There is thewell-known saying, “no hoof no horse”. Ensuring that a horse’s hooves aretrimmed and balanced about every 4 to 6 weeks is crucial to the overall healthof the horse. 8 A horse relies on their hoof to work in coordinationwith the leg to prevent increased stress or weight on any part of the leg. 7Therefore, a horse that has unbalanced feet is the prerequisite to many formsof lameness.
7 In order to evaluate if a hoof is trimmed, balancedand shod properly, you must take a variety of factors into consideration.Though it isnot the veterinarian’s job to trim and balance a hoof, it is important tounderstand the fundamentals needed to evaluate a hoof to ensure horse soundnessand health. This allows you, as a veterinarian, to properly advise a client,effectively reduce incidence of lameness and help the horse be the best athletethey can be.2 Remember, it is essential to work as a team to evaluateand come up with a farriery plan.2 As stated by Dr. Megan Cox, DVM,”It takes a village”. 2There arethree main areas to focus on when assessing a horses’ feet; these include: hoof balance, hoof length and hoof angle4.
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As such, the ideal foot is one that has a “parallel hoof-pastern axis, a thickhoof wall, adequate sole depth, a solid heel base and growth rings of equalsize below the coronary band”.4 Each of these areas focus on aspecific aspect, however it is important to take the rest of the horses’conformation and athletic endeavors into consideration as well. Thus, the goaland focus should be functional feet for that individual horse.4 Functionally,the conformation of the horses limb and hoof have direct effects on thebiomechanics of movement and the forces placed on the soft tissue structuressupporting the limb.4 As part of overall conformation assessment, itis important to take the hoof-pastern axis into account. To do so, the horseshould “be observed on a hard, level surface standing squarely on all fourfeet”.4 The ‘gold standard hoof angulation’ occurs when a line drawndown the dorsal surface of the hoof wall and a line drawn down along thesurface of the heel are in alignment or parallel to a line drawn through P1, P2and P3″.4Similarly,the hoof-pastern axis is determined by drawing a line down the dorsal surfaceof the hoof capsule and comparing that angle to a line drawn the dorsal surfaceof the pastern region.
If the angle of the pastern is steaper than the angle ofthe hoof wall, than it is said to have a broken-backhoof-pastern axis. However if the angle of the hoof is steeper than thepastern, it is said to have a broken-forwardhoof-pastern axis.4 In the weeks between each time a horse gets shod, ahorse can create uneven wear, or have uneven growth, in one or multiple hooves.It is important to also keep the individual horse’s anatomy and ridingdiscipline in mind when determining if the wear on the hoof is normal as it ismultifactorial and affected by things like confirmation, footing, shoeing andwork. The toe actsas a lever arm over which the limb rotates.4 Thus the longer thetoe, the greater the force necessary to pull the heel over the toe and completebreakover (“the phase of the stride between the time the horse’s heel lifts offthe ground and the time the toe lifts off the ground”.4) This inturn increases the length of the stance phase of the stride, increases theamount of time forces are placed and increases the tension within thesupportive soft tissues structures in the limb.
4 As such, it isimportant to evaluate the length of the toe to determine if it is appropriatefor that horse. This can most accurately be done by taking measurements of theapex of P3 on a lateral radiograph (as discussed below).3Just becausethe foot is level does not mean that the feet are symmetric.7 Oncethe foot is trimmed and leveled, a rasp and knife are used to make the hoovesmore uniform.
7 To do so, aspects such as toe length, hoof angle,ground surface characteristics, coronary band and landing of hoof while inmotion are evaluated. As suggested by Dr. Megan Cox of Empire Equine LLC, it isimperative to evaluate all of the hoof from all angles and sides while thehorse is standing still as well as while in motion.2 According to O’Grady et al, there are three maintechniques of assessing actual balance of a hoof. These include Natural Balance, Geometric Balance andDynamic Balance.GeometricBalance isdetermined by observing the horse at rest and thus does not take the landingpattern of the hoof or the hoofs relationship to the limbs conformation intoaccount. When looking at the solar surface of the hoof, it should be able to bedivided into two equal, symmetrical halves, when a line is drawn from the toeto the heel. In addition, the ground surface of the hoof should beperpendicular to the long axis of the limb.
4 When associated to theleg, on a flat surface, the radius, carpus, cannon bone and pastern will lineup with the hoof.5 So if you draw a straight lined down the dorsalside of the front leg, it will bisect the limb and go through the middle of thehoof.5DynamicBalance isdetermined by observing the horse in motion. The foot should always land flatwhen the horse travels, and just slightly heel first.
1 That is allaspects on the solar hoof of the wall land with symmetrical force and timing.The purpose of this is to make sure that the bony column lines up, and that theyare fully extending at any gate.1 However, it is important toconsider the horse’s limb conformation, as it can affect the landing pattern ofthe hoof. In such cases it could be detrimental to trim the hoof specificallyto land flat as it would add unnatural forces to the limb.4,2NaturalBalance “suggests that the footconformation of the domestic horse should be modeled after the foot in itsnatural state” 4. However there are several limitations to thistheory. Aside from being generally incompatible with traditional horseshoeingtechniques, domesticated horses live in a very different environment and havealtered genetic factors that have resulted in very different types of strainand wear on the hooves. In addition, “the feral horse is not a domesticatedathlete”.
4 While it isimportant to remember where the horse came from, we must be sure treat theanimal that is in front of us for the situation that it is in.4 Theimportance of a properly balanced hoof capsule is reflected in some common hoofabnormalities. For example, a poor dorsopalmer/dorsalplanter balance maycontribute to ‘long toe/underrun heel conformation’ which in turn results inaltered biomechanics and forces to supporting soft tissue structures. On theother hand, poor mediolateral balance is associated with sheared heels,distorted hoof walls and hoof cracks due to disproportional forces placed onone aspect of the foot.4A radiographof a hoof is typically taken to confirm certain disease processes, but theyalso works well for farriers to help guide them where they should trim thehoof. 6 If ever in question, films are always a good idea as theysurvey the lateral and dorsal planes.2 Be sure to clean out thehooves and have the horse stand on a level surface.6 If you are taking radiographs for a farrier,leaving the shoes on is perfectly acceptable.6 You willneed two views to accurately assess the hoof; a horizontal, dosopalmar and alateral-medial projection.7 When taking measurements, you want to lookat the tip of the capsule to center of rotation, hoof pastern axis and soledepth.2 The center of rotation should ideally be in the middle ofthe foot; to evaluate this, the distance from the center of rotation line tothe toe should be a ratio of 60% toe, 40% heel.6 If the sole depth does not seem correct, oddsare the toe is too long.6 Inaddition, radiographs show you the position of P3 and its angular relationshipto the hoof wall.6 If yourealize that the farrier being used isn’t the best at their job, be sure tohave that farrier present to use it as a learning experience for everyone.2As stated above, it takes a village.