Musculoskeletal ultrasound is a non-invasive diagnostic technique to capture images of the muscles, ligaments, tendons, and joints of the body. It is used to diagnose sprains, tears, and other soft tissue injuries.
What is the principle of musculoskeletal ultrasound?
Musculoskeletal ultrasound uses high-frequency sound waves to detect musculoskeletal injuries or other pathological conditions. Since ultrasound scanning captures images in real-time, this method can be used to evaluate both static and dynamic conditions of the musculoskeletal structures.
Mechanistically, a small transducer (probe), which is connected to an ultrasound machine, is used to generate high-frequency sound waves using multiple piezoelectric elements; in addition, ultrasound gel is placed directly on the skin to facilitate the transmission of sound waves from the probe into the body. The sound waves that are bounced back from the tissue are processed via the ultrasound machine to generate images of the target area.
The main advantage of the musculoskeletal ultrasound is its ability to produce dynamic images. This technique is ideal for imaging superficial musculoskeletal structures. Moreover, the technique is cost-effective, fast, and safe, and does not involve ionizing radiation. When superficial imaging is required, ultrasound can achieve extremely high resolution, quite comparable to that of MRI or CT scanning. The fact that implanted metal devices do not interfere with imaging of adjacent tissue is another advantage, though they do not allow the ultrasound to travel through them to image deeper tissues.
What are the uses of musculoskeletal ultrasound?
Musculoskeletal ultrasound is primarily used to evaluate traumatic, inflammatory, and degenerative conditions of musculoskeletal structures including joints, tendons, ligaments, and muscles. This technique is widely used to diagnose tears or inflammation of the tendons, especially the rotator cuff in the shoulder and the Achilles tendon in the ankle.
The technique is also commonly used to detect muscle and ligament tears or sprains. The presence of soft tissue masses with a diameter of less than 5 cm can be easily detected by this technique; moreover, the technique is useful in detecting fluid accumulation within the soft tissue, joint effusions, inflammation of the synovial membrane, and peripheral nerve lesions.
It is not used to pick out causes for a poorly localized pain or other vague symptoms, neither can it detect masses which are too large or too deep within the tissue.
High-quality imaging has enabled musculoskeletal ultrasound to become a preferred tool for diagnosing both benign and malignant soft tissue tumors, hernias, and ganglionic cysts. The technique is also suitable for detecting pathological changes associated with certain diseases, such as rheumatoid arthritis and carpal tunnel syndrome.
In pediatric healthcare, musculoskeletal ultrasound is frequently used to detect hip dislocation, neck muscle deformities, soft tissue masses, and fluid accumulation in the hip joint.
With the use of color flow imaging or color Doppler imaging, ultrasound helps diagnose active inflammations by detecting elevated blood flow in the soft tissue.
Therapeutically, musculoskeletal ultrasound is widely used to direct the needle during injections (as of steroids) into specific joints and adjacent soft tissue to treat joint pain, as well as aspirating fluids from specific target areas. Moreover, the post-treatment healing process can be easily visualized by this technique.
What are the limitations of this technique?
Since the sound waves cannot penetrate bones, this imaging technique is not suitable for evaluating bone-related conditions. It can only be used to analyze the outer surface of bony structures.
The high-frequency sound waves used in ultrasound cannot penetrate the tissue to any significant depth; therefore, deep structure imaging is not possible by this technique. In contrast, low-frequency sound waves are capable of entering deeper into the tissue, but generate images at lower resolution.