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Ultrasound examination of the shoulder is a fast, relatively cheap and dynamic way of examining the shoulder joint, which is especially informative in diagnosing the state of soft tissue structures (muscles, ligaments), cartilage component and assessing the degree of motor function disorders.
Preliminary preparation for ultrasound scanning of the shoulder joint and adjacent areas is not required.
The examination requires attention to technique and appropriate positioning of the patient. A polypositional dynamic study of the joint is performed in four projections. In this case, in each projection, the joint and all its structures are examined in two mutually perpendicular section planes (longitudinal and transverse). In case of limited mobility of the joint (trauma, pain), the shoulder joint can be successfully assessed comprehensively by moving the ultrasound transducer.
A high-frequency linear transducer (5.5-12 MHz) is required to provide sufficient anatomical resolution.
Shoulder joint
The shoulder joint is the most mobile joint in the body. This mobility provides the upper limb with a huge range of motion: around the sagittal axis – abduction to the horizontal level (further movement is prevented by the coracoid-acromial ligament, called the arch of the shoulder) and adduction; around the frontal axis – flexion and extension; around the vertical axis – rotation of the shoulder inward and outward. When moving from one axis to another, a circular motion (circumductio) is possible in the joint.
This wide range of motion also makes the shoulder joint unstable. This instability is compensated by the muscles of the rotator cuff, tendons, ligaments and the articular lip (labrum glenoidale).
The muscles and ligaments surrounding and strengthening the shoulder joint are subjected to the greatest load. The muscular, tendon-ligamentous apparatus keeps the humerus in the correct position in accordance with the glenoid cavity of the scapula and allows you to perform the entire complex range of movements of the upper limb.
The essence of the method
The ultrasound technique is based on sound waves emitted from a transducer, which then return back from the underlying structures based on the density of that structure. The computer interprets the returning sound waves and creates images that reflect the quality and density of the tissues from which the waves return. When the sound waves are beat back and quickly and with great force, like a blow to a bone, an intensely white image (“hyperechoic”) is seen on the screen. When sound waves collide with a substance that transmits these waves easily and they do not return, like air or liquid, then a dark image (“hypoechoic”) is displayed on the screen.
Research technique
Of course, there is an endless variety of potential methods, but there are fundamentals of shoulder ultrasound technique that all clinicians should adhere to. In most cases, for the most complete assessment of the state of the shoulder joint, patients are examined in several positions: lying on their back (the arm under study is located along the body), sitting with the arm bent at the elbow joint, sitting with the arm hanging freely, sitting with the arm brought to the body with an additional internal or external rotation.
Ultrasound examination of the tendon causes an optical phenomenon known as “anisotropy” (i.e. visualization of the structure of the tendon is directly dependent on the angle of incidence of the ultrasound beam). Therefore, each tendon needs to be scanned in several projections, and each has its own technique.
To make a correct diagnosis, it is important to visualize the various departments and structures of the shoulder along the length and diameter. Ultrasound of the left and right shoulder joint are performed similarly to each other.
The use of a high resolution transducer (7-15MHZ) is essential in assessing the superficial structures of the shoulder joint.
Biceps tendon
Patient position: arm in neutral position, elbow flexed 90 degrees, forearm supported (palm up). The long head of the biceps tendon is visualized in the intertubercular groove. It passes under the transverse humeral ligament and is visible in both transverse and longitudinal sections.
Normal results: The tendon should be located in a bony groove with minimal fluid around it (the tendon sheath communicates with the shoulder joint), and the tendon fibers should be visible without tearing, discontinuity, or thickening.
Visualized pathology of the biceps tendon: dislocations of the biceps tendons, or subluxation, tendinopathies, effusion in the shoulder joint, partial or complete rupture of the biceps.
Muscles that make up the rotator cuff
The rotator cuff of the shoulder joint is a muscular membrane that is located around the head of the humerus, including: subscapular, supraspinatus, infraspinatus and small round muscles.
Subscapularis tendon
Patient position: The arm is held in the same position as above and rotated outward. The tendon of the subscapularis muscle is pulled out. Image planes: tendon m. subscapularis should be traced both longitudinally and transversely. After a longitudinal examination, the transducer is placed in a transverse position (medially) over the head of the humerus with the transducer marker pointing away from the patient’s torso. The transducer is then moved from top to bottom to access the three parts of the tendon i.e. the top, middle and bottom fibers. Dynamic examination: During internal and external rotation of the arm, while the transducer remains stationary, a possible injury to the tendon can be assessed as it passes under the cortex. Transverse views: By rotating the transducer 90 degrees (now craniocaudal) towards the patient’s head, the short axis of the three parts of the tendon can be assessed.
The transducer slowly rises medially towards the lesser tuberosity of the humerus.
Visualized pathology: supraspinal tendinopathy, dynamic subluxation of the tendon of the long head of the biceps, damage to the transverse ligament.
Supraspinatus tendon
Patient position: internal rotation and lengthening of the shoulder. The supraspinatus tendons should be observed both longitudinally and transversely. Most tears occur in the most distal part and therefore this area should be explored with caution.
Normal Findings: The tendon is parallel to the curved contour of the humeral head, flattening when adjacent to the greater tuberosity of the humerus. The tendon has a fibrillar pattern. The subacromial bursa should be seen as a single thin hyperechoic line parallel to the tendon, the presence of fluid (exudation of a hyperechoic line with hypoechoic fluid) is abnormal, as is thickening of the bursa.
Visualized pathology: supraspinal tendinopathy, subacromial bursitis.
Infraspinatus tendon
Image Planes: The infraspinatus tendon should be observed both longitudinally and transversely. Normal results: separation of the infraspinatus tendon from the supraspinatus is so difficult that an arbitrary cut is used at a distance of 1,5 cm from the anterior edge of the supraspinatus tendon; i.e. the first 1,5 cm of the rotator cuff is labeled as the supraspinatus tendon and the next 1,5 cm as the infraspinatus tendon. The thickness of the posterior rotator cuff is significantly less than that of the anterior (3,6 vs. 6 mm), and therefore thinning should not be interpreted as partial tears.
Visualized pathology: tendinopathy, complete or partial tears.
Indications for ultrasound of the shoulder joint
Ultrasound is a valuable diagnostic tool for evaluating the following indications:
- muscle, tendon and ligament damage (chronic and acute);
- bursitis;
- effusion;
- vascular pathology;
- hematomas;
- soft tissue formations such as lipomas;
- to assess the structure of education, for example: dense, cystic, mixed;
- postoperative complications, such as abscess;
- for control during injection, aspiration or biopsy;
- some bone pathologies.
What can be determined by ultrasound of the shoulder joint?
With the help of ultrasound examination of the shoulder joint, it is possible to determine the development of such pathological processes:
- traumatic or degenerative damage to the muscle complex that provides mobility of the shoulder joint – the rotator cuff;
- fractures or fissures of the humerus;
- tenosovinitis or bursitis – various inflammatory diseases of the joint;
- injury or displacement of the humeral process of the scapula;
- rupture of the articular lip – cartilaginous tissue surrounding the cavity of the joint;
- excess or insufficient amount of fluid in the joint cavity;
- connective tissue damage – arthritis;
- muscle atrophy – a decrease in the number of muscles and a decrease in their functionality;
- synovial cyst – a benign formation, which on ultrasound looks like a small darkened area with uneven contours;
- osteoarthritis – a disease during which the cartilage tissue of the joint becomes thinner and loses functionality (usually accompanied by pain and limited mobility);
- inflammation of the synovial sac.
Restrictions on using the method
It is recognized that ultrasound provides practically no diagnostic information for the internal structures of the shoulder joint. Ultrasound is complemented by other forms of examination, including plain X-ray, CT, MRI, and arthroscopy. The method is absolutely safe, therefore it has no restrictions on use in any age group.
What happens during research?
Before starting the diagnosis, the patient is asked to sit or lie down on a special couch. A small amount of a special gel is applied to the skin, which improves the contact of the sensor with the tissues. During the diagnosis, the doctor evaluates the condition of the muscles, tendons and nearby tissues. To assess the state of the joint in dynamics, the patient is asked to change the position of the hand as needed: raise, retract, turn. Typically, the duration of the study is about half an hour, and at the end, the patient is given a protocol with a transcript.
Ultrasound examination of the shoulder joint is comparable in accuracy to MRI. It can be used as a targeted examination, providing fast, real-time diagnosis and treatment in required clinical situations.
Advantages of the method of ultrasound diagnostics of the shoulder joint
The first advantage is that each patient can undergo an ultrasound, since during the examination there are no interference from metal, pacemakers, and there are no restrictions for people with claustrophobia and obesity. Contralateral comparisons, palpation at the site of pathology, and real-time dynamic studies allow for a comprehensive diagnostic evaluation.
The ultrasound method for assessing the musculoskeletal apparatus of the shoulder joint is non-invasive, easy to perform, accessible and highly informative. If we compare ultrasound diagnostics with other research methods, for example, with computed tomography or X-ray examination, ultrasound has a significant advantage in the form of absolute harmlessness. If necessary, ultrasound can be done an unlimited number of times. Additionally, the use of Doppler examination methods expands the possibilities of ultrasound. With the advent of portable ultrasound machines, examinations can essentially be performed anywhere.
Ultrasound has many diagnostic applications for evaluating soft tissues, joints, and bones. Ultrasound can diagnose muscle, tendon, and ligament ruptures and reveal signs of inflammation, such as tendovaginitis.
Ultrasound detects such soft tissue pathology as hematomas, cysts, solid tumors. It can be used to rule out or confirm foreign bodies or infections. Also a big advantage is that the patient does not require any additional preparation before the examination. For bone disorders, ultrasound can diagnose fractures. The results of many studies have confirmed the reliability of the ultrasound research method in the diagnosis of fractures in the area of the bone diaphysis.
Relative contraindications to ultrasound of the shoulder joint are extensive damage to the skin and increased pain when pressed by the sensor. In this case, an MRI or X-ray is performed.