Welcome to the Ultrasound Leadership Academy (ULA) summary blog series. This week, we discuss the basics of shoulder ultrasound. The ULA is essentially an online advanced ultrasound education experience put on by the team from Ultrasound Podcast which brings cutting edge learning to emergency medicine personnel through a variety of interactive platforms including video lectures, google hangouts with experts, simulation, live conferences and real time scanning with a pocket-sized ultrasound device known as a Vscan.
Over the next year I will be posting summaries of the key learning points from my experience. If you want to learn more about the program you can visit Ultrasound Leadership Academy or Ultrasound Podcast to see more from the hosts of this awesome program.
Evaluation of the shoulder with ultrasound may appear like a daunting task in the emergency department, however with a strong understanding of the anatomy and an organized approach, the technique will rapidly become more within your realm of comfort. Furthermore, there is good evidence in the literature to support the use of ultrasound to accurately identify multiple shoulder pathologies including shoulder dislocation, rotator cuff tear, clavicle fracture and AC joint separation. For example, a systematic review of the accuracy of ultrasound for rotator cuff tear found it to be up to 96% sensitive for full thickness injuries and 84% sensitive for partial thickness injuries.
Point of care ultrasound is available to us immediately and at little cost, making this an exam that is definitely worthwhile to master in order to assist not only with diagnosis in shoulder complaints but also to allow you to provide patients with more information rather than saying their x-ray imaging is normal and they may need an outpatient MRI.
Let's get started.
When evaluating the shoulder an organized approach will be essential, utilizing systematic identification of key shoulder structures. Our main region of interest will be the rotator cuff but will also include evaluation of the biceps tendon, the gleno-humeral articulation, the AC joint and the clavicle.
As seen above the rotator cuff is made up of four tendons that attach to the proximal head of the humerus to assist with holding it firmly within its articulation with the glenoid.
- Supraspinatus (SS): Located in the suprascapular fossa with attachment at the greater tuberosity of the proximal humerus.
- Subscapularis (S): Located anteriorly with attachment at the lesser tuberosity of the proximal humerus.
- Infraspinatus (IS): Located posteriorly, inferior to the spine of the scapula, attaching to the posterior aspect of the greater tuberosity.
- Teres Minor (Tm): Located just inferior to the infraspinatus, also attaching to the posterior aspect of the great tuberosity.
Other structures of interest that we will be examining include:
- Biceps Tendon (B): Located anteriorly, coursing in a groove between the greater and lesser tuberosities of the humerus.
- AC Joint: This synovial articulation lies superiorly and is usually palpable on clinical exam.
- Subacromial Bursa: Usually located above the supraspinatus tendon and below the coracoid process. It is usually not seen or is very thin but enlarges visibly with pathology.
- Clavicle: Prominent anterior bony structure connecting the scapula to the axial skeletal structure.
- Supraspinatus/Subacromial Bursa
- Biceps tendon
- Infraspinatus/Gleno-humeral Articulation
- AC joint/Clavicle
Probe: Linear high frequency
Positioning: Have the patient sit upright with injured shoulder exposed. It is useful to use a stool with wheels to sit next to the patient to be able to maneuver from anterior examination of the shoulder to posterior examination.
1. The Supraspinatus/Subacromial Bursa
The supraspinatus lies directly under the acromion, so to expose it have the patient place their hand behind their back (Crass maneuver) in order to hyperextend and internally rotate the humerus. This can be uncomfortable for the patient, so a modified Crass maneuver can be also used which involves the patient placing their hand on the ipsilateral hip or buttock region.
Place the probe along the long axis of the tendon as seen above (if in modified crass position the probe will essentially be pointing towards ipsilateral ear). The tendon appears hyperechoic compared to the deltoid muscle superiorly. You may appreciate what is called the 'birds beak' view which shows the supraspinatus tendon tapering off to a sharp point where it attaches to the greater tuberosity of the humerus. You are looking for a smooth contour of the tendon. While you do see some thin black stripes medially on the left image above, remember that tendons display a phenomenon called anisotropy which refers to differing appearance depending on what angle the ultrasound beam is with regard to the tissue. For this reason you must scan through the entire tendon at various angles to ensure these are indeed artifact and not signs of tendon injury.
On this view you will often be able to visualize the subacromial bursa (or lack off). It will lie in the space just superior to the supraspinatus tendon and just inferior to the deltoid. In a normal shoulder it is not visible or is seen as a very thin black stripe. Enlargement of this space will suggest inflammation and pathology.
Remember that after viewing a tendon in long axis, rotate your probe 90 degrees and fan through the entire tendon in short axis. A complete exam will consist of both long and short axis views of each structure of interest.
2. The Subscapularis
The subscapularis is directly anterior so have the patient relax the arm down by their side and place their ipsilateral hand on their lap with palm facing upward. Place the probe slightly more inferior and anterior than you would when viewing the supraspinatus, as shown above. You should be able to visualize the lateral aspect of the subscapularis tendon attaching to the lesser tuberosity of the humeral head. After you identify this, rotate the shoulder externally to allow you to visualize the most medial aspects of the subscapularis which can hide beneath the coracoid process. Rotate your probe 90 degrees and examine the entire tendon from lateral (lesser tuberosity of humeral head) to medial (corocoid process). The subscapularis often demonstrates significant anisotropy so don't be fooled!
3. The Biceps Tendon
The biceps tendon sits right in the groove between the greater and lesser tuberosity. After assessing the subscapularis, move your probe slightly lateral to view the biceps tendon in the short axis (as seen above). The arm will usually need to be slightly externally rotated. You will appreciate a circular structure between the two hyperechoic bony surfaces surrounding it. Since the tendon dives deep to the skin surface, you may appreciate it appearing hypoechoic due to anisotropy. It should normally appear hyperechoic and fibrillar so be sure to fan your probe up and down in order to eliminate this artifact. Assess the tendon proximally until the bicipital groove becomes shallow and distally until your visualize the pectoralis major tendon. Then turn the probe 90 degrees to assess the tendon in long axis. It is important to note that the the biceps tendon communicates with the glenohumeral joint so if you notice fluid surrounding the tendon this can be an indicator of injury within the joint.
4. The Infraspinatus/Gleno-humeral articulation
Place the probe on the posterior aspect of the shoulder just inferior to the spine of the scapula. Your orientation should be oblique, pointing in the same direction as the scapular spine. Laterally your should visualize the smooth hyperechoic contour of the humeral head, articulating medially with the hyperechoic glenoid labrum. The infraspinatus tendon will run just superior to these structures. Note that this view will be useful when assessing for shoulder dislocation as you will be able to clearly appreciate abnormal articulation of the humeral head with the glenoid. If you find it difficult to visualize the distal aspect of the infraspinatus tendon, you can have the patient place their ipsilateral hand on their contralateral shoulder to move the tendon away from shadowing created by the acromion. After long axis assessment, be sure to turn your probe 90 degrees to assess the infraspinatus in short axis.
5. The AC Joint/Clavicle
This last step should be fairly quick and only focused on directly if you are concerned about AC separation or clavicle fracture. Identifying the clavicle is easy, place the probe on top on this palpable bony structure either in short on long axis to visualize any cortical disruption. Start medially and then follow the clavicle laterally until you come to the AC joint. Here you will see the bony cortex of the clavicle, separated by a small hypoechoic space, connecting to the acromion (as seen above). You are looking for widening of this space in AC separation. The joint should be approximately 5 mm in width however it is useful to use the other side for comparison if you are concerned for pathology.
THAT'S IT FOR THIS WEEK
If you are interested in learning more about the ULA learning experience, visit their website below:
More on MSK ultrasound can be found in "Introduction to Bedside Ultrasound," Volume 1 & 2, from Dr. Mallin and Dr. Dawson. If you are interested in purchasing these ebooks for less than $1, visit Ultrasound Podcast Consumables.