Hip Displasia Facts

1. It is an abnormal development or growth of the hip joints that usually occurs in both hips. There are varying degrees of laxity, instability, and malformation of the femoral head and hip joint. Later in the course there can be arthritis in the hips.

2. It is a genetic disease that can be influenced by environmental factors. The genes do not affect the skeleton primarily, but rather the cartilage, supporting connective tissue, and muscles of the hip region.

3. The hips are normal at birth. Failure of the muscles to develop and reach functional maturity concurrently with the skeleton results in joint instability.

4. Bony changes of hip dysplasia are a result of failure of soft tissues to maintain congruity between the femoral head and the acetabulum (hip joint).

5. Dogs with more pelvic muscle mass have more normal joints than those with a relatively smaller pelvic muscle mass.

6. The onset, severity and incidence of hip dysplasia can be reduced by restricting the growth rate of puppies.

Clinical Types

There are two distinct clinical groups of dogs: a. Young dogs between 4 and 12 months of age. b. Animals over 15 months of age with chronic disease.

Young Animals;

1. There may be a sudden onset of pain characterized by soreness in hind limbs, difficulty rising, decreased willingness to walk, run or climb stairs. The muscles in the pelvic region are usually poorly developed. There may be a clicking sound when the dog walks.

2. Subluxation results in an increase of the angle of

inclination of the femoral neck beyond 146 degrees over a period of time.

3. The pain results from tension and tearing of the nerves of the periosteum, microfractures in the acetabular rim, and stretching and tearing of the joint capsule.

4. Microfractures heal by the laying down of bone which may not be seen radiographically until 12-18 months of age.

5. By 12-14 months of age, the skeleton is mature, the hips become more stable, the joint capsule scars and contracts resulting in decreased pain. The dog may walk and run freely at this stage despite the radiographic appearance of the hip.

Older Animals;

1. These animals suffer from chronic degenerative joint disease and its associated pain.

2. Clinical signs may occur over an extended period of time or may occur suddenly after exercise that results in a tear or stretching of the soft tissues.

3. There is lameness, a waddling gait, crepitation in the joint, and a restricted range of motion in the joint. Thigh and pelvic muscles atrophy. The shoulder muscles become larger because the weight bearing is shifted to the front legs.

4. There is a 50% decrease in function before clinical signs are evident and 75% decrease in function by the time surgery is recommended.

Diagnosis!

1. Orthopedic examination and radiographs.

2. There are three categories of dysplasia:

a. Mild - minimal deviation from normal with only slight

flattening of the femoral head and minor subluxation. b. Moderate - shallow acetabulum, flattened femoral

head, poor joint congruency, subluxation, osteophytes

(arthritis) on the femoral head and neck, c. Severe - complete dislocation of the hip with severe

flattening of the acetabulum and femoral head.

Treatment;

1. Medical therapy:

a. Anti inflammatory medication.

b. Restrict activity to a level below that causing pain.

c. Avoid obesity.

2. Surgical therapy:

a. Pelvic osteotomy, b. Femoral neck lengthening, c. Total hip replacement.
d. Femoral head ostectomy (remove both femoral heads to relieve the pain)