The Tolerable Club Foot
Is it worth taking a chance on a horse with a “clubby” foot?
It’s the classic horse-buying dilemma. The prospect you’ve been eyeing for some time (and, let’s face it, that you’ve already fallen in love with) has a clean prepurchase exam report except for one small thing: radiographic evidence of a club foot in his right front. It’s not like you’re planning to compete in the Olympics this summer, but can this horse still do what you want athletically and stay sound?
Veterinarians diagnose club feet pretty frequently, says Stephen O’Grady, DVM, of Virginia Therapeutic Farriery, in Keswick. In fact, in a 2012 study, researchers found that almost one-third (116 out of 373) of Thoroughbred foals developed a club foot during a four-year observation period.
In an attempt to solve this club foot conundrum (i.e., to buy or not to buy?), we will briefly review its appearance, how and possibly why it occurs, and, most importantly, what you can do about it. We will also address the potential complications associated with a club foot.
What Exactly is a Club Foot?
In the bulk of the veterinary literature on the subject, a club foot is defined as “a shortening of the musculotendinous unit of the deep digital flexor tendon (DDFT) that results in hyperflexion of a given anatomic region of the limb.” Horses with such shortening, or contraction, have an imbalance from the front to the back of the foot characterized by a shorter-than-normal toe and a long heel.
That was a bit of a mouthful, so let’s break it down a bit. Although we often think of the DDFT as located primarily at the back of the cannon bone, the muscular part of the DDFT unit (think back to biology: tendons connect muscle to bone) actually originates behind the radius (forearm) near the elbow joint. Three muscle bellies extend the length of the radius before joining together just above the knee joint, or carpus. At this point, those three muscles are considered a single tendon—the DDFT. That tendon courses through the carpal canal at the back of the knee, travels the length of the cannon bone and the long (P1) and short (P2) pastern bones, and wraps around the navicular bone in fulcrum-fashion before finally attaching to the flexor surface, or the underside, of the third phalanx bone (P3), widely known as the coffin bone. There is also a small, but very important, “accessory” ligament between the DDFT and the suspensory ligament beneath it (which connects the bones of the knee or hock to the sesamoids at the back of the fetlock). This is commonly referred to as the inferior check ligament.
“Any prolonged shortening of this unit of tendon and muscle essentially pulls on the back of the coffin bone such that it changes position in the hoof, causing the coffin joint (the distal interphalangeal joint, or DIPJ, where P2 and P3 meet) to flex,” O’Grady says. “It is important to realize that the bones in the distal limb are no longer aligned; however, there is no rotation of the coffin bone (its tip pivoting downward) like in some laminitis cases,” a painful condition in which the leaflike laminae that connect the hoof wall to the coffin bone separate or fail.
Instead, the pulling on the coffin bone results in the horse shifting his weight-bearing from the heel to the toe. The heel bears less weight and grows longer to compensate for the shortened musculotendinous unit, while hoof wall growth at the toe becomes shorter. In addition to the characteristic dishing that develops in the dorsal hoof wall, many horses with club feet also have a bulging of the DIPJ that’s visible once the grade of the club foot is 2 or higher.
“This bulging is due to the persistent, abnormal flexion of the DIPJ, which is why the club foot is referred to as a flexural deformity,” O’Grady notes.
Club Foot Grading
|Grade of Club Foot
|A hoof angle 3-5 degrees greater than the opposite foot. The coronary band is pronounced.
|A hoof angle 5-8 degrees greater than the opposite foot. The hoof rings are wider at the heel than the toe. When trimmed, the heel might not touch the ground.
|A notable concavity of the dorsal hoof wall. The hoof rings are approximately twice the width at the heel compared to the toe.
|A severely concave dorsal hoof wall, with a hoof angle of at least 80 degrees. The coronary band is horizontal with the ground.
Indeed, club feet are generally graded on a scale ranging from 1 to 4, with 4 being the most severe (see the chart to the left). This grading system is based on the dorsal hoof wall’s deviation relative to P2. In a normal foot, you should be able to draw an imaginary line through the middle of P2 that is parallel to the dorsal hoof wall. In a club foot, this angle is broken forward because the abnormal hoof is “steeper” than the normal foot. It’s like the difference between the bunny slope and a black diamond run at a ski resort.
Potential Causes of a Club Foot
Although foals can be born with flexural deformities, such as a club foot, most affected horses are born normal and don’t develop a club foot until 2 to 6 months of age (but this varies). Most horses develop only one club foot, usually in the front.
While the exact causes of the DDFT musculotendinous unit shortening remain unclear, various theories exist, including:
- A genetic predisposition;
- Improper nutrition—a diet that provides too much energy (calories) or has unbalanced minerals, for example;
- Excessive exercise; and
- Conformation, in which the foal has long legs and a short neck, which means he grazes with one leg extended farther forward than the other. If foals extend the same leg consistently, then a flexural deformity could develop in the extended limb. (Think about it: If you always stood with your weight on one foot and pointing the toes of your other, like a ballerina, never flexing them, things would begin to change in that foot.)
“In my opinion, one of the main causes of club foot in foals is contraction of the muscular part of the musculotendinous unit, up where the muscle bellies exist at the back of the radius,” says O’Grady.
He adds, “It is possible that a source of pain causes the muscles of the DDFT to contract, such as pain in the growth plates, trimming feet too short, or trauma from exercising on hard surfaces.”
Essentially, any source of discomfort or pain in the lower limb that decreases the amount of weight the foal is bearing can lead to the development of a club foot. Subsequently, the musculotendinous unit of the DDFT contracts, leading to an altered DIPJ position, additional weight-bearing changes on the affected limb, reduced toe growth, and excessive heel growth.
“Pain is likely also the instigating feature in adults that develop club feet,” says O’Grady. “As such, the underlying source of pain must be identified and corrected through the course of managing the foot via farriery.”
Sources of discomfort in adult horses causing late-onset club foot include pain due to chronic low-grade laminitis, heel pain (e.g., navicular syndrome), exuberant trimming of the toe resulting in solar pain, or pain due to an old injury.
Shoeing and Surgical Strategies in Adult Horses
First and foremost, be warned: There is no “cure” for a club foot.
“No club foot, even the most mild of cases, can be completely resolved. It’s a maintenance condition,” says O’Grady.
When approaching a club foot case, farriers have two objectives, regardless of the horse’s age and use. The first is to improve or achieve normal P2 and P3 alignment, and the second is to achieve normal orientation and loading of P3 relative to the ground.
Although you might think that all your farrier has to do is extend the toe and shorten the heel as much as possible, this approach is unlikely to be effective. In fact, it will actually place more tension on the musculotendinous unit, leading to further hoof capsule distortion, separation or tearing of the dorsal laminae, and possibly pedal osteitis, defined as inflammation and remodeling of the coffin bone from concussion due to loss of sole depth (and increased concussion experienced by the bone).
Instead, O’Grady recommends trimming the heel incrementally. He also advocates trimming the toe, but with a gradual “rocker” just before the apex, or tip, of the frog. This rocker decreases breakover (the forwardmost point of ground contact when the hoof is on the ground) during locomotion and decreases tension on the DDFT caused by lowering the heels.
In more severe cases, a farrier might elevate the heel in conjunction with trimming.
“The rationale for raising the heel is to redistribute the weight over the entire solar surface of the foot and lessen the tension or ‘pull’ on the DDFT and associated structures of the musculotendinous unit,” says O’Grady.
In some cases resistant to shoeing alone, the veterinarian might perform a surgical procedure called a “check ligament desmotomy.” Cutting the accessory check ligament extending from the back of the knee/carpus to the DDFT allows the musculotendinous unit to lengthen, potentially resulting in a better response to corrective shoeing. A salvage operation is transection (cutting) of the DDFT, but this is only to spare the horse from loss of life and will render him a pasture pet.
Taking the Plunge With a Clubby
Now back to the horse purchase dilemma. The pros are that the horse described clearly has received good farrier care (especially if the club wasn’t noticeable on visual examination) if he is sound, and he’s currently at or near the desired level of athleticism. The cons are that there is X ray evidence (e.g., an altered angle between P3 and the hoof wall, dishing of P3) of a club foot and there is no “cure” for a club foot.
Keep in mind that there are some potential complications that could develop in a horse with a club foot, especially one that is not maintained properly:
- An overloaded toe can result in the decreased sole depth and pedal osteitis mentioned;
- Decreased weight-bearing at the heel causes capsular distortion and the classic concave dishing of the dorsal hoof wall due to more weight-bearing at the toe. Less weight-bearing of the heel also means the foot has a smaller surface area for absorbing and dissipating energy and vibrations during weight-bearing. These vibrations transfer instead to the bony structures, resulting in excess stressing of the bones;
- The change in angle between P2 and P3 seen can result in potential joint inflammation due to the abnormal alignment. As with any joint, inflammation can quickly spiral out of control, resulting in osteoarthritis;
- Inflammation of the navicular’s suspensory ligaments;
- A toe-first landing pattern during locomotion. In turn, hoof wall cracks, demineralization of P3 at the toe, hoof wall separation, and white line disease can occur; and
- At least in part due to inflammation in the hoof, some club foot cases have the potential to become laminitic, complicating the clinical picture immensely.
Equipped with this information, you can visit with your veterinarian, weigh the pros and cons discussed, and make a decision accordingly.
In summary, with appropriate treatment, patience, and time we can successfully manage and maintain most club-footed horses. The most important ways to manage or improve a club foot and minimize the chances of secondary complications are to examine your horses’ feet frequently (regardless of age and use) and provide appropriate routine farriery. The farrier will often notice excessive wear at the toes, an early first sign of a club foot. Further, once the farrier trims the foot properly, he or she will be able to more easily note decreased weight-bearing at the heel—a hallmark of a club foot.
Treating the equine club foot can be challenging and time-consuming, particularly in chronic cases. Whenever possible, identify and treat the underlying cause. If this is not possible, then rely on your veterinarian’s and farrier’s combined expertise to improve and maintain the adult club foot.
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