Hip dysplasia is the primary cause of painful hip osteoarthritis in dogs.

Dr Ingrid Goodman discusses the hip screening options available to breeders.

The key to the development of hip dysplasia osteoarthritis (HD-OA) is excessively loose hips (hip laxity). Hip laxity is highly inheritable. Breeders therefore aim to breed from dogs that have tighter (less lax) hips to reduce the severity of HD-OA in their lines.

Radiographic screening programs have been developed to determine which dogs have the better hips to breed from.

How are hips scored?

Many breeders are aware of the traditional Extended Hip View (EHV) system. It is similar to the EHV systems used by the British Veterinary Association (BVA), New Zealand Veterinary Association (NZVA), Orthopaedic Foundation of America (OFA) and Fédération Cynologique Internationale (FCI). There is also another screening system available, PennHIP.

Extended Hip View

One radiograph is taken under general anaesthetic (with the dog on its back and its legs stretched out).This view is used to assess hip laxity (looseness) as well as arthritis. Nine different parameters are given a score out of five or six. Hip laxity is assessed by two of the parameters.

Arthritis is assessed by the remaining seven. Hip-Dysplasia-low-1The total score is out of 106. The higher the score the higher the risk of developing HD-OA.

PennHip

Three radiographs are taken under general anaesthetic:

1. The Extended Hip View to assess for arthritis only.

2. The Compression View to assess how well the femoral head fits into the acetabulum (the hip).

3. The Distraction View to assess hip laxity by measuring how far the femurs can naturally be pulled (‘distracted’) out of the hip joint using a special hip distractor. It is the Distraction View that gives the hips their PennHIP score.

A measurement of less than 0.3 means the hips are tight, a measurement of more than 0.7 means the hips are very loose and the dog will almost certainly develop HD-OA.

 

Age

Dogs must be at least 12 months old for the EHV test in Australia, whereas PennHIP can be performed as early as 16 weeks old, according to the Australian Veterinary Association.

While EHV scores for an individual dog tend to worsen with age as more signs of arthritis become evident, the PennHIP score of a dog won’t change after five months of age.

 

Breeders

Those using PennHIP can make an informed decision about which dogs to keep for breeding earlier than those using EHV. Furthermore, puppies with loose hips can benefit from early medical therapy or interventional surgery.

Most importantly, nutritional and lifestyle changes can be put into place to minimise the onset and development of HD-OA in the susceptible puppy. At present, the downside to breeders using PennHIP is the added cost.

 

The end result

The EHV allows excellent assessment of arthritis,Hip-Dysplasia-low-2 but when it assesses hip laxity, it may mask the true situation.

The EHV can disguise hip laxity because the action of stretching out the dog’s legs while on its back causes the joint capsules to spirally tighten and compress, making hips appear tighter.

This means dogs considered to have good hips according to the EHV can be hiding a significant amount of hip laxity, which could be determined by a PennHIP distraction view. With accurate testing, breeders can confidently choose dogs with tighter hips to breed from, and may more successfully reduce HD-OA in their lines over fewer generations.

 

Find out more

To find out more about PennhIP testing, and where to find a registered PennhIP vet in NSW visit the University of Pennsylvania website.
W: http://research.vet.upenn.edu/pennhip

For more information on ehV scoring, contact Veterinary Imaging associates.
W: www.online-vets.com

 

About the author

Dr Ingrid Goodman is a veterinary surgeon at Maitland Veterinary Hospital.

Contact Dr Goodman for references used in this article.
Tel: (02) 4934 3044
Email: