When you incur an injury, uncertainty looms large. And when an injury doesn’t resolve itself in a few days to a few weeks, medical intervention is often necessary. Your doctor may order an x-ray initially or later order a magnetic resonance imaging (MRI) or electromyography (EMG), depending on the nature and extent of the injury. This article explains a little about each test and what you can expect if you or someone you know must undergo any of them.
The x-ray is most common. X-rays pass through your body, and produce a picture on an x-ray film. Dense structures, such as bone, block many x-rays and appear white on the x-ray film. Other structures, such as muscles, ligaments and fascia, appear in shades of gray. X-rays are especially helpful in determining if you have suffered a fracture, dislocation, bone spur or arthritic changes. They can also depict abnormal curvature of the spine and bone tumors.
X-rays are usually taken from several angles, and are interpreted by a radiologist or orthopedic surgeon. These x-rays are usually not recommended for pregnant women, since there is a chance of harm to the fetus. If x-ray results are negative, which means no injury or abnormality can be seen, and pain from an injury persists, your doctor may order an MRI if other orthopedic indications confirm the need for further diagnostic testing.
For example, in a knee injury, certain types of maneuvers to the knee performed by a doctor or physical therapist may indicate ligament or cartilage damage. An MRI could give more exact specifics. In a back injury, certain types of radiating pain or numbness, loss of reflexes or weakness in certain muscle groups often indicate the need for further diagnostic testing, especially if the symptoms aren’t improving on their own. In many cases, an MRI, or magnetic resonance imaging, may be performed.
An MRI produces images using a strong magnetic field and pulses of radio waves. Unlike x-rays, which most clearly outline bone problems, an MRI gives the best detail to tissues and structures that contain fluid. These include many joints and the spinal canal. Conditions such as disc bulges or herniations can be identified as well as their effects on surrounding nerves. Narrowing of joints caused by inflammation, infection or muscle or ligament damage can also be detected. Because an MRI uses a magnetic field, it is very important to tell your physician if you have any metal, such as pins, artificial joints, pacemakers or any implants that may be affected by the MRI.
The operation of most MRI machines requires you to lie still on a hard surface in a somewhat confined space for 30 to 60 minutes. If this poses a problem, you may be able to have the test done in an open MRI, which is less confining. But if this isn’t possible, your doctor may prescribe medication to relax you and make you more comfortable. Radio waves are used, so you may hear loud thumping or tapping noises during the test. Depending on the MRI machine and the clinic setting, you may be given headphones and/or glasses with small mirrors enabling you to see the opening of the MRI. You may also feel moving air from fans inside the MRI.
If your doctor suspects that the injury involves nerves and their ability to send signals to your muscles, an EMG (electromyography) and/or nerve conduction study may be done. These tests give information regarding the electrical activity of a muscle and how quickly the nerve sends its signal to the muscle. Conditions such as trauma to the limbs, carpal tunnel syndrome or herniated discs can be evaluated by this method.
In doing an EMG, surface electrodes or, more commonly, thin needles are inserted into specific muscles to be tested. The muscles’ electrical activity is recorded via wires from the needles when the muscles are resting and contracting. For nerve conduction studies, one electrode is placed over a muscle, and another electrode is placed over a nerve. Electrical impulses are sent through the nerve and the length of time it takes the nerve to conduct the impulse to the muscle is measured. The slower the conduction, the more prevalent a problem.
All these tests give physicians information that can assist in determining how best to treat an injury. Sometimes rest, physical therapy or, in some cases, surgery is recommended. No test is foolproof and interpretations of results can sometimes vary.
In the alphabet soup of diagnostic equipment, only you know your body from A to Z. Use your knowledge to help your healthcare professional help you.