Hoof Mechanics in the Chronic Laminitis Case - Part 2

This article is from the January 2021 Horse Deals magazine.

This is the second article in a two-part series on the hoof mechanics in the chronic laminitis case. Last article we focused on what is laminitis, how the laminitic hoof grows and the growth rate of the laminitic hoof. This article will focus on how we should trim the laminitic hoof and if required, what therapeutic devices we can use to help the laminitic hoof.

The key principles of trimming the laminitic hoof

Last article we discussed how hoof conformation dictates hoof growth, which is particularly important in the laminitic hoof.

Does a laminitic hoof grow a long toe or a wide toe?

One issue we find with the management of the laminitic hoof is over-trimming the hoof wall at the toe. There is a common misconception that the laminitic hoof grows a long toe - this is incorrect. The hoof, when the lamellar attachment breaks down and the hoof wall pulls away from the pedal bone, the lamellar attachment stretches. This actually creates a wide hoof wall - very different from a long hoof wall. We know and can see that if we look at the growth rings on a laminitic hoof, the growth ring is typically narrow at the toe and wider at the heels - this indicates a reduction in toe growth, compared to the heel.

If we trim all of this wall off, because of the orientation of the hoof wall which is no longer running along the hoof wall - we actually start to lose a significant amount of depth under the tip of the pedal bone. A reduction in depth under the tip of the pedal bone for a horse that is having a laminitic episode is very detrimental and can cause the lamellar attachment to further destabilise.

So what do we do about the wide toe in the laminitic hoof? Leave it alone until the growth ring at the toe is approximately one third of the wall down the hoof wall. Everything above the growth ring indicates healthy new lamellar attachment and means that the horse is more likely to be able to handle removing some of the wall. Before the growth ring grows down, we can add mechanics to the hoof - this will be discussed later.

How much heel to take off the laminitic hoof?

As we know, in many chronic laminitic cases, the horse will grow excess heel. It is important that the heel isn’t allowed to excessively grow. When this happens, as the heel grows down it also grows forward. This creates a fulcrum point at the heel and the toe of the hoof will flip off the ground. This is very painful for the horse and can cause damage to the coffin and pastern joints as well as the tendons and ligaments in the lower limb.

One of the mistakes made when trimming the heel is not taking enough off because the frog has also grown down with the heels. When the frog is at the ground surface, it creates the illusion that the heels aren’t very long.
To truly understand how long the heels are, the frog needs to be trimmed appropriately first. A general rule I use to know how much frog to trim off is I lay my thumb across the heels, parallel to the hairline at the heel bulbs. I trimmed the frog to my thumb, which is approximately 2cm from the hairline at the coronary band. Once this is done, you can truly see how much heel needs to be removed.

When trimming the heels, it is also important not to extend the trim forward towards the toe. As we have mentioned previously, the depth under the tip of the pedal bone is minimal in many cases, so if we extend our trim towards the toe too far, we’ll reduce the depth and cause further pain.

How to trim the laminitic hoof that toes out?

Laminitis is very common in ponies and one conformational trait of a pony is that they have a toe out conformation. As we discussed in the previous article, a horse with a toe out conformation will grow a long outside wall and will wear more/grow less on the inside wall. This is very important to know when trimming the laminitic hoof - if we trim this hoof flat, ie take the same amount from the inside wall as the outside wall, the inside wall will become shorter. This causes the pedal bone to tilt and results in pain. This is why many laminitic ponies become lame after a trim. To counteract this, it is important not to trim anything from the inside wall and concentrate on trimming the outside wall to re-establish a more symmetrical hoof.

What mechanics can we use on the laminitic hoof?

One of the most important components to dealing with the laminitic hoof is to shift load to the back half of the foot, away from the painful lamellar attachment at the front part of the hoof. One way this can be achieved is by providing heel elevation like a wedged heel or rockered heel shoe. It is a common misconception by owners, that elevating the heel will cause the load to shift to the toe - when a horse wears high heels it is not the same as when we wear high heels!

When we provide heel elevation we not only shift load to the back half of the hoof, but we also reduce tension on the deep digital flexor tendon. The deep digital flexor tendon attaches to the back of the pedal bone and counteracts the lamellar attachment in the healthy hoof. In the laminitic hoof, the lamellar attachment is fragile and the deep digital flexor tendon contributes to the rotation of the pedal bone away from the hoof wall.
As we mentioned previously, the hoof wall is wide at the toe, and this can be managed by providing a shoe or boot with a rolled toe. This will reduce the tearing of the lamellar attachment at the ground surface.

Finally, it is important to apply any boot or shoe parallel to the solar surface of the pedal bone. This is very difficult to do via conventional methods, i.e. nailing a shoe on, when the horse has moderate to severe rotation and minimal depth under the tip of the pedal bone. This can be achieved by glueing on a shoe so that there is no contact under the toe, and only contact at the heels.

Laminitic cases are difficult to manage long term, however by following the principles in this article, we can establish a healthy environment for the hoof to grow and the horse to live pain-free.

Luke is a veterinary podiatrist providing a high level of service to the Australasian horse industry through affiliated veterinary practices and an online consultancy portal. Luke is the founder of Motion Equine Podiatry Consulting and is available by appointment in multiple locations along the east coast of Australia.

luke.wellssmith@gmail.com | www.motionepc.com.au

Missed part one? Read it here Hoof Mechanics in the Chronic Laminitis Case - Part 1.