Canine Hip Dysplasia

Just what is canine hip dysplasia?

Canine hip dysplasia (CHD) is a genetic disease of large breed dogs that results in a puppy being born with an excessive amount of hip "laxity", or "looseness". The instability resulting from this laxity leads to painful and potentially debilitating osteoarthritis of the hips as the dog ages. Dogs suffering from the effects of CHD often require costly pain medicine and, in certain instances, surgery to treat the disease. The following is a summary of the diagnosis, treatment and, most importantly, the prevention of CHD.

Normal Canine Hips: The hip joint is a "ball and socket" type joint. The "ball" part of the joint is the rounded top part of the femur or thigh bone called the femoral head. The "socket" component of the joint is the "cup" part of the pelvis known as the acetabulum.
Dogs with normal hips have nice, round femoral heads that fit tightly into the acetabuli. The smooth round surface of the femoral head glides seemlessly over the correspondingy smooth surface of the acetabulum. The result is a remarkable natural machine with a dynamic range of motion.

Early Signs: The X-ray image to the right shows the hips of a dog with the early signs of CHD. Note that the femoral heads instead of being round are flattened. The femoral neck of the femur on the left is thickened and bony osteophytes are starting to form there. The hip on the right shows subluxation or poor seating of the femoral head within the acetabulum. These are loose, unstable hips; and as this dog walks or runs, the femoral heads and acetabuli grind against in stead of glide smoothly over eachother.

A dog at this early stage may show no signs of any problem at all. It is also possible that he may start favoring one or both of the hind legs or walk or run with a "bunny-hoping" gait.

Late Stage: This X-ray image is an example of late stage CHD. Notice the extreme thickening of the femoral neck on the left as well as the significant osteophyte production. Notice that the curved outline of the acetabulum on the left is very bright. This is called sclerosis and is an indication of long term inflamation and irritation in the hip. The dog that owns these hips is in a considerable amount of discomfort. He or she is most likely very "stiff", especially after first getting up from laying down. Such a dog is likely to be very lame and reluctant to walk long distances.

Treatment: Unfortunately, once a dog is diagnosed with CHD there is no cure per se, but most dogs can be managed with conservative medical therapy. This generally includes the use of non-steroidal anti-inflamatory drugs (NSAIDs) such as aspirin and Rimadyl. We at the DMVC also like to treat dogs with nutriceuticals: nutritional supplements containing glucosomine or chondroitin that help repair the cartilage in damaged hip joints.

It is also important to keep dogs with CHD at a healthy weight. Over-weight dogs put considerably more strain on their hips when compared to "fit" dogs.

Surgical options also exist for CHD. If caught early, intervention procedures such as total hip replacement and triple pelvic osteotomy can be performed. These are procedures done by orthopedic specialists. A salvage procedure called a femoral head ostectomy can be performed on dogs with either early or late stage disease that haven't responded well to medical therapy. With this procedure the entire femoral head is removed thus removing the primary source of discomfort for the dog,that being the "grinding" of the arthritic femoral head and acetabulum. The scaring that occurs between the cut end of the femur and the pelvis acts as a replacement joint.

Preventing Hip Dysplasia: The best hope our canine friends have for preventing hip dysplasia and the pain that comes with it is for us to select for breeding only those dogs with "tight" hips. To do this, we recommend the PennHIP method which stands for "University of Pennsylvania Hip Improvement Program". This method was developed by Dr. Gail Smith at the University of Pennsylvania and makes use of a distractor, a device which helps show on an X-ray film the natural degree of laxity that exists in a dog's hip joints. It involves anesthetizing a breeding candidate, positioning him on his back and taking a total of five X-ray films: One compression view in which the dog's hips are X-rayed with the femoral heads fully compressed into the acetabuli; one hip extended view (like those above) to deterimine the degree of arthritic change; and three distraction views which are used by PennHIP radiologists to quantify the degree of laxity a given set of hips have.

This quantification of a hip joint's laxity is called the distraction index (DI). It is derived by comparing the compression view with the three distraction views, measuring the distance that the femeral heads move away from the acetabulum during distraction and dividing that distance by the radius of the femoral head. Once the DI value is known it can be used to assess a dog's risk of developing osteoarthritis of the hips. Research has shown that DI less than 0.3 is associated with an extremely low likelyhood of developing arthritis. The PennHIP radiologists also compare a given dog's value with that of all the other dogs that have been "PennHIPped" for a given breed. It is recommended that only dogs with DI values that fall in the tighter half of a given breed's population bell curve be used for breeding.

Please visit the PennHipwebsite for more information.