Ultrasound of the Musculoskeletal System
Authors: Bianchi, Stefano, Martinoli, Carlo
After the biceps has been examined, the patient is asked to rotate the arm externally in order to evaluate the subscapularis tendon on the anterior aspect of the shoulder. This maneuver stretches the subscapularis and helps to move its tendon from underneath the coracoid process into a more superficial position for an adequate examination (Fig. 25). Dynamic scanning during passive internal and external rotation with the arm adducted may also be helpful to assess the integrity of the subscapularis. While the arm is in external rotation, the examiner must remember to neutralize the tendency for the patient to lift and abduct the elbow from the lateral chest wall. This can be easily avoided by keeping the hand in supination while rotating the arm externally. Conditions limiting external rotation, such as shoulder casting, may lead to a poor delineation of the anterior structures. Any of these constraints should be indicated in the report.
Fig. 25 a–f. Subscapularis tendon. a,d Gross cadaveric views over the subscapularis tendon after removal of the deltoid and the structures forming the coracoacromial arch with b,e corresponding long-axis 12–5MHz US images obtained in vivo while keeping the arm a,b in neutral position and c,d in external rotation. In the cadaveric images, observe the relationship of the subscapularis tendon (double arrow) with the long head of the biceps tendon (asterisks), the coracoid process (Co) and the conjoined tendon of the short head of the biceps and the coracobrachialis (arrow). In neutral position and, even more, in internal rotation, the US appearance of the subscapularis tendon (arrowheads) appears artifactually hypoechoic (curved arrow) due to its oblique course from surface to depth until it disappears, for the most, underneath the coracoid. In contrast, in external rotation (see also insert in d), the tendon is repositioned in a more superficial and lateral location for an adequate examination. Note the insertion of the subscapularis tendon into the lesser tuberosity (LT). The gray vertical bars indicate the overall tendon extension as it appears in the US images. c,f Schematic drawings illustrate the relationship between the probe and the subscapularis tendon (in black) while the arm is kept c in neutral position and f in external rotation (curved arrow).