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					            AAEP Wrap-Up 2009

hoof Care/Farriery
By CHrisTy WEsT

horse hoof Trimming Guidelines
   One of the biggest troubles with discuss-
ing horse hoof trimming and balance is
that when it comes to hoof balance, there
isn’t a set definition. One practitioner
discussed guidelines for characterizing
hoof balance and for trimming the foot to
achieve proper function.
   “The term ‘hoof balance’ has no mean-
ing, but we all say it,” said Stephen E.

                                                                                                                                                   CoUrTEsy Dr. sTEPHEn o’GrADy/AAEP ProCEEDinGs
O’Grady, BVSc, MRCVS, of Northern Vir-
ginia Equine in Marshall, Va. “It’s a con-
cept that means something different to
everyone. Hoof balance has been the term
used by veterinarians and farriers to de-
scribe the theoretical ideal shape or con-
formation of a given foot, the position of
the hoof relative to the limb above, and the
way that the foot should be trimmed.”
   The term “hoof balance” has been used
to refer to geometric balance (symmetry of     Illustration A shows a parallel hoof-pastern axis (HPA), B shows a broken-back HPA, and C shows a
hoof shape), dynamic balance (flat land-       broken-forward HPA. The red line in D denotes a parallel HPA.
ing of the hoof on a hard surface), three-
dimensional balance, and natural balance,      first guideline when trimming the foot,”           joints of the lower limb at different angles
said O’Grady. However, he said that no         said O’Grady. When you are looking at              than that for which they were designed,
method of “balancing the foot” will yield      the horse’s hoof from the side, the hoof-          which can result in lameness.
optimum foot conformation for every            pastern axis describes the alignment of the           O’Grady noted that the angle for a par-
variation of conformation (such as toeing      toe of the hoof wall with the pastern above        ticular hoof is suitable when the hoof-
in or out, or a club foot), and “balancing     it. If they are parallel, the hoof has a prop-     pastern axis is straight, not when hoof an-
the foot” might yield very different foot      er hoof-pastern axis. However, the pastern         gle approaches any ideal number.
shapes.                                        might have a steeper (more vertical) angle            The center of articulation is the center
   He offered an alternative: “An option to    than the hoof (a broken-back HPA) or vice          of rotation of the distal interphalangeal
the term ‘hoof balance’ would be to use a      versa (a broken-forward HPA).                      or coffin joint when viewed from the side.
set of biomechanical principles or land-           This axis has implications for load dis-       O’Grady said a vertical line drawn through
marks as guidelines that could be applied      tribution within the foot; a broken-back           it should approximate the middle or wid-
to every horse and have a universal mean-      axis is often caused by excessive toe or           est part of the foot from front to back
ing,” he said. “The foot can be evaluated,     minimal heel length and tends to result in         (when viewed from the bottom ).
trimmed, and/or shod in a consistent, re-      excessive load on the rear of the foot. This          “The widest part of the foot (center of
producible manner that considers:              can result in crushing of the digital cush-        articulation) forms a landmark on the so-
■ The hoof-pastern axis (HPA);                 ion in the rear of the foot, and it increases      lar surface of the foot that not only can be
■ The center of articulation;                  load in the deep digital flexor tendon.            used as a reference point when trimming,
■ Heels extending to the base of the frog.         Conversely, the broken-forward axis            but can also be used in evaluation of foot
   “These principles can be used by the cli-   (sometimes due to club foot) tends to              conformation and the existing farriery that
nician to evaluate every hoof and access       overload the toe; underuse of the digital          has been performed on the horse,” he said.
the type and suitability of farriery that is   cushion in the rear of the foot means less         “After the trim, the ground surface of the
presently employed,” he noted. “Addition-      shock absorption in the foot and more              ideal foot or good foot will be basically as
ally, they can serve as landmarks for trim-    jarring of some structures. In addition to         wide as it is long,” and the length of the
ming and shoeing.”                             overloading different parts of the foot, an        sole in front of and behind the widest part
   “The hoof-pastern axis (HPA) is our         improper hoof-pastern axis also loads the          of the foot will approximate each other.

44                                                                   AAEP Wrap-Up     The horse                March 2010
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   “The third landmark is the heels of the        slipping (much like football or baseball             Martinelli suggested several differences
hoof capsule extending to the base of the         cleats). However, there are increased stress-     between racing Quarter Horses and Thor-
frog,” said O’Grady. This means the heels         es on the limbs from this stronger grip on        oughbreds that might contribute to differ-
should not be long or underrun. The rear-         the ground and quicker “stops” of the feet        ences in risk factors for injury.
most point of the heels’ contact with the         when they land (normally the foot slides             Contrary to some long-held beliefs,
ground should be at the base of the frog,         forward just a bit on the ground before           Quarter Horses appear to pull with their
when possible.                                    stopping, but toe grabs arrest this slide).       forelimbs when launching from the gate,
   “Often there is limited soft tissue mass in    It’s also been suggested that toe grabs add       unlike Thoroughbreds. Martinelli showed
the palmar (rear of the) foot, or the wall at     stress to the limb by raising the toe relative    several slow-motion videos of both breeds
the heels cannot be trimmed to the base of        to the heel. Toe grabs on front feet have         breaking from the gate, demonstrating: “In
the frog; this necessitates that the branch       been associated with increased incidence          the case of the Quarter Horse starting a
of the shoe or some other form of farriery                                                          sprint race, the toes dig into the track and
extends to the base of the frog,” he added.                                                         the fetlock and carpus (knee) remain flexed
   “Becoming familiar with three basic                       As athletic                            (bent) during the first several strides. Thor-
landmarks will enable the veterinar-
ian and farrier to approach trimming the
                                                  performance gets more and                         oughbreds, conversely, tend to land flat-
                                                                                                    footed and hyperextend the fetlock within
equine foot in an individual, standardized,        more intensive, chances                          the first stride from the gate.”
and repeatable manner,” he concluded.                                                                  Quarter Horses race at shorter distances
“Another advantage of these landmarks is
                                                  are you’ll see more injuries                      (often 440 yards, one-quarter mile, or less)
the creation of a technical language that           just from the increased                         and higher speeds (47+ mph vs. 30+ mph
can be used to discuss farriery between                                                             for Thoroughbreds). They tend to get fast-
the professions, and it will form the writ-           physical stress.                              er with each segment of these short races,
ten basis for reports and records.”                                                                 while Thoroughbreds running longer dis-
                                                           Dr. MArk MArTinElli                      tances get faster toward the middle of the
racing Quarter horses, Toe Grabs                                                                    race, then fatigue and slow down.
   You’ve probably heard the old adage            of catastrophic injury in Thoroughbreds              Despite breeding for faster horses,
from mule fanciers: “Mules is just differ-        in at least four studies, reported Marti-         Thoroughbreds don’t appear to be getting
ent.” Well, it seems the same principle           nelli. (Editor’s Note: Research by Sue Sto-       faster, while Quarter Horses are. “As ath-
holds among racehorses; racing Quarter            ver, DVM, PhD, Dipl. ACVS, of the Univer-         letic performance gets more and more in-
Horses, it seems, are just different. From        sity of California, Davis, has demonstrated       tensive (in any species/discipline), chances
racing Thoroughbreds, that is. Veterinar-         that “high” toe grabs on front shoes make a       are you’ll see more injuries just from the
ians presented study results on racing            Thoroughbred 16 times more likely to suffer       increased physical stress,” Martinelli com-
Quarter Horse injuries and horseshoe toe          a catastrophic injury while racing.)              mented.
grabs that showed very different effects             However, many jockeys and trainers in             The two breeds tend to respond dif-
of toe grabs than those found in previous         the racing Quarter Horse industry feel that       ferently when they do get injured, he ob-
studies on racing Thoroughbreds.                  toe grabs on front feet are not a risk. In        served. When Thoroughbreds suffer a
   Catastrophic injuries in racing seem to        fact, they feel toe grabs are essential for re-   catastrophic injury, they often fall and roll,
be attracting more attention from media           ducing slipping as these horses break from        while Quarter Horses more often misstep,
and researchers these days. The increase          the gate. Slipping at the gate carries a risk     then keep running while the jockeys fight
in research directed toward reducing the          of injury not only to the horse that slips,       to slow them down.
incidence and severity of racing injuries is      but possibly to other horses or the jockey.          “Factors involved with catastrophic in-
certainly a good thing, and it has resulted          This study did not find a protective effect    juries in racing Quarter Horses have not
in some safety-oriented regulations and           of toe grabs, but it didn’t find any elevated     been studied to the same degree as those in
recommendations for Thoroughbred rac-             risks of injury when using them, either.          Thoroughbreds,” Martinelli summarized.
ing (i.e., mandates to use particular track          For the study, investigators measured          “Our recommendation is that the Ameri-
surfaces and certain shoeing practices).          toe grab height on horses suffering cata-         can Quarter Horse Association continue to
   It might be tempting to extend those           strophic injuries at a California track over      study these horses and make sure any rules
Thoroughbred flat-racing recommenda-              a two-year period. They compared these            applied to them take into account the dif-
tions to all racehorses, but research sug-        values with those for all 1,314 Quarter           ferences between racing breeds.” H
gests this might not be advisable. Mark           Horses racing at a California track during
Martinelli, DVM, MS, PhD, Dipl. ACVS,             January and June 2008, and they saw no
of California Equine Orthopedics, in San          significant difference in the distribution           more online
Marcos, discussed results of a study on the       of toe grabs between the two groups (one
relationship between toe grabs and cata-          would have expected a higher percentage              Click on the links below for more hoof
strophic injury in racing Quarter Horses.         of the fatally injured horses to have toe            care/farriery articles from the convention:
   A toe grab is a raised rim on the toe          grabs if they were a problem).                       ■ Therapeutic Shoeing Table Topic
area of a horseshoe; its purpose is to help          Why the difference between Quarter                ■ Foot Lameness Table Topic
the horse “dig in” to the track and reduce        Horses and Thoroughbreds?

March 2010          The horse      AAEP Wrap-Up                                                                       45

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