Page 1127 - Adams and Stashak's Lameness in Horses, 7th Edition

Foot Care and Farriery 1093

A line drawn across the widest part of the foot can be the limb above, and how the foot should be trimmed; how­
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used to evaluate both the shod and unshod foot and help ever, hoof balance lacks an intrinsic definition. The term
VetBooks.ir lifting off the ground and the toe lifting off the ground. methods for achieving balance, including geometric,
has been further subdivided to describe various proposed
determine whether previous farriery was appropriate.
Break‐over is the phase of the stride between the heel
dynamic, three‐dimensional, and natural balance. In prac­
The point of break‐over is best assessed from the ground tice, no single method of balance will achieve optimum
surface and should be located in the center of the toe. foot conformation for every horse. For example, a problem
However, the ideal point of break‐over is widely dis­ may arise with the exclusive use of either geometric or
puted. In a traditionally trimmed and shod horse, break‐ dynamic balance to address both dorsal palmar/plantar
over is positioned where the margin of the dorsal hoof and mediolateral trimming. If the landing pattern or limb
wall intersects the ground. In a biomechanical sense, conformation deviates from normal, one method of achieving
there are many situations in which it may be beneficial hoof balance may produce a foot with a different shape
to position the break‐over more palmarly. from another, or if the conformation of the limb causes the
The relationship between the longitudinal axis of the foot to assume a disproportionate load when landing,
frog and the overlying distal phalanx is more constant trimming the foot to land flat may be detrimental. 3,6
than the longitudinal axis of the frog to the ground sur­ “Hoof balance” is often used to communicate aspects
face of the hoof. The relationship of the untrimmed frog of hoof care to the farrier. A more effective option is to
to the sole indicates the position of the distal phalanx use a set of biomechanical principles or landmarks that
within the hoof capsule (i.e. the palmar angle). For can be used as guidelines that have a universal meaning
example, if the apex of the frog is deeply recessed and that can be applied to every horse, allowing the indi­
the incline of the frog appears to be angling toward the vidual foot to be evaluated, trimmed, and/or shod in a
coronary band at the toe, the distal phalanx is generally consistent, reproducible manner (Table 11.1).
similarly positioned, creating a negative palmar angle. These guidelines standardize the basic approach to
The central sulcus of the frog should be wide, solid, and farriery by both veterinarians and farriers. Furthermore,
shallow so that the index finger or ring finger fits easily they do not interfere with nor contradict the traditional
into it. Contraction of the central sulcus is so common concepts of static, geometric, or natural balance. The
that it is widely ignored by clinicians. Another impor­ guidelines can also be used to modify existing hoof con­
tant reference point is the dimensions of the frog; the formation and improve hoof capsule distortions and the
width of the frog should be 67% of the frog length. landing patterns of the foot.
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Ideally, the medial and lateral aspects of the ground The guidelines or landmarks described in this chapter
surface of the foot should be symmetrical on either side are applicable to both the forefeet and hindfeet, but for
of the central axis of the frog. The sole of the foot simplicity, only the forefeet are considered here. In the
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should be concave and possess sufficient depth such that section on foot preparation (trimming), the connotation
it does not deform when pressure is applied. of balance is replaced with anatomical landmarks along
with dorsopalmar/plantar and lateromedial orientation.
Dynamic Observation
Removing the Shoe
The key to observing the horse in motion is defining
the placement of the foot as it strikes the ground. The Removing the shoe may appear elementary, but it is
strike pattern should be viewed from the side, and ideally extremely important that veterinarians master the tech­
the horse should either land slightly heel first or flat, with nique to avoid damaging the hoof capsule during
the toe and heel contacting the ground simultaneously. removal. Shoes are removed during lameness examina­
Marked heel‐first landing generally denotes decreased tions to examine the solar surface of the foot that is cov­
ground surface in the palmar section of the foot or a shoe ered by the width of the shoe and during pre‐purchase
that is too small. Toe‐first landing is considered abnor­ examinations to evaluate the entire perimeter of the
mal, and it may be an attempt by the horse to avoid land­ sole–wall junction (white line) for abnormalities. Shoes
ing on its heels if they are painful or a club foot should also be removed for radiographs; otherwise, they
conformation where there is a shortening of the muscu­ prevent some of the hoof structures from being imaged.
lotendinous unit of the DDFT. Viewing the horse in The first step in removing the shoe is to raise the
motion from the front or from the rear allows the exam­ clinch—the small square section of the nail that exits on
iner to assess the mediolateral orientation of the heels as the outer surface of the hoof wall and is bent over to
they strike the ground. Ideally, both heels should contact secure the shoe—on the outer hoof wall. A clinch that is
the ground simultaneously, but often horses with a nar­ not straightened prior to pulling the shoe may damage
row chest and a rotational limb deformity impact the the hoof wall as the shoe is removed. The clinch can be
ground on the lateral hoof wall and then load the medial raised using a clinch cutter, a small chisel‐type tool
side. This type of strike pattern results in the medial (or
lateral) heel being displaced proximally; this type of hoof
capsule distortion is termed a sheared heel. Table 11.1. Hoof parameters to use as guidelines to evaluate
and trim the foot.

Hoof Balance
1. Hoof‐pastern axis
Veterinarians and farriers often use the term hoof
balance to describe the theoretically “ideal” shape or 2. The center of rotation
conformation of a foot, the position of the hoof relative to 3. Heels of the hoof capsule extending to the base of the frog