Page 1056 - Adams and Stashak's Lameness in Horses, 7th Edition

1022 Chapter 9

software. Amplitude and timing of hindlimb lameness fast walk. Some do not lead at all. This inconsistency of
(impact vs. pushoff) are correctly measured, but the side gait is inherently and normally asymmetric, unrelated to
VetBooks.ir right forelimb gyroscopic sensor? The combination of Missouri Foxtrotter, having the handler force the horse
pain, so incompatible for determining lameness. For the
of lameness is opposite of actual. So, why retain the
to move faster, by moving faster him/herself, may cause
the right forelimb gyroscope to detect forelimb footfall
order and a pelvic gyroscope measuring frontal plane the horse to begin to trot regularly, and the lameness
rotation to detect hind limb footfall order allows instan­ may then be seen or measured. But this may not be ideal,
taneous (on‐the‐fly) determination of ipsilateral from as the owner/trainer is complaining about lameness at
contralateral gait. Future versions of Lameness Locator the fox trot, and the handler will more quickly tire so
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are expected to include this capability, so users will not that additional observation trials are more difficult to
need to specify gait. collect. Instead, the lameness evaluation is more likely to
Many four‐beat gaits are characterized by suppressed succeed if conducted with the horse under saddle and
vertical torso movement (this is what makes them com­ ridden. In this manner, gait and speed are more consist­
fortable to ride) and, especially in the Missouri ent, and both the fox trot and trot can be evaluated. The
Foxtrotter, exaggerated vertical head movement. Vertical Mangalarga Marchador (performing the marcha batida)
movement of the head remains the best method of fore­ is very similar to the Missouri Foxtrotter both in gait
limb lameness detection in the four‐beat gaits; however and consistency while led and under saddle (Figure 9.60).
a small difference between right and left strides, which, Similarly, it is almost futile to attempt to have a han­
subjectively, are easily seen in a standard trotting horse, dler lead a Standardbred pacer and expect a consistent
may be more difficult to appreciate in the Missouri gait of either a trot or pace. The best method for evalu­
Foxtrotter and other breeds with exaggerated vertical ating pacers for lameness is to sit behind them in the
head movement. It is a question of seeing a small signal bike with the horse tacked up fully. Also, simply jog­
against the background of a lot of surrounding noise. ging slowly, even in hobbles, may not cause the horse
Also, because vertical hindquarter movement is damped, to gait symmetrically, until a certain speed (usually
detecting small differences in vertical pelvic movement faster) is attained (Figure 9.61). This can be accom­
between right and left is more difficult. plished with inertial sensors either by placing the
These same limitations affect objective measurement receiving tablet computer on the person of the driver or
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with inertial sensors. Lameness Locator software within the sulky, traveling in a vehicle within range of
includes a standardization algorithm that adjusts lame­ the moving horse, or connecting to and collecting data
ness measures based upon expected vertical movement from sensors as the horse is moving by the data collec­
of the head and pelvis. This is accomplished with algorithms tor holding the receiving tablet. Placing the receiver in
that decompose the vertical movement trajectories into the sulky with the driver or traveling next to the horse
harmonic components, the expected vertical movement allows collection of hundreds of strides with low
being the component at twice stride frequency. This is stride‐by‐stride variability, such that the effect of direc­
provided so that a mild lameness measure for a bound­ tional change in the turns is minimized over the entire
ing Warmblood in dressage competition (large range of trial. There is more side‐to‐side rolling in a Standardbred
expected vertical movement) will be approximately the pacer, but the torso (and head) still rise and fall twice
same as a mild lameness measure in a miniature horse per full stride. However, because the horse is pacing,
trotting across the exam room floor (small range of hindlimb lameness results must currently be flipped,
expected vertical movement). Larger asymmetric move­ right to left and left to right, but forelimb lameness
ments are needed to exceed normal reference ranges results are the same as if the horse were trotting at
when expected vertical movement is high. Smaller asym­ speed. Of course, flipping the hindlimb results is not
metric movements are considered normal reference necessary for the Standardbred trotter and other breeds
ranges when expected vertical movement is low. that trot at high speed, and a more ideal combination
However, at the extreme ends of the total vertical move­ of gait (the trot) and circumstance (ability to collect
ment spectrum, such standardization may cause discrep­ large numbers of contiguous strides at speed) for evalu­
ancy between what asymmetry is visually apparent and ation with inertial sensors would be hard to find.
what is actually measured. So, the exaggerated normal Because of the presence of the head check and crupper,
vertical head movement in the Missouri Foxtrotter may which occupy the body locations ideal for body‐
suppress forelimb lameness results and variation, and mounted inertial sensors, increased diligence is needed
the minimized normal vertical pelvic movement (actu­ for proper attachment of the head and pelvic sensor.
ally in some cases near zero) may exaggerate hindlimb Some users around the world have invented attach­
lameness results. Therefore, it is not uncommon for ment devices that seem to work well.
Missouri Foxtrotters (and other breeds that gait with There is no published information on using body‐
exaggerated vertical head and suppressed vertical torso mounted inertial sensors to evaluate American
movement) to measure with forelimb lameness that Saddlebred horses at the rack (an ipsilateral gait) or in
seems less than and with hindlimb lameness that seems other breeds like the Icelandic horse in similar symmet­
greater than that seen with the naked eye. ric ipsilateral gaits. These authors have evaluated some
Some breeds, most notably the Missouri Foxtrotter American Saddlebred horses for lameness at the rack
and the Standardbred pacer, will not move with a con­ and have found that the variability in gait is relatively
sistent gait when led on a lead shank by a handler, and high and trial length (ability to collect multiple contigu­
they do not commonly lunge. Instead, when in hand, ous strides) is relatively low, both of which significantly
they may move at a gait transitional between a walk and interfere with the ability to find small consistent asym­
fox trot or between a trot and a pace or simply at a very metries of mild lameness or to detect partial improvements