Elbow Dysplasia in Dogs
Dogs with elbow dysplasia, have one or more of the following inherited developmental defects, which may occur singly or in combination: ununited anconeal process, fragmented medial coronoid process, osteochondritis dissecans of the medial condyle of the head of the humerus, and incongruity of growth rate between the radius and ulna resulting in curvature of the radius. The first three defects are related to osteochondrosis. The fourth is related to an enlargement of the epiphyseal growth plate at the head of the radius.
The elbow joint is composed of the humerus, which articulates with the radius and ulna, and those two bones. The anconeal processunites with the ulna at about 6 months of age. It forms a curved depression in the ulna. The coronoid process forms part of the lower curved bone of the ulna.
Signs of elbow dysplasia usually appear in puppies at 4 to 10 months of age, but some dogs may not show signs until adulthood, when degenerative joint disease starts. The signs consist of varying degrees of front-leg lameness that worsens with exercise. Characteristically, the elbow is held outward from the chest and may appear swollen.
The diagnosis is made using detailed X-rays of the elbow joint, taken in extreme flexion. Radiologists are particularly interested in the appearance of the anconeal process of the ulna. In a dog with elbow dysplasia, the anconeal process has a rough, irregular appearance due to arthritic changes. Another sign of dysplasia is widening of the joint space associated with a loose, unstable joint. X-rays may be difficult to interpret before a pup is 7 months of age. A CTscan may be required to demonstrate a fragmented coronoid process.
The OFA evaluates X-rays and maintains registries for dogs with elbow dysplasia. Dogs must be 24 months of age or older to be certified by OFA, although it accepts preliminary X-rays on growing pups for interpretation only.
Surgery is the treatment of choice for most dogs. Several factors, including the age of the dog and the number and severity of the defects, govern the choice of surgical procedure. The more defects in the elbow, the greater the likelihood that the dog will develop degenerative arthritis-with or without surgery.