By Dr. Jennifer Miller-Bailey

 

Those whom are familiar with the use of Mechanics for horses with Laminitis can surely appreciate its value in that scenario. What about the average horse a Farrier sees every day who does not suffer from Laminitis? What about the horse with some variation of a “normal” foot that is not currently lame? Is there a reason to apply a mechanical package to this horse? To use the familiar saying, “If it’s not broken, why fix it?” Well, I implore you to consider what that “normal” foot really looks like.

Upon closer examination of the “normal” foot, might one not find subtleties of distortion, uneven loading, changes in wall thickness, inadequate sole or heel mass? Perhaps even conformations that predispose the foot to pathology such as long pasterns, broken hoof-pastern axis, rotational deviations of the leg, varus or valgus deviations of the leg, arthritis or injury-induced loading and breakover deviations. Given any one of these attributes, would not a single Farrier address them in a proactive way as to prevent or delay onset of degeneration or pathology? If the answer is no, why is it no? Try and explain to the owner why one would recognize such things but choose not to address them. Perhaps we don’t know how best to address them.

Let’s consider the not so “normal” foot; those with heels that run forward, crushed heels, negative palmar/plantar angles, thins walls, stretched white line, club feet, thin soles, etc. Those “normal” feet with already present pathology such as navicular/caudal heel pain, deep digital flexor/impar injuries, collateral ligament damage, ring bone, pedal osteitis, recurrent abscessation, quarter cracks, toe cracks, white line disease, etc. I think every Farrier would address these conditions proactively in one way or another.

Recognition of the Tendon Theory and alteration of the forces it describes is Mechanics. The application of Mechanics places the foot in a mechanically advantageous position as to reduce the forces that would otherwise lead to its deterioration. The Tendon Theory upon which Mechanics rely was proposed and developed by Dr. Ric Redden, a Veterinarian-Farrier of Versailles, KY. Through years of studying the foot with radiographs, venograms, and podiatry together with trial and error, the Tendon Theory was developed.

The foundation of his theory is centered on addressing two main structural systems of the foot: support components and suspension components. The support components are the hoof capsule, sole, bars, frog, and digital cushion. Suspension components are mainly the deep digital flexor tendon and the lamellae connecting hoof capsule to coffin bone. These two systems are simplistically represented in the image below. The support system is shown in green as coils and shock absorbers. The suspension system is shown in yellow as small springs (laminae between the hoof wall and coffin bone), large spring (deep digital flexor tendon), and pulleys (navicular apparatus). The red arrows show the directional forces at play around the various structures.

 

 

 

 

 

 

 

 

 

I've always understood the support system. That is where most farriers and veterinarians focus their attention. Shoes, pads, sole packing, etc. are all designed with support in mind. What I now realize is without addressing the suspension, we are missing the mark by a mile. The two systems are closely linked. Addressing only one of them will yield less than maximal results.

If we look at the two systems separately in the simplistic drawings below starting with suspension, the two main players are the deep digital flexor tendon (ddft) and the lamellar attachment between hoof wall and coffin bone. The ddft (orange line) is anchored at the elbow, runs down the leg to insert on the bottom/ventral surface of the coffin bone, and exerts a rotational force on the coffin bone via the pulley action of the navicular bone. In a healthy foot this force is equally antagonized by the strong Velcro-like lamellar tissue (purple arrows) that hold the hoof wall to the coffin bone. Therefore, the coffin bone, and thus the digit, is “suspended” within the hoof capsule by these two very robust structures. This can also be illustrated by picturing a hammock; one end anchored by the lamellar tissue, the other end by the deep flexor tendon. A large portion of the horse’s weight is directed down into this “hammock.” The remainder of the horse’s weight is distributed through the support structures.

​

​

​

​

​

​

​

 

 

 

If we now examine the support system, the main players are the hoof capsule, sole, frog, digital cushion and the phalanges (long and short pastern bones and the coffin bone). The weight of the horse is directed down through the skeleton into the foot and is represented by the green arrows pointed down through the middle of the phalanges. In a healthy foot, this force is equally opposed by the ground pushing up (as shown by the shorter green arrows pointing up from the bottom of the foot) via the hoof capsule, sole, frog and digital cushion, against the bottom of the coffin bone.

​

 

 

 

 

 

 

 

 

 

The support and suspension systems work together to keep the relationship between the bone and the hoof capsule stable throughout all sort of mechanical stresses placed upon the foot during the horse’s performance. In a “normal” appearing foot, meaning one that is not upright or clubby, nor does it have low underslung or crushed heels, these two systems are in perfect harmony. However, if one system is overwhelming or insufficient, the foot takes on either an upright or clubbed appearance (too much suspension), or a low angled underslung or crushed heel with minimal digital cushion (not enough suspension). Genetics can predetermine this arrangement, but environment, nutrition, injury and disease also affect it.

So, how do Mechanics benefit the average horse? Through years of study, Dr. Redden discovered the manipulation of the forces described in the Tendon Theory affected most every subtle and non-subtle distortion, abnormality, and disease process listed at the beginning of this article. Therefore, using Mechanics one could improve the quality of a hoof, and the longevity of the horse. What’s more, the observed improvement by the Farrier and the perceived improvement by the horse far surpassed what more traditional AFA (American Farrier’s Association) type approaches would produce. The caveat being that Mechanics were used properly.

Use of Mechanics should be by a Farrier and/or Veterinarian who understands the Tendon Theory well and its application in various scenarios. The degree of mechanical manipulation depends on the severity of disease, distortion or lameness, as well as the demands upon the horse. Nay Sayers may say the Mechanical approach can’t be used for horses performing at speed, or jumping, or traveling over rough terrain. I would argue improper use of Mechanics should not be used for horses performing at speed, jumping, or traveling over rough terrain. Proper use of Mechanics can be used in nearly every situation. Proper use of Mechanics often requires the assistance of radiographs to accurately assess the foot and its needs. Therefore, the Veterinarian and Farrier must cooperate on a common path toward a common goal. Without radiographs, Mechanics can easily become improper and lead to untoward results. It is my opinion this very scenario is what turns some people off the use of Mechanics; they weren’t given the radiographic assistance they should have, and the result of their attempt at Mechanics was disappointing.

So, I ask the question again. How can Mechanics benefit the average horse a Farrier sees every day? Unless the average horse a Farrier sees has perfect feet, great conformation, no metabolic issues, lives in the best of environments, is a pasture pet, has the best nutrition, no injuries, and no vices, Mechanics can be of use to every horse.