The superficial digital flexor (SDF) muscle is located on the back of the leg and functions to bend the toes. The tendon (SDFT) for this muscle runs directly over the heel bone and is held in place by connective tissue. This tendon can luxate off of the heel bone due to a traumatic injury to the connective tissue or as a result of congenital abnormalities. Often this injury occurs with quick turning or twisting motions in young, active dogs. The dog may yelp and become non-weight bearing on the leg. You may also feel a pop as the tendon shifts in and out of place.
Clinical signs of SDF luxations include the pet limping on the affected limb, feeling a “pop” over the pet’s heel when moving the joint through its range of motion, swelling near the heel, and/or changes in how the pet holds the limb both when standing and walking.
SDF Luxations are typically diagnosed on a physical exam performed by an experienced clinician. A consult with an orthopedic surgeon is typically advised. Radiographs may be recommended to assess for any bony injury or abnormality. A diagnostic ultrasound may also be recommended to ensure that there is no damage to the tendon itself or to any of the other muscles/tendons near the heel.
Treatment for a SDF luxation typically requires surgical repair with immobilization and rehab. In surgery, the damaged connective tissue that holds the tendon in place is repaired. After surgery, it is extremely important that the dog is not allowed to bend or extend their tarsus (ankle joint) to give the tissue time to heal. This can be accomplished through casting or a custom-made orthotic. The benefit of an orthotic over a cast is reduced risk for sores, better weight bearing, and the ability to gradually place more weight on the tarsus. Generally the dog will be in this brace for about 12-16 weeks, with progression of loading starting at 6-8 weeks after surgery.
We then help your dog learn how to bear weight on tendon again. We will progress through exercises that start of with gentle weight shifting. And then may progress through more dynamic exercises where they are shortening the tendon and lastly extending the tendon. Our goal is for the pet to get back up to full activity without the tendon dislocating again.
