Treatment considerations for angular limb deformities in foals

At CVC in Kansas City this year, Robert L. Linford, DVM, PhD, DACVS, a professor of equine surgery at Mississippi State University College of Veterinary Medicine, discussed angular limb deformities and reviewed treatment options and prognoses for this common orthopedic condition.

Angular limb deformities can be categorized as either valgus (lateral deviation of the limb distal to the location of the deformity) or varus (medial deviation of the limb distal to the location of the problem) in nature. In addition, they can be further subdivided based on when they appear in the foal's life—perinatal (those that are present at birth or develop soon after) or acquired (those that develop with age).

GETTY IMAGES/LIFE ON WHITE

Perinatal deformities

Perinatal deformities may be caused by incomplete ossification of the carpal or tarsal cuboidal bones, as seen in premature or dysmature foals, and can easily be identified radiographically. The key to successful treatment of this type of deformity is exercise restriction and early coaptation. Foals allowed unrestricted activity may endure irreparable crushing injuries in the affected area, so educating clients about the importance of controlled exercise is vital.

Another type of perinatal deformity results from ligamentous laxity, although this condition typically responds to exercise restriction and adequate rest alone.

Acquired deformities

Acquired deformities develop when there is a disruption of normal bone formation at the physis or epiphysis of a bone, with resulting disproportionate growth along the length of the bone. In some cases, the deformity can be corrected with exercise restriction and selective hoof trimming, if the deviation of the deformity is less than five degrees. However, if the deformity doesn't respond to this type of treatment or if the deformity is more severe (greater than five degrees of deviation), surgical intervention is appropriate.

With surgery, the intention is to either accelerate growth across the physis on the concave side of the deformity or slow growth across the physis on the convex side of the deformity. It's critical that once decided upon, a surgical procedure be performed without delay, as success depends on growth potential at the physis.

To accelerate growth across the physis, a periosteal transection can be performed. This procedure should take place before 3 months of age—although ideally between 1 and 2 months—for the distal metacarpal or metatarsal area and before 6 months of age for carpal deviations. Transphyseal bridging is used to slow growth across the physis and should be considered if more conservative methods have failed to correct greater than a four-degree fetlock deviation by 8 to 10 weeks of age. This treatment option can be performed at 2 months of age for metacarpal or metatarsal deformities, 4 months of age for tibial deformities and 6 months of age for radial deformities.