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Authors

  1. James Mattson

Table of Contents

Summary

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Introduction

  • Shoulder pain is a common chief complaint in seeking medical attention, accounting for 8-12% of athletic injuries. The shoulder joint has the largest range of motion of any appendicular joint, and as a result has inherent instability, accounting for 50% of joint dislocations presenting to the emergency room.1,2
  • While X-rays are often the first-line diagnostic imaging for shoulder pain, bedside ultrasonography is emerging as a useful diagnostic tool in select conditions, including both osseous and soft tissue injuries.1
  • Bedside ultrasound has the additional advantage of allowing for dynamic visualization of structures. This assists in evaluation of shoulder mechanics and diagnosis of some specific etiologies of shoulder pain, particularly for soft tissue disorders.3–5
  • Ultrasound is useful in guided procedures of the shoulder, including aspiration, directed nerve blocks for analgesia, or corticosteroid injection.6,7

Ultrasound Probes and Settings

  • For ultrasound of the shoulder, a high frequency linear transducer 10Hz or higher is generally used. For deeper structures such as the posterior glenoid, occasionally a lower frequency curvilinear transducer is used.8
  • Patient positioning
    • The ultrasound examination of the shoulder is best completed with the patient sitting, and the examiner positioned in front or to side of patient.8 If available, a rotating stool can allow for easy patient positioning during examination.9
    • The shoulder examination is completed in multiple positions and with dynamic visualization to allow evaluation of relevant structures. Neutral position consists of the patient resting with arm at the side, and hand with palm up in supination and resting on leg. From this position, the arm can be externally rotated for further evaluation of infraspinatus and biceps tendon (PICTURE). Further examination is done with patient in Crass position, which involves patient placing hand behind their back with shoulder internally rotated, or in modified Crass, which involves patient placing hand on ipsilateral hip with elbow directed posteriorly.3,8
    • Note that depending on patient presentation and degree of discomfort, repositioning the patient for ideal views may not be possible.

Anatomy

  • In musculoskeletal ultrasound, diagnostic point-of-care imaging can often be focused based on the presenting complaint and physical examination. This can be done in the shoulder as well, but with caution as pain in the shoulder can often be referred or diffuse.8 A standardized approach to ultrasound is highest yield in complete evaluation of the shoulder, particularly of the rotator cuff.3
  • Anterior – Biceps tendon and subscapularis
    • With the patient in neutral position, the primary landmark to identify in the anterior shoulder is the tendon of the long head of the biceps within the bicipital groove. In this orientation the biceps tendon can be visualized in short and long axis in between the lesser and greater tuberosities. In short-axis orientation, the tendon can be scanned over its course proximally where it courses over the humeral head and distally as it travels down the bicipital groove (PICTURE). The tendon is evaluated distally until tendon pectoralis major crosses over the biceps tendon to insert on the lateral lip of the bicipital groove. (PICTURE) Rotating the transducer 90 degrees will allow visualization of the tendon in long axis.3,4,8 (PICTURE)
    • A similar approach is used to visualize subscapularis tendon. With the patient in neutral position, the transducer is placed again over the bicipital groove and lesser tuberosity is centered on the screen. The patient then externally rotates the shoulder to bring the tendon of the subscapularis in to view. In this view, the subscapularis tendon can be seen in long axis, then in short axis after rotating the transducer 90 degrees. In short axis, is normal to see hypoechoic striations representing interfaces between tendon bundles (PICTURE). Visualizing the biceps tendon in short-axis as the patient eternally rotates the shoulder allows for evaluating for possible subluxation of the tendon from the bicipital groove.3,8,10 (see Biceps subluxation/dislocation below)
      Superior – acromioclavicular joint and subacromial bursa
      With the patient in neutral position, the acromioclavicular (AC) joint can be located by palpating and placing the probe in a coronal-oblique plane at the distal clavicle. The AC joint is identified by the hypoechoic joint space between the distal clavicle and acromion (PICTURE). From there the transducerthere transducer can be moved laterally in the coronalin coronal planeplan to evaluate for fluid in the dependent area of the subacromial-subdeltoid bursa (PICTURE). The shoulder can then be passively abducted by the examiner, with pooling of fluid in the bursa indicative of subacromial impingement.3,8,10
  • Superior – supraspinatus and infraspinatus
    • The Crass or modified Crass positions are used to anteriorly rotate the greater tuberosity in order to visualize the insertion of the supraspinatus and infraspinatus. In the modified Crass position the transducer is placed on the anterior shoulder in a transverse orientation in order to visualize the supraspinatus tendon in the long axis (PICTURE). Scanning should continue anteriorly until visualizing the intra-articular portion of the proximal biceps tendon (PICTURE). This allows for full evaluation of the anterior portion supraspinatus tendon. The transducer can be rotated 90° to visualize the tendon in short axis. In this orientation, hypoechoic lines may be seen, as fibers from the tendon descend to insert on the greater tuberosity. Moving the transducer posteriorly will allow for visualization of the infraspinatus, which inserts on the middle facet of the greater tuberosity.3,8,10
  • Posterior – infraspinatus, teres minor, posterior labrum, glenohumeral joint
    • With the patient in neutral position, place the transducer just inferior to the scapular spine in an oblique axial plan angled superiorly toward the humeral head. In this orientation the central tendon of the infraspinatus can be traced distally to its insertion on the greater tuberosity. This supplements evaluation in the modified Crass position described above. In this long axis orientation the glenohumeral joint and posterior labrum can be visualized (PICTURE). Sliding the transducer medially is necessary to identify the spinoglenoid notch, which is a potential site for a paralabral cyst. The transducer is then moved inferiorly to visualize the teres minor, and then rotated 90 degrees to visualize the tendons in short-axis.3,8,10

Normal Ultrasound Anatomy

  • The complete sonographic evaluation of the knee will include scanning all 4 quadrants: anterior, medial, lateral and posterior. The anterior knee can be further split into suprapatellar and infrapatellar views. Special attention should be given to quadrants and structures of interest based on clinical suspicion, history and physical examination. 
  • This section will focus on the views and anatomical structures that are of particular interest for Emergency Physicians. However, “additional” views and structures will be introduced that may be beyond the scope of the Emergency Department.
  • Anterior – Suprapatellar
  • Longitudinal view
    Place the transducer just above the patella in the sagittal plane with the probe marker facing towards the patient’s head to obtain a longitudinal view of the quadriceps muscles and tendon as it inserts onto the superior aspect of the patella. Deep to the quadriceps tendon will be the suprapatellar recess, a thin anechoic stripe which communicates with the rest of the joint, the prefemoral fat pad, and the anterior cortex of the distal femur. 
  • The optimal patient position is supine with the knee flexed to 30 degrees with a towel roll in the popliteal fossa. [IMAGE NEEDED]
  • Axial view
  • Rotate the transducer 90 degrees into the transverse plane to obtain an axial view of the quadriceps tendon and the suprapatellar recess. [IMAGE NEEDED] 
  • Anterior – Infrapatellar
  • Longitudinal view
  • From the initial transducer position, slide the transducer over the patella, which should appear as a smooth hyperechoic cortex. Then slide further down just below the patella in the sagittal plane to obtain a longitudinal view of the patellar tendon. Deep to the patellar tendon will be Hoffa’s (infrapatellar) fat pad. The patellar tendon should be tracked all the way to the tibial tubercle. [IMAGE NEEDED]
  • Axial view
  • Rotate the transducer 90 degrees to obtain an axial view of the patellar tendon and Hoffa’s fat pad. [IMAGE NEEDED]
  • Medial
  • Place the transducer on the medial knee in the coronal plane across the joint line to visualize the MCL, medial meniscus, and medial joint line. [IMAGE NEEDED]
    Additionally, the transducer can be moved inferiorly and anteriorly to visualize the pes anserine tendons (sartorius, gracilis, and semitendinosus) and bursa. [IMAGE NEEDED]
  • Lateral
  • Place the transducer on the lateral knee in the coronal plane across the joint line to visualize the lateral meniscus, and lateral joint line. [IMAGE NEEDED]
  • Additionally, when evaluating the iliotibial band, LCL, and biceps femoris tendon, move the transducer from anterior to posterior in a “Z” configuration [5]. [IMAGE NEEDED]
  • Posterior
  • Place the transducer on the posterior knee over the popliteal fossa in the transverse plane to locate the neurovascular bundle, including the popliteal artery and vein and the tibial nerve. Scan cephalad to visualize the sciatic nerve before it bifurcates into the tibial nerve and common peroneal nerve, which runs laterally [5]. [IMAGE NEEDED]
    Additionally, the semimembranosus and the medial and lateral gastrocnemius can be visualized in this position. The transducer can be rotated to the sagittal plane to visualize the posterior joint space and the posterior horns of the menisci. [IMAGE NEEDED]

Pathology

  • Biceps tenosynovitis and glenohumeral joint effusion

    • The tendon sheath of the long head of the biceps brachii tendon is continuous with the glenohumeral joint. Thus, effusion of the glenohumeral joint may often present with sonographic findings similar to biceps tendon tenosynovitis. Differentiating factors include focal tendon sheath distension and localized tenderness in tenosynovitis, in contrast to diffuse anechoic distension that is not sensitive or hyperemic in glenohumeral joint effusion. A joint effusion may also be visualized by distension of the joint capsule when examining the posterior shoulder. Intra-articular loose bodies may also become lodged in the biceps tendon sheath.8,10

    • The posterior shoulder examination can demonstrate a joint effusion and offer a point of ultrasound-guided intraarticular access in the need of diagnostic arthrocentesis. [Link to arthrocentesis chapter]

  • Biceps tendinosis and rupture [NEED IMAGE]

    • Biceps tendinosis appears as heterogeneity or thickening in the biceps tendon. This usually occurs within 3.5 cm of the proximal origin of the tendon. Rupture of the proximal biceps tendon presents as absence of the biceps tendon within the bicipital groove due to retraction of the tendon distally.8,9

  • Biceps subluxation and dislocation [NEED IMAGE]

    • Dynamic ultrasound is useful in evaluating for biceps tendon dislocation or subluxation. This injury occurs when the biceps tendon dislocates medial to the lesser tubercle over the subscapularis tendon. Recurring subluxation can be observed while passively externally rotating the arm.8 This has been described as a result of acute injury, chronic attrition, or a rotator cuff tear extending into rotator interval causing disruption of the biceps stabilizing structures.9

  • Rotator cuff tear [NEED IMAGE]

    • Most rotator cuff tears involve the supraspinatus, but can extend posteriorly to the infraspinatus or involve subscapularis. Visualization of the tendons can help diagnose rotator cuff tears or tendinosis. Rotator cuff tears can roughly be differentiated into partial-thickness or full-thickness tears.8

    • Visualization of the entire rotator cuff is necessary for full evaluation for tears, particularly for the most commonly injured supraspinatus. This may require multiple patient positions (neutral, external rotation, modified Crass).9

    • Ultrasound in a skilled user has similar diagnostic efficacies to MRI in evaluation for rotator cuff injuries.5,11 However, ultrasound has lower accuracy in diagnosing partial-thickness rotator cuff tears than full-thickness tears.12,13

    • Partial-thickness tears are characterized by anechoic or hypoechoic disruptions in the tendon fibers. These tears can be further characterized as articular-sided, bursa-side or intra-substance. Articular-sided tears are most common, often occurring at the level of the surgical neck of the humerus.9

    • A full-thickness tear is characterized by well-defined anechoic or hypoechoic disruptions of the tendon. These may be associated with retraction or atrophy of the proper muscle proximal to the tear,8 a finding referred as the
      “naked tuberosity sign.” These most commonly occur at the anterior portion of the supraspinatus tendon.9

    • Secondary signs of rotator cuff tears may also be visible on ultrasound. These may include cortical irregularities, joint effusion and bursal fluid, or the cartilage interface sign. Cortical irregularity adjacent to a hypoechoic or anechoic irregularity of a tendon may indicate an underlying tear, particularly of chronic nature.8,9 A glenohumeral joint effusion, commonly visualized as and anechoic fluid within the biceps tendon sheath as described above, in combination with fluid in the subacromial-subdeltoid bursa has a high likelihood of rotator cuff tear.3,8

    • Differentiating between rotator cuff tendinosis and a tear can be difficult as both may appear hypoechoic. While rotator cuff tears are well-defined and typically homogenous, tendinosis is generally ill-defined and heterogenous. Tears also typically are associated with cortical irregularities, while tendinosis typically is adjacent to smooth cortex.8

  • Calcific tendinosis [NEED IMAGE]

    • Calcific tendinosis occurs from calcium hydroxyapatite deposition in the tendon. Supraspinatus is most commonly involved. Though etiology remains unclear, it is generally accepted that calcific tendinosis may be asymptomatic, usually are not associated with concurrent acute rotator cuff tears, and the appearance of calcium deposits may change over time.9

    • Ultrasound findings include hyperechoic deposits with posterior acoustic shadowing. Calcifications can form a thick fluid or slurry in 7% of cases, which does not form a significant posterior acoustic shadow but can be differentiated from normal tendon by lacking anisotropy. Angulating the transducer from a perpendicular orientation with tendon causes the tendon to appear more hypoechoic, and this effect is less prominent in cases of calcific tendinosis.8,9

  • Subacromial-subdeltoid bursitis [NEED IMAGE]

    • Fluid can collect in the subacromial-subdeltoid bursa and can be visualized as a 1-2mm anechoic stripe in the plane between the rotator cuff and overlying deltoid muscle and acromion. The presence of hyperemia as indicated by increased signal with power doppler, as well as tenderness in the area are indicative of bursitis.8

    • Causes of bursitis most commonly include subacromial impingement or rotator cuff tear. Isolated bursa involvement may beusually associated with underlying systemic inflammatory conditions such as gout, rheumatoid arthritis, infection, or amyloidosis.8
      Presence of subacromial-subdeltoid bursitis as well as joint effusion has a high likelihood of underlying rotator cuff injury.3,8,9

  • Adhesive capsulitis [NEED IMAGE]

    • Adhesive capsulitis is largely a clinical diagnosis but may have associated sonographic findings. One potential finding is limitation in sliding of the supraspinatus beneath the acromion with active abduction.8 There may also be abnormal hypoechogenicitiy and hyperemia at the rotator cuff interval with thickening of the coracohumeral ligament, though this is not a universal finding.9 Finally, there will often be decreased ability to visualize the subscapularis due to limited external rotation.8

  • Posterior glenoid labrum and paralabral cyst [NEED IMAGE]

    • The posterior glenoid labrum can be visualized as a hyperechoic triangular structure lateral to glenoid. A well-defined hypoechoic or anechoic cleft may indicate a labral tear.8

    • It is important to scan medially along the scapular spine to evaluate for parameniscal cysts, particularly at the spinoglenoid notch and suprascapularsuprscapular notch.8 Parameniscal cysts can compress the suprascapular nerve cause denervation and atrophy of the infraspinatus muscle when located in the spinoglenoid notch, or of both the infraspinatus and supraspinatus when located in the suprascapular notch. This may demonstrate denervation changes such as muscle atrophy and hyperechogenicity.9

  • Shoulder dislocation [NEED IMAGE]

    • Evaluation of the posterior glenohumeral joint can provide rapid assessment for shoulder location. This simple evaluation has high sensitivity and specificity and may allow for rapid confirmation of suspected anterior shoulder dislocations.14,15

    • Glenohumeral separation distance measures the anterior-posterior displacement of the most posterior aspects of the glenoid fossa and head of humerus, when image obtained from posterior glenohumeral approach. A glenohumeral separation distance >0cm (glenoid measured posterior to humeral head) has a high sensitivity for anterior dislocations.16

    • Point-of-care ultrasound can also be useful in suspected posterior dislocations. This injury is easily missed on anterior-posterior radiographs, and axillary views can be difficult to obtain due to pain and difficulty with abduction. Thus, ultrasound is a useful tool in further evaluation when clinical suspicion is high.17

  • Clavicle fracture [NEED IMAGE]

    • To assess for clavicle fracture with ultrasound, one scans along the length of the clavicle to evaluate for a cortical step-off. This is particularly useful in pediatric evaluations to decrease radiation exposure in diagnostic evaluation.1

  • Greater tuberosity fracture [NEED IMAGE]

    • Greater tuberosity fractures appear as a cortical step-off and discontinuity at the junction between the greater tuberosity and humeral articular surface. This is not to be mistaken with cortical irregularities associated with rotator cuff tears which are located focally at the rotator cuff footprint on the greater tuberosity.18

  • Acromioclavicular joint disorders [NEED IMAGE]

    • Sonographic findings for pain attributed to acromioclavicular joint arthritis include joint effusion, narrowing of joint space, and osteophytic changes.8,9 AC joint dislocation can be visualized as well, with displacement of the distal clavicle from the edge of the acromion.

       

Links to ultrasound-guidance procedures

[LINK TO KNEE ARTHROCENTESIS CHAPTER]
[LINK TO KNEE INJECTIONS CHAPTER]

Pearls and Pitfalls

  • Anisotropy is a common artifact that depends on the direction of the ultrasound beam that leads to artificial hypoechoic or anechoic appearance of the tendon when not perpendicular to the tendon. This can be minimized by constantly tilting the angle of the transducer to remain perpendicular to the tendon fibers.19

  • The subscapularis is multipennate, which can be mistaken for tendinopathy or tear. It is important to visualize the rotator cuff tendon in two axes to avoid misdiagnosis.19

Transducer Location

Patient Position

Structures of Interest

Pathology

Anterior

Neutral

External rotation

Long head of biceps tendon

Subscapularis

Biceps tendinopathy

Biceps tendon rupture

Biceps tendon subluxation/dislocation

Joint effusion

Subscapularis tendinopathy

Superior

Neutral

Dynamic abduction

Acromioclavicular joint

Subacromial space

Supraspinatus

Clavicle

Acromioclavicular arthropathy

Subacromial impingement

Subacromial-subdeltoid bursitis

Supraspinatus tendinopathy

Calcific tendinosis

Clavicle fracture

Anterior

Modified Crass

Supraspinatus

Supraspinatus/infraspinatus tendinopathy

Rotator cuff interval

Posterior

Neutral

Infraspinatus

Teres minor

Glenohumeral joint

Posterior labrum

Infraspinatus/teres minor tendinopathy

Glenohumeral joint dislocation

Paralabral cyst