Aseptic Femoral Head Necrosis

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Aseptic Femoral Head Necrosis

By: Dr. Debra Primovic

Section: Overview

Aseptic necrosis of the femoral head, also known as Legg-Calvé-Perthes Disease, osteochondritis juvenilis or coax plana, is a progressive deterioration and collapse of the femoral head, cause is unknown. The deterioration generally follows an episode of disrupted blood supply to the affected bone. This causes the bone to die, and the continued use and weight of the pet on the joint causes the area to deteriorate and eventually the femoral head "collapses" and osteoarthritis ensues.

The disease is a painful, crippling disease. Clinical signs of lameness may be noticed around four months to one year of age involving one or both rear legs. The average age for diagnosis is five to eight months of age.

Aseptic necrosis of the femoral head (ANFH) is most commonly occurs in miniature, toy and small breed dogs, although it can occur in larger breeds.

Terrier breeds are predisposed and breed predilections include Manchester terriers, miniature pinschers, west Highland white terriers, cairn terriers and toy poodles.

The condition can occur bilaterally in about 15% of pets.

It is an inherited abnormality that is further described as an autosomal recessive mode of inheritance.

What To Look For

If your dog has ANFH, you might notice an abnormal gait, reduced function or lameness. Your pet may also be reluctant to exercise too far or have difficulty going up and down stairs. There may be overt lameness on one or both hind legs. Your older dog may show greater exacerbation of these signs and may struggle to lie down or get up from a lying position.

If your dog exhibits any of the following symptoms, consult your veterinarian:

Progressive hind leg lameness, often begins slowly and progressive to non-weight baring

Abnormal gait

Swaying or staggering

Discomfort when attempting to lie down or stand up

Reluctance to run and jump

Shortened leg or noticeably small muscles in the affected leg (muscle atrophy)

Diagnosis

When your dog is examined, your veterinarian will be checking the gait and will feel the hip joint. Your veterinarian will move the dog's hip joint to assess its range of motion and check for pain with the joint extended, and he or she will listen for the "click" of the hip popping out of joint and the grating sound of bone on bone that indicates cartilage loss.

Radiographs (X-rays) are required for definitive diagnosis. X-rays will show the degree of necrosis and deterioration.

In some dogs, this thorough evaluation may require sedation or even anesthesia because palpation and manipulation of the hips can be very painful.

Treatment

Various medical and surgical treatments are available today that can ease your dog's discomfort and restore mobility. The type of treatment depends upon several factors, such as the age of your dog, the severity of the problem and financial considerations.

Medical treatments such as weight loss, moderate restricted exercise and anti-inflammatory medication will help to alleviate the pain and inflammation around the hip joint. However, this often unsuccessful in many dogs as these palliative measure are unable to relieve the pain.

The most successful therapy for AFHN is surgery. If medical treatment fails to improve your dog's condition, surgical treatment is appropriate. The goals of the surgery is to eliminate the painful bone to bone contact while maintaining hip motion. For small dogs, a femoral head and neck ostectomy (FHO), also referred to as excision arthroplasty, is generally the treatment of choice. For bilateral disease, the surgery can be done on both legs at the same time or staged for to six weeks apart. Large breeds may respond favorably to a total hip replacement (THR).

Home Care

For dogs being managed medically, it's important that you monitor body weight and avoid obesity. You will also want to avoid strenuous exercise – exercise your pet regularly but moderately. If your veterinarian has recommended medication, you will need to be aware of potential side effects.

If your dog has had FHO surgery, early physical activity is encouraged. Physical therapy with passive range of motion exercises are often started soon after surgery. Controlled exercise with short, slow leash-walks should be started as early as 3 days after surgery. Because of the arthritis and muscle atrophy that occurs prior to the surgery, recovery after surgery may take three to six months. Early activity post surgery is encouraged to facilitate the use of the affected leg. Carefully observe the incision daily for swelling, redness or discharge.

Preventative Care

There are few things you can do in the way of prevention, but you should consider the following:

When selecting a small or miniature breed puppy, find out there is a history of AFHN. You should be looking to purchase offspring from parents with a perfect medical history.

Picking up the problem as early as possible affords your puppy the best chance of finding the right option, whether medical or surgical, to minimize the arthritic changes that will develop secondary to the AFHN.

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