The term "quarter crack" was heard much more frequently this year after Kentucky Derby and Preakness winner Big Brown was
treated for the hoof condition prior to the Belmont Stakes, but equine veterinarians, podiatrists and farriers know that quarter
cracks affect all types of racing and performance horses and sometimes work horses.
Photo 1: An example of a quarter crack.
Some question the terminology, preferring "hoof crack" instead, but agree that the condition can impede a horse's ability
because of pain and instability of the hoof wall.
It's "a common cause of foot lameness or decreased athletic performance in race and sport horses," says equine podiatry specialist
Stephen O'Grady, DVM, BVSc, MRCVS, at Equine Podiatry, Northern Virginia Equine.
Photo 2: Stainless steel wires (21 gauge) are used to "stitch" the crack. The ends are pulled tight and bent outward.
"It affects every lineage, breed, sex, every walk of (horse) life," says William Moyer, DVM, who heads the Large Animal Clinical
Sciences Department at Texas A&M University's College of Veterinary Medicine.
"They (quarter cracks) are more likely to occur, or seem to have a higher incidence, in horses that race for a living, and
probably the incidence in Standardbred racehorses is, in my experience, higher than in Thoroughbreds," Moyer says. "But you
occasionally see it even in a horse that isn't doing anything for a living, and you wonder how he ever got it."
Photo 3a: A sheared heel.
In performance horses, some type of hard blow to the foot is the most frequent cause of quarter cracks, according to Tom Curl,
a farrier with Global Lameness Consultants, Vero Beach, Fla. "Show jumpers and hunters, and some reiners and cutters, get
a trauma crack, either from smacking themselves or coming down hard off a jump and landing just on one side of the foot, or
they just whack the other foot and split it."
Photo 3b: The quarter crack present in Photo 3a, on the displaced side.
Typically, quarter cracks originate at the top of the hoof, at the coronary band, and proceed distally toward the floor of
the hoof. "A true quarter crack," says O'Grady, "is full-thickness, a fracture that extends into the dermis of the hoof, often
leading to instability, inflammation and infection.
"If you take your thumb and put it against either side of the crack and push on it, it will move, and usually the horse will
show signs of pain," O'Grady explains.
Causes, he says, "may include trauma to the coronary band, pre-existing damage to the corium from infection, abnormal
hoof conformation, focal foot imbalances, short shoes or an abnormal landing pattern when the foot strikes the ground."
Quarter cracks become more painful with infection and/or the result of instability caused by movement of the hoof wall posterior
to the crack. Vertical movement of the heel bulb on the affected side further complicates the instability.
"Rather than call it quarter crack, you're best to call it hoof crack, because a quarter crack is very specific. The quarter
is a portion of the foot, but you can have toe cracks, heel cracks, etc.," Moyer says.