Hip dysplasia is a common and often debilitating orthopaedic condition characterised by instability of the hip joint which affects many larger breed dogs. It is generally considered that puppies are born with normal conformation of the hip joint i.e. a smoothly fitting ball-and-socket joint comprising of the femoral head (ball) and the acetabulum (the socket). See Figure 1.

The mechanism by which dysplastic hips become lax and unstable is due to many factors but these include both genetic and environmental. The underlying cause is a laxity of the soft tissues supporting the hip joint; in severe cases this can be detected by your vet at first vaccination. However, because it occurs in young dogs when the bones are still partly cartilaginous so therefore soft instead of ossifying into a normal hard boney well fitting ball-and-socket conformation, the femoral head and acetabulum form a shallow, less congruous joint. Arthritic new bone also forms due to stresses on the soft tissue components of the joint and further remodelling changes occur. See Figure 2.

In 1984 The British Veterinary Association (BVA) in association with the Kennel Club instituted the BVA/KC hip dysplasia scoring scheme to replace the earlier Pass/Breeder’s Letter/Fail Scheme. Many countries have their own scoring scheme but in the UK, a single radiographic hip view is used. Best X-rays are achieved with a relaxed dog using either sedation or general anaesthesia.

The skeletally mature dog, over 12 months old, is usually laid in a trough on his/her back and the hind limbs are extended with the stifles parallel to each other, this is achieved by the strategic use of sellotape and ties! It is essential to have a marker to mark left or right together with the date and the dog’s kennel club registration number, which will show on the film. This can be the fiddly bit as there are strict rules governing the suitability of an X-ray. There must be no rotation of the pelvis, and this can be difficult sometimes in very thin, bony dogs.

The radiograph is then examined by two scrutineers, randomly paired, from a panel of (currently) thirteen, all who have been trained in hip dysplasia assessment. Each year they set a quality control exercise to check each scrutineer. Under the scoring scheme, nine radiographic features for each hip are assessed with a numerical score given to each (0-6). Points are given to each undesirable feature with zero being a perfect example of that feature.

The individual scores are then summated giving a total for each hip and a total score for the dog. One feature is scored between 0-5 (caudal acetabular edge) so with the other eight scoring 0-6, the total parameters for each hip may range from 0-53 and for a given dog so giving a possible total score of between 0 and 106. See Table 1.

This means that meaningful comparisons between dogs may be achieved.

Table 1: Nine different parameters are measured, the scores are then summated to get a total hip score for the particular dog. In the case of the Labrador in fig.3 the results are shown in red.

As with most things, this system has it’s limitations and is by no means foolproof.

1. It can only detect if a dog has reasonable hips not whether the dog carries hip dysplasia genes.
2. It cannot take into account environmental factors such as diet and body weight.
3. The score does not take into account the age of the dog except that it has to be over 1 year of age.
4. This a subjective scoring scheme and scrutineers do differ in opinion hence, the need for annual quality control to limit personal variations and ensure as far as possible scores do not have a large variance.
5. Due to the complexities of genetics, relying on a just a sire and dam with a low score may produce offspring with varying degrees of hip dysplasia, which can obviously be very disappointing.
6. Unfortunately, there are some veterinary surgeons in practice who do little to support the scheme. They bias the results by discouraging owners from submitting radiographs which they think may score highly.

As a summary of the scoring system the lower the score the better. Hips scores of 0,0 (Total=0) being perfect and 53,53 (Total = maximum 106) devastatingly dreadful. For each breed there is an average score obtained, which is continually being updated, this is known as the breed mean score (BMS). The BMS for Hungarian Vizslas is at present a total of 12.

As breeders and as potential puppy purchasers how is the scheme best used?

• Only breed from dogs with considerably less than the breed mean score (BMS). Currently for Hungarian Vizslas the BMS=12 (Up to 10/01/2005 after 930 hip scores submitted). I personally would suggest choose parents with scores of 10 or less. For example a dog with 0,0 is excellent, 3,3 very good, 6,6 not so good but still within the breed average whilst anything above this is not good so try to avoid.
• Even mating two low scored dogs, offspring may still have varying degrees of hip dysplasia.
• The most helpful way of using the scoring information is in progeny testing, for example, selecting parents who are known to have previously produced offspring with good hips as well as have good scores themselves.
• It has been proven that some dogs with good hips will consistently produce progeny with hip dysplasia whilst others do not.
• Ideally it is important to research the hip scores of as many offspring of individual dogs before considering a match for breeding. Obviously, this can be more easily applied to sires as they are likely to produce more offspring in their lifetime.
• It’s all in the genes! It is useful to check the grandparents too as their scores will have a bearing on the offspring.
• So by checking back through the line you can minimise the chances of throwing a pup with bad hips. But, if in doubt as to the suitability of your dog to breed it is best to seek advise from a vet who will have been sent the current breed mean scores when the certificate was returned to him/her. Or ideally a vet who has an interest in orthopaedics.

Temperament and ability obviously all count in choosing the right match but remember, it is theoretically possible for people who purchase a pup which develops hip dysplasia to sue a breeder who bred from affected parents.

In practice, the number of clients who continue to breed from their dogs either without hip scoring or who worse, ignore the score indication staggers me. Likewise there are the new puppy owners who look blankly when you ask what the parents hip scores were. Too often have I had to euthanase an otherwise healthy puppy which can’t bear it’s own weight or suffers pain. See Figure 4. I would prefer not to be put in this situation so I strongly urge responsible breeding in any breed let alone my own , the Hungarian Vizsla.