It is human nature to think that if a little is good, lots would be better. Applying that thought to most aspects of shoeing is incorrect, and giving support to the point of leverage is a good example.
I hope that this article can give you some thoughts on the subject, and a position to defend when discussing the benefits or downside to the application of different shoeing strategies. It is also important for every reader to easily understand these principles, so the math and physics of leverage are not what I am trying to explain, just some straightforward thoughts on the subject of placing a horseshoe under a horse.
Defining The Terms
Let’s begin with some definitions. First is support. The word has a lot of meanings in different contexts. For our purposes, support means to bear or hold up weight, mass structure, etc., provide a foundation without giving way. That is easy to understand, and ideally what a shoe provides to a foot, leg, limb and horse.
Now to the definition of leverage. Leverage by itself is defined as the use of a lever. So, what is a lever? It is a rigid object used with a fulcrum to multiply mechanical force. This can be termed “mechanical advantage,” and it is one of the six simple machines. As you can easily imagine, support taken too far creates leverage.
The terminology we are using here can be used in many different contexts. Consider politics, where an industry supports a politician until that politician gains power. At that point, the previous support can turn into leverage as the industry gets that politician to do what it wants. Everyone can understand the terms used in that context, and that may help you explain the differences to a customer or new farrier.
In the farrier industry, we often use the term support when we are transferring weight from one part of the foot to another. The heart bar is a great example of this (Figure 1), as it takes weight off the wall and transfers it to the frog. But this is not the type of support that this article is addressing; rather we are discussing the support that goes beyond the perimeter of the foot.
Here is my stance on this subject. Support, as needed, is a good thing. Taken too far, leverage is created. This means that too much support results in leverage. However, there are extreme cases in which extreme support (leverage) is called for. Our job is to know when and where.
Rule Of Thumb
As a general rule, when a shoe extends beyond the perimeter of a foot, the last point of contact between the foot and the shoe is the area of the foot that will bear the most weight. The flip side of this is that I don’t put the shoe where I don’t want weight. The Z-bar and W-shoe being good examples (Figures 2 and 3). When I am explaining this to fellow farriers or customers, I use the drawing on Page 36.
It provides a simplified description of what happens when an egg bar shoe is compared to a regular shoe. (Be aware that this is just a way of describing this principle. Since there is an angle to the pastern, the bony column behind the foot, the movement of the joints, the ground the horse is standing on, etc., there are a lot of variables.) In the top drawing of this illustration, the foot is bearing 300 pounds with a regular shoe, and there is 50 pounds applied to each section of the shoe from toe to heel.
Once a longer shoe increases the distance from toe to heel, the 50 pounds is applied to six larger areas. In the drawing, 2 1/2 of those areas are beyond the heel. The weight that is applied to that area of the shoe becomes concentrated by leverage on the heels of the foot. Now, there is too much weight on the heels of the foot as they deal with the shoe extended beyond the perimeter of the foot. You can compare this to wearing skis and then leaning back. There will be a lot of weight on the back of your heels from that action.
Means Of Support
Support can be applied in any direction. We use extensions, which can extend either to the lateral side or medial side of the foot. Figure 4 is an extension made out of acrylic by South African farrier, Robbie Miller, CF. These can also be created with a traditional shoe. We don’t have the chance to use a lot of toe extensions, which are used most often in my shoeing business on a horse that has had a deep flexor tendon tenectomy or check ligament desmotomy (Figure 5).
Perhaps the most common support is the heel extension. Supporting the back of the foot does change the way that the leg bears weight and it can be beneficial in a lot of instances. We use it most often on the hind feet to change the way that a foot lands for the Western horses that we shoe. Figure 6 shows extended heels on a plain stamped handmade shoe and Figures 7 through 10 show extended lateral heels that are used on horses with sore hocks, stifles or with a predisposition toward a cow-hocked conformation.
Take a look at Figures 11 and 12. This is an expensive foal that has flaccid tendons. I was spending some time with Simon Curtis, a Fellow of the Worshipful Company of Farriers in Newmarket, England, and he showed me this foal on which he had put some extended shoes. The support behind the foot is as long as the foot is from toe to heel, which would be considered excessive in some cases. Here, it is completely called for since the problem is severe enough to warrant it.
The Role Of Footing
One of the most important things that a farrier has to consider is the footing that the horse is going to be working in. If the horse is on softer footing, the width of the shoe in different areas will be a big factor as to how that leg will bear weight. The wider the shoe, the less it will penetrate, and vice versa. This means that we can play with different web widths to create different support at different times in different footing. This is a very important thing to take into account when deciding what type of shoe to use and when.
Sometimes support is needed for the entire horse. Figure 13 shows a horse that has suffered a bad cut on the fetlock that has become sick and in poor condition due to the injury.
In Figure 14, the injured leg has been shod with a patten bar, which acts as a rest shoe, allowing the injury to heal. This means the other legs have to support the horse while the bad leg is given some time off.
Figure 15 shows the amount of healing after one shoeing, while Figure 16 shows the shoe on the foot. With neglect, good support can become leverage, and changes can happen.
Look at Figure 17. This is a patten bar that was left on a foot for about 12 weeks. The amount of change that happened to that foot from the owner’s neglect is astonishing.
Support Done Right
Here are some examples of appropriate support:
Figure 18 is a keg shoe that has been punched on the inside of the web so that the shoe can be placed under the leg. Notice the amount of shoe that is showing on the right side of the foot on the ground.
Figure 19 is a bar shoe with a lateral-heel extension on a badly cow-hocked horse. This shoe allowed some support to the outside of the hock, and made this horse much more comfortable.
Figures 20 and 21 are radiographs of the worst case of ringbone I have ever encountered. The quality of life for this horse was not good, and even moving around the pasture took its toll. In Figures 22 and 23, the pre-trimmed foot is on the ground. Notice that the lateral heel is not supporting the bad leg at all. Figure 24 is the bottom of the foot before trimming and Figure 25 shows the balance of the foot and leg. Figure 26 shows what I could accomplish with the trim (which, by the way, was not as much as I would have liked).
I built a straight bar for this horse, and then made it into a convex ground contact that we refer to as a bowl or cupped shoe. The rigidity of the metal supports the foot where the foot would not be able to touch the ground. The bowl shape allows the horse to roll this foot around on the ground when standing or moving. Figures 27 and 28 show a couple views of this shoe to show how it is formed.
With the shoe nailed on the foot, there is a dramatic change in the balance of the foot under the leg (Figure 29). Figures 30 and 31 show the shod foot on the ground, and I finished it off with a pour-in pad of Vettec’s Equi-Pak (Figure 32). Horses like this one are part of what keeps us all shoeing. It was Grade 4 lame when it came down the aisle of the barn, and closer to Grade 2 when it walked out. Limp in, leap out is what we all try for when shoeing horses with conditions like this one.
While this horse will never go to work, it will have a better quality of life, which is all that the owner wanted. In a case like this, more extension could easily cause enough leverage to create substantial damage to an already damaged leg.