Cover Story | Lameness

Managing Hoof Wall Defects

By Marie Rosenthal MS

Successful management of hoof wall defects entails addressing the underlying causes and stabilizing the foot with the appropriate farriery, which should be initiated as quickly as possible, according to Stephen E. O’Grady, DVM, MRCVS, owner of Virginia Therapeutic Farriery, in Keswick, Va.

“Hoof wall defects are a common occurrence in sport horses, as we all know, and these cases often present with instability and lameness and can result in withdrawal from competition and lost use of the horse,” Dr. O’Grady explained at the 70th annual AAEP Convention & Exhibition meeting, held in Orlando, Fla.

Before the problem can be fixed, veterinarians and farriers must understand why hoof wall defects occur, he said. Despite its being a common problem, however, there is not a lot in the literature to explain why the hoof wall cracks. He offered this explanation: “Excessive load or a section of the hoof capsule over time is going to lead to a hoof capsule distortion. In other words, it’s going to change shape. And when the excessive load on a section of the foot exceeds the structural capacity of that section to accept increased load, a defect will occur.

“A hoof wall defect, either a quarter crack or a toe crack, is always going to be associated with a hoof wall distortion, no doubt about it,” he said. “The hoof wall’s going to change shape. And the 2 most common hoof capsule distortions we encounter are the sheared heel, where the proximal coronary band over 1 heel is pushed out of place, or an upright or a club foot,” he said.

A sheared heel often is correlated with a quarter crack, and the leverage on the toe from a club foot is going to cause a toe crack. Toe cracks also can be seen with a long toe, low heel confirmation.

“Managing a hoof wall defect must include addressing the hoof wall capsule distortion,” he said.

In his experience from a 2011 study on 70 horses, quarter cracks without a concurrent sheer heel are rare. Quarter cracks on barefoot horses are also rare because the heels move independently with a barefoot horse. A shoe locks the heels in place, restricting them, so it is easier to overload 1 heel, he explained. This is why farriery must play a role in resolving these defects, according to Dr. O’Grady, who was a farrier before he became a veterinarian and has spent his career practicing both.

A sheared heel is a hoof capsule distortion where 1 heel bulb is displaced proximally relative to the adjacent one. And this disparity, which is one-half centimeter or more, can be of the lateral or medial heel bulb.

The veterinarian will often see the medial side pushed up, the coronary bands pushed outward and the wall is moving inward toward the ground surface. The soft tissue between the coronary band above the defect, and the middle phalanx will be compressed.

With quarter cracks, veterinarians will see a proximal displacement of that coronary band above the defect, he said.

“You’re not going to see a quarter crack between the distal phalanx and the lamina,” Dr. O’Grady said. “The quarter crack is always going to be located palmer or plantar to the palmer process on the distal phalanx, and that will correspond with that area of the coronary band or soft tissue that has been displaced.”

Because the ground reaction force goes all the way around at the foot, if the rate of hoof wall growth is greater than the rate of hoof wall migration toward the ground, the coronary band is going to displace proximately, according to Dr. O’Grady.

“The heel will contract, and the wall becomes more upright on the affected side from the load. The frog narrows and recedes down below the heels to the hoof capsule. The heel on the overloaded side is going to start to roll under,” he explained. “And then there’s going to be a flare developed on the opposite side of the foot from the bending force where that horse contacts the ground. The soft tissue structures between the coronet and the middle phalanx will compress. And when they become compressed with the displaced hoof wall, the ungual cartilage will become trapped by the displaced hoof wall. Therefore, the foot on the medial side or the overloaded side will have decreased expansion when it’s loaded.”

Management Goals
The management goals are to improve the foot confirmation. Dr. O’Grady said the best way to do that is to leave the horse barefoot for 7 to 10 days, then trim and shoe to increase the ground surface on the affected side of the foot.

“This barefoot methodology is another option you have in your toolbox, and I’m just a big fan of it. When we remove the shoes, the heels will settle remarkably in a small amount of time,” Dr. O’Grady said, allowing the heels to settle onto the same plane. “It’s like a new starting point.”

He trims twice. The first trim uses the widest part of the horse’s foot because that area is going to be just in front of the center of rotation. And then he trims in proportions on either side with trimming a bit harder on the affected side to create more ground surface.

“I want to end with all heel structures on the same plane. In other words, the hoof wall, the frog, are on the same horizontal plane,” he explained. To test the trim, lay a rasp across the foot; it should touch all the structures.

If the horse has a significant quarter crack or hoof wall distortion, a bar shoe can help unload that side of the foot. He only uses straight bar shoes, he said.

The second trim is tapered from the toe quarter to the back of the heel to enable the load of the horse when he puts his foot on the ground to push the hoof wall back down to the shoe, which opens and closes as the horse moves. And in about 10 days, that’s just going to gravitate right down to the shoe. He typically recommends a bar shoe.

“A lot of trainers don’t like bar shoes,” he said, so he might choose a stabilizer or spider plate in that case because they protect the frog while stabilizing the foot and redistributing the load over the hoof wall.

If one side of the foot is overloaded, you can move the center of pressure toward the better side of the foot. “And this is easily accomplished by just taking and fitting your shoe flush or tight on the medial side and then forming a little extension on the lateral side of the foot,” Dr. O’Grady explained.

By doing this, the quarter crack will start to heal. If the horse must compete within a few days, the crack can be repaired, rather than wait for it to heal itself. However, he suggested waiting 24 hours after the farriery, and make sure the wall is stabilized before the repair. MeV