What Is Osteonecrosis?
Osteonecrosis is a condition that develops as a consequence of temporary or permanent loss of blood supply to bone. The lack of blood supply to bone causes that part of the bone to die. The bone may collapse as it dies, and if the affected bone is near a joint, the joint surface can collapse.
Osteonecrosis can affect any bone but most commonly affects the ends of the femur, upper arm bone, knees, shoulders, and ankles. Osteonecrosis of the jaw is considered rare and has been linked to bisphosphonate use. With osteonecrosis, one bone may be affected or more than one, either at the same time or at different times.
Osteonecrosis is also referred to as avascular necrosis, aseptic necrosis or ischemic necrosis of the bone.
How Prevalent Is Osteonecrosis?
The American Academy of Orthopaedic Surgeons estimates that 10,000 to 20,000 people develop osteonecrosis each year.
What Causes Osteonecrosis?
Often, the impaired blood supply that causes osteonecrosis develops following trauma (injury). However, there can be non-traumatic causes too.
Traumatic osteonecrosis occurs when a fracture, dislocation, or joint injury damages surrounding blood vessels, disrupting blood circulation to the bone. Hip fracture and hip dislocation are common causes of traumatic osteonecrosis.
Non-traumatic osteonecrosis develops without trauma or injury. Certain medical conditions are associated with non-traumatic osteonecrosis such as lupus, gout, vasculitis, osteoarthritis, cancer, diabetes, Gaucher's disease, Cushing's syndrome, liver disease, sickle cell disease, pancreatitis, tumors, and blood-clotting disorders. Chemotherapy, high dose or longterm corticosteroid use, organ transplantation, radiation, smoking, and chronic alcohol use are considered risk factors for osteonecrosis. Some sources consider corticosteroid use to be the most common cause of osteonecrosis.
For 20% of osteonecrosis patients, the cause is unknown and the condition is known as idiopathic osteonecrosis.
What Symptoms Are Associated With Osteonecrosis?
Initially, there may not be any noticeable symptoms associated with osteonecrosis. But as the conditions worsens, joint pain is typically present. At first, pain may occur only when bearing weight, but as osteonecrosis progresses, there may be pain even when resting. Over time, the pain can limit range of motion and become disabling. Loss of joint function can develop over a period of several months. While symptoms typically appear gradually, it is possible to experience sudden pain from osteonecrosis.
How Is Osteonecrosis Diagnosed?
X-rays are typically the first diagnostic test ordered when there is suspicion of osteonecrosis. However, x-rays will not pick up early stages of osteonecrosis. If x-rays appear normal, MRI is usually performed to offer the best chance of detecting early stages of osteonecrosis not yet detectable on x-ray.
Although they can be used to diagnose osteonecrosis, CT scans, bone scans, and biopsy are rarely used.
How Is Osteonecrosis Treated?
Treatment goals include improving use of the affected joint, stopping further joint damage, and promoting survival of the bone. In choosing the best treatment option, your doctor will consider your age, the stage of osteonecrosis, site of bone damage, and what initiated the problem.
There may be medications given to alleviate pain, or medications stopped if they are thought to be the cause (e.g., corticosteroids). Reduced weightbearing is typically essential for healing and can be achieved by limiting activities or by using crutches or other mobility aids. Range-of-motion exercises are typically included as part of the treatment plan. Electrical stimulation is sometimes used to promote bone growth. Eventually though, most people with osteonecrosis will require surgery to slow or stop progression of the condition. Surgery is most effective if osteonecrosis has not progressed to bone collapse. Procedures that are used for osteonecrosis include core decompression, osteotomy, bone graft, and total joint replacement.
Osteonecrosis. National Institutes of Arthritis and Musculoskeletal and Skin Diseases (NIAMS). June 2009.
Osteonecrosis. Bone, Joint and Muscle Disorders. Merck Manual. March 2008.