Diagnosis of osteoarthritis: ultrasound examination (ultrasound) of joints

The use of ultrasound (sonography) in rheumatology is a relatively new and promising direction. In the last decade, ultrasound (ultrasound) has been widely used as a visualization technique for examining patients with rheumatic joint diseases, as well as monitoring treatment. This became possible due to the improvement of computer technology and the development of sensors with a higher frequency. Usually sonography is used to assess soft tissue pathology and fluid detection, but also allows visualization of cartilage and bone surface structures.

A number of undoubted advantages - non-invasiveness (in contrast to arthroscopy), accessibility, simplicity, cost-effectiveness (in comparison with CT and MRI) - provided the method of ultrasound of the musculoskeletal system a priority among other instrumental methods for the study of joints and soft tissues. Ultrasound is highly informative in the reflection of fine details of the surface of bones, ligamentous tendon apparatus, and also allows to detect and control inflammatory changes in tissues. The advantage of ultrasound before the radiological method is also that the position of the sensor is determined solely by the goals set by the researcher, therefore, unlike radiography, there is no need for strict positioning of the patient for obtaining standard projections, i.e. The sensor can be polypositional. When carrying out an X-ray study to visualize certain structures in standard projections, you often have to take pictures several times, which leads to an increase in study time, additional expenditure of materials (film), and irradiation of the patient and laboratory personnel. Among the main shortcomings of ultrasound include the inability to visualize the structure of bone tissue, the subjectivity of evaluating the data.

In connection with the above, it is very important to correctly use the possibilities of ultrasound to detect pathological changes in various joints and soft tissues, for which it is necessary to know not only the possibilities of modern diagnostic equipment, but also the ultrasound anatomy of the study area and the most typical manifestations of the disease.

[1], [2], [3]

Equipment and methods of ultrasound

Ultrasound of soft tissues and joints should be performed using a high-frequency linear sensor operating in the range of 7-12 MHz. The use of a sensor with a lower operating frequency (3.5-5 MHz) is limited only by the study of the hip joint and the examination of joints in obese patients. It is also important to choose the right research programs for different joints. Many ultrasonic devices already today contain a set of standard programs for the study of various departments of the musculoskeletal system. Modern ultrasonic devices are also equipped with a large number of additional scanning modes, which greatly expand the diagnostic capabilities of conventional gray-scale scanning, such as native or tissue harmonics, panoramic scanning mode and 3D reconstruction mode. Thus, scanning in the native harmonic mode allows to obtain a more contrasting image of gentle hypo-echogenic structures reflecting the areas of ligament or meniscus rupture, than with conventional gray-scale scans. Panoramic scanning mode allows you to obtain an expanded image of several structures, for example, the structures that form the joint, and display their spatial arrangement and correspondence. Three-dimensional reconstruction provides not only volumetric information, but also gives the opportunity to obtain multi-plane sections of the structures under study, including frontal ones. Fundamentally new is the use of high-frequency ultrasonic sensors, which provide the ability to visualize a variety of echo and depth of structure. These sensors significantly increased the resolution in the zones close to the sensor, while simultaneously increasing the penetrating power of the ultrasonic beam. They use a narrow ultrasonic beam operating in the high-frequency range, which significantly increases the lateral resolution in the ultrasonic focus zone. The possibilities of ultrasonic scanning have also significantly expanded in connection with the introduction of new ultrasonic technologies based on the Doppler effect. New methods of ultrasonic angiography allow visualizing pathological blood flow in the zone of inflammatory changes in organs and tissues (for example, with synovitis).

[4], [5], [6], [7], [8], [9], [10], [11]

Artifacts arising from ultrasound of the musculoskeletal system

All artifacts arising from ultrasound of the musculoskeletal system are divided conditionally into standard ligaments that arise with all ultrasound, and specific ligaments and tendons characteristic of ultrasound.

[12], [13], [14], [15], [16], [17]

Artifacts due to refraction of the ultrasound beam

At the edges of the rounded structures, a distal shadow can appear at the boundary of two different acoustic media. Normally, this effect can be observed with transverse scanning of the Achilles tendon. Intramuscular septa can also give a shadow behind them. Behind the liquid structures there is an effect of amplification of the ultrasonic signal. Therefore, the structures behind liquid-containing objects may look more echogenic than normal. For example, the presence of a small effusion in the synovial membrane of the tendon increases its echogenicity.

[18]

Reverberation

This effect can occur behind highly reflective objects, such as a bone, aperture, resulting in the appearance of mirror or phantom images. In the study of the musculoskeletal system, this effect can be observed behind the fibula. Metal and glass objects cause a reverberation effect, called "comet's tail". As a rule, when studying the organs of the musculoskeletal system, it can be observed in the presence of metal prostheses or metal (glass) foreign bodies.

Refraction

Refraction occurs at the boundary of reflecting media with different sound conductors (for example, adipose tissue and muscles) as a result of the refraction of the ultrasound beam, which leads to the dislocation of the depicted structures. To reduce the refraction, keep the sensor perpendicular to the structures under study.

Anisotropy

Anisotropy is an artifact specific for an ultrasound of the musculoskeletal system, which arises when ultrasound scanning with a linear tendon sensor, when the scanning ultrasound beam does not fall strictly perpendicular to them. On the part of the tendon where there is no exact perpendicular reflection of the ultrasonic beam, zones of reduced echogenicity will appear, which can simulate the presence of pathological changes. Muscles, ligaments and nerves also have a weak anisotropy effect. Decreasing the echogenicity of the tendon leads to a deterioration in the quality of visualization of its fibrillar structure. However, in a number of cases, when it is necessary to visualize the tendon against the background of echogenic tissue, changing the scanning angle, the tendon will look contrasting (hypoechoic) against the background of echogenic fatty tissue.

Degenerative-dystrophic changes in osteoarthritis of other joints are also echographically manifested by narrowing of joint gaps, decreasing cartilage height, changes in periarticular soft tissues and bone articular surfaces with formation during long-term osteophyte flow, as is the case with gonarthrosis or coxarthrosis, so we do not dwell on them in detail .

Thus, ultrasound has advantages over traditional radiography in the early detection of local changes in the joints and near-joint soft tissues of patients with osteoarthritis.

An example of the protocol of ultrasound of a patient with gonarthrosis:

The articular relationships are preserved (broken, lost), without deformation (flattened, deformed). Bony extensions of the femoral and tibia are not determined (there are up to ... Mm, localization). Upper curvature is not changed (enlarged, with the presence of excess of a homogeneous or heterogeneous fluid, the synovial membrane is not visualized or thickened). The thickness of the hyaline cartilage in the area of the patello-femoral joint, the lateral and medial ligament within the norm to 3 mm (reduced, enlarged), uniform (uneven), the structure is homogeneous (with the presence of inclusions, description). The contours of the subchondral bone are unchanged (uneven, with the presence of cysts, surface defects, erosion). The integrity of the quadriceps femoris and its own patellar ligament is not compromised, the ligg.collaterales are not altered, the integrity of the fibers is preserved (ultrasound signs of partial damage or complete rupture). The anterior cruciate ligament is not changed (there are signs of calcification). Menisci (external, internal) - the structure is uniform, the contours are clear, even (ultrasound signs of damage - fragmentation, calcification, etc.).

[19], [20], [21], [22], [23], [24]