Elbow Dysplasia First published in Double Helix Network News, Winter 2001 by C.A. Sharp Elbow dysplasia (ED) is not common in Australian Shepherds, but it does occur and the wise breeder should consider it whenever he encounters an unexplained case of front-end lameness in one of his dogs. ED is not a single disease, but rather a group of related defects that are grouped under the term “elbow dysplasia.” If your dog is diagnosed with ED, it may have any of the following: Fragmented medial Coronoid Process (FCP) – another prominence of the ulna at the elbow becomes separated from the bone below it. This is the most common ED defect. Roughly 60% of dogs with FCP will also have OCD (see below). Ununited Aconceal Process (UAP) – a prominence at the upper (elbow) end of the ulna is completely or partially detached from the rest of the bone. This occurs because the bone growth center between the process and the rest of the bone fails to join the pieces together. This normally happens around 4-5 months of age. Osteochondritis Desicans (OCD) – an area of cartilage fails to mature and becomes separated from the underlying tissue. It may be partially attached, like a flap, or become free-floating in the joint. (OCD can also occur in other joints than the elbow.) Some dogs diagnosed with incomplete ossification of the humeral chondile, a failure of the elbow end of the humerus, the bone above the elbow joint, to harden as it matures. This particular problem seems to be restricted to Spaniel breeds and is probably not be a concern for Aussie breeders. Each of these conditions is probably inherited independently of the others, though the frequency of the FCP/OCD connection indicates that there may be some relationship between them at least in a significant number of cases. The mode of inheritance for each is not simple, unaffected parents can have affected offspring and if affected animals are bred together the offspring may not be affected. This kind of breeding result indicates that the conditions are polygenic in nature, resulting from the action of many genes. Veterinary opinion on the genetic nature of ED defects is not united. There is good evidence that OCD of the elbow is inherited. UAP can, in some cases, be caused by injury. The defects are most common in large, heavy-boned or fast-growing breeds, so it is possible that the disease may be secondary to body morph (which is itself inherited) but not all large, heavy-boned or fast-growing dogs get ED. All of the ED defects are developmental in nature; they all result from something going wrong during the growth of the bones that join at the elbow. Environmental factors play a part in shaping the growing puppy, but skeletal development is governed by the action of genes. Given that ED is more common in some breeds than others and in some families of dogs within a breed, an inherited cause should be given serious consideration by breeders. OCD, FCP and UAP all cause stiffness, stilted gait or lameness, usually while the dog is under a year of age and sometimes as young as 4 months. A few bilateral (both elbows) cases may not be detected until the dog is over a year. The affected joint will be swollen and painful. There may be atrophy of nearby muscles. The disease is often bilateral. Untreated, the joint will degenerate, resulting in diminished range of motion and chronic pain to the dog. For the sake of the dog, early surgical treatment, accompanied by weight reduction and restriction of activity, is recommended. Some type of medication may be necessary. It should be noted that while husbandry practices may impact the severity of the condition, it cannot be prevented or cured by diet, restriction of exercise and the like. Affected dogs remain affected and will pass ED genes on to their offspring if bred. Diagnosis of ED is usually confirmed by x-ray of the affected joint. In very young dogs, the bone changes may not yet be visible in an x-ray so it is recommended that the procedure be repeated in 4-6 weeks to see if there is evidence of change to support an ED diagnosis. If x-rays still fail to reveal a cause for laimness, magnetic resonance imaging (MRI) or arthoscopy may be necessary. Not all ED affected dogs will have clinical disease, so screening of apparently normal Aussies in ED families is very important. Screening of these dogs is vital to prevent it becoming more widespread in the breed. There are two health registries in the United States that provide screening services: the Orthopedic Foundation for Animals (OFA) and the Institute for Genetic Disease Control (GDC). OFA evauates a lateral flexed view of each elbow. In this side-on view the elbow is flexed as much as possible and. The x-rays are reviewed by board-certified veterinary radiologists and the elbows will be graded normal or dysplastic. They do not distinguish between the type of defect present (FCP, UAP or OCD.) If dysplastic, they are further graded I, II or III based on the amount of joint damage with III being worst. If the animal is 2 years or older, they will issue a numbered certificate which will also be reported to the appropriate breed club. OFA’s registry is “semi-pen.” It will release information about affected dogs with the owner’s express permission to do so, however since it charges the same fee on all submissions, most people with affected dogs do not choose to spend the extra money and the results never reach OFA’s database. GDC employes a different scheme, based on the findings of the International Elbow Working Group (IEWG), a group of veterinary radiologists and surgeons, geneticists and dog breeders who have developed a screening protocol to facilitate international exchange of data. It has proven effective for control of ED. They previously accepted the same single view as OFA, but as of January 1, 2001, they require two views, lateral flexed and craniocaudal. The latter is taken with the joint extended and viwed from the top. IEWG does not feel a single view is adequate for diagnosis in all cases. The particular defect is noted in their evaluation. They issue an ED score (for the type of defect) plus an ARTH, or arthrosis, score indicating the degree of damage to the joint, Grade ) (normal) to Grade III (worst). Dogs must be at least one year of age at time of screening. ED is rare in Aussies and it is crippling to the affected dog. Correction requires expensive surgery. Because of these facts, a stringent culling process should be employed whenever it is identified. Obviously, the affected animal should not be bred. First-step relatives (parents, full and half siblings) should not be bred. More distant relatives should be screened and bred with care to avoid crossing back on their own pedigrees or into other families with a history of ED. Since each type of ED defect is probably inherited separately, it will be important to note and share information about exactly what defect(s) were involved.