Elbow dysplasia (ED) is a common condition of domestic canids, with a reported prevalence of 17% in Labrador retrievers in the UK, and 70% of Bernese mountain dogs in the Netherlands.1,2 ED can occur in any breed of dog, and is typically a condition of large and giant breed dogs, however, it has been reported in small and toy breed dogs. Recent reports suggest that the Labrador retriever, Rottweiler, German Shepherd dog, and Staffordshire Bull Terrier are at increased risk for development of ED. ED is generally a bilateral disease, most commonly present at a young age. Look out for signs of persistent unilateral forelimb lameness, which may be refractory to conservative management. Subsets of the diseased population present later in life due to progression of degenerative joint disease associated with this condition.
The definition of ED by the International Elbow Working Group (IEWG) in 1993 has been broadly accepted and describes the components included in the disease. The components are medial coronoid process fissure/fragmentation, osteochondrosis of the humerus, ununited anconeal process, and incongruity of the elbow joint. Patients suffering one, some, or all components can be described as suffering from elbow dysplasia.3
Many aetiopathogeneses for ED have been proposed, including humeroulnar incongruity, radioulnar length mismatch, biceps/brachialis mismatch, radioulnar incisure incongruity, joint incongruity, osteochondrosis and genetic causes.3-6 At present, evidence for many of the proposed mechanisms is lacking, but what has become apparent is that multiple permutations of disease are likely to exist, and a simplistic or singular approach to identifying ‘the’ underlying aetiopathogenesis of elbow dysplasia is unlikely to succeed.
We believe that the location of the pathology in a subset of cases implicates the proximal radioulnar joint. For this reason, we chose to focus on the canine antebrachium, and to identify relationships between the radius and ulna. We are specifically interested in the rotational and translational movement of the radial head relative to the medial coronoid process of the ulna during ambulation.
It has been experimentally demonstrated that there is internal rotation of the radius with extension of the carpus and that this movement is likely due to the conformation of the opposing joint surfaces of the antebrachiocarpal joint.7 It has also been shown that the internal rotation of the radius that occurs when the carpal joint is extended is antagonised by the interosseus ligament which causes outward rotation of the radius when the carpus is flexed. Cutting the interosseous ligament results in a significant decrease in the rotation of the radius during flexion and extension of the carpus.
This research is a collaboration between the UCD School of Veterinary Medicine, UCD School of Mechanical and Materials Engineering, and Koret School of Veterinary Medicine. Stephen Martin, Professor Barbara Kirby, and Professor Joshua Milgram are in the testing phase of a biomechanical research project using cadaveric canine specimens. Specimens are mounted and subjected to physiologic forces under a range of surgical, and non-surgical manipulations, in a bid to identify surgical and non-surgical extra-articular interventions which may alleviate or slow progression of dysplastic elbow disease in affected dogs. It is considered that this research study represents the first step in development of an alternative treatment option for dogs suffering from elbow dysplasia, and more specifically medial compartment disease.
References available on request.