Inertial sensor systems—gait analysis devices that measure the kinematics of horses’ limb and body movement—give veterinarians a way to collect objective lameness data when they’re conducting research and to record subtle movement abnormalities when they’re assessing difficult-to-pinpoint and/or multiple-limb lamenesses in patients. Ideally, veterinarians and assistants place wireless sensors consistently in specified locations. But, because humans are not machines, there can be some slight variation in that application. One research group wanted to see if the system remained accurate when sensor locations were altered.

Valerie Moorman, DVM, PhD, Dipl. ACVS, and colleagues at Colorado State University’s Orthopaedic Research Center, in the College of Veterinary Medicine and Biomedical Sciences’ Department of Clinical Sciences, looked at the effects of changing two sensor placements ever so slightly. She reported their results at the 2015 American Association of Equine Practitioners Convention, held Dec. 5-9 in Las Vegas.

The team hypothesized that shifting the position of the right fore pastern sensor would not significantly affect the system’s output, but that moving the pelvic sensor would significantly influence readings. They examined 12 horses trotting on a high-speed treadmill, which, while it does not exactly mimic a horse trotting over ground, does help ensure consistent speed and data collection between trials. On each horse the team tested the right forelimb sensor in its recommended spot (dorsal midline) and then 2 cm medially (toward the center axis of the horse’s body) and 2 cm laterally (toward the outside). In another session, they tested the pelvic sensor in five different locations: in its recommended position (again, midline), 2 cm to the right and left of midline, 2 cm cranially (toward the head), and 2 cm caudally (toward the tail).

“The output variables that we examined were the difference in maximum and minimum height of the head or pelvis between the left and right stance phases of stride,” she explained. “In nonlame horses, these values should be close to zero, but the more lameness a horse shows, these numbers get larger