Femoral Head Ostectomy (FHO) in Dogs

By Malcolm Weir, DVM, MSc, MPH; Catherine Barnette, DVM

What is FHO surgery?

An FHO, or femoral head ostectomy, is a surgical procedure that aims to restore pain-free mobility to a diseased or damaged hip by removing the head and neck of the femur (the long leg bone or thighbone).

How does an FHO change the hip?

The normal hip is a ball-and-socket joint. The acetabulum, which is a part of the pelvis, composes the socket of the joint. The head of the femur, a projection from the long bone located between the hip and the knee, composes the ball that fits within the socket. The head of the femur fits within the acetabulum, allowing the hip to move freely in all directions.

When the hip becomes damaged or diseased, however, this mobility can be affected. If the acetabulum and the head of the femur do not fit together properly, this poor fit can influence the degree of movement that the joint can achieve. In addition, this poor joint fit can lead to chronic pain and inflammation.

An FHO restores mobility to the hip by removing the head of the femur. This removes the ball of the ball-and-socket joint, leaving just an empty socket. The muscles of the leg will initially hold the femur in place and, over time, scar tissue will form between the acetabulum and the femur to provide cushioning that is referred to as a 'false joint'. Although this joint is anatomically very different from a normal hip joint, it provides pain-free mobility in most patients.

Is my dog a good candidate for FHO?

This procedure is primarily recommended for small dogs (under approximately 45 pounds) and cats, especially those who are at a healthy weight. The false joint that is created in an FHO works very well to support the weight of small animals but may be less effective in large-breed dogs. There are exceptions, however, and veterinarians may recommend an FHO for a dog over 50 pounds if the specifics of the case dictate that doing so would be appropriate.

"Active dogs often experience better results with FHO than less active dogs."

Active dogs often experience better results with FHO than less active dogs. The muscle mass that has been built up through activity helps to stabilize the joint, allowing the dog to regain pain-free mobility more quickly than inactive pets. Inactive dogs have less muscle mass around the joint, making the joint less stable post-operatively and leading to longer recovery times.

Why is FHO performed?

The primary goal of an FHO is to remove bone-on-bone contact, restoring pain-free mobility. The most common reasons for FHO include:

Fractures involving the hip. When a fracture involves the hip joint and cannot be repaired surgically (either due to patient considerations or financial considerations for the owner), an FHO may provide the best option for pain-free mobility.

Hip luxation/dislocation (associated with trauma or severe hip dysplasia). In some cases, a hip that is out of the socket cannot be replaced with manipulation or other medical means. Surgical repair of hip luxations can be costly and is not always successful, so many dog owners elect FHO for small dogs with hip luxation.

"The primary goal of an FHO is to remove bone-on-bone contact, restoring pain-free mobility."

Severe arthritis of the hip. In chronic, end-stage arthritis, the cartilage that protects both the head of the femur and the acetabulum can become eroded away, leading to painful bone-on-bone grating whenever the hip is moved. Performing an FHO can remove this point of contact and alleviate pain.

Legg-Perthes disease (also known as avascular necrosis of the femoral head). This uncommon condition, most frequently seen in miniature and toy breed dogs, causes the bone within the femoral head to begin to die at an early age. The bone collapses due to these degenerative changes, leading to severe pain. Removing the femoral head via FHO removes the source of pain for the dog.

What can I expect on the day of surgery?

This surgery is performed under general anesthesia. In most situations, you will take your dog to the veterinary clinic early in the morning on the day of surgery. Your veterinarian will likely instruct you to withhold food the morning of surgery to prevent vomiting that may occur under anesthesia.

After surgery, your dog will remain in the hospital for several hours to several days depending on the specific circumstances of his health and his surgery. When you pick him up from the hospital, your dog probably will not be bearing any weight on the leg that had surgery.

An incision will be visible in the area of the hip, and this incision may or may not have visible external sutures. Some veterinarians use dissolving sutures that are placed under the skin. Your dog will likely be wearing an Elizabethan collar (cone) to prevent licking at the surgical site.

What care will my dog need after FHO surgery?

Care varies based on the needs of the specific patient but, in general, the post-operative recovery can be divided into two phases. In the first several days post-operatively, your dog will be healing from the surgical procedure. Because bones and muscles are cut during this procedure, the focus during this period will be on pain control. Please give all medications as prescribed by your veterinarian. Moist heat may also be recommended during this period to provide comfort and decrease stiffness. Your veterinarian may also recommend laser therapy to reduce inflammation and encourage healing.

Your veterinarian may recommend activity restrictions during the first several days after surgery. If this is the case, confine your dog to a crate or a small room within the house, with only very brief leash walks outside to eliminate. If your dog will tolerate it, you can attempt passive range-of-motion (PROM) exercises during this period, gently moving the hip forward and backward through its range of motion. This should not be performed, however, if it causes pain for your dog.

Your veterinarian will likely recommend introducing more physical activity approximately one week after surgery. During this phase of recovery, the focus shifts to rebuilding muscle mass and strength. Keeping your dog mobile will help keep the scar tissue within the false joint from forming too tightly, allowing your dog to remain flexible. Good exercises during this period include walking (especially up flights of stairs), holding the front portion of your dog’s body in the air while allowing him to 'walk' on his hind legs, and walking through water. Walking should be slow to encourage your dog to bear weight on the affected leg; when running, your dog will be more tempted to carry the affected leg.

"Keeping your dog mobile will help keep the scar tissue within the false joint from forming too tightly, allowing your dog to remain flexible."

In the first 30 days after surgery, it is important to avoid rough play or any activity that encourages sudden twists and turns. These high-impact motions will slow the healing that is occurring within the joint and muscles.

Most dogs will show signs of complete recovery approximately six weeks post-operatively. At this point, your dog can resume his regular activities. Healing may be more rapid in dogs that had normal function up until shortly before the FHO (i.e., in the case of a dog that had a sudden, traumatic injury to the hip) and may be slower in dogs with longstanding, chronic issues (because these chronic issues often lead to muscle atrophy, which takes time to resolve).

If your dog is not showing significant improvement by six weeks post-operatively, you may want to consider a formal rehabilitation or physical therapy program. Ask your veterinarian for recommendations if your dog is still having difficulties at or after six weeks.

What is the prognosis after FHO surgery?

Most dogs recover fully after FHO surgery and regain essentially normal function of the affected leg. Although the leg may have a slightly decreased range of motion or decreased limb length after surgery, these impacts are typically minimal and do not impact the pet’s quality of life.

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