Ask Dr Iain-Hip Dysplasia Testing



 The pelvic model above shows how the pelvis and hind legs are positioned for a HD X-ray. The hip seen on the left is virtually perfect while the one on the right has severe dysplasia with arthritis and cannot be properly extended.

 

HIP DYSPLASIA TESTING.

 

What this fuss about Hip Dysplasia (HD) in Griffons?

 

In my opinion we all deserve to have healthy hips. Me, you and the dogs we breed! Dogs naturally evolved to have healthy hip joints that have smooth, rounded and well-lubricated femoral heads that fitted snugly into a secure pelvic socket (acetabulum). A healthy hip joint that will work efficiently to allow the muscles to drive the body forward, allow easy and rapid changes in direction without discomfort and restriction and will resist degenerative changes and injury well into old age. Breeding healthy hips that aren’t dysplastic is something all dog breeders should be aiming for, not just those whose breeds have HD Litter Registration Limitations (LRL’s).

However, with the exception of sporting and working dogs that have been selected for their athletic ability, we have actively selected for the various characteristics that are unique in our purebred dogs and that has resulted in neglectful attention being given to their hips, which has led to deterioration in the health of hips in most purebred dogs. You only have to glance at the AVA/ANKC Canine Hip Dysplasia Scheme Breed Average Scores (available on the AVA (Australian Veterinary Association) website) to acknowledge that conclusion. The current Griffon Bruxellois HD score average is 27.4, compared with the German Shepherd, 11.1 or Rottweiler, 7.3, these latter breeds have had ANKC LRL’s for HD for many years and have had significant improvement in their HD scores and subsequent incidence of hip disease.

Hip dysplasia  (HD) is a disease where the development of the hip joint is abnormal and allows excessive laxity (instability) to develop in the joint which in turn leads to osteoarthritis or degenerative joint disease (DJD) and its associated pain and lameness later in life. It does have an inherited component but environmental factors such as excessive exercise and poor nutrition during development can play a role. This is why you shouldn’t allow your pup to jump excessive heights or do intensive exercise and should feed moderate amounts of a properly balanced puppy diet. The inherited component of Hip Dysplasia is significant and is polygenic, meaning that there are many genes involved in the development of a healthy hip, which in turn means that the probability of a DNA test becoming available is unlikely. However, HD testing schemes where the hips are X rayed and scored and selecting individuals with low scores, i.e. relatively healthy hips, have proven extremely successful. Hip dysplasia is very prevalent in Griffons and like many other breeds it is recommended that breeding animals be tested by radiographing their hips and sending the X-ray to a specialist veterinary radiologist for scoring. Dogs with scores well above the breed average should not be used for breeding while those with scores at about the breed average should ideally be mated with an individual with a lower score than average.

What exactly is a HD X-ray?

A HD X-ray is recommended for all potential breeding animals of all breeds and can be done from 12 months of age. In Australia it must be done under a general anaesthetic. It is not only ridiculous to try and properly position a dog for an accurate HD X-ray whilst they are conscious or sedated but it also leads to substandard occupational and health practices where vet clinic staff are exposed unnecessarily to X irradiation when attempting to restrain dogs that aren’t properly anaesthetized.

In Australia, radiologists who provide HD scores require an X-ray that shows an extended ventro-dorsal (VD) pelvic view, i.e. the dog is lying on their back with the hind legs extended so that they lie virtually flat to the X ray table surface. Ideally, the radiograph (X-ray) should cover an area from the iliac crest (waist) to the stifle joint. The femora should be parallel to each other and the stifles rotated inwards so that the patellae (kneecaps) lie in the centre of the femoral trochleas (the grooves found at the end of the femur bone in which the patella sits). There is another way that dogs can be positioned to assess their hips, which is called PennHIP technique. This method is not recognised by the ANKC for litter registration limitations (see below) nor is it used for providing HD scores for other breeds. The PennHip X-ray technique requires specialized equipment and training and is used by many Australian Veterinary orthopaedic surgeons to assess dysplastic hips that require surgery but isn’t necessary for routine HD X-rays. The extended VD position has the advantage in that it is easy and repeatable for all vets and gives an excellent view of both hip joints showing all the relevant anatomical areas required to give a meaningful hip score.

Some breeds in Australia have Australian National Kennel Council (ANKC) Litter Registration Limitations (LRL’s) where it is compulsory that a HD X-ray to be done with breeding animals but may also require that the score for each hip be no higher than a particular value. For example, in the German Shepherd, where the parents have been born after 1.1.10, they must record a score of no more than 12 on either hip, or in the case of imported animals, a grading that is deemed to be acceptable for breeding in their country of origin. Our breed doesn’t have a LRL for any disease at this stage but our Victorian Club does recommend HD X-rays to be done for breeding stock and for the results to be used as a guide for selecting away from individuals with high scores as described earlier.

 

 

This is Virginia's HD X-ray. Her report is shown below. 

How do they come up with a HD score?

OK, this is a pretty complicated topic and those readers who want details of how a score is formulated can select this link, the BVA, and then click on ‘an article on the interpretation and use of BVA/KC hip scores in dogs’. The same scoring system is used here in Australia as in the UK and the article mentioned is the best explanation of scoring I have read.

Briefly, the HD score is a total of each hip being assessed for 9 different anatomical features, each feature given a score between 0-6 (with the exception of cranial acetabular edge, which is scored between 0-5). Thus, a dog’s total HD score can be anything from 0 (excellent hips, and some dogs do score ‘0’!) up to 106 (absolutely terrible and would represent a dog with excruciatingly painful hip disease).

Some of the anatomical features assessed indicate the degree of joint laxity or instability, such as the Norberg angle and the degree of subluxation of the femoral head from the acetabulum (hip socket). These are particularly important features and high scores with these will mean that the dog will eventually have higher scores with the other features if they haven’t already. This is because the other features are describing secondary changes in the joint that are a result of instability and resulting arthritis and remodeling, e.g. the cranial, caudal and dorsal acetabular edges (assessing arthritic proliferative bone changes at these sites), femoral head recontouring and exostoses etc. In other words, if a HD X-ray is taken later in a dog’s life who has joint laxity then we would usually expect a higher score due to ongoing joint disease affecting the several joint features that are scored.

What does the total score mean?

Bearing in mind that one hip may be particularly badly affected with hip dysplasia and so give a high score, most veterinarians involved in HD research and scoring would agree that a total score of,

0-4; represents perfect or near perfect hips.
5-10; indicates borderline changes that are unlikely to worsen with age.
11-20; mild changes that may worsen with age and may develop into osteoarthritis
21-50; moderate to marked hip dysplasia where arthritis is already prominent or severe hip dysplasia before arthritic change is evident.
above 50; severe to very severe osteoarthritis secondary to hip dysplasia.

Using the hip score and breed average score?

A dog’s HD score must be compared with it’s own breed average (or Breed Mean Score, as it is called in the UK). What is an acceptable HD score for one breed may not be acceptable for another for the purposes of selecting individuals for breeding. Some larger breeds such as the German Shepherd, Rottweiler and Labrador once had terrible incidences of debilitating hip arthritis due to HD. Their Breed Clubs in conjunction with the ANKC instituted compulsory Hip Dysplasia Schemes where LRL’s were introduced. These schemes have dramatically reduced the prevalence of Hip Dysplasia. Now the breed average score for German Shepherds is 11.1, and generally only dogs with scores of no more than 12 in each hip can be used for breeding.

As mentioned earlier, the current Griffon Bruxellois breed average score in Australia is 27.4. Indeed, this score is based on not many Griffon HD X-rays but probably underestimates what the true average would be in common with other breeds. This is simply because many X-rays won’t be submitted for scoring if the vet taking the X-ray can see evidence of obvious significant hip dysplasia on the X-ray.

Take a look at the scale above and you’ll see that 27.4 represents a dog that has moderate to marked hip dysplasia. I think most responsible breeders familiar with Hip Dysplasia would agree that this average score is unacceptably high and that we should be breeding towards producing dogs with significantly lower scores. Although the physical symptoms of lameness caused by hip joint disease due to HD are less marked in toy breeds compared to those bearing more weight load on their hips, they will nevertheless be affected and will experience hip disease and pain as they grow older. Have I seen Griffon’s affected with hip dysplasia in veterinary practice? Most definitely and I’ve also seen Griffons in the show ring with gaits very suggestive of hip dysplasia that ANKC judges may not always recognise.

If you have read the BVA article mentioned earlier you will have discovered that a better indicator for Hip Dysplasia is to use the Breed Median Score. Why? The Breed Average (mean) score will be distorted upwards due to some very high individual scores. If you were to view the table on the AVA website showing the AVA/ANKC Canine Hip Dysplasia Scheme Breed average scores, you will see that the highest score seen in a Griffon HD X-ray scored in Australia is 89. You can see how this would increase the average score. However, it means that a dog with a score at about the average is actually among the worst half of scores for the breed. As discussed in the BVA article, ‘Several years ago it was realised that a more meaningful number was the median, that is, the core of the average or middle dog (not the same as the average score), at which equal numbers of dogs are both less severely and more severely affected. The median hip score for a breed is inevitably lower than the BMS (Breed Average/Mean Score) over a given period of time, usually by several points.’

The point I’m making is that the score we probably should be using to determine if a dog should be used for breeding and so more effectively lower the incidence of Hip Dysplasia in Griffons will be actually less than 27.4. Unfortunately, the AVA/ANKC does not publish Breed Median Scores.

This is why the Griffon Bruxellois Club of Victoria recommends all breeding stock to be HD scored and for individuals with scores less than the breed average to be used, or if an individual is moderately higher than a average score then they should be bred with another with a lower than average score. It would be unrealistic to advocate setting a compulsory HD score significantly lower than the average for a dog to be allowed to be used for breeding, as we would then have to eliminate the vast majority of Griffons as being suitable for breeding which would greatly reduce the already small gene pool and see the incidence of other inherited diseases soar. Instead, it is more responsible to accept a more gradual approach to reduce HD in our breed as it is with all other Toy breeds.

This is the score for the X-ray seen above. We would expect a higher score if this X-ray was repeated a year or so later because the scores are indicating some instability of the hips but no resulting arthritic changes/remodelling has yet occurred, but it is still an acceptable score for breeding purposes. The breed average was lower when the X-ray was taken than it is now.

 

How do I get my dog or bitch HD scored?

Make a booking with your vet!

The dog must be at least 12 months of age. Your vet will probably recommend a pre-anaesthetic blood test and will ask you to fill in a HD X-ray submission form. You need to provide a copy of the dog’s ANKC Pedigree/Registration Certificate. Your vet needs to have information including the dog’s ANKC registered name or number, microchip number, your surname, date of X-ray and left/right markers labeled on the X-ray image. The submission form may be a AVA/ANKC Canine Hip & Elbow Dysplasia Scheme Form (you don’t have to submit elbow X-rays) that will be sent with the X-ray (whether a X-ray film or more commonly nowadays it will be a copy of a digital X-ray on a CD) to the AVA, where it will be scored by a member of a panel of Australian Veterinary Radiologists. For more details visit, Canine Hip and Elbow Dysplasia Scheme.

Alternatively, you and/or your vet may choose to fill in a submission form for a specific radiologist who is recognised by the AVA/ANKC as being qualified to score the submitted X-ray. I use,

Lavelle's Diagnostic Imaging

Dr Roger Lavelle MA VetMB MRCVS DVR FACVSc FAVA
, 80 Ashworths Road
, Lancefield 3435 Australia 
[email protected]

Other radiologists include,

Dr RJ Rawlinson BVSC DVR(LOND) MACVSC FACVSC

PO Box 1626

Mt. Barker

SA 5251

[email protected] 

 

Veterinary Imaging Associates

Graeme Allan and Robert Nicoll

PO Box 300

St. Leonards NSW 1590

[email protected]

 

From one to four weeks later (private radiologists are usually about a week while the AVA is usually 3-4 weeks) you will have the score returned to you. Apart from your vet’s fee for taking the X-ray, you will pay a HD score reading fee that covers the radiologists expenses including adding your dog’s score to the AVA database. Your dog’s score needs to be added to the database so as to formulate as accurate a breed average as possible but you and your dog’s details are kept confidential.

My dog has hip dysplasia, what can I do?

This will vary depending on the severity of the hip disease. Warm bedding, moderate exercise and weight reduction will often be beneficial.

Generally any dog with osteoarthritic changes should start on chondroprotective therapy, which will slow the progression of the arthritis and help improve joint lubricant production and help repair damaged joint cartilage. Examples include a course of pentosan or cartrophen injections given weekly for 4 weeks then a maintenance dose can be given every 1-6 months. Another treatment is daily supplementation with glucosamine/chondroitin available in powder form that can be added daily to their food, e.g. Sashas Blend or Joint guard. Some foods are available that are fortified with glucosamine/chondroitin and essential fatty acids, e.g. Hills j/d diet.

Those with more advanced arthritis may also require a daily anti-inflammatory medication. Sometimes your vet will advise routine blood monitoring when using these drugs to help reduce the risk of gastrointestinal side effects when these drugs are used particularly with dogs that have renal and/or liver disease. Always follow your vet’s advice when using anti-inflammatories, as many human products are actually very toxic to dogs and cats and your local pharmacist often isn’t actually trained in veterinary pharmacology. I’ve had clients, including pharmacists, kill their pets using products available at the local chemist or supermarket!

Finally, surgery may be necessary to adequately treat a dog with severe hip dysplasia or arthritis. Hip replacement surgery is now a common procedure performed by veterinary orthopaedic specialists or quite often with smaller breeds like our Griffons, many vets can perform a femoral head arthroplasty. This is where the femoral head (i.e. the ball component of the hip joint) is removed thereby removing the source of ongoing pain of an arthritic joint. The leg will actually be shortened as a result of this procedure and the dog will have a slightly abnormal gait but not a painful gait.

Dr. Iain Mitchell B.V.Sc(Hons), MANZCVSc.    


Contact Details

 

 President - Mrs Beth Canavan p[email protected]

Secretary -Mrs Robin Simpson [email protected]

0409 255 369

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03 5664 1275