Hoof cracks: Finding cause is key to treatment, repair - DVM
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Hoof cracks: Finding cause is key to treatment, repair
Incidence is higher in race and performance horses, but not limited to them


"Basically there are two ways to end up with a hoof crack, though there are really more than two," he says.

"One is to have an injury to the tissue that is responsible for creating the horn. For instance, I've got an old wound on my left thumb and therefore a permanent defect in the thumbnail because the germinal tissue that produces horn is absent," Moyer explains. "You'll see horses with the same thing."

Previous injury may produce a defect, which in turn produces a permanent crack, sometimes because of an infection around the coronary tissue, or the horse stepping on it. "Any situation that can cause trauma to your fingernail or toenail could happen to a horse," Moyer says.

The second most common situation, Moyer explains, is that hoof cracks repre-
sent a failure of the hoof wall, where sheer forces are such that the hoof just splits. "For the most part, these are horses with reasonably weak feet, that tend to have a low heel, longish kind of toe, flat foot and a thin hoof. That describes an awful lot of Thoroughbreds," says Moyer. "In most cases, it's a mechanically induced injury."

Cause is critical to treatment

"Basically the repair process is two-fold," notes Moyer. "One is to try to figure out, if you can, how did it get there? The second objective is to stabilize the crack, because the thing that hurts is motion at the crack site, initiating inflammation and pinching below it."

O'Grady agrees that determining cause is crucial to the proper treatment. "There are as many ways to repair a quarter crack as there are quarter cracks, but ... (learning the) cause is most important," he says.

Quarter cracks originate from three areas: limb conformation, foot conformation and landing pattern.

LIMB CONFORMATION: It may start from the shoulder or knee down, when the limb is rotated outward in such a way that the horse lands on one side of the foot and then puts pressure on the inside.

FOOT CONFORMATION: A horse's foot may be offset to one side, so it bears more load on that side; or it may have a low or under-run heel, where sufficient structure in the back of the foot is lacking. "This type of heel may be weak due to insufficient hoof-wall growth and there may be insufficient solar surface to adequately support the palmar/plantar part of the foot," O'Grady says.

In addition there may be increased pressure in the quarter and heel during the stance phase, as a result of delayed breakover caused by the long toe. Upright hoof conformation with high heels promotes heel-first landing, which increases pressure through the heels and quarters.

LANDING PATTERN: A horse with a quarter crack generally is one that lands or impacts the ground asymmetrically, impacting first on one side of the hoof and then loading the opposite side. This strike pattern often is related to conformation, but also can be caused by improper trimming.

Asymmetric landing may place extra forces on one side of the hoof wall, producing enough force to proximally displace the heel bulb. Along with abnormal conformation, this landing pattern can lead to a shearing force or increased pressure within the lamina.

The landing pattern and the conformation of the foot also may perpetuate quarter cracks caused by trauma to the coronary band or a previous abscess.


Source: DVM360 MAGAZINE,
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