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Introduction The term ‘dysplasia’ means abnormal growth; thus hip dysplasia is the developmental condition that results in abnormal looseness or laxity of the hip joints. It is currently accepted to be a multifactorial disease with heredity, nutrition, trauma, and exercise, etc. all influencing the outcome of the condition. The inherited component is caused by the interaction of many genes – hence it is a polygenetic condition. However, the expression of the genes may be modified by the environmental factors listed above. These environmental factors do not cause hip dysplasia but they may influence how unstable the hip joint becomes and how much osteoarthritis ultimately develops as a result of that instability. Unlike other breeds, the Border Collie does not usually show physical signs of HD. Border Collies can appear normal and have good movement, but on examination by X-Ray clearly show that they are affected by HD to varying degrees. Border Collie breeders have been known to say that their lines are clear and that they have no problem with HD, but unless they have all their breeding stock X-Rayed and scored this statement may be unfounded. If breeders have been scoring their breeding stock and offspring for many generations and the scores are low, for example, less than five, then they may consider that they have a reduced chance of producing a severely affected animal. What Happens The hip joints of all puppies are reported to be normal at birth, but some time after two weeks of age the femoral head (or ball) of a dysplastic puppy fails to sit firmly within its acetabulum (or socket) and the joint becomes unstable. It tends to occur more frequently in large, well fed, fast growing, active breeds of dogs, such as German Shepherds, Labradors, Saint Bernards, Great Danes and Newfoundlands. It has a genetic basis and affects both sexes with equal frequency. Affected dogs are born with normal hip joints that subsequently undergo progressive structural changes. There are marked variations in the severity of time of onset of such changes, the age at which clinical signs occur, the rate of disease progression and the degree of pain and impaired mobility. Some dogs will be lame in a few months while others may not have pain for years. Signs and Symptoms Difficulty in rising form a sitting position or reluctant to walk up stairs, as well as morning stiffness after sleeping. A swaying or waddle gait in the hind legs when walking or actual lameness. Pain if the pelvis area is pressed. Reluctance to jump, with stiffness after exercise Inability to take full weight on the back legs alone Wasting or poor development of hind legs musculature in advanced cases A clicking sound can sometimes be heard as the femoral heads subluxate. Not all of these signs are necessarily seen at the same time. Diagnosis The diagnosis of hip dysplasia is made by physical examination and radiographic evidence. Within Australia a dog has to be over the age of 12 months for the X-Ray to be officially scored. The X-Ray is taken with the dog placed on its back with its pelvis symmetrical and both hind legs extended and parallel. It is generally necessary to anaesthetise the dog to position it correctly. Several tests are done on both hips to determine the degree of laxity and dislocation of the joints. When the X-Ray is scored, the following parameters are assessed: - The degree of subluxation of the femoral heads (ball) - The condition of the dorsal, cranial and caudal acetabular (socket) rims - The shape of the femoral heads and necks - New bone formation - Other evidence of osteoarthritis The hips of a racing Greyhound are generally regarded as normal and are used for comparison. The X-Ray is sent off to one of three assessment schemes, where veterinary radiologists provide an opinion on the HD status. Each hip is given a score from 0 to 53 and then based on this the degree is graded 1 – 6, with 6 being the most severe. It should be noted at this stage that there is no relationship between the degree of change seen on the X-Ray and the severity of pain seen clinically. Treatment Treatment depends on results of the HD assessment and falls into 4 categories:
In addition, several successful total hip replacement operations have now been performed in Australia, although the cost of such operations is very high in comparison with other methods. The long term outlook depends on the dog’s clinical condition and the owner’s attitude. It should be remembered that radiographic (X-Ray) diagnosis of HD alone should not be a reason to euthanase (put to sleep) the dog. Euthanasia should be considered if the dog is suffering with the condition and treatment is not helping. However, HD on an X-Ray is an indication to avoid breeding with the dog if HD is ever to be successfully controlled in dogs generally. What You Can Do Currently many dog clubs are requiring HD assessments be performed before allowing pedigree dogs to be used for breeding. It is advisable to check the HD status of the parents of any pup you are purchasing. All breeders, as a minimum should X-Ray all breeding stock and submit all X-Rays for scoring. The importance of submitting all X-Rays for scoring, particularly if they appear poor, is to obtain a true breed average. What has happened in the past is that X-Rays that definitely show a moderate to severe problem were not necessarily submitted for scoring. Therefore the higher scores are not included in the data. We have a breed average that is not a true reflection of the degree to which Border Collies are affected by HD and an artificially low breed average score. For example, you dog has received a total score of 13 but because only moderately affected dog’s X-Rays have been submitted for scoring, the breed average is 9. Therefore you dog may not be recommended for breeding because it exceeds the breed average. However, if all X-Rays were submitted the breed average may be 15 and therefore you dog would be suitable for breeding. The more Border Collies are X-Rayed and hip scored, the more information we will have concerning this disease and the better the ability of breeders to improve the breed. Other breeds are undertaking such control measures through their club regulations. Prevention It is questionable whether HD can ever be fully eliminated from a breed because often dogs are used for breeding before clinical signs appear in them. Indeed, some dogs with HD are never X-Rayed or assessed because owners do not seek a HD assessment if clinical signs do not appear in their dogs. Hence, further control can only be achieved on a general basis if owners and breeders become more aware of the facts concerning HD in their dogs Resources Used Veterinary Notes For
Dog Breeders – Annette M Carricato Click here for: More Hip Dysplasia Information
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