W(h)ither the Peripheral Cushion?

There are giant misunderstandings surrounding horse’s hoofs – even among barefoot practitioners. Vast numbers of trimmers are daily trying to balance off hooves, applying magical mapping templates, doing their best to ensure the heels are at the right height and allowing just the right length of hoof wall to protrude below the sole. They all pay homage to the reference manuals, instruction books, websites and fora that define this, describe that and advise on anything remotely resembling a hoof, be it “good” or “bad” – according to the prevailing wind!

blood vessels of the hoofBut in all this information, a small but key piece of anatomy keeps being overlooked: the peripheral cushion. In fact, you won’t find the peripheral cushion specifically named – it is a “made up” name, albeit accurate, and attributed to Pierre Enoff, the French hoof and locomotion specialist.
There are reams of drawings of hoof cross-sections; and yet not one actually fully depicts the sagittal dissection of a hoof. The peripheral cushion is clearly visible under the tip of the third phalanx (the coffin bone) and is in fact present around the whole of the periphery of the P3 – also being clearly represented in the casts of the circulatory system in the hoof. If we look carefully at Dr C. v. Horst’s now famous cast, we see a thickening up of the vessel structures just under the rim of the P3.

So what is this structure and what should it tell us?

Well, a look at that other well fed area might give us a clue – the digital cushion. As we (should) know, the digital cushion is a tremendously well fed area of the hoof designed to absorb, and retransmit, the impact of landing. It is this area of the hoof that is subjected to upward of 50.000 joules of kinetic energy when the -unshod – horse is in full flight. As anyone who has ever seen athletics and gymnastics will know, we need a very thick cushion to take up the impact of the pole-vaulter when he lands but the floor exercises only demand a thin layer since the landing is from a low height and the gymnast also needs to have sufficient purchase to make her/his figures.

We can thus conclude that this area is not intended to receive an impact of any great intensity whereas the digital cushion is. It is therefore of tremendous consternation that we see just where the impact of landing is concentrated in the shod horse. The digital cushion is rendered to all intents and purposes ineffectual – it cannot contact the ground and, if it should, it is not acting as a cushion but rather as suspended elastic which is not its design ethic.

Heel meter
Example of a heel template

It is basic mechanics but it is ignored by so many, owners, farriers, vets and, sadly, even a large number of barefoot specialists. Even among the last group, there are still many tied to the idea that the hoof wall is part of the weight bearing structure. They will try and “balance” the hoof to make sure there is even contact around the hoof wall, or try applying templates to “get the height right”. Pete Ramey states that the hoof wall should protrude about 1/16″ (about 1.6mm) below the level of the sole. Aside of the conceived ability to be so accurate, this is the application of the flawed insights of the farrier.

These insights are often also perpetuated by the equine specialists in the veterinary world. A reason for many people to point to these techniques as being “right” despite the majority of vets having only very restricted mechanical knowledge. Typically, the specialist clinics treating laminitis will suggest the application of special orthopædic shoes to support the hoof. When we realise that the susceptible, loose, laminitic hoof wall is now being used as the support point to aid healing, we cannot help but wonder about the teachings of veterinary colleges and farriers’ schools.