Avascular Necrosis

What is avascular necrosis?

The blood supply to the ball of the hip joint (femoral head) reaches the bone by travelling up the femoral neck and into the ball via tiny blood vessels. As a result the hip joint is particularly vulnerable to any conditions or events which cause damage or blockage to small blood vessels in your body. Avascular necrosis (AVN) of the hip is the name for a condition in which the blood supply to the femoral head is disrupted. Without adequate nourishment from a steady blood supply, the bone in the head of the femur dies and gradually collapses. With time this can lead to disabling arthritis.

What causes avascular necrosis?

Avascular necrosis can affect anyone, and the cause is not always known. Most people affected are between 30 - 50 years old. There are a number of well-recognised risk factors:

  • Trauma

    • Fractures or dislocations of the hip joint can directly damage the blood supply

  • Excessive alcohol use

    • This is a common cause of AVN, probably due to the formation of fatty deposits which block the blood vessels to the hip

  • Steroid use

    • High dose steriods such as prednisone (used in the treatment of conditions such as asthma, lupus and other inflammatory conditions) are a well recognised cause of AVN

  • Deep sea diving

  • Sickle cell anaemia

  • Chemotherapy or radiation therapy for cancer

  • Inflammatory conditions

    • Rheumatoid arthritis, SLE, Gaucher’s disease, gout, inflammatory arthritis

What are the symptoms of avascular necrosis?

The main symptom of avascular necrosis is hip pain, normally felt in the groin or buttock region. This typically progresses over the course of several months until the pain is constant, walking becomes difficult, and sleep is disturbed.

How is avascular Necrosis Diagnosed?

Avascular necrosis can often be diagnosed from your symptoms and clinical examination. X-rays can appear normal in the early stages so an MRI scan is required to confirm the diagnosis. In the later stages of AVN x-rays may show flattening and collapse of the hip (femoral head) and eventually the development of arthritis.

Hip AVN MRI T1.jpg
Normal hip left, AVN with collapse right

Normal hip left, AVN with collapse right

How is Avascular necrosis treated?

The best treatment for AVN is largely determined by the stage at which the condition is detected, and how much of the femoral head is involved. Patients in which AVN is caught in the very early stages (before the femoral head collapses) are potential candidates for hip-preserving treatment.

Non-surgical treatment such as anti-inflammatory medications, activity modification, and using crutches, can help relieve pain and slow the progression of the disease. However, these treatments will not prevent AVN from progressing. Medications designed to prevent bone resorption (called bisphosphonates), may have some beneficial effects in the early stages of the disease. The most successful treatment options for AVN are surgical. The most widely used surgical procedure for early AVN is an operation called a core decompression.

A core depression procedure involves drilling several small holes into the femoral head to relieve pressure in the bone and create channels for new blood vessels to grow into the affected areas of the hip. When osteonecrosis of the hip is diagnosed early, core decompression is successful in preventing collapse of the femoral head and the development of arthritis in 50-80% of patients. Once the femoral head has started to collapse, hip preserving surgery is no longer effective. The treatment at this stage is a total hip replacement. Please click this link for more information about hip replacement.

 
Hip AVN Forage.jpg