What PTs Want You to Know about Avascular Necrosis (AVN)

Why Does AVN Develop in the Hip?

The hip joint is one of the true ball-and-socket joints of the body. The hip socket is called the acetabulum and forms a deep cup that surrounds the ball of the upper thigh bone. The thigh bone itself is called the femur, and the ball on the end is the femoral head. The thick muscles of the buttock at the back and the thick muscles of the thigh at the front surround the hip.

There is a thin layer that covers the surface of the femoral head and the inside of the acetabulum. This is called articular cartilage. This material is about one-quarter of an inch thick in most large joints. Articular cartilage is a tough, slick material that allows surfaces to slide against one another without damage.

All of the blood supply comes into the ball that forms the hip joint through the neck of the femur bone (the femoral neck), a thinner area of bone that connects the ball to the shaft. If this blood supply is damaged, then, unfortunately, there is no backup. Damage to the blood supply can cause the death of the bone that makes up the ball portion of the femur. Once this occurs, the bone is no longer able to maintain itself.

Living bone is always changing. To maintain a bone’s strength, bone cells are constantly repairing the wear and tear that affects the bone tissue. If this process stops the bone can begin to weaken, just like rust can affect the metal structure of a bridge. Eventually, just like a rusty bridge, the bone structure begins to collapse.

When AVN occurs in the hip joint, the top of the femoral head (the ball portion) collapses and begins to flatten. Why is this happening in the hip? Because the hip joint is where most of the body weight is concentrated. The flattening creates a situation where the ball no longer fits perfectly inside the socket. Like two pieces of a mismatched piece of machinery, the joint begins to wear itself out. This leads to osteoarthritis of the hip joint and pain.

Why Do I Have This Condition?

Unfortunately, anything that damages the blood supply to the hip can cause AVN.

• Injury to the hip (Fractures, dislocations, etc)
• Some medications (Long-term Cortisone use)
• Alcoholism
• Deep sea divers and miners

Injury to the hip itself can damage the blood vessels. Fractures of the femoral neck (the area connecting the ball of the hip joint) can damage the blood vessels. A dislocation of the hip out of the socket can tear the blood vessels. It usually takes several months for AVN to show up, and it can even become a problem for up to two years following this type of injury.

Some medications can be a risk factor for developing AVN. The most widely recognized for this is cortisone. This is usually only a problem in patients who must take cortisone every day due to other diseases, such as advanced arthritis, or to prevent rejection of an organ transplant. In this case, there are often no better options and doctors notify the patients that AVN could occur. If you have only had one or two injections to treat arthritis or bursitis, there is no need to worry. Thankfully, short courses of cortisone treatment are not likely to cause AVN.

However, a clear link exists between AVN and alcoholism. Excessive alcohol intake somehow damages the blood vessels and leads to AVN. Also, deep sea divers and miners who work under great atmospheric pressure also are at risk for damage to the blood vessels. Why? the pressure causes tiny bubbles to form in the bloodstream which can block the blood vessels in the hip, damaging the blood supply.

What Are the Symptoms of AVN?

• Pain with walking in the hip, groin, buttock, and front thigh
• Walking with limp
• Stiffness in the hip
• Pain interfering with sleep

How do Doctors Identify the Condition?

The diagnosis of AVN begins with a history and physical examination. The doctors will want to know about the following:

• Details of your symptoms
• Occupation and physical demands of it
• Other medical concerns
• Medication use
• Alcohol consumption

A physical examination will determine how much stiffness you have in the hip and whether you have a limp. If there is a high chance that you have AVN, the doctor will order X-rays.

X-rays will usually show AVN if it has been present for long enough. In the very early stages, it may not show up on X-rays even though you are having pain. In contrast, in the advanced stages, the hip joint will be very arthritic, and it may be hard to tell whether the main problem is AVN or advanced osteoarthritis of the hip. Either way, the treatment is basically the same.

If the X-rays fail to show AVN, you may have a bone scan or magnetic resonance imaging (MRI) done to determine if the pain in your hip is coming from early AVN. Magnetic Resonance Imaging (MRI) is a more common imaging tool to make the final diagnosis. The MRI scanner uses magnetic waves instead of radiation. The MRI scanner will take multiple pictures of the hip bones. The images look like slices of the bones. The MRI scan is very sensitive and can show even small areas of damage to the blood supply of the hip, even just hours after the damage has occurred.

Do I Need Surgery to Fix AVN?

It depends. Once AVN has occurred, the treatment choices are determined by how far along the problem is and your symptoms. While pain medications and anti-inflammatory medications can reduce the symptoms, no medical treatments will restore the blood supply to the femoral head and reverse the AVN, which is what we need to fix the source of the problem.

If you caught AVN early, keeping weight off the sore-side foot when standing and walking may be helpful. Medical providers will show you how to use a walker or crutches to protect the hip. The idea is to encourage healing and prevent further damage to the hip. They might also show you Patients stretches to avoid a loss of range of motion in the hip. Anti-inflammatory medicine is often used to ease pain. In some cases, surgeons also prescribe an electrical stimulator in an attempt to get the bone to heal. Sometimes these measures may help delay the need for surgery, but they rarely reverse the problem.

3 Most Common Surgeries for AVN

If the femoral head has not begun to collapse, your surgeon may suggest an operation to try to increase the blood supply to the femoral head. There are several surgeries developed to encourage this.

Decompressing the femoral head

The simplest operation is to drill one or several holes through the femoral neck and into the femoral head, trying to reach the area that lacks blood supply. The drill bores out a plug of bone within the femoral head. There are two primary goals in this procedure:

1. It creates a channel for new blood vessels to quickly form in the area that lacks a blood supply
2. It relieves some of the pressure inside the bone of the femoral head.

Relieving this pressure seems to help decrease the pain patients experience from AVN. There will be a very small incision on the side of the thigh for a fluoroscope. A fluoroscope is a type of X-ray that shows the bones on a TV screen. The surgeon uses the fluoroscope to guide the drill where it needs to go. This will take place as an outpatient procedure, and you will be able to go home with crutches the same day.

Fibular Bone Graft

A more complicated procedure to try to increase the blood supply to the femoral head is a vascularized fibular bone graft procedure. This is actually a tissue transplant.

1. The graft is taken from the fibula (the thin bone that runs next to the shin bone). The graft is vascularized, meaning it has a blood supply of its own. Because it supports the femoral head, the graft is also referred to as a strut graft.
2. The surgeon removes a piece of the small bone in your lower leg (the fibula) along with the blood vessels to the bone.
3. The surgeon then drills a hole through the side of the femur and into the femoral head.
4. The surgeon attaches the blood vessels from the fibula to one of the blood vessels around the hip.

This creates instant blood flow into the bone graft and into the head of the femur. The fibular bone graft is strong and keeps the femoral head from collapsing as the bone heals itself.

This procedure is an inpatient procedure and will require you to stay in the hospital for several days. This is a very complicated operation and is not commonly done. It is not always successful because the blood supply to the graft is fragile and may not form completely.

Artificial Hip Replacement

When AVN is in the advanced stages, the condition is no different from osteoarthritis of the hip joint. Your surgeon will probably recommend replacing the hip with an artificial hip joint. This surgery often has a high success rate and positive patient outcomes, followed by physical therapy.

How Does a Physical Therapist Treat AVN?

At Advanced Physical Therapy, we start with a thorough evaluation going over your medical history and the specific details of your case of AVN. For example, we will measure your current range of motion and strength of the hip, as well as the level of pain. Additionally, we will discuss movements that cause discomfort and how to modify them. Our focus is to understand your needs to live your life to the fullest without pain in the hip. Here are some examples of the goals you will set with your phyiscal therapist.

• Learn safe stretches and mobility drills to keep your hip flexible
• Build a habit of using a walker or crutches in a safe manner to promote healing of the hip bone
• Gradually start strengthening the muscles around the hip

Remember that we are here to assist you to overcome the struggles caused by AVN. Ready to start physical therapy with Advanced Physical Therapy? We have seven clinics around central Connecticut. Connect with us and book an appointment today!

If you have further questions about starting physical therapy with us, check out our frequently asked questions.

The therapists and staff at Advanced Physical Therapy in Prospect are superior. Their professionalism and attention to both patient rehabilitation, health and safety have me returning when their services are warranted. There are a number of very good options available, but I would recommend them unreservedly!

Patricia / A patient at Advanced physical therapy in Prospect