Overview

Avascular necrosis of the femoral head, also known as Legg-Calvé-Perthes disease (LCPD), is a painful condition that affects the hip joint of young, growing dogs, particularly small breeds. The condition occurs when the blood supply to the developing femoral head (the “ball” of the hip's ball-and-socket joint) is disrupted. Without adequate blood flow, the bone is deprived of oxygen and nutrients, causing bone tissue to die and weaken.

As the disease progresses, the femoral head becomes misshapen. This creates an irregular hip joint and eventually leads to osteoarthritis. LCPD most commonly affects one hip, and affected dogs typically develop progressively worsening pain and lameness.

Fortunately, the prognosis following appropriate treatment is generally very good, and most dogs can return to comfortable, active lives after surgery and rehabilitation.

Cause

The exact cause of LCPD is not fully understood. It is thought to begin with disruption of the blood supply to the developing femoral head, depriving the bone of oxygen and nutrients and causing bone tissue to die (necrosis) and weaken. While the exact trigger for this disruption is still unknown, studies suggest that, in susceptible small-breed dogs, the blood vessels supplying the femoral head may be particularly vulnerable to injury during development.

Genetics appear to play an important role in LCPD. Studies have identified inherited risk factors in several susceptible breeds, although the exact pattern of inheritance has not been established and may involve multiple genes. Because of the suspected hereditary component, dogs diagnosed with LCPD should not be used for breeding.

Breed predisposition

LCPD most commonly affects small-breed dogs including terriers (Yorkshire Terriers, West Highland White Terriers, Cairn Terriers, Jack Russel Terriers), Miniature and Toy Poodles, Miniature Pinschers, Chihuahuas, Papillons, Pomeranians, among many others. The disease can also occur in small mixed-breed dogs.

Clinical signs

Clinical signs most commonly appear between 4-11 months of age, while the hip is still developing. Most dogs develop a gradually worsening limp in one hind leg. Some owners may notice a more sudden onset of pain, even though changes within the hip have been developing over time. Although LCPD usually affects only one hip, both hips can occasionally be affected.

Signs may include:

• Limping, or reluctance to bear weight on a hind leg
• Pain or yelping when the hip is touched or moved
• Stiffness, or reluctance to run, jump or play
• Muscle loss in the thigh of the affected leg
• A grinding or "crunchy" sensation in the hip during movement (crepitus)

Diagnosis

Your veterinarian will consider your dog's age, breed, history and physical examination findings. The diagnosis is typically confirmed with X-rays (radiographs) of the hips.

Radiographic changes depend on how far the disease has progressed. Early changes may be subtle, while more advanced disease can cause flattening, irregularity, fragmentation and collapse of the femoral head. Secondary osteoarthritis develops as the hip becomes increasingly deformed. Because changes can initially be subtle and evolve over time, repeat radiographs may sometimes be recommended to confirm a diagnosis. 

Treatment

Surgery provides the best opportunity for a comfortable, functional limb in dogs with LCPD. The most common procedure is a femoral head and neck ostectomy (FHNO), also called a femoral head and neck excision. During an FHNO, the damaged femoral head and neck are removed. This eliminates the painful bone-on-bone contact between the abnormal femoral head and the hip socket. The body then forms a functional “false joint” from fibrous tissue and surrounding muscles, which allows for comfortable movement. 

For some dogs, a total hip replacement (THR) may also be considered. This procedure replaces the damaged hip joint with artificial components and is performed by a veterinary orthopedic specialist.

Pain management is an important part of treatment. Your veterinarian may prescribe medications such as non-steroidal anti-inflammatory drugs (NSAIDs), along with other pain-control strategies as indicated.

Physical rehabilitation is also an important part of recovery. Dogs with LCPD often have significant muscle loss in the affected leg before surgery. A structured rehabilitation program can help restore muscle strength, range of motion, and normal use of the limb. Your veterinarian may recommend a rehabilitation plan, or they may refer you to a Sports Medicine and Rehabilitation specialist.

Outcome

The prognosis for dogs with LCPD following appropriate treatment is very good. Most dogs regain very good use of the affected leg and can return to normal activities.

Early recognition and treatment can help minimize the period of pain and disability and prevent the progression of severe hip deformity and secondary osteoarthritis. With surgery, appropriate pain management, and rehabilitation, most affected dogs can go on to lead comfortable, active lives.