Articles
Foal foot care III
A foundation for future athletic performance
In this series of articles by Jason Lowe we have looked at the importance and aims for trimming your foal's foot and then at some of the more serious flexural limb deformities. In this third and final article Jason reviews the types of Angular Limb Deformities (ALD's) that can be encountered and how they can be managed.
Foals with angular limb deformities have traditionally been referred to as "knock-kneed" or "bow-legged" in the front limbs. Angular limb deformities can also appear in the hind limbs but not as commonly. The toed-in or toed-out appearance that accompanies this is a rotational deformity and should not be confused with the angular deformity.
There are no confirmed breed or sex predilections, but subjectively there may be a genetic predisposition. Remember that for a foal to be born with a mild carpal valgus and toed out appearance is normal and as the foal grows and the chest widens, the limb straightens progressively.
ALD's are normally congenital (something they are born with) but some can be developmental, and have numerous possible causes. Regardless though, the problem is an imbalance of growth in the long bones of the leg, and this happens at the physis or growth plate. For various reasons, growth proceeds faster on one side of the growth plate than on the other side. The most commonly affected site is the growth plate just above the carpal joint (knee), although the bottom of the canon bone just above the fetlock can also be affected.A valgus deformity is the most common one you see and is defined as a deviation of the limb away from the midline (knock-kneed); a varus deformity is a deviation of the limb toward the midline (bow-legged).
The cause, severity and progression of the deformity are vital pieces of information that need to be understood before formulating a treatment plan. "Foals are like moulding plastic!" The foal should be evaluated with the amount of remaining growth in mind and not just at its's present state. Growth rates are most rapid in the newborn and slow considerably within the first year. Most of the growth from the tibia and radius is within the first 6 months, and from the canon bones in the first 3 months of age. Minimal change takes place beyond these times. A normal foal should be within 5 to 7 degrees of normal by 4 months of age and almost straight by 8 to 10 months of age. These are good " rules of thumb' to remember.
EVALUATION
Evaluate the foal carefully whilst standing and moving. Radiography (x-rays) may also be useful in some cases as it provides an objective assessment but your vet can advise you on this. Radiography is essential if an injury or malformation of the small (cuboidal) bones of the carpus (knee) or hock is suspected. This can happen in immature or dysmature foals especially, or you might suspect this if the foal is lame. The prognosis for an athlete in these cases is poor, as the range of motion will always be affected.
PERI-ARTICULAR LAXITY
This is a major cause of congenital ALD's. It is where the structures around the joints are too elastic and so don't support the joints enough. However it often improves dramatically within the first 4 weeks of life without intervention as the tissues around the joints strengthen. This is seen most dramatically in "wind swept' foals and limited exercise (box rest with 1 to 2 hours small paddock turnout) is usually all that is required for these foals to become normal.
TREATMENT
In my experience splints are usually contra-indicated to try to push or pull a limb straight in situations of angular limb deformity. Rigid support tends to lead to greater soft tissue laxity, and soft tissue wounds from the bandaging, increasing the problems you already have! Every foal must be managed on an individual basis with the goal of achieving normal weight bearing and function while providing the minimal support necessary.
In most situations minimal intervention is required to correct ALD's. A few days of box confinement on firm bedding with limited exercise in a small paddock (one hour twice a day) is a rewarding, cost-effective treatment. You are trying to get some muscle and joint strength to develop with the exercise but not let the foal get too tired, as the pressure on the joints will worsen the problem if this happens.
Trimming the foot and using toe extensions can also influence the foal's ability to self-correct the problem. Again, a good farrier and vet relationship is essential to a good outcome here. We need to look at the break-over point of the foot (remember this from the first article?). A foal with moderate carpal valgus (bow-legged), toed out appearance would benefit from dorso-medial extensions, that is on the inside of the foot. This encourages the foal to push out the limb through the knee and turn in more through the foot when breaking over. The result is a more physiologically normal strain on the limb that in turn will act to correct it.
(A similar effect can be attained with just over-trimming the outside of the foot but this is not as good a practice in the long term).
If you have a varus (knock-kneed) foal then an extension on the outside of the foot will help in the same way. The foal is regularly assessed at 2 week intervals and the extension and foot can be trimmed accordingly. Most ALD's can therefore be adequately managed in this way. The important thing to remember is that if it is not getting better, then change what you are doing!
 Periosteal elevation or "p" strip aims to accelerate the growth on the concave side of the limb (near fore in this picture). |
Surgical intervention is reserved for those foals not improving fast enough or those more severely affected. You get the biggest effect by doing this by 6 weeks of age so again early assessment of a bent legged foal is essential.A variety of techniques aimed at accelerating or decreasing the growth on a particular side of the growth plate have been described. The technique used will depend upon the age of the horse, the degree of deformity, the site and whether it is valgus or varus.
The most common and perhaps overdone technique is that of periosteal elevation or "p" strip. This technique aims to accelerate the growth on the concave side of the limb (the outside of the left leg in the picture at left). It is important with this technique to also cut the remnant of the ulna or remove it completely to get the best result.
Recent studies have shown that foals treated surgically were no more likely to improve compared with those managed properly conservatively. Perhaps this is a result of the more extensive New Zealand management that we are happier to operate than restrict and manage a foal conservatively?
Risks for surgery include the foal having a general anaesthetic, scarring, and infection.
 "Insert a single bone screw but directly into the growth plate on the fast growing side". |
CONCLUSION
Foals are remarkable creatures with the genetic potential to develop into the athletes and companions we expect and desire. It is up to us to mould them as they grow through careful, educated and dedicated management, care and nutrition. Regular assessment and early intervention with an informed plan for treatment is essential to achieve the right outcome.