Foal Deformities: New Treatments (Bluegrass Laminitis Symposium)
Isn't it just a rotten feeling to look at your foal and notice for the first time that he's crooked? Even if you have your veterinarian and farrier on speed dial and they're already on the way to work miracles, you can't help but worry if the foal will straighten out enough to make a good sale and/or a good athlete.
Angular and flexural limb deformities in foals are concerns, to be sure, but they're not necessarily kisses of death. At the recent Bluegrass Laminitis Symposium, held January 25-28 in Louisville, Ky., host Ric Redden, DVM, founder of the International Equine Podiatry Center in Versailles, Ky., discussed treatments for foal deformities.
"There are several basic deformities that we must deal with: Angular, axial, rotational, spiral, weak flexor and contracted flexor, and windswept deformities," he began. "I rank each deformity on a grade of one to five, with one being visible only to the well-trained eye, and five being an off-the-scale deformity. Foals may have a deformity in one limb or a combination of deformities in one or all limbs. Regardless, each deformity is graded before selecting the best treatment option.
"It sounds simple enough to say a foal toes in or out, but it is actually much more complex than that," he went on. "We need to be able to recognize the deformity, classify it to some degree, have knowledge of growth plate closure, and be alert to the stress that corrective aids can put on the rest of the limb and foot."
How to Watch a Foal
The first step in fixing a crooked foal is determining exactly where the crookedness lies. Redden described what he looks for when evaluating these foals.
"I use the imaginary dot system; I watch the foal walk away and in my mind I place dots on the center of his heels, pasterns, bottoms of his hocks, points of his hocks, and in that dimple between his hocks and buttocks," he said. "When he walks back, I place imaginary dots at the center of his toes, coronary band, center of the fetlock, top of the cannon bone, bottom of the knee, top of the knee, and center of the radius (that swirl of hairs up near his chest). I'll closely observe the air space under the foot as it lands, watch the alignment of the forelimbs and the response of his body as he goes through strides.
"Foals will tend to follow the mare and are usually not taught to lead early, so they can be really hard to watch," he noted. "You can put the foal between the mare and the fence or barn to get them to go straight."
Angular deformities are either valgus (part of the limb deviated outward, as with knock knees) or varus (part of the limb deviated inward, as with a foal that toes in at the fetlock). Attempts at correction usually involve extensions (placing a shoe or composite material that is wider than the foot on one side or the other) to help realign the limb, but Redden advised that caution is due when using extensions or altering the medial-lateral balance of the foot too early in the valgus foal.
"The foot will start changing along the lines of stress, and with continuous correction it can become grossly out of balance, requiring months to correct," he warned. "First examine the foal, watch him walk both ways, assess deformities and degree of involvement and where they are on the leg, and only then determine how to treat that foal. Very few foals have only one deformity on one leg--usually there is a combination of problems with foot flight and leg alignment."
When there is a problem, he notes that correction should not be considered instant. "With foals bred for market, the owners often want those foals to be correct constantly," he said. "But we are just influencing the foal's growth plates to assume a healthier conformation, which, in turn, influences the growth rate of the long bones in his legs. That doesn't happen overnight. And as we use the foot to influence the bones above, we have to be careful to not lose the healthy balance of the foot."
Valgus deformity The term "valgus" describes a lower limb that deviates away from the midline when viewed from the front (as in knock knees). "Valgus conformation to a small degree is normal in young foals that have longer legs than necks," Redden said. "Be patient when correcting valgus knee deformities in the first 90 days of life. These foals often self-correct, and if you use too much correction too early, you can create a varus (inwardly deviated) fetlock. The valgus foal will often have a rotational component as well."
Treatments are relative to the age and degree of deformity. Stall rest or small round pen confinement works great for the newborn with 8-10 degrees angular deviation. Other possible treatments include medial shoe extensions (to apply outward leverage) as the next step, therapeutic trimming, and surgical correction.
- Medial extensions (making a shoe wider than the medial side or inside of the foot): "Once foals reach 30 days old, medial extensions can be considered," says Redden. "Be cautious, though. If the foal is steadily improving, be patient with any method that moves the load towards the midline, as the fetlock is first influenced by foot manipulation and it can become varus with overzealous cranking."
- Corrective trimming (lowering the lateral side of the foot): "This should be avoided until the foal is 90 days old for the same reason stated above," he noted. "We must be first concerned with the early closure of the fetlock growth plate."
- Surgery: Surgical options might include using periosteal elevation to stimulate the slow-growing side of the growth plate or staples/screws and wire to restrict it on the "long" side of the limb. Redden noted that these are used for nonresponsive cases or those with more than 15ï¿½ of deviation. "Periosteal elevation is a strongly recommended treatment in some areas and is seldom used in others," he commented. "The large majority of valgus foals will self-correct by the time the foal is 10-18 months of age. It all boils down to how quickly you want to see correction, and what the risks are of the downside. Physeal (growth plate) bridging (with screws and wire) is also used to delay the faster-growing side of the bone in the higher-scale cases. This works great, provided the implant is taken out before the leg becomes straight, as the correction continues for several weeks following the removal of the wire and screws, and overcorrection (bowed knee) can result."
Varus deformities These foals have an inwardly angled lower limb when viewed from the front (this is more common at the fetlock). This is a more serious case than a valgus deformity, said Redden.
"Self-correction does not exist for this problem," he said. "Early detection, aggressive lateral extensions, and/or surgical correction are indicated. The pastern is basically through growing by the time they're three months old, so you've only got about one month to make things really happen. Correction needs to occur within a few days of birth to have optimum response because your window of response is so short for the fetlock. Try to achieve correction as quickly as possible and maintain it until the fetlock is through growing at about three months of age.
"I put a lateral extension on them at four to five days of age; at that age they're made of rubber," he said with a laugh. "That extension might only stay on four or five days, or I might put on a bigger one if the correction isn't going as I'd like. You need to stay on top of these to make sure they keep progressing in the right direction. Seldom does it take more than a couple of shoes when used at this age.
"I try to give the foot a little rest, maybe 24 hours, between extensions as well," he added.
A rotational deformity is very different from the valgus and varus deformities, Redden explained, because in this case the whole leg is rotated outward. Also, it is muscular in origin rather than due to bone alignment. "The forelimb attaches to the body by muscle, not bone," he explained. "If you tranquilize this foal and gently pull his elbow out (while he's standing), you can actually derotate the limb. This is an easy way to distinguish this deformity from the often misdiagnosed valgus fetlock, which is a very rare deformity.
"Do not try to correct that with a rasp," he warned. "If they're rotated outward, they will not land flat--they will always land lateral side first. If you make them land flat, you can cripple them. When you create mediolateral imbalance as a corrective mechanism, take a radiograph and see what you've done to the joints. The goal is to load the joints as evenly as you possibly can."
It's quite likely that no correction is needed, he said. "As they develop a chest, most horses, especially Thoroughbreds, will self-correct a rotational deformity and push that elbow outward," he reported. "Colts do this quickly, fillies slower. If you try to crank these things early, you'll end up with a good limb, but a warped foot, and now you've got a different problem. Leave them be.
"The medial heel is often pushed up; a medial extension can be useful for controlling crushing of the medial heel," he added. "Don't be aggressive before three months of age, because using this extension earlier can cause a problem with the fetlock."
Spiral deformity exists when the lower end of the cannon bone is twisted inward compared to the upper part of the bone. The twist causes the fetlock and foot to face inward. "No therapeutic trimming will fix these," said Redden, who also terms this problem "heeled-out." "It's not an angular issue. If the center of the fetlock was in the same plane as the front of the knee, I could place an imaginary arrow straight through the face of the knee and center of the fetlock. With the spiral foal, however, I have to step away from his midline to look straight through the face of the knee." Most of these deformities twist at the lower third of the cannon bone, he noted.
"To distinguish the spiral from the varus fetlock, imagine you're evaluating the left front limb," he went on. "Pick up that left front limb and cradle the cannon bone in your left hand. Place your right index finger on the front of the pastern and flex the fetlock. The pastern and cannon bone will be in a relatively straight line, but the foot is turned inward. The deformity lies in the bone under your left hand. The varus fetlock will appear quite different as the pastern will not be in line with the cannon bone when the fetlock is flexed.
"It is common to see a combination spiral and varus deformity," he commented. "I score each on a scale of 5 and make all efforts to reduce the varus component in the first 30 days of the foalï¿½s life."
There is no correction for these foals, but this problem is not necessarily critical; Redden noted that most horses can race quite well with this deformity. As with many things, it's a matter of degree.
"They are tough to get sold, though, as most buyers equate this deformity to being varus," he added.
"When the center line of the cannon bone is lateral to (outside) the center line of the knee, it is offset," Redden described. "This is not a desirable deformity, as it is often associated with knee problems.
"The ï¿½cantedï¿½ knee is often diagnosed as offset, but this variation is found on many top horses and is not a threat to their future soundness," he went on. "It looks similar at first glance, but both the center of the bottom of the knee and top of the cannon bone are positioned properly. The face of the knee is tipped inward at its top, which puts the radius medial to (inside) the vertical alignment of the cannon bone.
"The shape of the canted knee varies from horse to horse--focus on the bottom of the knee and its relationship with the cannon bone," he explained. "This will help clearly distinguish it from the undesirable offset knee.
"When a combination of offset and canted knee exists (bones not entering the knee on center, with the knee tipped as well), they look like a wreck," he said. "They often have severe soundness issues."
Contracted tendons This term describes a foal whose deep digital flexor tendons are contracted so his knees and/or fetlocks are always flexed. "Splint these babies early!" urged Redden. "I splint most foals when they are just a few hours old. They wear the splints for six hours before I take them off to check progress. Then I put the splints back on for another eight hours when indicated, and normally that is all that is required. The older they are when first treated, the longer the splint must be worn."
He reported success with a custom-fit splint made using half of a thin-walled four-inch PVC pipe applied over a heavily bandaged leg. "The plastic is made soft with a heat gun or propane torch to accommodate the shape of the bandaged leg," he explained. "The splint is placed on the back of the leg from a few inches below the elbow to just below the fetlock, never on the front.
"Shaping the PVC to the bandage and applying it on the back of the limb offers optimum results and prevents pressure sores and the telltale white hairs," he went on. "Caution is due. The goal is to achieve slight overcorrection, which will appear as back in the knee. Don't turn these foals out while they are back at the knee! Hand walk them or put them in a small, confined, portable round pen until the knee has returned to its normal alignment.
"Often I apply a glue-on rocker-style shoe on an older foal while they are wearing the splint," he added. "This keeps the toe from wearing out as they drag the foot around in the splint. Bedding on shavings is a must, as they cannot walk in straw bedding when the leg is splinted. I also apply bilateral splints when indicated; foals do reasonably well getting up and down while both legs are in splints."
Redden uses tetracycline to encourage tendon relaxation, but he relies on the mechanics of the splint as a primary means of correction.
"Superficial digital flexor tendon contracture is a real bear; it's the toughest deformity you have to deal with," Redden said. "It is not as common in Thoroughbreds as it is in other breeds. Saddlebreds and Quarter Horses appear to be more prone to this deformity. It generally appears around weanling age and appears to be related to growth spurts, and the low-grade ones can be managed fairly successfully with an extended-toe, elevated-heel shoe in conjunction with bandages and splints to weaken the superficial apparatus. Those that do not respond favorably require surgery.
"Cutting the superior and inferior check ligaments has been advocated as a means to help this problem, but in the cases I have seen it has not offered favorable results," he went on. "My surgical approach involves cutting the superficial flexor tendon mid-cannon and using the shoe described to open a large gap in the severed tendon. A splint down the back of the limb, custom-fit over the surgical bandage, secures the fetlock in place while the ends of the tendon fibrose (adhere) to the deep digital flexor tendon. This assures maximum tendon length. If they are allowed to heal without an inch and a half gap in the tendon, you are back to square one very quickly. The toe and heel extensions are weaned off over the next two to three resets."
Most surgery cases will show a favorable response and a fair number will go on to be useful riding and slow sport horses, Redden reported. "However, I have had several cases that recontracted several months later and once again began to knuckle over," he advised. "Using a cast and/or splint to hold them through their growth period helps preserve the effects of the previous surgery. Once they are knuckled over again, however, additional surgery is required and results are not as favorable."
Flexor laxity (tipped up toes) This occurs when the flexor muscles behind the leg above the knee and/or hock are not strong enough to support the leg in a normal position. "The muscle lacks tone, and the tendon is only the extension of the muscle," Redden explained. "The foal ends up walking on his heels or even the back of his fetlocks. These are not hard to correct even if the foal is weeks old; it is not as critical to jump on them early as it is with tendon contracture. However, early correction will help prevent the crushed heel that invariably occurs with most cases.
"Rasping off the heels to take away the pivot point is often all that is needed for the mild cases," he said. "The more extensive cases may need an artificial tendon, so to speak, for a few days to help them support the foot and fetlock in a more normal position."
To do this, he applies a heel extension shoe and fits a loop on the heel of the shoe to which he attaches a bungee cord. The leg is bandaged and the bungee is secured to the top of the bandage running across the back of the fetlock. The tension can be adjusted as needed; the elastic nature of the bungee pushes the fetlock upward and allows the deep digital flexor muscle to gain strength. Normally only a few days are needed to fix even the most stubborn weak flexor, he noted.
Quick action is needed to correct some, but not all, foal limb deformities. And care is needed to provide the right amount of correction to straighten the deformity without sacrificing other aspects of conformation.
About the Author
Christy West has a BS in Equine Science from the University of Kentucky, and an MS in Agricultural Journalism from the University of Wisconsin-Madison.
POLL: University Equine Hospitals