to find more practical and portable ways to measure asymmetry. In recent years researchers have focused more on developing inertial measurement unit (IMU) technology, based on gyroscopes, accelerometers, and magnetometers (to measure rotation, acceleration, and orientation, respectively), says Braganca, which don't get blocked or tricked by leg movements. Over the years researchers have moved IMU sensor placement up from the hooves to the legs, body, pelvis, and withers. A commercial IMU system called Lameness Locator features three sensors—one each on the poll, pelvis, and one limb. It's designed to help identify the lame limb, degree of asymmetry, and affected stage of the stride. Feedback and investigation of IMU systems in practice have led the Utrecht team to develop a similar system called EquiMoves, based on eight IMU points, which Braganca says shows promising results in field tests. "We have come so far with technological developments that IMU sensors are becoming as accurate as OMC or, in some cases, even more accurate since the sensor inside the IMU (the gyroscope) can measure limb angles directly," he says. Meanwhile, researchers at The Royal Veterinary College (RVC), in Hatfield, U.K., have come up with a method that benefits from practical IMU technology already available in certain smartphones. Trained veterinarians could potentially strap a phone onto the horse's hindquar- ters during a farm call to get a basic gait COURTESY CAMBRIDGE EQUINE HOSPITAL, NEW ZEALAND The Lameness Locator is an inertial measurement unit (IMU) that comprises three sensors. It's designed to help identify the lame limb, degree of asymmetry, and affected stage of the stride. COURTESY INGRID KERKHOVEN An IMU system called EquiMoves is based on eight inertial measurement unit points.

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