“I cannot end the story of the horse without writing with regret that the health of this useful and precious animal has been up to now surrendered to the care and practice, often blind, of people without knowledge and without qualification.” - Georges-Louis Leclerc (1707-1778)
Leclerc De Buffon was a French naturalist known for his comprehensive writings on natural history. He ended his zoological description of the horse with the preceding quotation, which, sadly, is still very much the case. For example, I attended a presentation at the Equine Affaire last weekend that was a mixture of good anatomy and bad advice concerning what a horseshoe can and cannot do for the horse. And a number of the presenter’s comments were directly relevant to the subject of this post: the relationship between the internal structures of the hoof and the external hoof wall.
Let’s start by talking about what matters to the horse. After all, he’s the real beneficiary (or victim) of hoof care. First and foremost, he doesn’t care about what his foot looks like; he cares only about how it functions. And the point of departure for proper function is correct alignment of the bones of the lower limb, as shown in the accompanying illustration.
However, I want to point out three things about this image before I continue. First, it’s not quite correct; the bottom rim of the coffin bone isn’t really parallel to the ground. Rather, it forms about a 3° angle with respect to the bearing surface. Second, they haven’t labeled the navicular bone – that tiny bone directly behind the short pastern/coffin joint. And third, note that in this lateral (side) view, the “front” of the bones (not counting the navicular bone, of course) are roughly in line with each other.
This last observation is the source of the difficulty, and the logic behind it goes like this:
- From the side, the “front” of the hoof wall is parallel to the “front” of the coffin bone, and,
- In a properly-trimmed hoof, the bones of the lower limb line up; therefore,
- If the angle of the “front” of the hoof wall matches the angle of the “front” of the pastern bones, the hoof must be properly trimmed.
The flaw in this train of thought lies mainly with the first item, because the statement is true only for a 100% healthy and properly-trimmed hoof. It’s a misconception that the dorsal hoof wall necessarily accurately reflects the position of the coffin bone inside the hoof capsule. Many, many horses have some degree of thickening of the dorsal hoof wall due to long-term imbalances coupled with bad farriery practices, and so that relationship will no longer hold true. Even a slight amount of thickening will affect the angle read on a hoof gauge by several degrees. And that’s in an otherwise-healthy horse; in the laminitic horse where the white line has stretched to one extent or another (particularly at the toe), the angle discrepancy between the dorsal hoof wall and the coffin bone can be anything from a few degrees to dozens of degrees. Take a look at these radiographs –
Which one would you want your farrier to use? If you’re 100% certain your horse’s hoof is like the one on the upper left, things would probably be fine. But the upper-right hoof is pretty typical-looking in appearance, yet the radiograph reveals a 5° discrepancy between the hoof wall and coffin bone. That means if your farrier uses this horse’s wall as a reference, he/she is going to “rotate” the coffin bone 5° out of alignment, causing an imbalance in the tendon and ligament tensions.
From here, it only gets worse. While fairly long, the hoof in the lower-left radiograph has a smooth-looking hoof, which means many farriers and vets would attempt to match the hoof-pastern angle, leaving the heels too long with respect to the toe and/or wedging up the heels with a shoe/wedge pad. The result? A horse with a misalignment of 15°! Then, when the horse starts having heel pain (because he’s pounding down on his heels), someone will eventually x-ray the horse and declare the coffin bone is “rotated” 15°. The horse can’t win!
Remember – the horse doesn’t care what his foot looks like. He cares only about how it functions. And bone/joint misalignment means he’s not going to function as well as he could. The lower-right image shows a laminitic horse with at least three distinct hoof angles. Which should your farrier follow?
As I’ve mentioned in the past, I’m a big fan of much (but not, I hasten to note, all) of what Dr. Deb Bennett has to say about hooves. I like the following illustration and quotation from her Principles of Equine Orthopedics. In the quotation, she’s rendering her opinion of a particular “method” of trimming based on proportions of the hoof (Russell) –
“If you want to cordially make yourself insane, try analyzing proportions in horses’ feet. It is a very slippery business. Because the pastern and ankle are driven to take on whatever angle they have by the shape and angle of the hoof capsule, this “ideal” from Russell is just that — one possibility out of many theoretically possible. Particularly, I am critical of the idea that the toe of the hoof should line up perfectly with the pastern axis. I think this can happen but is not in fact the relationship most likely to keep most horses sound….The pastern angle must never be used as a basis for predicting the “proper” angle of the hoof….The toe must not be trimmed to parallel the line of the pasterns. It may – or may not – wind up there after the fact.”
This is why trimming methods based on lengths and angles and numbers of any sort can’t possibly work. The only way to ensure the foot will be properly balanced is to use the bottom of the foot – with an accompanying comprehensive understanding of the characteristics of the various tissues present – as the singular guide for trimming. Armed with that knowledge, every foot you trim will always be correct!