Aseptic femoral head and neck necrosis (Legg Calvé Perthes disease)

Aseptic femoral head and neck necrosis is an uncommon disease of immature or young adult toy breed dogs. It is most often seen in terrier breeds, miniature poodles and miniature pinschers. Affected dogs develop hind leg lameness from around 5 months. The condition usually occurs on only one side and affects males and females equally.

This disease has many names: avascular femoral head necrosis (meaning death or necrosis of the ball part of the “ball-and-socket” hip joint because of a reduced blood supply); aseptic femoral head necrosis (aseptic meaning without infection, to distinguish this from infectious joint diseases in young animals); Legg Calvé Perthes disease (named after the physicians who first described the condition in people). The cause of the condition is unknown but it is inherited in some breeds. The disease develops because the blood supply to the ball of the femur (thigh bone) is disrupted and the bone dies. As the bone dies, it collapses with weight bearing, leading to osteoarthritis of the hip joint. Affected dogs develop progressive hind leg lameness and hip pain. Because the limb is painful, the dog minimizes the amount of weight bearing on the leg and loses muscle mass (the affected leg may look thinner.)

Owners usually notice something wrong with their dog in the first year of life, although some dogs are fully grown before they first show signs of lameness. Some owners report their dog becomes irritable if touched, probably as a response to the hip pain.

If your veterinarian suspects femoral head necrosis, a radiograph (x-ray) of the hips will usually confirm the diagnosis and rule out other conditions that can result in hip pain and lameness.

If the condition is recognized in its very earliest stages before there is significant collapse of the ball part of the hip joint, then placing the limb in a sling to prevent weight bearing may be successful. Unfortunately, the early signs are very subtle and often unappreciated and the bone continues to collapse, making slings or even cage confinement ineffective.

The vast majority of cases are not diagnosed before there is collapse of the ball of the hip joint. In such cases, the changes are irreversible and osteoarthritis will continue to progress. Although analgesics (pain killers) and other medical strategies for managing osteoarthritis may make the dog more comfortable, surgery is generally the best course of action. Replacement of the hip with an artificial hip (total hip replacement) is now possible in small breeds and offers the best function but is also more expensive and requires greater care and diligence on the part of the owner while the dog is recovering from surgery. The traditional surgical approach involves removing the collapsed ball (the femoral head) and creating a fibrous joint at the hip (called a femoral head ostectomy). This procedure is generally successful if proper surgical technique is used and aggressive rehabilitation therapy is done after surgery. Most affected animals are able to have a relatively normal life following surgery. Breeds that have a genetic background for this disease, such as West Highland White Terriers, Manchester Terriers, and Miniature Poodles, should not be bred to avoid passing the condition along to their offspring.