[email protected]20 October 2012 • USDF CONNECTION I s he lame? Which leg? Which joint is it? Equine veterinarians are skilled at detecting the signs of lameness and identifying which limb is the most se- verely afected. A more difcult part of the diagnostic process is monitoring how a lameness changes over time. Te veterinarian may perform a nerve block or a joint block, then re- evaluate the horse’s movement, to see if the lameness improves. Sometimes the improvement will be dramatic, but often there is only a partial resolution of lameness, which can be difcult to quantify visually. One of the goals of locomotor re- search is to develop tools to assist veterinarians in the objective assess- ment, diagnosis, and monitoring of lameness. Currently, the most popular measurement equipment for this ap- plication is the Inertial Measurement Unit (IMU). Tese units are attached to specifc areas on the midline of the horse’s body—usually the poll, with- ers and croup, and sometimes also to the points of the hips (Figure 1). IMUs are based on the same technology used in Nintendo’s Wii game devices, which detect the velocity and orientation of the body part to which they are at- tached. When applied in lameness di- agnosis, IMUs detect movement asym- metries on the left and right diagonals. Asymmetry and Lameness Research has shown that the most con- sistent signs of lameness are the head nod in forelimb lameness and the hip hike in hind-limb lameness. Both of these telltale signs involve asymmetri- cal movements of the body during the stance (grounded) phases of the lame and compensating diagonals. In forelimb lameness, the head is raised just before the lame forelimb contacts the ground and then sinks through the stance phase of the com- pensating forelimb, producing the characteristic head nod. Te hip hike refers to the relative amounts of mo- tion in the left and right hips. How- ever, evaluating the hip hike requires a skilled eye because, even in a sound horse, hip elevation is diferent in the stance and swing phases. Typically, a horse with hind-limb lameness shows an increased vertical excursion with exaggerated hip elevation on the side of the lame hind limb at trot. To identify the lame limb, the veterinarian evalu- ates the vertical motion of the poll, croup, and hips relative to the move- ments of the left and right diagonals. Te traditional lameness evaluation consists of walking and trotting the horse frst in a straight line and then on a circle in both directions. Te out- side limb carries more weight than the inside limb on a circle, and anatomi- cal structures on the medial and lateral sides of each limb may be loaded dif- ferently in the two directions. Conse- quently, lameness may change with di- rection and is often more apparent on one rein than the other. However, we don’t fully understand the mechanics of turning in horses and how the nor- mal gait pattern changes when a sound horse turns. Locomotor Study In order to address the above issue, researchers from the McPhail Equine Performance Center partnered with horse-health connection Te Science of Lameness Diagnosis Ever play Wii? Similar technology is advancing the science of equine locomotor research By Hilary M. Clayton, BVMS, PhD, Diplomate ACVSMR, MRCVS Figure 1. A horse outftted with Inertial Measurement Units (IMUs) on the poll, withers, croup, and hips for data collection. A GPS unit is attached to the croup. Te transmitter unit is visible on the surcingle beside the withers. COURTESY OF THE MCPHAIL EQUINE PERFORMANCE CENTER
equine veterinarians are skilled at detecting the signs of lameness and identifying which limb is the most se-verely afected. A more difcult part of the diagnostic process is monitoring how a lameness changes over time.
Te veterinarian may perform a
nerve block or a joint block, then re-evaluate the horse’s movement, to see if the lameness improves. Sometimes the improvement will be dramatic, but often there is only a partial resolution of lameness, which can be difcult to quantify visually.
one of the goals of locomotor re-search is to develop tools to assist veterinarians in the objective assess-ment, diagnosis, and monitoring of lameness. Currently, the most popular measurement equipment for this ap-plication is the inertial Measurement Unit (iMU). Tese units are attached to specifc areas on the midline of the
horse’s body—usually the poll, with-ers and croup, and sometimes also to the points of the hips (Figure 1). iMUs are based on the same technology used in nintendo’s Wii game devices, which detect the velocity and orientation of the body part to which they are at-
tached. When applied in lameness di-agnosis, iMUs detect movement asym-metries on the left and right diagonals.
Asymmetry and Lameness
Research has shown that the most con-sistent signs of lameness are the head nod in forelimb lameness and the hip hike in hind-limb lameness. Both of these telltale signs involve asymmetri-cal movements of the body during the stance (grounded) phases of the lame and compensating diagonals.
in forelimb lameness, the head is raised just before the lame forelimb contacts the ground and then sinks through the stance phase of the com-pensating forelimb, producing the characteristic head nod. Te hip hike refers to the relative amounts of mo-tion in the left and right hips. How-ever, evaluating the hip hike requires a skilled eye because, even in a sound horse, hip elevation is diferent in the stance and swing phases. typically, a horse with hind-limb lameness shows an increased vertical excursion with exaggerated hip elevation on the side of the lame hind limb at trot. to identify the lame limb, the veterinarian evalu-ates the vertical motion of the poll, croup, and hips relative to the move-ments of the left and right diagonals.
Te traditional lameness evaluation consists of walking and trotting the horse frst in a straight line and then on a circle in both directions. Te out-side limb carries more weight than the inside limb on a circle, and anatomi-cal structures on the medial and lateral sides of each limb may be loaded dif-ferently in the two directions. Conse-quently, lameness may change with di-rection and is often more apparent on one rein than the other. However, we don’t fully understand the mechanics of turning in horses and how the nor-mal gait pattern changes when a sound horse turns.
Locomotor Study
in order to address the above issue, researchers from the McPhail equine Performance Center partnered with
horse-health connection
Te Science of Lameness DiagnosisEver play Wii? Similar technology is advancing the science of equine
locomotor research
By Hilary M. Clayton, BVMS, PhD, Diplomate ACVSMR, MRCVS
Figure 1. A horse outftted with Inertial Measurement Units (IMUs) on the poll, withers, croup,
and hips for data collection. A GPS unit is attached to the croup. Te transmitter unit is visible
Dr. Tilo Pfau, an engineer from the Royal Veterinary College in London who has expertise in the use of iMUs in lameness diagnosis. our goals were to measure the efects of circle size and speed on symmetry of move-ment in dressage horses trotting on the lunge. We are grateful to dressage trainers Kathy Connelly, Jen March-and, and their staf and students for lending their horses and welcoming us into their barns and arenas while we collected data for this project.
our study used iMUs attached to the poll, withers, mid-croup, and both hips together with a GPS unit on the croup that tracked the horse’s move-ments (see Figure 1) so that we could measure circle diameter and trot-ting speed. A transmitter attached to a surcingle relayed the information to a laptop computer so the horse could move freely in the arena.
We wanted to study the efects of circle size and trotting speed on the symmetry of body movement in sound horses. With the iMUs attached, the horses were frst trotted in a straight line on hard and soft surfaces to deter-mine the inherent symmetry of their movements. With all the horses being clinically sound and in active training, we did not expect to see large asym-metries between the iMU readings on the left and right diagonals. Howev-er, we did not expect perfect symme-try because horses, like people, have a sidedness pattern that involves limb preferences in providing support and propulsion. evaluation of the hors-es trotting in a straight line indeed
showed a high degree of symmetry, in-dicative of soundness in all horses.
next, the horses were lunged in an arena in both directions (Figure 2), without side reins, on circles of dif-ferent diameters and at diferent trot-ting speeds. Te GPS unit allowed us to track the horse’s exact moves so that we could measure the diameter of each circle and the horse’s average speed on that circle.
Te lunging technique was similar to that used in a veterinary evaluation, in which the horse is allowed to lean into the turn and to hold his head and neck at a natural angle. (Te way a horse chooses to turn may ofer valu-able clues in a lameness evaluation.) Tis is diferent from dressage train-ing on the lunge, in which the handler infuences the way the horse moves and carries himself.
Using the laws of physics, we can calculate how much a horse needs to lean inward in order to turn on circles of diferent sizes. Te calculations de-pend on the diameter of the circle, the trotting speed, and the efects of grav-ity. After analyzing more than 3,300 strides, we had an average circle size of ten meters in diameter and an aver-age speed of three meters per second (working-trot speed). Under these conditions, we predicted that hors-es would need to lean inward by 11.7 degrees, which was very close to the average of 10 degrees by which they actually leaned inward. interesting-ly, when circling to the left, all horses were very close to the predicted angle; circling to the right produced more C
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Figure 2. FEI-level dressage trainer Kathy Connelly lunges a horse during the data collections.
