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What is Hip Dysplasia?
Hip Dysplasia is a condition caused by a progressive deformity of the hip joints. It develops primarily in the first twelve months of age causing the `ball and socket' joints to be excessively shallow, and hence partially dislocating. The consequent instability of the hip joints results in osteoarthritic changes.

The condition affects many breeds (especially larger types), and is of particular concern to dog breeders and specialist breed clubs. Hip Dysplasia is essentially an inherited disease i.e. genetically passed on from the parent dogs. However, environmental factors such as nutrition (imbalances and/or overfeeding), exercise and trauma affecting the immature skeleton and the muscle support, also play a significant role.

Severely affected dogs may very possibly exhibit hind leg lameness under one year of age. Onset of clinical signs in moderately affected dogs can vary according to the individual's weight and level of exercise. The early signs the dog owner might notice are an increasing tendency to sit, reluctance with jumping or mounting steps, stiffness on rising and ultimately permanent hind leg lameness.

Diagnosis of Hip Dysplasia
Your veterinarian may suspect Hip Dysplasia based on a dog's breed, age, size, growth rate and presenting clinical signs. A radiograph (X-ray) is essential to determine the depth of the hip joints (which can be measured) and any osteoarthritic changes. The dog has to be positioned on its back with its hind legs extended back and parallel. The scheme stipulates that dogs must be fully anaesthetised to ensure full muscle relaxation during the radiographic procedure. Radiographs taken for Hip Dysplasia evaluation are diagnostic aids, and as such remain the property of the veterinarian as part of his/her clinical records.

Scoring system
The standardised scoring system that the NZVA Hip Dysplasia Scheme uses for dogs over twelve months of age is the same as that used in Australia and the United Kingdom. It is based on a series of nine separate scores for each hip joint, the maximum total being 106. A low combined score is desirable, with as little difference as possible between left and right.

While the ideal score is less than five, anything up to eight is considered good. Undue significance should not be placed just on the numeric score, as the range within which the score falls indicates whether the hip joints are 'excellent', 'good', 'suspect', or 'bad'.

Arithmetic mean (or average) scores are calculated for each breed and are regularly published in `NZ Kennel Gazette' and veterinary publications. The breed mean scores for some breeds are much higher than eight, so they are not necessarily a guide-line for an acceptable score.

Treatment
Anti-inflammatory or pain relieving medication may be prescribed to reduce the clinical effects of Hip Dysplasia. In milder cases weight control and sensible exercise, avoiding stressful extremes, may be adequate. In severe cases surgery may be necessary. Corrective surgery to improve the depth of the joints is only possible in young dogs before gross osteoarthritis has occurred. Otherwise artificial hip joint replacement is a possibility. Less expensive surgery is also available to ease the pain and/or restricted movement of arthritic hip joints.

Relevance of the hip score
Having had your dog scored you are faced with two considerations, these being long term prospects for fitness and for breeding. If the score is greater than eight, or greater than four on one side, it is important to discuss the relevance of the score with your veterinarian for two reasons. Firstly, it may be unwise to use the dog for breeding and secondly, the dog may show signs of Hip Dysplasia either now or later in life.

By consistently breeding only from stock achieving low scores (with no developing lameness later in life), and with as many progeny (offspring) as possible also being examined as they mature, it is possible, in time, to reduce the incidence of Hip Dysplasia.

Why is a control scheme important?
Owners choose the breed or type of dog they prefer, and it is the ethical responsibility of breeders to ensure that pups go to new homes with some guarantee of likely soundness and good health.

Many established dog breeds carry debilitating conditions which may be inherited from one or both parents. These carriers may not show any clinical signs of these conditions.

The heritability for Hip Dysplasia is quite complex. It is only through long-term adherence to a well designed, supervised control scheme that real progress can be made. This involves removing high-risk stock from the gene pool for each breed.

How the scheme works
The New Zealand Veterinary Association has commissioned a panel of veterinarians trained in the precise reading of canine hip joint radiographs. Each radiograph is examined by at least two panellists, who remain anonymous. A veterinary radiologist acts as an independent referee.

If you are interested in having your dog's hips scored please inquire at your veterinary clinic regarding the costs, which include anaesthesia, radiography and a NZVA submission fee. Your veterinarian should be able to supply you with a form to fill in details of the dog's NZKC registration number (this scheme is only intended for pedigrees), tattoo (if any), microchip number (if any), description, sex, age (it must be over 12 months of age), plus full pedigree name as well as those of its parents and grand- parents.

You will be required to sign a declaration stating that your dog has not been previously scored by either the AVA or BVA HD Scheme. You also give permission for a copy of your certificate to be sent to the geneticist of the BVA/KC Scheme whose summarised statistical reports may be published. Individual details are treated as confidential.

Your veterinarian is responsible for posting the fully labelled radiograph along with the submission fee and completed form. You should have a result within a month, if not sooner. The top copy of the self duplicating certificate will be returned to you with a detailed score box.

For additional information, ask your veterinarian or contact:

New Zealand Veterinary Association
Hip Dysplasia Scheme
PO Box 11-212
Wellington
Phone: 04 471 0484
trish.thorpe@vets.org.nz

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