Limb deformities should be given early attention to provide your foal with the best chance of a future sound athletic career.

The foaling season is upon us and with it the gamut of conditions that will affect the future and viability of the new born foal. Fortunately many foals are born easily, healthily and with normal limbs. However, if you are in any way concerned with your new born, call your vet. Limb deformities should be given early attention to provide your foal with the best chance of a future sound athletic career. Corrective work can only be carried out while the growth plates are still open.

Angular Limb Deformity is a deviation in the bones of the limbs that can cause performance limiting lameness and aesthetic problems. The deviation of the limb may be laterally (valgus) or medially (varus) when viewed from the frontal plane of the foal. Assessment is made from the front, rear, when the foal walks and how the limb hangs when it is manually flexed. There are two main forms. If the toe turns out it is a valgus deformity. Varus deformities present with a pigeon or turned in toe. Congenital ALDs are present at birth and usually develop as a result of perinatal factors that are present during the later stages of gestation or during the neonatal period. Factors include malpositioning of the foal in the uterus, and joint laxity secondary to weakness of the supporting periarticular soft tissue structures. These can lead to abnormal loading of the articular surfaces thus leading to ALD. Cases of placentitis, and premature and twin birthings can also predispose foals to incomplete ossification of the cuboidal bones of the carpi (knees) and tarsi (hocks). Any abnormal loading on these soft and easily deformable cartilaginous structures can result in permanent deformities once these bones become fully ossified.

Acquired ALDs develop after the foal is born and are mostly due to disproportionate long bone growth at the level of the physeal level, dietary imbalances, trauma, and excessive weight bearing secondary to opposite limb lameness.

Diagnosis of these deformities is based upon physical examination and ultimately radiography. Early diagnosis is critical, especially in foals suspected of having incomplete cuboidal ossification.

Treatment (nonsurgical) Foals with incomplete ossification and normal conformation should have their exercise restricted (box rest). Strenuous exercise can result in deformation of the partially ossified carpal and tarsal bones. As a result these bones may become abnormally ossified, giving rise to degenerative joint disease. The duration of stall rest is determined by the status of sequential radiographs, which can be taken at one to two week intervals.

These foals can also be treated with splints or casts, which maintain the limb in proper alignment and transfer some of the weight bearing stresses from the cuboidal bones. This treatment should be maintained as long as incomplete ossification is still present. Due to the sensitive nature of the foal’s skin, care must be taken when applying these devices, as improper placement can lead to the development of skin sores. Adequate padding must be applied under the cast or splint. The splint should be changed every other day, while the initial cast should be changed within seven to ten days. A new cast can be applied at this time, or the original cast can be reapplied after being cut down its longitudinal axis. It is imperative that the cast or flint is not applied below the level of the fetlock. Incorporation of the foot will result in weakening of the flexor tendons. These devices should never be applied to foals that are solely experiencing tendon laxity, as they will further worsen the condition.

Foals with inherent weakness of the periarticular support structures and nonnal cuboidal ossification should be exercised daily for twenty to twenty-five minutes to promote strengthening of the involved tendons and ligaments.

Mild ALDs can be treated conservatively with corrective hoof trimming or shoeing combined with restricted exercise. With valgus deformities the outside half of the hoof is rasped down. In contrast the inside wall of the hoof is rasped down with varus deformities. Shoes (glue on) with lateral or medial extensions can be applied to the feet of foals with varus and vulgus deformities respectively.

Surgical techniques such as periosteal transection, stripping and transphyseal bridging may also be used. This surgery needs to be undertaken while there is still growth potential. Growth occurs from the growth plate or physis and these stop growing at varying ages depending on the site (fetlock five months and knee eighteen months). Strips are performed above the growth plate on the shorter side of the limb to accelerate growth on the short side of the limb. The relatively simple surgical technique involves a skin incision above the growth plate which is extended to expose the tissue that coves the bone (periosteum).

A cut in the shape of an upside down T is made through the periosteum and the limb is then elevated to release tension, causing inflammation and stimulating growth of the bone. It is important that the limb is bandaged following the procedure. Exercise is restricted and foot trimming continues. The lump which occurs at the site usually resolves over a period of months. This technique has few complications, requiring minimal aftercare and is cheaper than bridging. However it does need to be done early in life. The recommendation is for fetlock strips to be performed at two to four weeks and knees at three to six weeks.

TRANSPHYSEAL BRIDGE Bridges are placed on the longer side of the limb to temporarily stop growth, allowing the shorter side time to catch up and straighten the limb. Once the limb has straightened or the growth plate has shut the bridge is removed. These surgical techniques will not improve deformities where the whole limb is rotated inwards or outwards.

FLEXURAL LIMB DEFORMITIES Flexor tendon laxity occurs fairly commonly in the new born foal. It is especially common in foals that are premature/dysmature at birth and/or systemically ill. The hind limbs are frequently more severely affected than the forelimbs. The severity varies with some foals exhibiting a dropped fetlock while others walk with the plantar surface of the fetlock on the ground. Mild cases respond well to exercise, good nutrition and supportive care. The more severe cases in addition to all the above, may require the application of special shoes with heel extensions. This will reposition the weight bearing surface of the foot on the ground, and protects the heels from being abraded and bruised. An immediate improvement should be observed upon application of the shoe. Casting or splinting these patients is not recommended unless other problems exist concurrently.

Contracted tendons are less common in new born foals. The condition is often attributed to malpositioning of the fetus in-utero. Mild contraction may correct with passive manipulation of the limb along with bandaging to relax the tendons. Fetlock contractures may respond better to toe extensions to stretch the deep digital flexor tendon. Moderate cases of carpal and fetlock contracture may require splinting along with physical therapy and exercise. In severe cases in which the foal is unable to rise due to rigid flexion of the joints, prognosis is grave. Constant supportive and nursing care is required, and the deformities are rarely responsive to the techniques mentioned above.