FCI CANINE HIP DYSPLASIA CLASSIFICATION

Introduction

Canine Hip Dysplasia (CHD) is the most common heritable orthopaedic problem seen in dogs. It affects virtually all breeds of dogs, but is especially problematic in large and giant breeds. CHD develops into a degenerative condition (osteoarthritis) of the hip joints.

Conventionally, CHD is diagnosed radiographically by the presence of degenerative changes and/or subluxation of the hip. The role of subluxation is crucial in the development of CHD but is often camouflaged on the most commonly used radiographic projection of the hips.

Radiographic evidence of osteoarthritis confirms secondary changes of CHD, characterised by periarticular osteophyte formation (bone spurs), signs of subchondral bony sclerosis and bony remodelling

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Cause

Many factors work together to cause this disease, which is a combination of a dog genetically inclined to get this disease interacting with environmental factors that bring about the symptoms. These environmental factors excess calcium in the diet of puppy food for large breed dogs, along with obesity, high protein and calorie diets, and a lack of or too much exercise. The breeding of dogs that already have hip dysplasia is one of the primary reasons the disease is still present. A dog that has hip dysplasia in one socket is prone to having a problem with the ligaments of the knee in the other leg (anterior cruciate rupture).

Pathophysiology

During the degenerative process the cartilage that lines the hip joint, called hyaline cartilage, is damaged. The damage results from the abnormal forces on the cartilage from the deformed hip socket. Small fractures can occur in the cartilage also. Eventually an enzyme is released that degrades the joint further and decrease the synthesis of an important joint protectant called proteoglycans. The cartilage becomes thinner and stiffer, further compromising its ability to handle the stresses of daily movement and weight bearing.As the problem progresses more enzymes are released, which now affect the precursors to proteoglycans, molecules called glycosaminoglycans and hyaluronate. Lubrication is negligible, inflammation occurs, and the joint fluid can no longer nourish the hyaline cartilage. This viscious cycle continues until pain occurs. The body attempts to reduce this pain by stabilizing the hip joint. New bone is deposited at the joint, both inside and out, along with some of the ligaments and muscle attachments to the area. This causes thickening and a decrease in the range of motion. This is the actual arthritis noted on a radiograph, which will not go away and will continue to progress.

FCI SCORES  Dortmund 1991

This classification has been made up on account of the radiological features only. It is as objective as possible. This classification scheme may be adopted for older dogs, but secondary arthrotic changes have then to be evaluated according to the age of the dog.

 A

	No signs of Hip Dysplasia The femoral head and the acetabulum are congruent. The craniolateral rim appears sharp and slightly rounded. The joint space is narrow and even. The acetabular angle according to Norberg (adapted for Pos. I) is about 105 degrees (as a reference). In excellent hip joints the craniolateral rim encircles the femoral head somewhat more in laterocaudal direction.
B	Near normal hip joints The femoral head and the acetabulum are slightly incongruent and the acetabular angle according to Norberg (adapted for Pos. I) is about 105 degrees or the center of the femoral head lies medial to the dorsal rim of the acetabulum and the femoral head and the acetabulum are congruent.
	C Mild hip dysplasia The femoral head and the acetabulum are incongruent, the acetabular angle according to Norberg is about 100 degrees and/or there is a slightly flattened cranilateral rim. Irregularities or no more than slight signs of osteoarthrotic changes on the margo acetabularis cranialis caudalis or dorsalis or on the femoral head and neck may be present.
	D Moderate hip dysplasia Obvious incongruiency between the femoral head and the acetabulum with subluxation. Acetabular angle according to Norberg more than 90 degrees (only as a reference). Flattening of the cranilateral rim and/or osteoarthrotic signs.
	E Severe Hip Dysplasia Marked dysplastic changes of the hip joints, such as luxation or distinct subluxation, acetabular angle according to Norberg less than 90 degree, obvious flattenting of the margo acetabularis cranialis, deformation of the femoral head (mushroom shaped, flattening) or other signs of osteoarthriosis.