Flexor tendon flaccidity or tendon laxity is a relatively common limb deformity seen in newborn foals usually involving the hind limbs although all four limbs can be involved. Weak flexor tendons is thought to be the cause which results in digital hyperextension where weight-bearing is placed on the palmar/plantar aspect of the proximal phalanges and the toe of the hoof is raised off the ground. The condition often tends to self-correct within days after birth as the foal gains strength and is allowed moderate exercise. However the tendon laxity often persists and it is not uncommon to see a fool that still has digital hyper-extension at 4 weeks of age.
Treatment is sequential depending on the severity of the tendon laxity and the response of the foal to treatment. Therapy begins with controlled exercise allowing the foal access to a small area with firm footing for 1 hour three times daily, the toe of the foot can be shortened and the heels can be rasped gently from the middle of the foot palmarly/plantarly to create ground surface and a palmar/plantar extension can be applied if necessary. This extension which extends approximately 3-4 centimeters beyond the bulbs of the heels immediately relieves the biomechanical instability. A cuff-type extension shoe is commercially available or a small aluminum plate extension with clips. In either case, the author feels that either type of extension should be attached with adhesive tape rather than a composite if the foal is less than 3 weeks of age as this avoids excessive heat being applied to the fragile hoof capsule as the composite cures and prevents contracture of the hoof capsule at the heels. Regardless of the method of application, the extensions should be changed at 10 day intervals. Bandaging the limb is contraindicated as this will further weaken the flexor tendons.
Photo: uncorrected adult legs in 7 year old mare
Angular limb and deformities are common limb abnormalities in foals that require early recognition and treatment. The pathogenesis of this problem is not clearly understood. Angular limb deformities can be classified as either congenital or acquired in the first few weeks of life. The primary lesion is an imbalance of physeal growth; for various reasons, growth proceeds faster on one side of the physis.