Diagnosis, Assessment, and Treatment Strategies for Angular Limb Deformities in the Foal

Incomplete ossification is an important parameter to keep in mind in newly born foals with angular limb deformities (ALD). Because these animals need immediate veterinary attention, client education is of pivotal interest. In most other inciting causes of ALD, time is not as important. Many deformities may correct on their own as long as skeletal maturity is present. Especially in foals with mild to moderate valgus deformities of the carpal region treatment may be postponed until 8 to 10 months of age, because at this time some accelerated growth is usually noted at the lateral aspect of the radius, correcting the deformity. Varus deformities of the third metacarpal/metatarsal bones (McIII/MtIII) should be diagnosed in the first couple of months of age and treated immediately, because around 3 months of age, the distal physis of these bones closes. After that time surgical growth manipulations are ineffective. Care should be taken to also evaluate the proximal phalanx, because frequently an opposing deformity develops in this bone, seemingly straightening the limb axis, but orienting the joint not parallel to the ground, which results in an abnormal ambulation of the foal and disproportionate loads exerted on the medial versus lateral aspect of the joint and subsequent development of arthritis. Some foals are born with “offset” or bench knees. This conformational defect may prevent some foals from ever becoming successful athletes. There is some controversy among specialists as to the development of this deformity. One school of thought is a lateral displacement of the small carpal bones within the carpal region, whereas the other explains the deformity as a combination of a valgus deformity of the radius with a varus deformity of McIII. The purpose of this article is to critically discuss the development and treatment strategies of ALD. The actual management of the different problems is discussed in a subsequent article.