How is avascular necrosis diagnosed?After performing a complete physical examination and asking about the patient’s medical history (for example, what health problems the patient has had and for how long), the doctor may use one or more imaging techniques to diagnose avascular necrosis. As with many other diseases, early diagnosis increases the chances of treatment success. It is likely that the
doctor first will recommend a radiograph, commonly called an x ray. X rays can help identify many causes of joint pain, such as a fracture or arthritis. If the x ray is normal, the patient may need to have more tests. Research studies have shown that magnetic resonance imaging, or MRI, is the most sensitive method for diagnosing avascular necrosis in the early stages. The tests described below may be used to determine the amount of bone affected and how far the disease has progressed.
X Ray: An x ray is a common tool that the doctor may use to help diagnose the cause of joint pain. It is a simple way to produce pictures of bones. The x ray of a person with early avascular necrosis is likely to be normal because x rays are not sensitive enough to detect the bone changes in the early stages of the disease. X rays can show bone damage in the later stages, and once the diagnosis is made, they are often used to monitor the course of the condition.
Magnetic Resonance Imaging (MRI): MRI is quickly becoming a common method for diagnosing avascular necrosis. Unlike x rays, bone scans, and CT (computed/computerized tomography) scans, MRI detects chemical changes in the bone marrow and can show avascular necrosis in its earliest stages. MRI provides the doctor with a picture of the area affected and the bone rebuilding process. In addition, MRI may show diseased areas that are not yet causing any symptoms.
Bone Scan: Also known as bone scintigraphy, bone scans are used most commonly in patients who have normal x rays. A harmless radioactive dye is injected into the affected bone and a picture of the bone is taken with a special camera. The picture shows how the dye travels through the bone and where normal bone formation is occurring. A single bone scan finds all areas in the body that are affected, thus reducing the need to expose the patient to more radiation. Bone scans do not detect avascular necrosis at the earliest stages.
Computed/Computerized Tomography: A CT scan is an imaging technique that provides the doctor with a three-dimensional picture of the bone. It also shows “slices” of the bone, making the picture much clearer than x rays and bone scans. Some doctors disagree about the usefulness of this test to diagnose avascular necrosis. Although a diagnosis usually can be made without a CT scan, the technique may be useful in determining the extent of bone damage.
Biopsy: A biopsy is a surgical procedure in which tissue from the affected bone is removed and studied. Although a biopsy is a conclusive way to diagnose avascular necrosis, it is rarely used because it requires surgery.
Functional Evaluation of Bone: Tests to measure the pressure inside a bone may be used when the doctor strongly suspects that a patient has avascular necrosis, despite normal results of x rays, bone scans, and MRIs. These tests are very sensitive for detecting increased pressure within the bone, but they require surgery.