Placing a tarsal orthosis to treat the most common orthopedic problem in dogs – the cranial cruciate disease of the stifle – may confuse many people but there is a significant clinical background to justify this intervention as well as a solid biomechanical rationale.
Late Dr. Karel Crama, a highly respected Dutch veterinary surgeon, had treated some 400 dogs with torn cranial cruciate ligament by bandaging the hock joint in extension. His experience remained unpublished due to his early death. He related his experience to one of us in person (S.T., around 2006) in searching for a biomechanical explanation of his success in treating a major disorder of the stifle by intervening on the tarsus.
We have recently found solid evidence for what we have presumed was the main reason for the success of Crama’s treatment – reduction of the muscle force exerted on the stifle by gastrocnemius muscles. In vitro experiments conducted in collaboration with Virginia Tech professors Otto Lanz and Noelle Muro at the Kyon facility and with the support of the Kyon team in Boston simulated the main muscle groups acting on the cadaver hind limb. Reducing the ratio of the gastrocnemius to the hamstrings force stabilized the stifle under simulated gait forces even with a transected cranial cruciate.
Maintaining the tarsus in extension shortens the working length of the gastrocnemius muscle group and thus the force that they can generate when innervated. To counterbalance the force of the quads in controlling the moment around the stifle in gait, dogs will learn to favor hamstrings over gastrocnemius muscles.
A further argument in support of this seemingly unusual intervention is the observational study by Prof. Dominique Griffon, Western University of Health Sciences, Pomona, presented at the ACVS meeting in 2011. Gastrocnemius dominance over hamstrings was a highly significant predictor for the cruciate disease.
Most intriguing aspect of Crama’s experience was that his patients retained good function of the limb even with the bandage removed after 3 to 4 months. Apparently, bandaging the tarsus facilitated permanent reprogramming of the muscle groups responsible for agonist-antagonist balance at the stifle.
We may add here that natural adaptation to untreated cranial cruciate rupture in dogs and in people results in strengthening of the hamstrings. Guarding the stifle with PALADIN brace should accelerate this process of adaptation while protecting against damage to menisci that are crucially important for good long-term outcomes.
PALADIN™ has been designed jointly by Kyon, Zurich, and OrthoPets, Denver, to replace the bandaging, which is difficult to apply consistently and is likely to cause skin and other soft tissue damage. There are other, common, orthopedic issues near the tarsal joint, e.g., rupture of the Achilles tendon, where this brace has advantages over bandaging, casting, or use of conventional braces, which may restrict the movement of the joint but provide only a modest capacity to resist the bending moments.