There's Nothing Hip About Hip Pain

Avascular Necrosis Strikes Young Adults

By Mark A. Katz, MD

Simply because of their age, young, healthy adults will often attribute hip pain to sitting at a desk too long, working out a little too hard, nagging muscle strains, or thinking it’s just bursitis. Many think the pain will go away and most often it will. But for others, hip or groin pain could signify an orthopaedic condition called avascular necrosis. Yearly, there are about 20,000 people, most aged in their 20s or 30s, newly diagnosed with hip avascular necrosis.

Hip avascular necrosis (commonly called "AVN"), now better known as osteonecrosis ("osteo" means bone; "necrosis" means death), results from interruption of the normal blood flow to the femoral head, or the "ball" that fits into the hip’s socket. If left untreated, this loss of blood flow to the hip ultimately causes the "ball" to die and collapse, leading to extreme pain, loss of hip motion, and eventually, severe arthritis.

What Causes Avascular Necrosis?

There are two major forms of AVN, traumatic or non-traumatic (meaning no injury). Hip fractures or hip joint dislocations, partial or complete, are the most common causes of AVN. Direct damage to the hip blood vessels can occur with these injuries, resulting in loss or compromise of blood flow to the femoral head. The mysterious loss of blood flow to the hip in the non-traumatic form has been associated with many risk factors, but the exact cause is not always well understood. In fact, about 25% of patients with AVN of the hip develop the disorder for no apparent reason.

The most common risk factor is the use of oral or IV steroid medications (corticosteroids such as Prednisone). These medications are typically used for patients with asthma, inflammatory arthritis, Crohn’s disease, severe allergies, spinal cord trauma, and many other disorders. Although there is no absolute risk of developing AVN with use of limited steroids (like short-course steroid dose packs), there have been few reports in the literature of its possible risks.

Another very common risk factor is excessive use of alcohol. The greater the consumption of alcohol, the higher the risk of developing AVN. The exact mechanism of how alcohol, or steroids, causes AVN is not absolutely understood, but it is believed that excessive fatty substances are produced and build up in the very small blood vessels of the bone. Blockage then occurs which decreases blood flow to the femoral head causing bone death.

Other risk factors or causes include blood clotting disorders, sickle cell disease, hyperlipidemia, deep sea scuba diving, smoking, radiation treatments and chemotherapy, pancreatitis, Gaucher’s disease, Lupus or other connective tissue diseases, and pregnancy. Women have rarely developed AVN during the second or third trimester of pregnancy. However, there are several theories of how this occurs. One thought is that the fetus can compress on the large veins of the pelvis causing increased venous pressures and obstruction of blood flow to the hip. These women seem to always present with left sided groin pain and with more advanced AVN of the left hip. Occasionally, both hips can be involved (about 30%), but the left hip usually shows further progression.

How Do You Know its Avascular Necrosis?

Diagnosing avascular necrosis can be very difficult. Most young adults do not think about themselves getting ill or let alone having "arthritis" - a right of passage envied by anyone over 40 years of age. However, this youthful mindset can delay its diagnosis. But what makes the diagnosis of AVN most elusive is its ability to exist "silently." Some patients may never have any symptoms in the early stages of disease (before collapse of the "ball"), while some may only experience minimal aches and pains in its later stages (after collapse of the "ball"). Some, in contrast, may experience quite severe groin pain at any stage of the disease, either early or late. In the earliest stages of AVN, x-rays of the hip are actually negative, only making a prompt diagnosis truly more difficult. However, based on the patient’s young age and possible history of risk factors, a magnetic resonance image (MRI) of the hip is typically obtained. MRI is the most reliable method for detecting AVN, even in the earliest stages. MRI can distinguish changes in the bone marrow caused by loss of blood flow well before changes in bone are seen on a routine x-ray. Additionally, since both hips are routinely imaged in the same sitting, MRI becomes extremely useful in the detection of a "silent" hip — the presence of AVN in the absence of symptoms. Over 50% of patients with hip AVN will develop involvement of both hips. Thus, MRI can afford patients an early diagnosis of the "silent" hip that permits earlier intervention for treatment.

What are my Options for Treating Avascular Necrosis?

Avascular necrosis of the hip is a devastating, life changing experience for young adults. Unfortunately, there is a relatively small window of opportunity for saving the dying hip joint. Once the hip joint is severely damaged (severe collapse and arthritis), then hip replacement essentially becomes the only reasonable treatment option. Hip replacement surgery ideally lasts about 20 years. However, hip replacements in younger patients (under the age of 50) typically have poorer results and shorter life-spans, leaving patients with the need for additional, more difficult revision hip replacement surgeries that are associated with even poorer results than the first. The youngest of patients in their teens or 20s could anticipate one, two, or possibly three or even more revision hip replacement surgeries over his or her lifetime. There are also hip resurfacing procedures, a form of partial hip replacement with metal, available, but the long-term results for these surgeries are years away.

If AVN is diagnosed in its earliest stages and the diseased area of the femoral head is very small, a procedure called core decompression and bone grafting can be done with some success. This procedure involves removing a limited amount of dead bone from the "ball" of the hip in hopes of relieving pressure within the femoral head and allowing the body to restore its own blood supply over time. The true success of this procedure, however, can be inconsistent. As mentioned, the success of core decompression surgery is very much dependent upon an early presentation and a small size of disease.

Fortunately, there is good news for adolescents and young adults under the age of 50 diagnosed with hip avascular necrosis, including select patients with later stages of disease, larger sized lesions, and limited collapse. A highly specialized surgical procedure called free vascularized fibular grafting - a unique form of bone grafting - can restore the dying hip and prevent hip replacement with much greater success.

What is Free Vascularized Fibular Grafting for the Hip?

Due to its high complexity, free vascularized fibular grafting for the hip is performed at only a few medical centers throughout the country by fellowship-trained Orthopaedic Surgeons, who are highly experienced with this procedure. Vascularized fibular grafting involves removal of dead bone from the "ball" of the hip that has poor or no blood supply and replacing it with a healthy, vascularized (blood-rich) bone from the lower leg, the fibula. A portion of the fibula (the smaller bone in the lower leg) is removed with its own blood vessels and then inserted into the "ball" of the hip. With use of a microscope, the blood vessels of the fibula are then attached to the blood vessels around the hip to restore blood flow to the "ball."

The major advantage of a vascularized bone graft is that the bone placed into the hip is alive. This means an immediate blood supply along with living bone is inserted where dead bone was removed. Since the fibula bone graft becomes a strong living strut to help support the "ball" from collapse, a much larger amount of dead bone can be removed allowing for a better decompression and for improved ability to restore blood flow to the femoral head during the healing process. The fibula bone graft then fuses to the surrounding bone within the femoral head.

Life After Free Vascularized Fibular Grafting

After vascularized fibular grafting surgery, the patient remains in the hospital for a few days and is typically discharged to home. Most importantly, protected weight-bearing must be maintained with the use of crutches or a walker for six months after surgery. No weight is allowed on the operated hip for the initial six weeks, and then gradual partial weight on the hip is permitted over the ensuing months. The aid of crutches is necessary for a total of six months to protect the hip from collapse as the bone graft heals. After six months of protecting the hip, full weight on the hip is allowed. To completely insure the success of surgery and proper healing, certain activities, such as running or sports, are on hold for about a year.

Free vascularized fibular grafting is a surgical procedure that can restore a pain free, active life.

###

Dr. Mark A.Katz is a board certified Orthoapedic Surgeon with fellowship training in hand, upper extremity, microvascular surgery and vascularized bone grafting for the treatment of hip avascular necrosis. He has experience in over 100 cases of vascularized fibular grafting for hip AVN and is a member of the National Osteonecrosis Foundation. Log on to www.orthodoc.aaos.org/MarkKatzMD and www.sahandtoshoulder.com for more information.