Last Updated on March 29, 2022 by Allison Price
There are many symptoms associated with flexor tendon disorders, including foot and postural changes, lameness, debility, and lameness. These conditions can be congenital, so they are detected in newborn foals. Contractures in newborn foals have been linked to uterine malposition, teratogenic injuries (arthrogryposis), or genetic defects. Acute tendon contracture is most commonly caused by chronic pain. There are many causes of pain, including osteochondrosis and degenerative joint disease, physitis, physitis, pedal bone fractures, soft-tissue injuries, infection, and physitis. The pain causes reflex muscle contraction and shortening the flexor musculartendinous units. Horses can walk on their toes, or sometimes in the pastern joint. The condition is closely linked to nutritional problems, such as osteochondrosis or physitis. These issues must be addressed as part the treatment. (See also Contracted Tendons, and Angular Limb Malformations.
Clinical Findings
Foal acquired flexural deformity, distal intraphalangeal joint, and foal
Newborn foals have a wide range of signs. Some foals cannot stand, others attempt to walk on their dorsums. Others can only knuckle in their carpi or fetlocks. While one foal might improve naturally, another foal, who may have been healthy at birth may get worse. Older foals may experience rapid onset. They may be able to walk on their heels and their toes. An upright hoof and concave toe are signs of a slower onset. These horses are often afflicted by physitis. It is quite common for horses to involve both the forelimbs, with one leg being more severe than the other. Toe abscesses can be a common complication of the hoof or locomotion changes. They add to the pain, deformity, and are often a complication.
Older horses (between 1 and 2 years old) often knuckle in their metacarpophalangeal joint. Younger animals are often more affected and harder to treat than yearlings. Although it is essential to try to determine the cause of any bone or joint disease, this can often be difficult.
Treatment:
Most newborn foals will not require treatment for mild cases. Supportive therapy is required for more severe cases. If the foal is not able to properly nurse, it is important to correct passive transfer of immunity. Because rubbing sores can be serious and common, splints need to be fitted and managed carefully. Casts that are used for a short time (5-7 days) are safer. High-dose oxytetracycline treatment is common (40-60 mg/kg).
Analgesia, nutritional correction and proper hoof trimming can be used to manage early acquired cases in foals and weanlings. However, if the deformity has been present for more than one week, it is difficult to treat. The degree of involvement can vary in complexity and simplicity. The most common and successful procedure to correct flexural deformities of the distal leg is desmotomy of the accessory tendon of the deep digital. It does not affect future performance. Horses with fetlock defects may require superior check ligament desmotomy. Sectioning of the tendons for insertion onto the Ullaris lateralis or flexor Carpi ulnaris can be performed to correct carpal deformities. Because the inferior check ligament can often be vestigial, hindlimbs may require tenotomy to the medial head and deep digital flexor. As a rescue procedure, it is possible to tenotomy the deep digital flexor tendon in severe cases. When surgery is done, it is important to provide nutritional correction, proper foot trimming, as well as analgesia. If horses are properly managed and diagnosed early, the prognosis for them is good to excellent.
