Overview of Osteonecrosis
The bones of the human body are made up of living cells that need a blood supply to stay healthy. In osteonecrosis, blood flow to part of a bone is disrupted. This results in death of bone tissue, and the bone can eventually break down and the joint will collapse. Osteonecrosis is also called:
- Avascular necrosis.
- Aseptic necrosis.
- Ischemic necrosis of bone.
Osteonecrosis can happen to any bone, but most often it develops in the ends of long bones, such as the:
- Thigh bone (femur), especially the upper part—the ball in the hip socket. The lower end, which is part of the knee joint, is also often affected.
- Upper arm bone (humerus), especially the upper part—the ball in the shoulder joint.
When the disease involves part of a bone in a joint, it can lead to the breakdown of the bone and arthritis.
Less often, the bones of the elbows, ankles, feet, wrists and hands are affected.
The primary symptom of osteonecrosis is pain, and doctors usually diagnose the disease using imaging methods such as x-rays or magnetic resonance imaging (MRI). Most people require surgical treatment to prevent further bone damage, to protect the bones and joints, and to improve use of the joints.
Who Gets Osteonecrosis?
People of any age can get osteonecrosis, but it is most common in people in their 30s and 40s. Cases of osteonecrosis that stem from an injury are said to be traumatic, while all other cases are considered nontraumatic or atraumatic.
Doctors have identified a number of risk factors that may make a person more likely to get osteonecrosis. However, some people who get the disease do not have any known risk factors. The risk factors may include:
A broken or dislocated bone or a joint injury may damage the surrounding blood vessels. This can decrease the blood supply to the bone and lead to osteonecrosis.
- Corticosteroids. These medicines, commonly used to treat asthma, arthritis, systemic lupus erythematosus (lupus), and other conditions, act by reducing inflammation. While the reasons are unclear, they increase the risk of osteonecrosis when they are used for long periods at high doses. The risk of osteonecrosis is low when they are used on a short-term basis at lower doses.
Excessive Alcohol and Tobacco Use
Excessive use of alcohol is a risk factor for osteonecrosis, but why it makes people more likely to develop the disease is unclear. Overuse of alcohol can cause fatty substances to build up in the blood vessels and can increase cortisol (hormone that can cause blood vessels to narrow) levels in the blood. Together, these may decrease blood flow to the bone and lead to osteonecrosis. Research has also shown that excessive tobacco use is also a risk factor.
Some medical conditions may increase the risk of osteonecrosis, including:
- Certain blood disorders, such as sickle cell disease.
- Certain types of cancer, such as leukemia.
- Decompression sickness, also known as divers’ disease, the bends, or caisson disease.
- Gaucher disease.
- HIV infection.
- Rheumatoid arthritis.
Some medical interventions may increase the risk of osteonecrosis, including:
- Kidney or other organ transplantation. The use of corticosteroids to avoid organ rejection may be a contributing factor.
- Radiation treatment.
Types of Osteonecrosis
Health care professionals describe two types of osteonecrosis:
- Traumatic, which follows an injury. The most common causes of traumatic osteonecrosis are a bone fracture or dislocation.
- Nontraumatic (or atraumatic), when there is no history of injury.
Symptoms of Osteonecrosis
There may be no symptoms of osteonecrosis at first, but as the disease progresses, you may gradually start to feel pain, especially in weight-bearing bones such as the thigh bone (femur). The disease most commonly affects the hip joint, and the pain is usually felt in the groin or, less commonly, in the buttock area.
Most people first experience pain when they put weight on the affected joint, but eventually the joint may feel painful even when resting. Over time, the joint may stiffen and lose its range of motion, and osteoarthritis may set in. If the end of the bone collapses, the pain may intensify abruptly.
The time period between the start of symptoms and loss of function of the joint varies from person to person and ranges from a few weeks to more than a year.
Cause of Osteonecrosis
Osteonecrosis happens when the blood supply to part of a bone is disrupted, depriving bone tissue of essential nutrients and oxygen. If the affected part of the bone is small and not subject to major weight-bearing forces, it may not cause a problem or the body’s repair processes may be able to rebuild the damaged area. But in most cases, the repair mechanisms do not work and the bone erodes or develops fractures; eventually, it may break down and collapse.
In traumatic osteonecrosis, which develops from an injury, the loss of blood flow is likely due to damage to blood vessels. The reasons for the loss of blood supply are less clear in nontraumatic cases, but may be due to blood clots blocking the circulation or elevated pressure within the bone constricting the vessels and decreasing blood flow.
While the underlying causes of nontraumatic osteonecrosis are not fully understood, scientists believe that genetics, along with other factors—such as alcohol overconsumption, certain medications, or other diseases--may play a role.
Diagnosis of Osteonecrosis
If your doctor suspects you have osteonecrosis, he or she may take your medical history and do a physical exam. Your doctor may also order one or more imaging tests to see which bones are affected and to assess the degree of bone or joint damage. This information helps determine the stage of the disease. Early diagnosis increases the chance that treatment will be successful.
X-rays are usually the first type of imaging study the doctor will order because they can also help rule out other causes of joint pain, such as a fracture or arthritis. However, an x-ray is not sensitive enough to detect bone changes in the early stages of osteonecrosis, so your doctor may order more tests if your x-ray is normal. If you are diagnosed with the disease, x-rays are often used to monitor the bones in the later stages.
Magnetic Resonance Imaging (MRI)
An MRI is a highly sensitive tool for visualizing bones and joints and can detect early signs of osteonecrosis before they are seen on an x-ray. An MRI may even pick up signs of osteonecrosis before you experience symptoms. MRIs can help provide your doctor with information on the degree of bone damage and the overall structure of the joint.
Computed Tomography (CT) Scan
A CT scan creates a clearer image than a plain x-ray does. Doctors can use a CT scan to assess the extent of bone damage, but they are less commonly used than MRIs because they are less sensitive.
Treatment of Osteonecrosis
The goal of treatment is to preserve joint function for as long as possible. If the disease is caught early, the bone is not weight bearing and the damaged area is small, the bone may heal on its own, and your doctor may recommend one or more nonsurgical treatment options. But in most cases, treatment involves surgery. At first, surgical procedures focus on preserving your natural joint; however, if the disease progresses and non-operative treatments do not work, some people may need a total joint replacement.
Your doctor will determine the best treatment for you based on:
- Your age.
- The stage of the disease.
- Which bone is affected and the amount of damage.
Nonsurgical approaches may help manage the symptoms of osteonecrosis, but generally they do not cure the disease or slow its progression. Your doctor may recommend one or more options, including:
- Anti-inflammatory medicines, to reduce pain and swelling.
- Physical therapy, to help reduce joint tenderness and stiffness, and to increase the joint’s range of motion.
- Use of a cane or crutches if the bone is weight bearing, to provide support and help relieve pain and weakness when walking.
- Corticosteroid injections to reduce pain and swelling. Because they are potent drugs, doctors typically prescribe the lowest dose possible to achieve the desired benefit.
Most people with osteonecrosis eventually need surgery as the disease worsens.
There are three main types of surgery aimed at preserving the joint, but if these fail or if the diseased bone has already collapsed, you may need joint replacement surgery.
- Core decompression surgery. This is the most common surgery for osteonecrosis, and it usually helps treat the disease in the earlier stages. It involves drilling one or more narrow shafts through the bone, lowering the pressure within it The procedure helps to relieve pain and slow disease progression. Core decompression is often combined with bone grafting to promote bone repair.
- Osteotomy. Doctors may recommend this procedure for cases that involve small areas of bone damage. In an osteotomy, surgeons reorient the position of the remaining bone so that healthy tissue supports the weight placed on the joint. This reduces stress on the damaged joint.
- Bone graft. This surgical option treats advanced cases. The bone in a bone graft can come from your own body or from a donor, or it can be totally synthetic. In a procedure called a vascularized bone graft, a section of healthy bone from another part of your body is transplanted along with its blood supply, which helps to heal the area of osteonecrosis.
- Total joint replacement. If the bone in the joint has broken down too much, the joint will need to be replaced with an artificial one. Surgeons remove the damaged bone and cartilage and replace them with plastic, ceramic, and metal parts. Total joint replacements help relieve pain and increase the joint’s range of motion.
Who Treats Osteonecrosis?
Osteonecrosis is usually treated by:
- Orthopaedic surgeons, who specialize in treatment and surgery for bone and joint diseases.
- Mental health professionals, who provide counseling and treat mental health disorders such as depression and anxiety.
- Occupational therapists, who teach ways to protect joints, minimize pain, perform activities of daily living, and conserve energy.
- Physical therapists, who can help strengthen your muscles and improve joint function.
- Primary care doctors, such as a family physician or internal medicine specialist, who coordinates care between the different health providers and treats other problems as they arise. Primary care doctors can provide nonsurgical treatment for osteonecrosis.
- Rheumatologists, who specialize in arthritis and other diseases of the bones, joints, and muscles and can provide nonsurgical care for osteonecrosis.
Living With Osteonecrosis
Having a painful disease like osteonecrosis can be challenging, but the following may make it easier for you to manage the disease:
- Talk to your doctor about the types of exercises that are best for you, as well as whether you should avoid certain activities or exercises.
- Care for your joints by using cold packs to ease swelling and numb pain. Heat treatments, such as hot showers or heating pads, help soothe stiff joints and muscles.
- People who have conditions that cause chronic pain are at greater risk of having emotional or mental health problems, such as depression. Consider seeking help from a mental health professional or joining a support group, which can help you learn more about coping and living with the disease.
Remember to follow the recommendations of your health care providers.
Research Progress Related to Osteonecrosis
Investigators supported by the National Institutes of Health and other research centers across the country are working to understand what causes osteonecrosis, which may lead to new treatment strategies. Many efforts are aimed at comparing the efficacy of current and new therapies, which require clinical trials.
Following are examples of other types of studies that are ongoing:
- Researchers are actively searching for pharmaceutical alternatives to surgical procedures, which are currently the mainstay of treatment. One study is testing whether low doses of aspirin, which has anti-blood clotting properties, can increase blood flow to an affected bone and slow disease progression.
- The underlying causes of osteonecrosis are not known, but genetics may play a role. Some studies are aimed at uncovering genetic factors that confer a higher risk of the disease. If found, these genetic factors could help physicians identify high-risk individuals that need to be closely monitored for signs of the disease.
- Research on osteoarthritis has shown that stem cells called mesenchymal stem cells are drawn to arthritic knee joints. Scientists are investigating whether these cells collect at osteonecrotic sites as well, and if their concentration correlates with disease severity. If so, physicians may be able to use mesenchymal stem cell levels to help inform disease staging and treatment decisions.
- Osteoporosis drugs called bisphosphonates tend to accumulate in the jaw bones, and in rare cases this can lead to osteonecrosis of the jaw. Investigators have discovered that certain types of oral bacteria are drawn to these osteonecrotic sites, suggesting that they may play a part in damaging the bone. By exploring the relationship between bisphosphonates and these bacteria, the researchers hope to find ways to prevent bone death without losing the treatment benefit.
- Scientists are testing various approaches involving bone marrow stem cells to regenerate healthy bone. Some studies are examining the benefit of transplanting the stem cells directly into channels generated by core decompression procedures. Another approach is focused on testing the efficacy of bioengineered stem cell-based composite materials in restoring bone lost to the disease.