ultrasound of the shoulder

Ultrasound of the shoulder is a fast, relatively cheap and dynamic way to examine the rotator cuff and is particularly useful in diagnosing:

• shoulder impingement
• shoulder instability
• rotator cuff disorders

The examination requires attention to technique and appropriate patient positioning. A high-frequency (7-12 MHz) probe is required to give sufficient anatomical resolution, and the examination can be performed from either in front or behind.

Suggested technique

Of course, there is an infinite variety of potential techniques. A 'typical' approach is presented here. It is important to remember about tendon anisotropy in MSK ultrasound. Hence, each tendon needs to be scanned in multiple projections.

Biceps tendon

Patient position: arm in neutral position, elbow flexed 90 degrees, forearm supinated (palm up).

Imaging planes:

• long head of biceps tendon is imaged both transversely and longitudinally in the intertubercular groove as it runs under the transverse humeral ligament
• it is traced superiorly through the rotator cuff interval towards its insertion on the superior labrum and glenoid

Normal findings:

• the tendon should be located in the intertubercular groove, with minimal fluid around it (tendon sheath communicates with the shoulder joint)
• the tendon fibers should be seen without tears (discontinuities), heterogeneity or thickening (beware of anisotropy)

Visualized pathology:

• long head of biceps tendon dislocation or subluxation
• long head of biceps tendon tear
• long head of biceps tendinopathy
• shoulder joint effusion

Subscapularis

Patient position: the arm is kept in the same position as above and is externally rotated, pulling the insertion of subscapularis tendon with it.

Imaging planes: the subscapularis tendon should be traced both longitudinally and transversely:

• longitudinal images: the probe is placed in the transverse position (mediolaterally) over the humeral head with the marker of the probe away from the patient's torso; then, the transducer is moved from top to bottom to access three portions of the tendon: superior, middle, and inferior fibers; then:
  • dynamic study: by internal and external rotation of the arm while the probe is held still, possible impingement of the tendon can be assessed; as demonstrated by bunching of the tendon during internal rotation while it passes under the coracoid process
• transverse images: by turning the probe 90 degrees (now in craniocaudal direction) with the marker towards the patient's head, the short axis of the three portions of the tendon can be assessed by a slow sweeping of the probe from its insertion on the lesser tubercle towards the midline

Normal findings:

• the flat subscapularis tendon can be seen inserting onto the lesser tubercle
• most tears/tendinopathies involve the cranial portions of the tendon, which are also the hardest to visualize
• if the biceps tendon is dislocated, it will lie anterior to the subscapularis tendon which keeps it out of the joint. Indeed long head of biceps tendon dislocation is commonly associated with subscapularis tears, as well as with a history of previous anterior shoulder dislocation

Visualized pathology:

• supraspinatus tendinopathy
• long head of biceps tendon dislocation or subluxation

Supraspinatus

Patient position: Shoulder internally rotated and extended ("reaching to get wallet from back pocket" or "scratching between shoulder blades" positions).

Imaging planes:

• the supraspinatus tendon should be traced both longitudinally and transversely
• remember that most tears occur in the extreme distal portion, therefore this region should be examined with care

Normal findings:

• the tendon parallels the curved contour of the humeral head, flattening out as it inserts onto the greater tuberosity
• it has a fibrillary pattern
• the subacromial-subdeltoid bursa should be seen as a single thin hyperechoic line paralleling the tendon superiorly
• presence of fluid (separation of the hyperechoic line by hypoechoic fluid) is abnormal, as is thickening of the bursa

Visualized pathology:

• supraspinatus tendinopathy
• supraspinatus tendon tear
  • cartilage interface sign
• rotator cuff calcific tendinitis
• subacromial-subdeltoid bursitis

Infraspinatus

Patient position: Patient reaches across their chest and holds the contralateral shoulder with their hand.

Imaging planes: the infraspinatus tendon should be traced both longitudinally and transversely.

Normal findings:

• the separation of the infraspinatus tendon from the supraspinatus tendon is difficult; so much so that an arbitrary cut-off of 1.5 cm from the anterior edge of the supraspinatus is used, i.e. the first superior 1.5 cm of the rotator cuff are designated as the supraspinatus and the next 1.5 cm the infraspinatus tendon
• the thickness of the posterior rotator cuff is significantly less than that of the anterior part (3.6 mm vs 6 mm), therefore thinning should not be interpreted as partial tears

Visualized pathology:

• infraspinatus tendinopathy including tears (note: it is rare for the infraspinatus to be torn without concomitant supraspinatus tears)

Glenoid labrum

Patient position: Same as for infraspinatus and inferior to this for the more inferior part of the posterior labrum. For the anterior part, transverse as for biceps tendon, and for the more posterior part, hand behind the head with shoulder abducted. The literature claims high sensitivity and specificity, especially for the posterior labrum.

Imaging planes: transverse is the most useful.

Normal findings:

• the normal labrum is a sharply demarcated hyperechoic triangle continuous with the underlying glenoid.
• Buford complex (unknown sensitivity/specificity)

Visualized pathology:

• Hill-Sachs lesion
• labral tear: >2 mm hypoechoic zone; vacuum phenomenon between labrum and glenoid; absent labrum; movement of the labrum during dynamic examination
• sublabral foramen (unknown sensitivity/specificity)

Suprascapular notch

Patient position: as for infraspinatus.

Normal findings: small notch in the scapular spine.

Visualized pathology:

• paralabral cyst associated with SLAP lesions
• suprascapular notch ganglion

Acromioclavicular joint

Patient position: either position is fine.

Normal findings: the problematic undersurface of the acromioclavicular joint is, unfortunately, not visible.

Visualized pathology:

• degenerative change of the joint: osteophytes; subchondral cyst formation
• Os acromiale
• joint instability

Dynamic examination

Patient position: depends on which tendon is being interrogated. "Chicken flapping" (abduction and adduction) can demonstrate the supraspinatus tendon sliding under the acromioclavicular joint.

Imaging planes: typically longitudinally along the tendon.

Normal findings: a thin hyperechoic subacromial-subdeltoid bursa should be seen sliding effortlessly between the ACJ and the supraspinatus tendon.

Visualized pathology:

• shoulder impingement
• shoulder instability