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December 18, 2009

Sheared Heels Must Be Stopped In Their Tracks

Floating the heel so it doesn't bear weight and using a full bar shoe can help to stabilize the hoof and relieve pain. Photo courtesy of Rood & Riddle Equine Hospital.

There’s no doubt about it, having a horse with sheared heels can be stressful. If you’re the owner, that stress may show up when you worry about your horse not feeling 100 percent—or not being able to make it to his next show. But for the horse, that stress shows up in his heels and needs to be closely monitored.

If a horse has good hoof and leg conformation, his feet hit the ground evenly, without one side suffering extra stress. But a horse with crooked legs or poor joint angles will have unbalanced feet that wear crookedly, and one side of the hoof will have a different shape than the other.

If the frog is off center, for instance, there’s often a flare in the hoof wall on one side. Sometimes poor trimming and shoeing (leaving the sides or heels of the foot uneven and out of balance) or neglect (bare feet growing too long), combined with one side of the long foot breaking off, will create an imbalance that can lead to sheared heels.

This unbalanced hoof puts uneven stresses on the rear part of the foot, resulting in jamming forces on one side and a tearing of the tissues as one heel bulb becomes higher than the other—that’s sheared heels.

The side that gets the most impact becomes steeper because the rate of hoof growth on that side speeds up, due to increased blood circulation. The side receiving less impact will flare outward.

Going barefoot is one option in correcting sheared heels, allowing the frog, bars and sole to contact the ground and help take weight.
“This unloads the wall and allows it to relax a little,” said Scott Morrison of Rood and Riddle Equine Hospital (Ky.). “One cause of sheared heels and quarter cracks is
too much loading of the perimeter of the foot—the hoof wall—and not using the other structures of the foot for weight bearing. Thus going barefoot can be another option for horses who don’t have to compete with shoes on.”
If the horse can have time off from work and adjust to going barefoot, this can
work well.
“If you can control the environment and the footing (having the horse in a large enough area, with dry footing instead of wet and boggy) going barefoot

If one side of the foot continually hits the ground first (and harder than the other), the heel bulb on the side receiving the most concussion may eventually be driven upward, creating sheared heels. If not corrected, the condition becomes more extreme, and the horse will go lame. The side that lands first bears the brunt of impact and is prone to injury (bruising, quarter cracks and/or sheared heels).

If the tissues between the heel bulbs start to tear (as the bulbs become more and more out of line and distanced from each other) the horse feels discomfort each time the foot takes weight.

Scott Morrison, DVM, of Rood and Riddle Equine Hospital, Lexington, Ky., most commonly finds this problem in horses that toe in or out, putting more stress on one side of the hoof wall (and heel) than the other.

“The conformation that can lead to sheared heels is usually feet that turn out a little bit (splay footed). In other
instances, horses don’t have the hoof and pastern in a straight line,” he said. “If you look at them from the front, it looks like the hoof is offset to the outside, like the foot is put onto the pastern too much toward the outside. The pastern comes into the hoof capsule from the medial side (a little to the inside). Those feet tend to develop really bad sheared heels.”

The earlier an owner becomes aware of the problem and addresses it, the better the outcome. The feet can be trimmed and shod more carefully to bring the foot into better balance and relieve some of those stresses—preventing the distortion of the heel bulbs.

“Sheared heels are interesting, and some of them are related to contracted heels. If you look at most sheared heels they are like a unilateral contracture (a contracted heel on just one side),” said Morrison. “A normal foot should have a nice shape with sloping hoof walls. If you look at sheared heels, most of the time it’s the medial (inside) heel. That wall does not have a nice slope; it becomes quite vertical and straight.”

The foot is too vertical on the inside wall and may be flared out on the outside wall.

“As the one heel gets more and more contracted and that wall becomes vertical, it begins to be displaced upward. My theory on sheared heels is that first of all, the part of the foot that’s under the most vertical load tends to develop a straight wall. The side with a more horizontal load develops a flare.

“I see a lot of normal horses (with relatively normal hoof conformation) get more of a straight medial wall and more flared lateral wall, but when this becomes more exaggerated—a larger outside flare and a more vertical inside wall, with more hoof capsule distortion—the inside heel be-comes aligned directly beneath the bony column (the vertical line of force) and gets pushed upward, creating the sheared heel,” Morrison added.

Corrective Trimming

The goal of trimming and shoeing a horse with sheared heels is to restore the balance of the foot, since the symmetry has been distorted and one heel is bearing most of the weight.

Some farriers address a mild case by trimming the longest heel and using a full bar shoe to stabilize the heel area and spread the weight evenly. In many cases, however, simply removing the shoes, trimming the foot to try to help restore balance, and letting the horse go barefoot in an area where there is room for lots of movement and natural exercise will eventually correct the condition. This enables the foot to function more normally and redistribute the weight properly.

Severe cases where the heel bulbs are distinctly distorted may need several trimmings and shoeings with a full bar shoe to restore foot balance and relieve the pain. A special type of bar shoe that “floats” the jammed up heel (so it doesn’t bear weight) utilizes the horse’s own body weight to gradually force the heel back down into proper position and alignment.

The best method for trimming these feet is often a subject of debate, but one way to settle the debate is to have good quality radiographs taken, and share these with your farrier.

“You can easily be making the problem worse, otherwise,” Morrison said.

Morrison has seen some farriers trim the sheared heel side lower, while some trim the opposite side lower.

“Those who try to trim the sheared heel lower are trying to match wall length,” he said. “The inside wall is shoved upward, and if you measure the actual length of the wall it is longer, while the outside (flared side) is actually shorter. The same school of thought looks at the coronary band and tries to trim the hoof so that the coronary band will be parallel to the ground.”

But radiographs prove this method ineffective. “We find that trimming them this way is probably the opposite of what you want,” said Morrison. “The radiographs show that the coffin bone is tipped lower on the medial side. The length of wall and alignment of coronary band really can’t be used as guides for trimming because they are distorted, and this type of trimming may be adding more stress.

“If you trim that side lower you may be tipping the coffin bone even lower on that side,” he added. “You want to keep it parallel to the ground.”

Shoeing For The Occasion

Depending on what causes a sheared heel, some farriers may float that heel or use a shoe with a hinge and a spring to push that heel and contracted wall out again.

If the medial heel starts to shear, it first becomes more vertical, looking almost like half a contracted foot, and the inside part becomes too narrow.

“We’ve actually made a spring shoe to address this, putting pressure on and opening up just half the hoof—just the one side—to get it away from the vertical line of force and get a better shape to it,” said Morrison. “The spring shoe has a hinge in the toe and a spring at the end of the heel branch. We usually glue the shoe under the horse’s foot and put the spring into the shoe.”

This shoe should move that inside contracted heel out to where it should be and drop it lower as well. “If it’s been shoved up and sheared, it actually drops down and relaxes when you get it pushed back out, getting that medial wall away from the vertical line of force. The spring shoe can work well for this,” said Morrison.

In many cases, quarter cracks tend to go along with sheared heels. “Often a horse with sheared heels will also have a quarter crack, due to the stress on the hoof wall,” said Morrison.

“I’ve had some that were so sheared and overloaded that the wall was separated and undermined. Some of these heels actually need to be resected (surgically corrected). Usually these will heal nicely afterward. The most important thing is rebalancing the foot, using radiographs to guide you,” he said.

Although sheared heels can be corrected, and the heel can drop back down to its proper location, the horse’s conformation has not changed, and he will always be predisposed to displacing that heel again.

“I always give these horses some type of support over their frog if they have to be shod, either with a heart bar shoe or a shoe with a plate across the heel to support it,” said Morrison. “You certainly want to distribute that load over the frog and more structures of the heel.”

Morrison has seen several cases where he’s fixed the condition, but the horse came back less than a year later with the heel sheared right back up where it had been.

“Just because you have it looking good doesn’t mean it’s corrected forever,” said Morrison. “That foot is predisposed to do it again if shod in traditional fashion. That horse needs careful trimming and shoeing for the rest of its life.”

The Barefoot Prescription

Going barefoot is one option in correcting sheared heels, allowing the frog, bars and sole to contact the ground and help take weight.

“This unloads the wall and allows it to relax a little,” said Scott Morrison of Rood and Riddle Equine Hospital (Ky.). “One cause of sheared heels and quarter cracks is too much loading of the perimeter of the foot—the hoof wall—and not using the other structures of the foot for weight bearing. Thus going barefoot can be another option for horses who don’t have to compete with shoes on.”

If the horse can have time off from work and adjust to going barefoot, this can work well.

“If you can control the environment and the footing (having the horse in a large enough area, with dry footing instead of wet and boggy) going barefoot

If you enjoyed this article and would like to read more like it, consider subscribing. "Sheared Heels Must Be Stopped In Their Tracks" ran in the December 18, 2009 issue. Check out the table of contents to see what great stories are in the magazine this week.

 
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