OklahomaHorses Magazine May 2021

22 OklahomaHorses • May/June 2021 pain or dysfunction of the locomotor system. The source of lameness must be localized to a specific area so that an accurate diagnosis can be made. In many instances, localizing the source of lameness can be especially challenging. To identify the source of lameness, a veter- inarian commonly uses the horse’s signalment (age, breed, discipline) and historical informa- tion in combination with clinical examination findings. Traditionally, the lame limb and the severity of lameness is subjectively determined by the veterinarian using a 0-5 grading scale de- veloped by the American Association of Equine Practitioners (AAEP) in which a grade of 0 is not lame and a 5 is non-weight-bearing lame. Veterinarians, who routinely evaluate horses for lameness, develop a keen eye allowing them to subjectively recognize the mildest of lame- ness. However, research has shown that there can be much discrepancy between veterinarians as to the severity and even sometimes the limb displaying the lameness when subjectively evalu- ating the same horse. Fortunately, there are tech- nologies that can provide objective information to assist the veterinarian in lameness detection. One of these technologies is a force plate, which is an instrument that measures the amount of force applied to it. In sports medi- cine, this force is termed the ground reaction force. The force plate has long been consid- ered the “gold standard” for equine lameness detection. Lameness is often not consistent in severity during every single stride, so multiple measurements must be collected to determine the average ground reactive force of each limb. Generally, the average ground reaction force exhibited by each of the horse’s fore or hind limbs should be similar from side to side. If there is a significant difference, the limb exhibit- ing the lower ground reactive force is designated the lame limb. Although subjective evaluation and the force plate are both valid methods of lameness assessment, there is little correlation between the AAEP grading scale and ground reaction force measurements. This is because these methods are evaluating different movement parameters. The force plate measures the force of movement, otherwise known as kinetics, where the human eye evalu- ates the geometry of movement, or kinematics. Due to the time and effort it takes to obtain the required measurements, the force plate is not often used in clinical lameness evaluations but is a valuable research tool. Inertial sensors offer another objective way to evaluate lameness in horses. They can measure movement down to a fraction of a millimeter at 200 times per second, far more sensitive than the human eye. Once attached to specific locations, inertial sensors record the movement patterns of a horse over 25 to 35 strides and communicate this information to a computer program, which then generates a report describ- ing any asymmetries. Veterinarians can use this information to help determine if a horse is lame, the lame limb and the severity of the lameness. Inertial sensors can also be used to evaluate response to flexion tests, improvement following local anesthesia or to document treatment success at re-evaluations that may be weeks to months later. Inertial sensors have been validated by several research studies using both subjective assess- ments and force plate analysis. This meth- odology more closely correlates to subjective Another tool Dr. Mike Schoonover uses when evaluating a horse for lameness is an inertial sensor system attached to the horse’s head, hip and lower right forelimb. The inertial sensors will measure head and pelvic movements relative to the horse’s stride. The sensors communicate wirelessly to a tablet computer, which reports any asymmetries from left to right. Small but significant asymmetries in head or pelvic movement can indicate lameness.