Ultrasound of the shoulder
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Ultrasound of the shoulder is a fast, relatively cheap, and dynamic way to examine the rotator cuff and is particularly useful in diagnosing:
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.
Of course, there is an infinite variety of potential techniques. A "typical" approach is presented here. It is important to remember tendon anisotropy in MSK ultrasound. Hence, each tendon needs to be scanned in multiple projections.
Long head of biceps
Patient position: the arm is in a neutral position, elbow flexed 90°, forearm supinated (palm up).
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)
long head of biceps tendon dislocation or subluxation
Patient position: the arm is kept in the same position as above and is externally rotated, pulling the insertion of the 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:
transverse images: by turning the probe 90° (now in the 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
the flat subscapularis tendon inserts 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
Patient position: shoulder internally rotated and extended ("reaching to get wallet from back pocket" or "scratching between shoulder blades" positions).
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
the tendon parallels the curved contour of the humeral head, flattening out as it inserts onto the greater tubercle
it has a fibrillary pattern
the subacromial-subdeltoid bursa should be seen as a single thin hyperechoic line paralleling the tendon superiorly
the presence of fluid (separation of the hyperechoic line by hypoechoic fluid) is abnormal, as is thickening of the bursa
Patient position: the 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.
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
infraspinatus tendinopathy including tears (note: it is rare for the infraspinatus to be torn without concomitant supraspinatus tears)
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.
the normal labrum is a sharply demarcated hyperechoic triangle continuous with the underlying glenoid.
Buford complex (unknown sensitivity/specificity)
sublabral foramen (unknown sensitivity/specificity)
Patient position: as for infraspinatus.
Normal findings: small notch in the scapular spine.
Patient position: either position is fine.
Normal findings: the problematic undersurface of the acromioclavicular joint is, unfortunately, not visible.
osteoarthritis characterized osteophytes; subchondral cyst formation
this is a common incidental finding 13
tenderness to palpation may be helpful
joint instability 2
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 acromioclavicular joint and the supraspinatus tendon.