Rheumatologists and other doctors who diagnose and treat arthritis and rheumatic diseases have a new helper: ultrasound. Most of us think of ultrasound in connection with obstetrics, as a means to visualize fetuses in utero, but it’s been used for many years to visualize different parts of the body. In the past 10 years, however, ultrasound has become firmly established as part of the arsenal of weapons in the fight against many types of crippling and painful arthritis.
Imagine yourself in your doctor’s office, wondering whether you have one of the 100 types of arthritis. Your doctor will no doubt have discussed your history, completed an extensive examination, and ordered blood and other tests based on what type of arthritis you might have. Nowadays, one of those tests might be a musculoskeletal ultrasound, a non-invasive examination of a joint or part of a joint that could shed light on a possible diagnosis. Luckily for you, no preparation is needed, no pain is expected, and answers are quickly available.
In addition to helping identify a specific arthritis diagnosis, ultrasound may be used to identify physical changes occurring in a joint and may provide a baseline so improvement and change in the involved area can be verified. An ultrasound exam could be part of a treatment regime or might be ordered before treatment has begun. In addition, if an injection into the joint is required, ultrasound makes it easier and more accurate.
Let’s look at the definition of ultrasound, its history, and its history in rheumatology. Musculoskeletal ultrasound is relatively new, so we’ll review the guidelines for use, the training for ultrasound technicians and physicians, and the appropriate indications for use. Finally, we’ll examine the success of musculoskeletal ultrasound and its future in rheumatology.
What is ultrasound?
Ultrasound uses high-frequency sound waves to view internal body structures as a means of diagnosis without the use of invasive techniques. An ultrasound device bounces sound waves off internal organs, soft tissues, and body cavities and reads the “echoes,” or reflected sound waves, which are converted into a picture called a sonogram.
History of ultrasound
In the 18th century, Lazzaro Spallanziani, an Italian biologist, noticed that bats could avoid flying into string strung across a dark room. In his investigation, the biologist first covered the eyes and later the ears of the bats he was studying; he discovered the bats were able to avoid the strings when their eyes were covered, but when their ears were covered, they could not. The bats were actually “seeing” by hearing. Although Spallanziani knew hearing was the answer, he was not aware that ultrasound was what made this possible.
By 1843, Austrian astronomer, physicist, and mathematician Christian Doppler noticed that a sound source, called a mechanical wave, changed in frequency in relation to the movement between the source and an observer. This phenomenon, now known as the “the Doppler effect,” has applications in astronomy, radar, and weather forecasting. Modern ultrasound became a reality when the military developed sonar as a navigation aid for submarines during World War I. Subsequently, submarines and ships used sonar to locate enemy submarines in the ocean near and below them, helping identify enemy submarines near our shores.
Probes for medical purposes were used as early as 1880, and medical diagnostics began in 1942, when neurologist Karl Dussik used ultrasound to help identify brain tumors and ventricles. Soon thereafter, Scottish obstetrician Ian Donald was using ultrasound with the help of an engineer named Tom Brown to look for masses in the abdomen. Nowadays, doctors use an ultrasound beam to measure many body processes, including velocity of blood flow, such as that seen in swollen inflamed synovial tissue.
History of ultrasound in rheumatology
Ultrasound was first used to diagnose musculoskeletal problems in 1972, to differentiate between a thrombophlebitis or a Baker’s cyst. Thrombophlebitis is an inflammation of a vein that causes a blood clot to develop; Baker’s cyst is a collection of fluid caused by swelling in the knee joint that causes pain in the back of the knee that extends into the calf muscle. A one-way duct allows the fluid to move into the calf, but it does not allow it to return into the joint capsule, resulting in pain, heat, and hardness in the calf of the muscle. The two conditions feel similar to both patient and physician, so it’s a difficult differential diagnosis to make, but treatment is very different, so a correct diagnosis is crucial.
By 1978, a radiologist named Peter Cooperberg used ultrasound to visualize synovitis, an inflammation and thickening of the lining of the joint. By 1981, ultrasound imaging was being used to see inflammation in smaller joints, ligaments, tendons, rheumatoid nodules, cartilage, bursas, and bone surfaces. It was also used to assist physicians with joint injections, in which a needle is inserted into a joint capsule either to remove fluid for examination or to inject medications.
By 1992, ultrasound allowed physicians to see inflammation of the synovia in a hip joint that looked normal when imaged with a traditional X-ray. The ultrasound could also scan for expected cartilage thickness in joints of patients with osteoarthritis and rheumatoid arthritis. By 1995, inflammation of blood vessels could also be seen, enabling identification and diagnosis of vasculitis, an inflammation in small and large vessels. Just as importantly, as ultrasound has gained popularity and been refined to provide higher-quality images that are more easily interpreted, ultrasound scanners have become more affordable and thus more accessible to most rheumatology offices.
Ultrasound guidelines in rheumatology
To insure proper use of ultrasound for musculoskeletal issues, standards needed to be developed. In 2001, The Annuals of Rheumatic Disease published guidelines for musculoskeletal ultrasound in rheumatology, compiled by Backhaus, et al. Guidelines were developed for joints, joint areas, joint tissue, issues needing diagnosis or observation, and positioning of the joint to be used. They now include information for scans of the shoulder, elbow, hand, knee, hip, ankle, and heel and foot joints, with pictures of the position of the joint during the ultrasound, the location and positioning of the probe, and examples of expected pictures. These are available in print and as PowerPoint slides.
Ultrasound exams often are used to confirm a physician’s suspicions regarding joint problems: complete or partial tears, dislocations, hematomas, erosions, lesions, inflammation of bursas, tendons, and synovia, compressions, ganglions, and calcification. Scans can be accomplished with the joint in various positions of extension and internal rotation: bent and straight, and from all sides, front, or back of the joint. The position chosen depends on the problem the doctor wants to confirm, learn more about, or treat.
For example, the guidelines for a wrist exam for carpal tunnel contain very specific criteria for diagnosis.
• Carpal tunnel: diagnosis of tenosynovitis, morphostructural (see sidebar) changes of median nerve and/or ganglion.
• Involvement of the extensor tendons: diagnosis of tenosynovitis, alteration of extensor tendons, rheumatoid nodules, ganglions.
• Radio-ulno-carpal joint involvement: diagnosis of synovial proliferation, effusion, ganglions, lesions of triangular fibrocartilage complex, or bony lesions.
• Position of the patient: Have patient sit, place his/her hand on top of thigh or examining table or pillow, and actively flex (bend) and extend (straighten) fingers during examination.
As experience with ultrasound grew, rheumatology ultrasonographers interested in providing additional guidance created a task force (OMERACT). Their work, announced in 2005, was titled “Outcome Measures in Rheumatology.” The task team initially developed definitions and later a scoring system for synovitis and an ultrasound joint count. Because ultrasound originally was used mainly to improve the understanding and treatment of rheumatoid arthritis, the detection, grading of severity of inflammation, and evaluation of response to treatment of synovitis received the most attention.
As ultrasound equipment improved, doctors hoped to detect increased blood flow in the synovia (see sidebar) that would correspond to actual inflammation in the joint. When compared to magnetic resonance imaging (MRI) and actual examination of the tissues, the Doppler properties of ultrasound examination provided an accurate representation of inflammation. At first, only black and white images of inflammation were available; now color imaging correlates with the blood flow of inflamed tissue.
In 2012, after years of use and in recognition of perceived success of ultrasound in rheumatology, the American College of Rheumatology (ACR) published a report in Arthritis Care and Research to confirm the reasonable use of musculoskeletal ultrasonography in rheumatology in clinical practice.
Reliable information is crucial, so the expertise and experience of the operator of the ultrasound machine are vitally important. Operators are trained in principles of sound waves and knowledge of human anatomy, the positioning of patients, the location and placement of the ultrasound probe, and the interpretation of Doppler images. The combination of ultrasound images, the clinical history, and physical examination of the patients will help confirm and/or enhance the ultrasound images and further aid in diagnosis and treatment. In the United States, training courses now provide hands-on experience, and ongoing local training is also essential. When an ultrasonographer works closely with a clinician such as a rheumatologist, his or her expertise in the area of musculoskeletal ultrasound grows, but while some physicians still work with ultrasonographers, most scans are now executed by trained rheumatologists.
Ultrasound equipment used in rheumatology is similar to that used for obstetrics and abdominal visualization such as examination for gallstones in the gall bladder. It includes the ultrasound machine with touch and flat screens and probes that are sometimes called “hockey sticks”: large ones for large joints and smaller ones for smaller structures such as tendons and finger joints. Ultrasound gel provides good contact between the ultrasound probe and the patient’s skin. The machines have become smaller, allowing them to be moved between patients’ rooms in clinics or doctors’ offices. High- and low-frequency machines are available. High-frequency linear transducers produce the best images of tendons, ligaments, and small joints. Low-frequency transducers are better suited for larger, deeper joints such as hips or shoulders.
Most common uses
Although the guidelines outline several uses for musculoskeletal ultrasound, physicians most commonly use ultrasound for bursitis, tendonitis, and rheumatoid arthritis.
• Bursitis: Bursas are sacs of fluid located near joints that help lubricate areas where tendons may rub against bones. The rubbing can cause inflammation and pain. The swelling and pain may be so uncomfortable that the patient does not use that joint normally, which can lead to permanent loss in the joint’s range of motion. Injecting the inflamed bursa with cortisone helps reduce the swelling, which stops much of the rubbing once the bursa shrinks and allows the joint to move normally. Injection into the bursa can be a problem because the doctor may be unable to locate the troublesome bursa well enough to properly inject the medication. Using ultrasound, the physician can locate the bursa more accurately, thereby increasing the chances of success. Sometimes joint areas contain a number of bursa, and again, ultrasound can help the physician determine which bursa is the problem.
• Tendonitis: Tendons are long, narrow strips of collagen tissue that connect muscles to bones. Strain, trauma, or repeated rubbing of the tendon on a bony prominence can cause it to become inflamed. Cortisone injections can help reduce the inflammation, but the medication must be deposited inside the tendon with the needle and in the correct area where the swelling and inflammation is occurring. Ultrasound images can help confirm that the tendon is swollen and inflamed and identify the best location for an injection.
• Rheumatoid arthritis (RA): Part of the joint deterioration found in rheumatoid arthritis occurs in the cartilage at the ends of the bones. Erosion of the cartilage usually starts small, but it can grow until little to no cartilage is left to cushion the ends of the bones and allow for normal smooth gliding of the two surfaces of the bones as they move—and once the cartilage is gone, the joint becomes deformed and dysfunctional. If a physician suspects RA, ultrasound can be used to determine whether early joint erosion has occurred, and seeing the erosion can influence the treatment plan, such as the recommendation of stronger medication. Follow-up ultrasounds can identify improvement or further deterioration and support the need for continuing or changing the treatment regimen for success.
Not recommended for OP screening
Although portable ultrasound machines have been and may still be used in screening for osteoporosis, their readings have not correlated well with actual Dual Photon Absorptimetry Xray (DEXA) scans, which can demonstrate the existence of normal bone mass, osteopenia, or osteoporosis. DEXA, considered the best scan for determining that metric, needs to be completed in conjunction with education and prescribed treatment. Small, portable radiographic scanners are available for screening, but they’re more difficult to transport and require a physician’s or nurse practitioner’s prescription for the screening.
Frequency of use in rheumatology
Ultrasound, used in musculoskeletal diagnosis for more than 30 years, has become routine in rheumatology as well. A study of rheumatologists in practice published in Rheumatologia Clinica indicated that more than 50% use ultrasound regularly. Its popularity has increased because of its ability to let physicians visualize the site of the problem and learn more about what’s going on. In the past, physicians had to rely on palpation rather than any type of visualization. Now swelling of various structures can be observed even when joint movement is limited, and the scan can help locate the problem prior to and in preparation for a joint, bursa, or tendon injection.
Additionally, recent technological developments, increases in documented success, improved training, and lowered costs have combined to make the use of ultrasound more accessible to more rheumatology practices. Courses are also available in the United States, and the official European League Against Rheumatism website, www.eular.org, lists courses available for training in ultrasound throughout the world. However, while Medicare covers ultrasound exams, only about 50% of other insurance companies cover the procedure for musculoskeletal or rheumatologic use.
As the technology is refined further, ultrasound scans are expected to include more color Doppler images and more guidelines in the use of ultrasound for the less common types of arthritis: Sjogren syndrome, Wegener’s granulomatosis, systemic sclerosis, gout, and pseudogout. Power Doppler bubble intravenous contrast agents are being developed to increase sensitivity and improve images. On the horizon are 3D and 4D ultrasound, elastography (a visual record of changes in tendon or tendon fiber flexibility, which demonstrates degeneration), and fusion imaging, in which CAT scans and MRIs are combined with ultrasound.
As ultrasound becomes more sophisticated, useful, and accessible, it will provide more physicians with the opportunity to provide faster and more accurate imaging of joints and related structures. These can assist with early detection of joint inflammation, assessment of ongoing disease activities and the ability to monitor the patient’s response to various therapeutic modalities and treatments. Coverage by more insurance companies will help make it more available to patients.
Dr. Amy Evangelisto, a rheumatologist in clinical practice at Arthritis, Rheumatic, and Back Disease Associates in South Jersey, has been on the forefront of using scans and training other physicians in musculoskeletal ultrasound. In the past 10 years, she has helped promote the use of ultrasound in rheumatology by training rheumatologists throughout the United States. Evangelista says ultrasound should be part of the required curriculum in medical training. Currently, only some doctors are trained during their fellowship training in rheumatology; most receive their training by taking special certification courses. “Ultrasound has helped rheumatologists understand rheumatic disease and take better care of their patients,” Evangelisto says. Given that, we can expect to see ultrasound usage increase.