Figure 3: Craniocaudal and neutral lateral projections of the right elbow of the Bernese mountain dog with dyssynchronous physeal closure and bilateral MCD at 11.4 months of age. The open physes of the distal radius are indicated with white arrows, and the closed physes of the proximal radius and distal ulna are indicated with grey arrows.
Elbow dysplasia is a common cause of progressive, crippling osteoarthritis in dogs. It is most prevalent in large and giant breed dogs like German Shepherd, Rottweiler, Mastiff, Newfoundland, and Bernese Mountain dogs. Elbow dysplasia is an umbrella term for multiple diseases of the elbow including medial coronoid disease (MCD), ununited anconeal process (UAP), and osteochondrosis of the humeral condyle. MCD is the most common.
The incidence of elbow dysplasia has declined in some populations of high risk breeds, largely due to the efforts of groups such as the International Elbow Working Group, who identify affected dogs and recommend their removal from the breeding pool. These dogs are primarily identified through grading elbow radiographs of one-year-olds.
While selective breeding using this method has decreased the prevalence of elbow dysplasia, it does not select out dogs that are bred before one year of age. A method is needed for diagnosing elbow dysplasia in young, growing dogs in order to remove them from the breeding pool, and to develop methods of early intervention in dogs that are at high risk for elbow dysplasia.
Dr. Sarah Nemanic, Assistant Professor of radiology, recently completed a clinical trial in the OSU Veterinary Teaching Hospital, with the objective of identifying radiographic risk factors for the development of elbow dysplasia in giant breed dogs less than one year old. In the study, twenty-five giant breed puppies received elbow radiographs monthly or bimonthly from 2-12 months of age, until the radius/ulna growth plate closure. This was followed by two months of elbow computed tomography (CT).
Parameters measured in the study included presence of a SCOAP, presence of medial coronoid disease (MCD), UAP, humeral osteochondrosis, as well as length of the radius and ulna, the radius-to-ulna ratio, and date of closure of the radial and ulna physes.
Fifteen dogs completed the clinical trial. Although, the presence of a SCOAP was seen in 8/9 Bernese Mountain dogs, and in 4/6 English Mastiffs, none of the dogs with a SCOAP developed UAP. However, the dogs who did develop MCD had a radius/ulna ratio lower than those who did not develop the condition, and they had dyssynchronous closure of the physes of the radius and ulna.
The study concluded the presence of a SCOAP was not a radiographic risk factor for development of elbow dysplasia, but dyssynchronous closure of the physes of the radius and ulna, and a decrease in the radius-to-ulna ratio, could be a risk factor.
Further research is required in larger numbers of dogs, and in other breeds affected by elbow dysplasia, before applying the results of this study to clinical cases.
