Angular Limb Deformities Dean A. Hendrickson, DVM, MS Diplomate, ACVS Definition - A valgus angular limb deformity (ALD) is one where there is a deviation of the lower leg in a lateral direction from the normal axis, whereas a varus ALD is a deviation in a medial direction of the lower leg from the normal axis. In most cases, the terminology is derived by combining the name of the involved joint or the joint immediately distal to (below) the affected growth plate (physis) and the direction of the deviation. (Figure 1. Carpal Varus, Figure 2. Carpal Valgus) The most common type of ALD is a carpal valgus.

Clinical and Physical Examination - The age of the foal at the onset of clinical signs is very important in determining the possible causes of the ALD. The most common reason for an ALD is abnormal growth at the growth plate, and often is seen at birth. However, it is possible for an ALD to occur as the foal matures when it bears too much weight on the leg. Another cause of ALD occurs when the cubiodal bones of the carpus (knee) and hock are not formed properly in-utero, and they collapse as the foal bears weight. This is most commonly seen in premature foals. The use of radiology is necessary to determine if the cuboidal bones are normal. (Figure 3. Malformed cuboidal bones,

Figure 4. Abnormal growth plate). Consequently, it is very important to get your veterinarian involved very early to make sure what is going on in the joint. Cuboidal bone problems can be career ending if not treated immediately. Treatment – There are many ways to treat ALD’s, dependent on the degree of abnormality and the age of the foal. Foals with cubiodal bone problems generally need to be placed into a “tube” cast to protect the abnormally formed bones from collapsing. (Figure 5) Foals with growth plate abnormalities can be treated with anything from limited exercise, to foot trimming, to glue on shoes, and finally to surgery to help to straighten the leg. It is important to realize that the growth plates close at different times, and that after the growth plate closes, it is much more difficult to change the deformity. It is also important to realize that severe ALD’s need to be aggressively treated with surgery. (Figure 6) This table will give some rough guidelines as to when conservative versus surgical therapy should be instituted. However, it is critical that your veterinarian be consulted as soon as possible to give your foal the best opportunity to have a straight leg as it matures. Region Conservative Treatment Transphyseal Bridging Stops Growing Fetlocks <2-3 weeks 4 weeks 9 months Carpus (knee)/Hock <2-3 months 4 months 21 months

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