NO FOOT, NO HORSE
The Importance of Correct Hoof Balance.
The foot is a common source of equine lameness. Correct trimming and shoeing are therefore two of the most important influences on the soundness of a horse.
A correctly trimmed and shod hoof should be functionally and biomechanically efficient. This minimises strain on the tendons and ligaments higher up the limb while maintaining resilience of the hoof wall. The hoof’s natural balance should be maintained by ensuring a correct toe length and a correct hoof-pastern axis.
The angle of the hoof wall and the coffin bone should lie parallel to each other, and these should both be parallel to the angle of the pastern and the shoulder. This will maximize limb efficiency and shock absorption and minimize excessive strain on the soft tissues of the limb.
A “broken-back” hoof-pastern axis, where the horse commonly has long toes and under-run heels, will put more stress on the structures at the back of the leg such as the navicular bone, suspensory ligament, and the digital flexor tendons. This conformation predisposes a horse to navicular disease, chronic heel pain, tendon and ligament strains and quarter cracks in the hoof. A shoe that is not placed far enough back on the foot will also contribute and encourage the development of this conformation as it will bring the majority of the weight-bearing surface of the hoof in front of the vertical, encouraging the heels to under-run.
An upright hoof with a “broken forward” hoof pastern axis will put excessive strain on the knee and fetlock joints which may predispose to arthritic changes in these joints.
Another important consideration when trimming or shoeing a horse is to ensure that the weight –bearing surface of the hoof extends back as far as possible. A vertical line drawn down from the midpoint of the coffin joint should divide the hoof into two halves. At least 50% of the weight bearing surface of the hoof should lie behind this vertical, which will improve break-over and support healthy growth of the heels. In some horses, this may be require the heels of the shoe to extend back further than the heels of the hoof.
A correct break-over point is important in reducing leverage pressures on the hoof. The break-over is the final phase in the stride, as the hoof is leaving the ground to be advanced forward, where the heel is lifted and the limb rolls or “breaks-over” the toe, using the toe as the pivot point (Figure 5). Toe length and hoof-pastern axis affect break-over. A long toe acts as a long lever arm, thus increasing strain on the tendons and ligaments and slowing break-over, while also increasing the risk of over-reaching by the hind foot. Break-over can be improved by decreasing toe length during trimming, rolling or squaring off the toe of shoes or using a rocker shoe.
Medial-lateral hoof balance should also be considered. When in motion, the hoof should land square and parallel to the ground. When standing, the coffin bone should sit parallel to the sole of the hoof and the ground. Thus, there should be an equal distance from the edge of the coffin bone on the inside (medial aspect) of the hoof to the ground, as there is on the outside (lateral aspect) of the hoof. This ensures that the forces are distributed evenly across the joints higher up the limb.
Hoof balance is best assessed by taking radiographs (x-rays) of the feet. These allow us to accurately assess the hoof-pastern axis and how the coffin bone is sitting within the hoof capsule. Generally, 2 xrays are taken- one from the front, the other from the side. These xrays can be used by your vet and farrier to ensure your horse is trimmed and shod in the best balance with their conformation.
Please call us if you are interested in getting a hoof balance assessment performed on your horse.