HOW IS THE DIAGNOSIS OF CANINE HIP DYSPLASIA MADE?
Canine hip dysplasia is due to an excessive laxity of the femoral head within the hip joint cavity. As the articulary surfaces are wrongly positioned, they can become worn out prematurely, inducing arthrosis i.e. a degenerative disease of the joint, very painful for the dog. It is very important to detect this disease as early as possible, both:
- for the dog himself: 40 to 50 % of dysplasic dogs can live without suffering from it, thanks to a well-managed physical activity and to a proper diet;
- for the breed: as hip dysplasia is transmitted in a hereditary way, the genetic selection is the basic method to try to eradicate the disease.
What are the methods for diagnosing hip dysplasia ?
In a severely affected puppy, his owner may notice that the dog bunny-hops while running. Lameness may also affect one or both rear legs, aggravated by exercise. However, clinical symptoms are more frequently observed in an adult dog, already victim of degenerative joint disease. The dog is stiff, he may have difficulties to stand up, he tends to have a waddling gait. He is reluctant for running, jumping, climbing stairs. Posterior muscles get progressively atrophied.
This is the method used for the systematic detection of hip dysplasia. To make a good X-ray picture, the dog must lie down in dorsal recumbency ( a “ cradle ” allows to make him comfortable), both rear legs extended, the stifles rotated internally to place the patellas on the midline. A good picture shows the entire pelvis and femurs, and the latters should be parallel to the spinal cord. When it is possible, anaesthesia should be avoided: it induces an extreme muscular relaxation that could be responsible for a wrong interpretation of the picture. For the same reason, this radiologic examination should not be performed in a bitch during heats.
What does the vet focus at in a X-ray picture ?
- He looks at the form of the femoral heads, and what part of them are covered by the hip joint cavity (= acetabulum). The greater the percentage of coverage, the more congruent the joint.
- He measures the so-called “ Norberg Olsson (N.O.) ” angle, represented on the scheme below. In a healthy dog, the value of this angle must be equal or superior to 105°. The more it tends to 108°, the most reliable is the diagnosis of absence of dysplasia.
Measuring of the Norberg-Olsson angle
What are the criterions of classification of different dysplasia stages ?
according to the International Cynologic Federation
A : normal dog no sign of dysplasia
B : borderline dysplastic uncompleted congruence of the joint and N.O. >105°
or good congruence but N.O. < 105°
C : mild dysplasia unsufficient joint congruence and N.O. between 100 and 105°
D : moderate dysplasia very deficient congruence and N.O. between 90 and 100°
E : severe dysplasia subluxation or articular luxation, signs or arthrosis and N.O. < 90°
At what age can be detected hip dysplasia ?
Providing that the radiologist has got a good experience, radiologic detection can be performed from 4 months old. The reliability of this preliminary evaluation is 70 to 100 %, depending on the result. A dog that is first judged dysplastic has got little chance to be found normal later. On the opposite, a contentious result will have to be confirmed after one year old or even 2 yrs old for large breed dogs. Hip dysplasia is included in the list of latent defects (i.e. rendering a sale guarantee invalid): if the dog has been sold during his 1st year, all the examinations performed until this age will be taken into account.
Overfeeding during growth is now well-known to be the main aggravating factor to a genetic predisposition. The faster the puppy grows up, the more likely he is to show dysplasia signs. This is why Maxi junior is recommanded for all “ risky puppies ” (German shepherd, Labrador…). It is very important to keep the puppy slim during growth, and to control his bodyweight evolution once he got the adult stage.
Donated by the Borg Cardona and Co. Ltd. visit Borg Cardona website