Veterinarians at Rood and Riddle Equine Hospital answer your questions about sales and healthcare of Thoroughbred auction yearlings, weanlings, 2-year-olds and breeding stock. Email us at [email protected] if you have a question for a veterinarian.
QUESTION: What's the deadline for performing corrective surgery on a yearling prospect for angular deformities of the ankles or knees?
DR. WES SUTTER: The deadline for performing corrective surgeries is based on functional growth plate closure times and sale date. There are surgical procedures that can be done for growth acceleration and procedures that can be done for growth restriction. Growth acceleration procedures, (i.e. periosteal stripping and elevation) are most effective when done in the first few months of life. I will focus on growth restriction procedures because they are now more common and provide a more predictable and consistent result. Transphyseal screws are used for ankle and knee angular deformities and transphyeal bridges (screws and wire) are used for knee angular deformities. They are applied to the side of the limb that is longer and removed when the limb is correct.
Corrective surgeries on the ankles need to be done as a suckling before growth plate closure. In most foals, the growth plate used to correct deformities in the fetlock functionally closes between four to five months. While there are some exceptions, the ideal time for surgery to correct fetlock deformities is approximately 60 days. This gives time for natural correction of deformities present at birth and sufficient remaining growth to correct the deformity. Transphyseal screws can prematurely permanently close the growth plate, therefore if the surgery is done too early, there is a higher risk of over-correction. If the procedure is done later, there is a higher risk of under-correction. Depending on the age of the foal, growth rate and severity of the deformity, most screws are removed in four to eight weeks.
The growth plate used to correct angular deformities of the knee stays open much longer than the ankle. This growth plate is still functionally open past the yearling sales in most horses. Severe deformities of the knee will often need to be addressed as a suckling or weanling to prevent damage to small bones of the knee. Mild to moderate deformities can often be corrected as a yearling.
In general, these procedures are usually done between April and June of the yearling year. Similar to ankles, it generally takes between four to eight weeks for the limb to correct. Correcting the deformity earlier increases the risk of the knee drifting back to the original angle possibly necessitating a second surgery. If a transphyseal screw is used at an early age, premature closure of the growth plate can occur causing severe permanent overcorrection. This is less of a concern as the yearling ages and the amount of potential long bone growth diminishes. Because a transphyseal screw immediately stops physeal growth, it typically works much more quickly than a screw and wire. This technique allows correction much closer to the sale and while not recommended it is possible in some instances to correct deformities as late as July for the September sale.
Please consult your veterinarian when making the decision on performing corrective surgery.
Dr. W. Wesley Sutter graduated from veterinary school at Colorado State University, completed a surgical residency at The Ohio State University and entered private practice at Ocala Equine Hospital. He co-founded Lexington Equine Surgery and Sports Medicine in Lexington, Ky. before joining Rood and Riddle in 2018.
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