Last week, we defined several terms to describe issues with the horse’s feet. These included sole depth, heel height, negative coffin bone angle and breakover. So now let’s talk about how this applies to specific foot-related problems. Before we do that, we must recognize a critical member of the team. Your farrier. It’s all well and good to come up with suggestions for improving your horse’s foot, but the farrier will also have an opinion about this. Your farrier needs to be involved in this discussion and will play a key role when it comes to trimming the foot and applying the correct shoe.
Before proceeding with hoof radiographs, it is important to know how your farrier wants to be involved in the process. Ideally, he or she is present when the radiographs are taken. Alternatively, the radiographs can be emailed to the farrier or even printed off and left at the farm. Either way, it is important that the farrier and veterinarian talk to each other to determine the best course of action before any final decisions are made.
Let’s concentrate on our most common problem, and the root of much evil, the horse with low heels, low hoof angles and long toes. Let’s look at three causes of the case of low heels/negative coffin bone angle:
Some horses have a low hoof angle based on genetics and events that occur early in the horse’s life. These causes are not well understood but most horses will have one foot with a slightly higher angle than the other. And the higher angled foot tends to be the right front foot (in the northern hemisphere).
The lower angled hoof wall will wear away the heel portion of the foot faster than the toe because the horny tubules are not as perpendicular to the bearing surface (shoe) as the more upright foot. Those horny tubules, which grow down from the coronet at an even rate from the toe to the heel, will wear minimally when perpendicular to the ground or shoe surface but will wear rapidly if they approach the ground surface at an angle. Consequently, the toe wears minimally, the heel wears excessively.
When shod, the toe of the foot and the shoe are in constant contact with little or no motion between them. The heel is another story. The heels tend to expand and contract with each step, more so at speed or when jumping. This movement creates friction which wears the heel down more quickly, regardless of the angle of the foot.
Conventional horse shoes work well for most horses but if a horse is prone to excessive wear in the heels, the conventional horse shoe will exacerbate the issue. To prove this, look at your horse’s front shoes the next time your farrier pulls them. You will notice that the toe area of the shoe is unchanged from when it was applied and maybe even a bit rusty. The heels, on the other hand, will be shiny and there will even be a small divot where the heel contacts the shoe, more so on the medial heel.
Because horses tend to be base-wide and toe-out while moving, the medial heel will undergo more wear than the lateral heel. The tendency to wear the medial heel more than the lateral heel results in uneven heels with the medial heel being lower than the lateral. As if it wasn’t enough to have the heels crushed, uneven heels wreak havoc on the coffin joint and its associated structures.
So why do we worry about low hoof angles? Negative coffin bone angles create added strain on the deep digital flexor tendon. This added strain also takes a toll on the navicular bone and its associated structures. Negative coffin bone angles also put compressible forces on the front of the coffin joint. Although we tend to regard issues of the coffin joint and navicular bone as manageable or inevitable, we can go a long way preventing and treating these conditions with close attention to hoof angles, sole depth, heel height and breakover distance.
Low heels are also hard on the heel structure itself. Low heels are prone to bruising and chronically low heels will ultimately damage the important digital cushion. As proof of chronic inflammation in the heels, we often see new bone growth in the heel region subsequent to chronic heel bruising.
Let’s look at some solutions for under-run heels. Our first challenge trimming and shoeing the horse with low heels is that some solutions (for instance, wedge pads) tend to be good for changing the hoof angle but will place excessive pressure on the heel structures. In general, we make recommendations that provide a larger platform for the heels that go beyond the conventional horse shoe. This could include bar shoes, heart-bar shoes, frog-pressure pads and flip-flop shoes.
The most important consideration for helping the heels is to bring the breakover of the toe as far back as possible. This is accomplished with rolled toes, rockered toes, squared toes or simply setting the shoe back as far as possible. Whichever method is chosen, the key to bringing the breakover as far back as possible is by using radiographs to determine how far is far enough.
This solution below worked well for this horse. As you can see, this shoe provides a large platform for the heels and frog to land on and as the radiograph shows, provides a very early breakover at the toe:
It is important to remember that every horse with low heels will have a different solution based on what the horse does for a living, the experience and past experience of the farrier and veterinarian and the unique characteristics of the foot and the underlying structures. There is no cookie-cutter recipe for shoeing any horse with hoof-related problems!
Next week we'll tackle the issue of horses pulling their shoes off. Stay tuned.
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