b'STEP BY STEPanalysis, says Thilo Pfau, PhD, senior lecturer in bioengineering at the RVC. While inferior to the quality of an IMU or OMC test in a clinic, the method could give veterinarians an early indication of the possible presence of subtle hind-limb lameness before referral, he says. COURTESY EMMA PERSSON-SJODINA Human TouchMachines might be able to give us information about precise asymmetries, but many researchers argue that nothing can replace the analytical powers of the human brain for diagnosing lameness. Im not opposed to using objective Objective systems measure asymmetry, speci\x0ecally, but not all asymmetries are lameness-related. measurement systems, but their useDr. Marie Rhodins team, for instance, used sensors to determine that rider effect and circling can should not be at the expense of looking atexacerbate or cancel out asymmetry.the horse clinically, Dyson says. I think one of the real problems is that some ofobjective measurements can tell you. says. They cant explain pain thats mak-the users of the system stopped looking atObjective measurements cant, foring a horse unwilling to canter one direc-the horse, and they expected it to answerexample, distinguish mild nonpain- tion but trot symmetrically in a straight all their problems. Some people dontful asymmetry from mild painfulline. They cant pick up other signs of really recognize the limitations of whatasymmetrywhich is true lameness, shepain related to subtle lameness, such as difficulties performing specific move-ments when ridden, conflict behavior, A History of Force Plates, OMCs, and IMUs or alterations in facial expressions. They cant currently see when horses compen-Researchers first started using force plates on the ground in the mid-1970s to help clini- sate for pain in ways other than up-down cians give lameness exams some objectivity. Horses would walk or trot over the plates, andasymmetry, such as swinging a limb out machines would calculate the forces each foot applied at each moment. While the use ofor moving hind limbs on a separate track force plates continued into the 21st century, researchers recognized the need for something from the front limbs. We have used a more practical, because the plates are bulky, heavy, and only measure one stride in one GPS to objectively evaluate leaning in on place at a time.Around the turn of the millennium they came up with a force-measuring treadmill anda circle, reflecting lameness, but this can-pressure sensors veterinarians could place directly on the horses feet. But those tools stillnot be done with (IMUs), says Dyson.lacked practicality for gait analysis, says Filipe Serra Braganca, DVM, a PhD candidate inAll these units measure is the asym-equine musculoskeletal biology in Utrecht Universitys Faculty of Veterinary Medicine Depart- metry in the ability to land and push off ment of Equine Sciences, in the Netherlands. a leg, so theres obviously an inherent Optical motion capture (OMC) became popular in the early 2000s for objective gaitlimitation there, she continues. When analysis and is currently the gold standard for objective kinematic analysis of movement inI evaluate horses, I always look at them horses. But its complicated to set up, Braganca says. It requires 10 to 15 reflective markers,ridden, and Im looking at any differences placed at strategic points on horses bodies, and about 18 infrared cameras recording mo- in the way the horse performs globally tion capture data at 200 Hz. in not only trot but also canter. Does it Inertial measurement units (IMUs) measure linear and angular motion, mainly usinglook happy? Is it accepting the contact accelerometers and gyroscopes. The technology originated in the 1930s for use in aircraft.properly? Does the rider have an equal German scientists incorporated accelerometers into lameness exams in the 1990s. Infeel in the hands? I use many other things the early 2000s scientists developed a micro IMU that could fit into modern technologi- to help tell me if theres residual pain.cal equipment such as mobile phones. That catapulted IMU technology into a variety ofOn the contrary, objective evaluations branches, including equine medicine by the middle of the decade, with a 2004 study by acould lead to excessiveand needlessUniversity of Missouri team appearing in The American Journal of Veterinary Research.additional testing, including nerve blocks By 2012 Thilo Pfau, PhD, senior lecturer in bioengineering at The Royal Veterinary College,(which numb a limb area temporarily in the U.K., was analyzing equine footstep readings and ataxia (incoordination) with an IMUto see if the horse moves normally after, attached to the horses pelvis. Meanwhile, an American team led by Colorado State Univer- indicating thats where the pain is com-sitys Valerie Moorman, DVM, PhD, Dipl. ACVS-LA, was evaluating gait symmetry analysis with ing from), she adds. If you find yourself an IMU attached to horses hooves. driven by objective gait analysis, you Since those first tests, veterinarians and researchers have used IMU increasingly in equine gait analysis, leading to more than 30 published studies in peer-reviewed journals inmight keep using nerve blocks everywhere the past six years.Christa Lest-Lasserre, MA for asymmetry that is just natural and not related to pain and lameness.They can also lead to inaccurate 64November 2018The Horse|TheHorse.com'