Podiatric Diagnostic Tests
Podiatric surgeons use a variety of diagnostic tests to help identify the specific nature of your musculoskeletal injury or condition. Podiatrist also use results of these tests to plan an appropriate course of treatment. Here are some of the most frequently used diagnostic tests for foot and ankle injuries and conditions.
Arthrography is often used to help diagnose the cause of unexplained joint pain. A contrast iodine solution is injected into the joint area to help highlight the joint structures, such as the ligaments, cartilage, tendons and joint capsule. Several X-rays of the joint are taken, using a fluoroscope, a special piece of X-ray equipment that immediately shows the image. You may be asked to fast prior to the exam. During the examination, you may be asked to move the joint into various positions as the images are taken. It is normal to experience some discomfort or tingling during the procedure. If you are or may be pregnant, or are allergic to iodine or shellfish, notify your physician; you may be at a higher risk of complications.
As part of your examination, your podiatrist may order a variety of blood tests. Some conditions, such as rheumatoid arthritis, may be identified by the presence of a specific substance in your blood. You may be asked to fast prior to the exam. Usually a blood test is a simple matter that involves withdrawing a small amount of blood from your arm.
Two very different kinds of tests may be called bone scans. One type tests the density of the bone and is used to diagnose osteoporosis. This type of bone scan uses narrow X-ray beams or ultrasound to see how solid the bone is. No preparation is required for this test, which takes only a few minutes and has no side effects. (See Dual-Photon Absorptiometry, Dual-Energy X-ray Absorptiometry, and Peripheral Bone Density Testing.)
The second type of bone scan is used to identify areas where there is unusually active bone formation. It is frequently used to pinpoint stress fracture sites or the presence of arthritis, infection, or cancer. About three hours before the scan, you will be given a dose of a mildly radioactive substance called “technetium” through an intravenous line (IV). This substance occurs naturally in your body and is used in the bone formation process. The bone scan itself is performed about three hours later, which gives the bone time to absorb the technetium. As you lie on a table, a special nuclear camera takes a picture of your entire body. This process takes 30 to 90 minutes. Areas of abnormal bone formation activity will appear brighter than the rest of the skeleton.
No fasting or other preparation is required. The amount of radioactivity absorbed during a technetium bone scan is minimal, and there are usually no side effects. You may feel some discomfort as the IV line is placed. Some people may feel nauseous. Tell your physician if you are or may be pregnant or are a nursing mother before you schedule this test.
Computed Tomography (CT Scan)
A CT scan (computed tomography) combines X-rays with computer technology to produce a more detailed, cross-sectional image of your body. It may be ordered if your doctor suspects a tumor or a frature that doesn’t appear on X-rays (such as in your collarbone or pelvis) or if you’ve had severe trauma to the chest, abdomen, pelvis or spinal cord. The process is painless. You lie motionless on a table as it slides into the center of the cylinder-like CT scanner. An X-ray tube slowly rotates around you, taking many pictures from all directions. A computer combines the images to produce a clear, two-dimensional view on a television screen. You may need to drink or be injected with barium sulfate or a dye so that certain parts of your body can be seen more clearly. The drink has a chalky taste and may make you feel nauseous; a dye injection may be moderately painful. Tell your doctor if you are pregnant before undergoing a CT scan.
An podiatrist who suspects that you have a blockage in the blood vessels of your legs or arms may prescribe an ultrasound test. An ultrasound uses high-frequency sound waves that echo off the body. This creates a picture of the blood vessels. The Doppler audio system transmits the “swishing” sound of the blood flow. This is a noninvasive test that has no side effects.
A clear jelly is applied to the skin over the blood vessels being tested. The technician uses a sensor that looks like a microphone. The sensor is placed against the skin and moved up and down across the area being tested. The technician will apply pressure every few inches to see if the blood vessels change their shape. The test takes about 30 minutes, and most people experience no pain or discomfort.
An electromyography (EMG) records and analyzes the electrical activity in your muscles. It is used to learn more about the functioning of nerves in the arms and legs. For example, a fracture of the upper arm bone (humerus) may tear or pinch the radial nerve. An EMG can be used to identify the damage if nerve function doesn’t return within 4 months of the injury.
During an EMG, small, thin needles are placed in the muscle to record the electrical activity. When the needles are inserted, you may feel some pain and discomfort. The doctor will ask you to relax the muscle and then to tense it slightly. The electrical signals generated by your muscle are broadcast on a TV-like screen. When the needles are removed, you may experience some soreness and bruising, but this will disappear in a few days. There are no long-term side effects. If you are taking blood-thinning medications, have lung disease or are at risk for infection, tell the physician who is conducting the test. On the day of the test, do not put any lotions or creams on the area to be tested and do not wear any jewelry. Usually, you can get the results immediately after the test.
Flexibility tests are used to measure the range of motion in a joint and are often part of the physical examination. They may be used to help determine whether you have a muscle imbalance or arthritis in a joint. They may also be used to help determine the progression of a condition such as shoulder impingement or a sprain. There are several different kinds of flexibility tests, geared to specific joints and muscles. Your doctor may ask you to reach or bend or to move the affected extremity in a certain way. No preparation is required, and normally these tests are not painful.
Intrathecal Contrast Enhanced CT Scan
This test uses contrast dye to better visualize the spinal canal and nerve roots in the spine. It may be used to help diagnose back problems such as spinal stenosis, particularly in patients with pacemakers or others who cannot have an MRI. The physician applies a numbing medication to the skin, which may sting for several minutes. The doctor uses X-ray guidance to inject a very low dose of contrast fluid (dye) into the spinal fluid. The CT scan is then administered. (See Computed Tomography.) Although no special preparations are required, strict bed rest is necessary for at least 24 hours after the test to prevent spinal headaches. These severe headaches can occur because some of the fluid that surrounds the brain and spinal cord may leak out through the injection site. The test itself may take several hours because it may take that long for the dye to reach the area of interest.
Joint Aspiration and Analysis
Joint aspiration may be both a diagnostic test and a treatment option. In conditions such as bursitis, there is a fluid build-up that results in swelling and pressure. A similar fluid build-up around the joints can occur with injuries and arthritis.
Aspiration, or removing the fluid through a syringe, can reduce swelling and relieve pressure. The doctor will swab the skin with an antibacterial solution before inserting the aspirating needle. You may feel some pressure and pain as the needle is inserted, but this should be relieved as the fluid is removed.
After the test, your doctor may send the fluid to a laboratory for analysis. In an injury situation, there may be blood present in the fluid or fat droplets from bone marrow, which indicates the presence of a fracture. The analysis can also determine if the fluids result from an infection or an inflammatory response.
Laboratory studies of blood, urine or joint (synovial) fluids are used to identify the presence and amount of chemicals, proteins, and other substances. Your doctor may order various laboratory studies depending on what he or she finds during the initial examination. For example, laboratory studies can identify the amount of uric acid in the blood, which is an indicator of gout. A high white blood cell count in joint fluid may indicate severe inflammation or infection. Laboratory tests are usually required before surgeries to identify medical abnormalities.
You may be required to fast for a specific number of hours before donating samples for a laboratory test.
Magnetic Resonance Imaging (MRI)
An MRI (magnetic resonance image) uses magnetic fields and a sophisticated computer to take high-resolution pictures of your bones and soft tissues, resulting in a cross-sectional image of your body. It can be used to help diagnose torn muscles, ligaments and cartilage, herniated disks, hip or pelvic problems and other conditions. As with a CT scan, you lie on a table that slides into the tube-shaped MRI scanner. The MRI creates a magnetic field around you, then pulses radio waves to the area of your body to be pictured. The radio waves cause your tissues to resonate. A computer records the rate at which your body’s various parts (tendons, ligaments, nerves) give off these vibrations, and translates the data into a detailed, two-dimensional picture. You won’t feel any pain while undergoing an MRI, but the machine may be noisy. An MRI takes 30 to 90 minutes, and is not available at all hospitals. Tell your doctor if you have implants, metal clips or other metal objects in your body before you undergo an MRI scan.
Because muscles are soft tissues, they do not appear on X-rays. So muscle testing is an important part of the physical examination. Weakness in a muscle may indicate injury to the tendons that connect the muscle to bone, injury to the nerves that enervate the muscle, or a generalized weakness of the muscle itself from disuse.
To test the strength of your muscles, your physician may ask you to move in certain ways while he or she applies a resistive force. For example, your physician may ask you to sit in a chair and then attempt to raise one knee as the doctor presses down on your upper leg. Or, your physician may hold your elbow at a 90-degree angle and ask you to bend your wrist down. Measuring grip strength by asking you to squeeze the doctor’s hand is another type of muscle test.
Nerve Conduction Study (NCS)
Nerve conduction studies are often done along with an electromyogram to determine if a nerve is functioning normally. It may be recommended if you have symptoms of carpal tunnel syndrome or ulnar nerve entrapment. The doctor conducting the test will tape wires (electrodes) to the skin in various places along the nerve pathway. Then the doctor stimulates the nerve with an electric current. As the current travels down the nerve pathway, the electrodes placed along the way capture the signal and measure its speed. In healthy nerves, electrical signals can travel at speeds of up to 120 miles per hour. If the nerve is damaged, however, the signal will be slower and weaker. By stimulating the nerve at various places, the doctor can determine the specific site of the injury. Nerve conduction studies also may be used during treatment to test the progress being made. Although you may initially be startled by the suddenness of the stimulation, it is not usually painful and most people are comfortable during the testing procedure. The shock is similar to one received when you touch a doorknob after walking across carpeting.
Palpation means touching. During the physical examination, your doctor may feel your joints to see if they are warm or swollen, signs of inflammation. He or she may apply pressure to a muscle or joint to identify an area of tenderness. Palpation can also be used to identify the location of growths such as tumors or cysts. A physician may place a hand over a joint and ask you to move the joint, particularly if you complain of a “popping” or “snapping” sensation. This enables the physician to feel the tendons as they move over the joint. If you have a joint dislocation, the doctor may palpate the area before attempting to realign the bones.
Your physician can tell a lot about your health simply by looking at you. Obvious signs and symptoms include weak (atrophied) or asymmetrical muscles, improper alignment, swelling, changes in skin color (such as bruises or redness that might indicate inflammation) and growths such as cysts, calluses or corns. But the physical examination is much more than just a cursory look. It can also involve gait analysis (how you walk), palpation, muscle testing, flexibility (range of motion) testing, reflex response, and laboratory tests such as a complete blood count and urine analysis.
X-rays (radiographs) are the most common and widely available diagnostic imaging technique. Even if you just complain about a sprain in your wrist or ankle, your doctor will probably order radiographs to make sure no bone is broken. X-rays are always used for fractures and joint dislocations, and may also be recommended if your doctor suspects damage to a bone or joint from other conditions such as arthritis or osteonecrosis (bone cell death). The part of your body being pictured is positioned between the X-ray machine and photographic film. As you hold still, the machine briefly sends electromagnetic waves (radiation) through your body. This exposes the film, creating a picture of your internal structure. The level of radiation exposure from X-rays is minimal, but your doctor will take special precautions if you are pregnant. Bones, tumors and other dense matter appear white or light because they absorb the radiation. Soft tissues and breaks in bone let radiation pass through, making these parts look darker. Sometimes, to make certain organs stand out in the picture, you are asked to drink barium sulfate or be injected with a dye. Several X-rays from different angles may be needed. If you have a fracture in one limb, your doctor may want a comparison X-ray of your uninjured limb. Your X-ray session will probably take 10 to 15 minutes; no specific preparations are required.
Range of Motion Testing
Range of motion tests may also be called flexibility tests. They are used to measure how well you can move a joint. Some joints like the thumb and shoulder have a wide range of motion, almost a complete circle. Other joints like the knee are like hinges and have a more limited range of motion. Range of motion tests may be active or passive. In active tests, you do all the movement. In passive tests, the doctor will hold the extremity and move it. He or she may also hold the next joint steady to isolate the movement of the joint being tested. For example, while you are seated, the doctor may hold your lower leg still while moving your heel in and out. (See Flexibility Tests.)
A treadmill stress test measures the effectiveness of your cardiovascular system (your heart, lungs, and blood vessels). However, because your bones, muscles and connective tissues (ligaments and tendons) are constantly responding to stress (pressure or force), your podiatrist may use applied stress to measure their response. For example, your doctor may hold your lower leg still with one hand and move your heel up and around with the other. This motion applies stress to the ligaments connecting the heel and your lower leg. Excessive or asymmetrical motion indicates that your ligaments are overstretched or loose.
This is the same kind of test as the Doppler ultrasound, but without the audio effect.