The first documented protocol for using musculoskeletal (MSK) ultrasound to evaluate the shoulder was published in 1984 by Middleton et al. Since 1984, there have been ongoing advances in ultrasound imaging technology, and techniques that have increased the utility of MSK ultrasound for shoulder evaluation. In 2013, the Society of Radiologists in Medicine recommended MSK ultrasound as the primary imaging modality for rotator cuff disease.
Using ultrasound as a primary imaging modality to evaluate shoulder anatomy has several advantages for clinicians and patients. Ultrasound can be done in any clinical exam room. In a few minutes, a clinician can make a diagnosis and, if necessary, use ultrasound to guide injections and procedures. The ultrasound images can be used in real time to inform patients about their shoulder pathology. There are no known side effects from ultrasound imaging, and all patients can have ultrasounds regardless of prior surgery. The financial savings from using ultrasound as the initial imaging modality for shoulder evaluation are significant and have been previously documented.
The most significant barrier to more rapid adoption of MSK ultrasound as the primary imaging modality for shoulder evaluation is the need for clinician training. The addition of MSK ultrasound training in residency and fellowship programs has led to more clinicians being capable sonographers. There are many postgraduate training courses and seminars that give the practicing clinician opportunities to hone their sonography skills. Organizations such as the American Institute of Ultrasound in Medicine (aium.org), the European League Against Rheumatism (eular.org), and the European Society of Musculoskeletal Radiology (essr.org) all promote MSK ultrasound training and have published scanning protocols. As a real-time dynamic imaging modality for soft tissue evaluation and for guiding invasive procedures, MSK ultrasound is the only practical imaging choice for a clinician’s office. Simply put, a clinician who sees shoulder patients on a routine basis should be adept at shoulder ultrasound for diagnosis and image guidance.
The 13-point shoulder ultrasound exam was first developed in 2008 by orthopedic surgeons Don Buford, MD, and Ben DuBois, MD. There are simplifications in patient positioning and transducer alignment that are designed to make MSK ultrasound of the shoulder efficient for the clinician and more comfortable for the patient. The 13-point exam was also designed as a teaching tool to shorten the learning curve for the practicing clinician. As with any training tool, the 13-point exam has strengths and weaknesses. The 13-point shoulder exam protocol is a practical, simplified framework to diagnose and treat the most common extra-articular shoulder conditions.
Exam room, ultrasound machine basics, exam preparation, basic scanning tips
Clinicians can use portable MSK ultrasound machines in any typical patient exam room. No special room construction or protective clothing or eyewear is required.
MSK ultrasound machines are currently available in formats as small as smartphones and tablets to larger laptop computer–sized units. The most common transducer used in shoulder ultrasound is the linear phased array transducer. The linear transducer is a high-frequency transducer with an effective depth of penetration from 2 to 7 cm. There are wired and wireless versions of linear transducers available commercially, and clinicians can choose a transducer based on their preferences. All of the current MSK ultrasound machines have the ability to store images and to annotate images for procedure documentation.
It may be helpful to darken the exam room so that the ultrasound grayscale images are easier to see. It is helpful for patients to sit on a stool facing a desk, table, or ultrasound stand, with the clinician positioned behind the patient. With this arrangement, the MSK ultrasound machine can be placed in front of the patient so that both the patient and clinician can see the images. Alternatively, the patient can sit on an exam table, and the clinician can perform the exam from in front of the patient. Patients can provide access to both shoulders so that a comparative exam can be done if necessary. If the patient’s clothing is restrictive, then a gown or halter top can be used to allow access to both shoulders for the ultrasound examination. For diagnostic exams, patients can be seated. For ultrasound-guided procedures, we try to position the patient in the lateral decubitus position whenever practical for patient comfort and to make the procedures ergonomic for the sonographer.
Ideally, the clinician should hold the transducer at its base, as close to the patient as possible to increase stability. By securely holding the transducer on the patient, clinicians can make small transducer alignment adjustments to optimize the image and minimize anisotropy. Clinicians can also use dynamic stress testing to improve diagnostic accuracy of shoulder pathology such as partial tendon tears or nondisplaced full-thickness tendon tears. Clinicians should display images by a convention and annotate images where clinically indicated.
The long head of the biceps tendon is evaluated on its short axis at Point 1. The view obtained is equivalent to a magnetic resonance imaging (MRI) axial view of the biceps tendon as it courses through the bicipital groove. The patient is positioned so that the hand is placed comfortably on the ipsilateral thigh, with the elbow flexed 90 degrees and the hand resting pronated on the thigh. The arm is adducted by the patient’s side. If necessary, a pillow can be placed in the patient’s lap for comfort.
We orient the image on the ultrasound display to be consistent with how axial MRI and x-ray images are viewed. For most patients, the initial ultrasound machine depth setting is 2 to 4 cm, depending on patient size, and the higher frequency ranges of a linear transducer are typically used to improve imaging resolution. The linear transducer is oriented transversely across proximal biceps at the level of the bicipital groove, and the transducer is manipulated until the biceps is centrally located on the screen image.
The image obtained is equivalent to an axial MRI view of the bicipital groove. The biceps tendon typically appears as a hyperechoic oval-shaped signal located in the bicipital groove. Because of potential anisotropic effects, clinicians should make sure that the transducer is perpendicular to biceps tendon and bicipital groove at point 1 so that there is not a misdiagnosis of biceps tendon pathology. Biceps tendon tears in this extra-articular position within the bicipital groove can be diagnosed by the appearance of multiple biceps tendon signals or a difference in the overall size of the biceps tendon when compared with the contralateral biceps. The absence of the biceps tendon within the bicipital groove can confirm the diagnosis of a long head biceps tendon tear with retraction distal to the bicipital groove. Increased fluid around the biceps tendon, seen with bicipital tenosynovitis or with glenohumeral effusion, can be visualized as an increased hypoechoic area surrounding the biceps tendon at point 1. The presence of fluid deep to the anterior deltoid and superficial to the biceps is a sign of an anterior full-thickness rotator cuff tear ( Figs. 49.1 through 49.3 ).
At Point 2, we evaluate the proximal biceps tendon on its longitudinal axis. The patient positioning is unchanged from Point 1. The transducer is rotated 90 degrees compared with Point 1. We orient the screen image so that the proximal biceps is at the top of the screen and the distal biceps is at the bottom of the screen. The image and orientation will then match a sagittal MRI scan of the shoulder and arm. The tendon can be seen from where it exits the glenohumeral joint through the rotator interval down to its connection to the biceps muscle. The tendon typically appears as longitudinal fibers of mixed echogenicity because of anisotropic effects. The normal tendon thickness ranges from 5 to 10 mm. Any abnormal thickening or tearing of the tendon can often be visualized at this point. Bicipital tenosynovitis can be diagnosed by the presence of increased fluid seen as a large hypoechoic area surrounding the biceps tendon. The sonographer can also see tears in the biceps tendon and other structural abnormalities in the anterior humerus ( Figs. 49.4 through 49.6 ).
The subscapularis tendon is evaluated on its longitudinal axis at Point 3. This is equivalent to an axial MRI of the subscapularis tendon. We prefer to orient the image equivalent to how an axial MRI scan would be viewed. The transducer is placed transversely over the bicipital groove and slightly medial as compared with the transducer position for Point 1. The subscapularis tendon can be evaluated as it inserts into the lesser tuberosity in this position. To fully examine the tendon, it is helpful to have the patient externally rotate his shoulder while maintaining elbow flexion at 90 degrees. This allows for visualization of the subscapularis tendon from the muscle-tendon junction to its insertion on the lesser tuberosity. The patient can also rotate the shoulder in internal and external rotation to give a dynamic picture of the subscapularis muscle and tendon. A stress test can also be performed under direct visualization if the examiner resists the patient’s internal rotation. A positive stress test occurs when there is motion in the tendon despite the tendon insertion not moving. One of the easiest ways for the clinician to assess when there is a partial tendon tear is to note a change in the hypoechoic area of a tendon while performing the stress test in which the arm is held stationary in external rotation while the patient attempts to internally rotate the shoulder. The sonographic finding of tendon motion or a change in a hypoechoic defect in the normal tendon architecture may make the diagnosis of a subscapularis tendon tear at this time. Partial-thickness tears of the tendon also can be assessed at Point 3 as varying degrees of hypoechogenicity within the tendon, typically at its superior insertion into the lesser tuberosity ( Figs. 49.7 through 49.9 ).