Osteonecrosis of the Hip

Osteonecrosis of the Hip, or avascular necrosis (AVN), is caused by a lack of blood flow to the femoral head of the hip joint. Without an adequate blood supply, the bone begins to break down, which leads to destruction and ultimately arthritis of the hip joint. It is more common in males aged 35 to 50 and often affects both hip joints. 1,2

The hip is one of the largest ball-and-socket joints in the body and can move in multiple directions. The acetabulum of the pelvis forms the socket, while the femoral head (upper end of femur/thigh) creates the ball. Articular cartilage covers the femoral head and acetabulum to create a smooth surface for the bones to move together. The synovial lining covers the joint surface and provides lubrication to the cartilage.

Causes

When blood flow to the femoral head is disrupted, osteonecrosis sets in. There are many suspected causes of osteonecrosis, including trauma, disease processes, and even genetics. Trauma that damages the medial femoral circumflex artery, the main blood supply to the femoral head, usually leads to osteonecrosis. Disease processes or a genetic disposition tend to create a thrombosis (blood clot), which stops blood flow to the femoral head and leads to osteonecrosis.

Some risk factors for developing osteonecrosis include:

Irradiation
Trauma to the hip joint causes damage to blood vessels affecting circulation.
Excessive alcohol use causes fatty deposits in blood vessels and restricts blood flow.
Corticosteroid medicine is used, often for the management of chronic diseases such as asthma, rheumatoid arthritis, and systemic lupus erythematosus.
Transplant patient
Viral infections (CMV, hepatitis, HIV, rubella, rubeola, varicella)
Use of protease inhibitors, which are used to treat viral infections like HIV/AIDS, hepatitis C, and COVID-19
Pancreatitis
Subacute bacterial endocarditis (inflammation of the inside lining of the heart)
Blood diseases such as leukemia or lymphoma
Inflammatory diseases such as polyarteritis nodosa (a blood vessel disease), giant cell arteritis (affects large blood vessels of scalp, neck, and arms), sarcoidosis (which affects organ tissue), and rheumatoid arthritis
Sub-clinic decompression sickness most common in divers
Bone marrow diseases
Sickle cell disease
Patients with hypercoagulable states and higher risks for blood clots
Systemic lupus erythematosus (SLE)

Symptoms

If you are experiencing hip pain, it is important to visit a qualified orthopedic specialist early on. There are many conditions that share the common symptoms of osteonecrosis of the hip. A proper diagnosis can ensure the right treatment plan going forward. The most common symptoms of osteonecrosis of the hip include:

Gradual onset of hip pain, often with no obvious event.
Pain is worse when going from seated to standing, taking stairs or inclines, and impact activities (jogging, running).
Pain is located anteriorly (groin).
Pain starts as a dull ache or throb and progresses to a more significant pain that can affect the ability to bear weight.

Diagnosing

The earlier osteonecrosis of the hip is diagnosed, the better the outcome following treatment. The diagnostic process includes a physical examination, a full medical history, and diagnostic tests. During the exam, your physician will test for tenderness and pain in the hip area as well as evaluate any radiating pain you may have. Range of motion, neurovascular examination to determine sensory and motor function, and other basic tests will be performed to understand more about the function of the hip.

X-rays are the first and often definitive diagnostic imaging test we use to determine the breakdown of the femoral head. An MRI can detect early bone changes that are not visible on x-ray imaging and may show early onset of osteonecrosis.

Treatments

Non-operative treatments tend to focus on symptom relief and slowing the progression of femoral head breakdown. However, surgery is more successful in treating osteonecrosis of the hip. Visit a qualified orthopedic specialist if you experience prolonged or significant hip pain.

Conservative Treatment Options

Conservative treatment is focused on the relief of pain and slowing the progression of the disease.

Anti-inflammatory medications
Activity modification
Offloading weight-bearing by using an ambulatory device such as a walker or crutches.

Surgical Treatment

When pain and function limit your lifestyle, you may need to consider surgical treatment.

Core decompression and grafting: This procedure has the best outcomes if the osteonecrosis is detected early. During this procedure, holes are drilled into the femoral head to improve blood flow. If detected early, this procedure can help prevent femoral head collapse, progression to severe arthritis, and the need for a total joint replacement. Bone and cartilage grafting is common.
Vascularized fibula graft: During this procedure, a hole is created in the femoral neck and head. Then part of the fibula (lower leg bone) is cut out (including its blood supply) and transplanted into the hole.
Total hip replacement: During this procedure, the ball and socket are replaced with metal and plastic parts that imitate the natural joint. Total hip replacements are very successful in returning function and relieving the pain of severely deteriorated joints.

Complications

All treatment options, whether conservative or surgical, come with risks. Discuss these risks and potential complications with your provider. Common risks with surgery include infection, bleeding, blood clots, and damage to blood vessels or nerves. Joint replacements have the included risk of hardware failure with a possible need for future surgeries.

References:

Wells, MD, FAAOS L, Sheth, MD, FAAOS NP, Foran, MD JRH, Miller, MD MD. Osteonecrosis of the Hip. OrthoInfo. Published March 2022. https://orthoinfo.aaos.org/en/diseases–conditions/osteonecrosis-of-the-hip/
Hsu H, Nallamothu SV. Hip Osteonecrosis. PubMed. Published 2022. https://www.ncbi.nlm.nih.gov/books/NBK499954/#:~:text=Introduction-