Frequently Asked Questions About Hip Avascular Necrosis (AVN) & Free Vascularized Fibular Grafting



Bone is living tissue with living cells that require a blood supply. “Avascular” means loss of blood supply; “necrosis” means death. Loss of blood supply to the hip can result in the death of bone or avascular necrosis, or in other words, “dead bone.”

Avascular necrosis is commonly referred to as “AVN.” More recently the name osteonecrosis (“ON” for short) has been used. “Osteo” means bone; Osteonecrosis means death of bone.

The femoral head (the ball part of the ball and socket hip joint) is the most frequent bone involved.

AVN affects about 20,000 new patients per year in the United States.

Several hundred thousand patients are living with this disease in the United States.

Of the 250,000 joint replacements done each year, about 10% are done for patients with AVN.

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The risk in a healthy person is probably less than 1 in 100,000.

Most patients are between the ages of 20 and 50 years old (average age 38 years) although any age group may develop AVN.

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There are 2 major forms of AVN, traumatic or non-traumatic (no injury from trauma). Fractures or dislocations of the hip are one of the most common causes. Direct injury to the hip blood supply can occur causing AVN.

The most common non-traumatic risk factor is a history of high dose steroid (corticosteroid such as prednisone) treatment for some medical problems such as severe asthma, Lupus, rheumatoid arthritis, organ transplantation, and many others.

The next most common risk factor is a history of high alcohol use. The greater the alcohol consumption, the higher the risk of AVN.

Other risk factors include blood clotting problems, sickle cell disease, kidney disease, liver disease, smoking, and many others.

About 25% of patients develop AVN for no apparent reason (idiopathic).

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There are 6 stages to describe the advancement of disease by x-rays. Stage 1 is the earliest stage, and Stage 6 is the final stage of disease.

X-rays of the hip appear normal in the earliest stage of disease (Stage 1). The diagnosis is made using MRI.

Some patients may not have pain (or symptoms) in the early stages. AVN may be present for some time before any symptoms begin, which is referred to as a “silent” hip.

Initial symptoms are usually pain and aching in the groin during activities, but it may be felt in the thigh or knee. Pain may begin slowly and occur “off and on,” or it may occur suddenly and severely without notice.

As AVN progresses, hip pain worsens, and the hip may become stiff with increasing loss of motion. Limping becomes common. Basic activities of daily living can become difficult to perform.

With further progression of the disease, AVN of the hip can be seen on x-rays. In the later stages (Stages 3 and 4) of AVN, the dead bone in the ball part of the hip begins to fail as stress fractures occur through the dead bone. The ball begins to flatten as it is unable to support the large forces across the hip. The hip joint becomes severely damaged with rapid loss of the joint cartilage leading to severe arthritis (Stages 5 and 6). The damage to the cartilage is irreversible.

An additional factor of importance with advancing AVN is the extent of disease. How much of the ball part of the hip is involved? Larger size lesions are more difficult to treat successfully, especially those involving more than 50% of the ball (femoral head).

Progression of disease with flattening of the ball and developing severe arthritis is usually certain to happen. Over 80% of patients, who have hip pain and are not treated for AVN, will develop collapse of the ball part of the hip.

Collapse of the ball part of the hip can occur as early as one month or in several months. Although difficult to predict, progression usually occurs in less than 20 months.

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Free vascularized fibular grafting consists of removing dead bone from the ball part of the hip that has a poor blood supply and replacing it with a healthy segment of vascularized (blood-rich) bone from the lower leg, the fibula. (View the illustration)

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Patients with avascular necrosis (AVN) of the hip are candidates for the surgery.

The goal of the free vascularized fibular graft is to preserve the femoral head (the ball of the hip joint) rather than replace it with an artificial joint or total joint replacement.

The surgery is limited to patients under 50 years of age and to patients who do not have sickle cell disease.

If the hip is severely damaged (severe collapse and arthritis) with significant loss of joint motion, then preservation or salvage of the hip may not be possible with this type of surgery.

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Dr. Katz had specialized training in this technique, free vascularized fibular grafting, at Duke University Medical Center under the direction of James R. Urbaniak, MD.

During the surgery an incision is made at the hip for removal of the dead bone and for preparation of the hip to receive the fibular bone graft. Additional bone graft is taken from the healthy portion of the femur (thigh bone) to supplement the vascularized fibular bone graft.

A separate incision is made in the lower leg to remove a segment of the fibula (the smaller bone of the leg) along with its attached blood vessels.

The fibular bone graft is then inserted into the ball part of the hip where the AVN was removed. The vessels (artery and vein) attached to the fibular bone graft are then connected to the vessels in the hip region using a microscope. (View the illustration)

The circulation of blood flow to the hip and fibular bone graft is carefully checked after the vessels are connected.

The incisions at the hip and lower leg are closed. A bandage is applied to the hip, and a bulky dressing is applied to the leg for comfort. Drains are placed at both incisions and are removed 2 to 3 days after surgery.

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After surgery the patient is given blood thinners (anticoagulant) which help prevent the blood from clotting as quickly and helps blood flow to the bone grafted area of the hip.

An epidural (a form of anesthesia given to pregnant women during baby delivery) is typically used for pain control after surgery for about 36 hours. Pain is then controlled with pain medication taken by mouth.

The hospital stay is usually four to five days. Discharge from the hospital is typically to home.

Physical therapy (PT) begins instruction on basic stretching exercises on the 1st day after surgery. On the 2nd or 3rd day after surgery, PT will begin teaching crutch-walking and limitations of activities that need to be strictly followed during the recovery time. NO WEIGHT on the operated leg is allowed for 6 weeks after surgery. Basic exercises for muscle strengthening are allowed around 3 weeks after surgery.

After the initial 6 weeks, gradual weight-bearing is allowed on the operated leg with the use of crutches or a walker. Crutches will be necessary for 6 months to protect the hip as the bone is healing. After 6 months of protected weight-bearing, full weight is allowed on the operated leg. But activities are limited for an additional 6 months (no sports, running, etc.) since it takes 1 year for complete healing of the bone in the hip. At 1 year from surgery, normal activities are allowed.

Follow-up checks with the doctor after surgery are done at 6 weeks, 3 months, 6 months, and then yearly. If you live a great distance away, then these checks can be done with your local Orthopaedic Surgeon, who can forward the follow-up radiographs and notes for our review.

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Advantages:
The major advantage of vascularized fibular bone grafting is that the bone placed into the hip is alive. This means an immediate blood supply with living bone is provided to the hip where dead bone was removed. The blood vessels from the fibula graft spread out and help form new bone. The body does not have to rebuild a new blood supply, which is not always possible.

A larger amount of dead bone can be removed from the hip since the strong fibula bone becomes a living strut to help support the ball from collapse during the healing process.

This surgery can be used in some patients with later stages of AVN (with limited collapse of the ball).

Disadvantages:
The procedure is complex and requires a longer operation time.

A segment of bone (fibula) has to be taken from the leg, which requires another incision. Looking at 195 patients with 247 consecutive fibular grafts taken at Duke University, some sensory loss (numbness) was present in 11.8%, and some motor weakness (muscle weakness) was present in 2.7%. Ankle pain was reported in 11.5% of legs.

The rehabilitation after surgery requires 6 months of using crutches for protected weight-bearing.

If both hips are involved, only one hip can be operated on at a time while the other hip surgery is delayed until 3 to 4 months later.

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AVN is a progressive disease. To determine exactly when collapse of the hip will occur is unpredictable.

Progression of AVN may be as early as 1 month or may take several months (usually in less than 20 months).

Treating the hip before collapse occurs is the goal.

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The fibula is a minimally weight bearing bone and acts as a strut for muscle attachment.

Only the middle portion of the bone is removed leaving the top and bottom of the fibula without change. The lower portion of the fibula remains in place with its ligament attachments, which prevents the ankle joint from being unstable.

No major change in the appearance of the lower leg is seen except for a scar on the skin from the incision.

Sometimes patients have swelling, numbness, pain, and/or weakness in the leg, which usually resolves during the recovery period after surgery.

Stretching exercises of the toes, foot, and ankle are necessary to avoid flexion contracture from scarring of muscles in the leg to the foot. But simple stretching exercises starting early after surgery eliminate this problem.

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Therapy is usually only necessary while in the hospital.

The specific exercises that can be done by the patient will be described in detail in a booklet provided to each patient.

If a therapist were needed at home, it would be necessary for home safety evaluation, to ensure safe use of crutches or a walker, and to instruct progression of weight bearing after the initial 6 weeks following surgery.

Swimming and stationary bicycling (with no resistance) are recommended after the first 6 weeks from surgery.

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Routine blood thinning and blood vessel dilating medications are given after surgery, which include aspirin and Persantine (dipyridamole). The aspirin and Persantine are given for 6 weeks.

Sometimes an iron supplement is given to rebuild the red blood count.

Pain medication will be given for use after surgery and will be discussed before discharge from the hospital.

Some variations in medications will be based on the patient’s medical history as necessary.

A dentist may ask if your orthopaedic surgeon instructed you to take antibiotics before dental work. Patients with total joint replacements are required to take antibiotics before any dental work. Inform your dentist that you are not required to take antibiotics after your hip surgery since your hip remains your own bone with your own bone graft.

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Less than 2% of patients require a blood transfusion.

Some patients prefer to donate their own blood (autologous blood donation). However, ample time of more than several weeks is needed for self-donated blood collection to be arranged before the surgery date.

There is always blood available from the blood bank.

Some new medications (such as Procrit) can be used to boost your red blood count which avoids donating blood.

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You will be admitted the morning of surgery by way of the operating room.

You will be contacted by our nurse on instructions for arrival time on the day of surgery.

Family members may wait in the family waiting area at the hospital. Dr. Katz will speak to your family after the surgery.

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Bring your personal items and toiletries that you are used to having at home.

You may want your own pajamas a day or two after your surgery. Generally, a hospital gown is preferred immediately after surgery.

A pair of comfortable, flat tie shoes are recommended.

Bring your own medications since the hospital pharmacy may not have exactly your medication.

Large amounts of money or jewelry should be left at home. No jewelry is permitted in the operating room.

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You will need an elevated toilet seat, crutches, or a walker.

Optional things include a wheelchair, handrails around the toilet, and a tub seat.

The discharge planner and social workers will assist you with any special needs.

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Yes. But it takes time for you to feel like your old self.

After the first 6 months of protected weight bearing with crutches on the operated hip, it is recommended that you limit your activities to walking, swimming, and stationary bicycling for the next 6 months.

After 1 year from surgery, you may resume your activities. Well-tolerated activities include bicycling, walking, swimming, and golf. It is generally recommended to avoid sports that cause jarring or aggressive starting and stopping such as jogging, singles tennis, soccer, and basketball.

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The length of disability or out of work time will vary for each patient depending on the type of work you return to and the severity of the AVN.

As a rule, most patients return to sedentary (desk) work, with the use of crutches at 6 weeks from surgery.

Patients who return to work that require walking without crutches may return at 6 to 12 months after surgery.

Patients returning to hard manual labor return to work after 1 year (or about 15 months if both hips are operated on). Some other form of work may be allowed at an earlier time.

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