Ask Your Veterinarian Presented By Equistro: Trimming To Balance Conformation Issues

Veterinarians at Rood and Riddle Equine Hospital answer your questions about the healthcare of Thoroughbreds. Email us at i[email protected] if you have a question for a veterinarian.

QUESTION: I've heard farriers can help compensate for conformation issues by the way they angle a young horse's feet during trimming. Is there an age at which this becomes ineffective?

DR. CRAIG LESSER: Regular trimming is an essential part of proper hoof care for all horses, but for the young horse it is even more important because trimming can impact lifelong conformational changes. When foals are born they have growth plates, or physes, that are still producing additional bone allowing horses to grow.  Different forces can be placed upon these growth plates by the interaction of the hoof to the ground and it can cause the growth rate to differ medially and laterally.

To correct foals with angular limb deformities, they should be evaluated and trimmed every two to three weeks to ensure we are doing everything possible to correct these deformities, starting as early as day one of life if necessary. Every evaluation begins by walking the foal away from and towards the examiner to determine the severity of the deviations in all four legs. The angular deformities are then graded using a four point grading scale where every three degrees of deviation off of straight vertical line is a grade, with grade one being the mildest and grade four being the most severe.

When considering correction, we have, effectively, four months to correct the angular deformity of the distal metacarpal/tarsal physis, aka the fetlock growth plate, before that is the horse's permanent conformation. When a foal is born, the rate at which this physis grows is decreased by approximately 50 percent with every month of age. Therefore, by four months of age this physis has effectively stopped growing, even though they don't fully fuse radiographically until six to seven months of age.

There are a lot of non-surgical options when dealing with angular limb deformities starting with a proper trim.

The majority of foals with angular limb deformities of the distal limb have a varus, or toed-in, conformation.  This can be helped in foals by trimming the medial (inside of the) heel lower thus leveraging the hoof to have a wider stance and putting increased load on the lateral (outside of the) growth plate. This excessive force slows the growth at the lateral physis and allows the medial physis to grow uninhibited. With time, this will allow for straighter conformation.

In moderate angular limb deformities we can look into using extensions to put additional forces on the growth plates. For fetlock varus foals, a lateral extension can be applied in a variety of ways depending on the leverage needed to be achieved. They can be as basic as a formed acrylic extension to glue-on shoes with lateral extensions built into them for more severe cases. However in more severe cases, or in cases that adequate progress hasn't been made by two months of age all correction should be removed and surgery should be considered, if it is an option.

After the distal cannon physis has fused the fetlock angle is set for life, however consistent trimming is still essential to ensure horses' knees are straight, the horse doesn't develop a club foot, or a variety of other abnormalities.

When we consider the carpus (knee), we cannot put as much forces on the knees as we did the fetlock due to the distance from the hoof. With that being said, the same concepts can be applied to trimming and shoeing these horses to treat or prevent horses with poor carpal conformation.

Regular evaluation of your foals by someone educated in evaluating and correcting young horses can make a world of difference in their conformation and future performance, but the key is to start trimming them early and always keep in mind the mechanics we are trying to achieve.

Dr. Craig Lesser, CF graduated from Colorado State University College of Veterinary Medicine in 2015.  Following the completion of an internship at Anoka Equine, he moved to Lexington to complete a podiatry fellowship at RREH and has continued with us as an associate. As an extension of podiatry Dr. Lesser has an interest in lameness and imaging.