Anatomical review:
1. Patient seated faceing towards you. Arms resting on knees. Hands supinated.
2. AC joint:
- Acromion and clavicle must be at the same level
- AC joint space 2-4 mm normaly
- Looking posteriorly, you can visualize the Supraspinatus muscle
3. Long head of the biceps tendon
Fluid surrounding the biceps tendon within the tendon sheath is a fairly sensitive indicator of glenohumeral pathology, though as this space communicates with the shoulder capsule, such pathology is not necessarily limited to the biceps tendon and may represent a sign of synovitis or adhesive capsulitis.
Medially find the Subscapularis muscle:
4. Subscapularis muscle
The subscapularis tendon is imaged in the same position as the biceps tendon, with the transducer placed more medially. Slight external rotation of the glenohumeral joint is helpful to elongate the tendon and allow more sensitive evaluation for tears. Images obtained during dynamic maneuvers in which the radiologist performs passive internal and external rotation of the shoulder with the elbow flexed 90 degrees helps to assess normal motion of the tendon, and allows further evaluation for tendon tears which will typically become more conspicuous with external rotation. Dislocation of the biceps tendon medially from the bicepital groove, indicative of full thickness tear of the transverse ligament of the supscapularis, may also be inapparent until passive external rotation.
Superiorly finde the supraspinatus muscle:
5. Supraspinatus muscle
These images are obtained in the modified Crass position, in which the patient extends and externally rotates the glenohumeral joint by placing the palm of his or her hand on the posterior aspect of the ipsilateral iliac wing and projects the flexed elbow joint posteriorly. This allows better visualization of the supraspinatus tendon, as in this position it will extend lateral to the acromion. Rotator cuff tears occur most commonly in this tendon, and are usually seen as hypoechoic defects in the contour of the tendon. Partial thickness tears can involve either the superficial (bursal) or deep (articular) surfaces of the tendon, and may be seen as either a mixed hypo- and hyperechoic focus or a solely hypoechoic focus extending to either tendon surface. Tears usually occur in the region of the critical zone, an area of relative avascularity within the tendon approximately 1 cm proximal to its insertion.
6. Infraspinatus muscle
Place the transducer over the posterior aspect of the glenohumeral joint with the arm in
the same position described at point-2 (or with the hand on the opposite shoulder) and
increase the depth to include the structures of the posterior fossa within the field-of-view
of the US image. Use the spine of the scapula as the landmark to distinguish the
supraspinous fossa (transducer shifted-up) from the infraspinous fossa (transducer
shifted-down) on sagittal planes.
