This article provides a comprehensive understanding of a standardized shoulder US examination and describes the basic US technique, common indications for shoulder US, normal shoulder anatomy, and characteristic findings of common shoulder diseases at US.
Abstract
Shoulder pain is one of the most common musculoskeletal conditions encountered in primary care and specialty orthopedic clinic settings. Although magnetic resonance (MR) imaging is typically the modality of choice for evaluating the soft-tissue structures of the shoulder, ultrasonography (US) is becoming an important complementary imaging tool in the evaluation of superficial soft-tissue structures such as the rotator cuff, subacromial-subdeltoid bursa, and biceps tendon. The advantages of US driving its recent increased use include low cost, accessibility, and capability for real-time high-resolution imaging that enables dynamic assessment and needle guidance. As more radiologists are considering incorporating shoulder US into their practices, the development of a standardized approach to performing shoulder US should be a priority to facilitate the delivery of high-quality patient care. Familiarity with and comfort in performing a standardized shoulder US examination, as well as knowledge of the types of anomalies that can be evaluated well with US, will enhance the expertise of those working in musculoskeletal radiology practices and add value in the form of increased patient and health care provider satisfaction. This review describes the utility and benefits of shoulder US as a tool that complements MR imaging in the assessment of shoulder pain. A standardized approach to the shoulder US examination is also described, with a review of the basic technique of this examination, normal anatomy of the shoulder, common indications for shoulder US, and characteristic US findings of common shoulder diseases—with select MR imaging and arthroscopic correlation.
Online supplemental material is available for this article.
©RSNA, 2016
SA-CME LEARNING OBJECTIVES
After completing this journal-based SA-CME activity, participants will be able to:
■ Discuss the regional components of a standardized shoulder US examination and how it is performed.
■ Identify US findings of normal shoulder anatomy and common indications for shoulder US in clinical practice.
■ Recognize characteristic US findings of common shoulder diseases and the correlative MR imaging and arthroscopic appearances of these diseases.
Introduction
Shoulder pain is one of the most common musculoskeletal symptoms that prompt medical evaluation and can result in disability, lost wages, and substantial health care costs. It is the third most common reason for musculoskeletal consultations in the primary care setting, affecting up to one-third of the general population—particularly older individuals (1–3). Ultrasonography (US), magnetic resonance (MR) imaging, and MR arthrography are advanced imaging modalities that have been used to examine patients with shoulder pain, and each has unique advantages and disadvantages (3). Advances in technology, training, and research have improved clinicians’ ability to diagnose common shoulder diseases with high accuracy using US and MR imaging.
US and MR imaging have been shown to have comparable diagnostic accuracy in the evaluation of diseases involving the rotator cuff (RC) (3–6), subacromial-subdeltoid (SASD) bursa, and long head of the biceps tendon (LHBT), which are the most common origins of shoulder pain (7,8). During the past decade in the United States, as more academic institutions and private medical groups have incorporated musculoskeletal US into their practices, US has emerged as a valuable tool to complement MR imaging. The advantages of US prompting its increased use include low cost, accessibility, and capability for real-time high-resolution imaging that enables dynamic assessment and needle guidance. The additional benefits of US, as compared with MR imaging, include patient satisfaction; the opportunity for patient-clinician interaction and real-time feedback; the lack of contraindications such as pacemakers, which preclude the use of MR imaging; the capability for evaluation in the setting of artifact-prone surgical hardware; and the capability for comparison with findings in the contralateral anatomy (9,10).
However, several barriers preclude the widespread use of US. These barriers include the steep learning curve in becoming proficient in performing high-quality evaluation, the lack of dedicated musculoskeletal imaging training for sonographers and technologists in U.S. training programs, and the limited time that radiologists have to perform these examinations in the absence of musculoskeletal imaging–trained sonographers. Using a standardized approach to the shoulder US examination can help reduce these barriers and provide a framework to facilitate high-quality diagnostic imaging(11).
The purpose of this review is to describe the components of a standardized shoulder US examination, review the basic technique of shoulder US and the normal shoulder anatomy, identify common indications for shoulder US in clinical practice, and illustrate characteristic US appearances of common shoulder diseases, with MR imaging and arthroscopic correlation.
Comprehensive Shoulder US Examination: A Standardized Approach
Real-time diagnostic US of the shoulder should be performed in a logical and systematic fashion by using an approach that is accessible and easy to understand and thus facilitates coherent reproducibility and implementation in daily practice. At our institution, we perform a standardized shoulder examination that is divided into four regional components, which can be easily remembered by using the acronym ASAP: anterior, superior, anterolateral, and posterior (Table). Although the order in which the examination is performed is subject to institutional preference, each component of the examination is intended to facilitate optimal evaluation of specific anatomic structures and the common diseases that affect these structures. Each component of the examination should be performed in the same reproducible manner, with standard and cine imaging to allow efficient interpretation and patient throughput.
Components of Standard Shoulder US Examination
Note.—AC = acromioclavicular, IST = infraspinatus tendon, SGN = spinoglenoid notch, SST = supraspinatus tendon, SubST = subscapularis tendon, TMT = teres minor tendon.
The shoulder US examination is performed using high-frequency (9–15-MHz) linear broadband array transducers. The patient is imaged while seated, with the radiologist or musculoskeletal imaging–trained sonographer either seated in front of or standing behind the patient. In general, each anatomic structure is evaluated in orthogonal planes (ie, long and short axis), with the patient implementing specific positional maneuvers as needed. To highlight the importance of the standardized approach, the pertinent shoulder anatomy, US technique, imaging findings of the normal shoulder anatomy, and common shoulder diseases are reviewed in detail according to the four regional (anterior, superior, anterolateral, posterior) components.
Anterior Examination
Pertinent Anatomy
Long Head of the Biceps Tendon.—The LHBT is a noncontractile traction tendon that guides and directs the humeral head as it glides along its path of motion. The LHBT assists in anterior shoulder stability, provides resistance and support, and compensates for abnormal forces about the shoulder—particularly in the setting of severe RC injury or dysfunction (12). The LHBT is anchored to and originates from the superior glenoid labrum and supraglenoid tubercle. The intracapsular LHBT courses through the rotator interval and makes a 30°–45° turn as it enters the bicipital groove, where it is subtended by the transverse humeral ligament. The rotator interval structures serve to stabilize the intracapsular LHBT, maintaining its position as it enters into and passes through the bicipital groove.
Rotator Interval.—Although the rotator interval cannot be evaluated completely with US, it has an important role in shoulder stability and common shoulder diseases. It is a tetrahedron-shaped space that is a natural opening in the anterior region of the RC and is located between the anterior margin of the SST and the superior edge of the SubST. The rotator interval is bounded by the joint capsule anteriorly and the articular surface of the humeral head posteriorly. The coracohumeral and superior glenohumeral ligaments merge with the joint capsule to form the biceps pulley, providing external and internal reinforcement of the rotator interval capsule, respectively (13). Injuries to the rotator interval structures can result in glenohumeral instability and/or biceps tendon subluxation and injury and can be associated with anterosuperior impingement (14).
Subscapularis Tendon of the Rotator Cuff.—The SubST is the most anterior tendon of the RC and has an important role in stabilizing the anterior shoulder. The subscapularis muscle has a multipennate configuration and originates from the subscapular fossa. It fans out laterally to insert onto the lesser tuberosity of the humerus and functions to internally rotate and adduct the arm. The superficial SubST fibers overlie and blend with the coracohumeral ligament and transverse humeral ligament.
US Technique and Imaging Appearance of the Normal Anatomy
US examination of the anterior region of the shoulder begins with the patient seated in an upright position—preferably on a backless rotating chair—with the shoulder in neutral resting adduction, the elbow flexed 90°, and the palm supinated and resting gently on the thigh. The LHBT is examined in short and long axis, from the proximal (superior aspect of bicipital groove) to the distal (pectoralis major tendon–humerus attachment) aspect (Fig 1, Movie 1). The equivalent MR imaging planes for the short- and long-axis planes of the LHBT are the oblique axial and oblique sagittal planes, respectively.
Figure 1.
Right: Computer-generated three-dimensional image of the anterior region of the shoulder shows the positioning of the transducer for evaluation of the LHBT. Left: Corresponding short-axis US (top) and oblique axial proton- density–weighted fat-suppressed MR (PDFS) (bottom) images were obtained in two healthy volunteers. BG = bicipital groove.
Movie 1.
Computer-generated animation demonstrates the US examination technique used to evaluate the LHBT on the long and short axes.
On US images, the LHBT should have a normal fibrillar pattern, which represents the parallel collagen fibers of the tendon. The high resolution achieved with US (∼150 µm with a 10-MHz transducer), as compared with that achieved with MR imaging (∼450 µm at 1. 5 T with a 256 × 256 matrix and a 0.5-cm section thickness), enables direct visualization of individual tendon fibers (9). Real-time US examination of all of the shoulder tendons should be performed with gentle toggling (ie, rocking and angling) of the transducer to eliminate the anisotropy artifact that may mimic tendinopathy or a tear.
Next, dynamic US of the LHBT is performed to evaluate for possible tendon subluxation or dislocation. The patient’s arm is gently manipulated in internal and external rotation, with the arm in resting adduction, the palm supinated, and the transducer fixed in the short-axis orientation over the proximal bicipital groove (Fig 2, Movie 2). The dynamic examination is used to evaluate the stability and positioning of the LHBT with dynamic maneuvering. A potential pitfall is that maintaining a static imaging position can cause artifactual anisotropy within the tendon substance that mimics tendinopathy. The transducer pressure should be minimized to allow biceps tendon dislocation when it is present.
Figure 2.
Right: Computer-generated three-dimensional image shows the positioning of the transducer with internal and external rotation for dynamic evaluation of the LHBT. Left: Corresponding short-axis US images were obtained in two healthy volunteers.
Movie 2.
Short-axis cine capture US image in a healthy 36-year-old female volunteer during dynamic evaluation of the LHBT. The LHBT remains positioned within the bicipital groove throughout rotation; the subscapularis ligament and transverse humeral ligament are intact. The apparent hypoechogenicity within the tendon is due to intermittent anisotropy artifact.
The SubST is best evaluated using the same arm and hand positions that were used for evaluation of the LHBT (Fig 3). The SubST is identified anteriorly as it inserts onto the lesser tuberosity. The patient’s arm is maneuvered into external rotation, which causes the lesser tuberosity to move laterally, elongating the SubST and bringing it into view. Short- and long-axis US images of the tendon are obtained. The equivalent MR imaging planes for the short- and long-axis planes of the SubST are the oblique axial and oblique sagittal planes, respectively. The normal tendon is hyperechoic and has a uniform fibrillar appearance in the long-axis plane. The short-axis image will largely show hypoechoic muscle with interspersed linear hyperechoic tendon fibers, which should not be mistaken for partial tears.
Figure 3.
Right: Computer-generated three-dimensional image of the anterior region of the shoulder shows the positioning of the transducer for evaluation of the SubST. Left: Corresponding long-axis US (top) and oblique axial proton-density–weighted fat-suppressed (PDFS) MR (bottom) images were obtained in two healthy volunteers. GT = greater tuberosity, LT = lesser tuberosity.
Common Indications and Diseases
LHBT disease is an important source of shoulder pain that is often coexistent with or secondary to other shoulder anomalies—namely, RC tears involving the SubST or SST (15), superior labral tears (eg, superior labral anteroposterior tears), and impingement. The most common clinical indications for US examination of the anterior region of the shoulder include LHBT tendinosis, LHBT rupture, LHBT subluxation or dislocation, SubST tear, and needle guidance.
Although arthroscopy is the reference standard for evaluation of the LHBT (Fig 4) and MR imaging is the imaging modality most widely used preoperatively, US has emerged as a useful tool for preoperative evaluation in the appropriate clinical setting. US is accurate and reliable for evaluating the extracapsular LHBT—particularly in the setting of potential tendon rupture and subluxation or dislocation. It has 88%–100% sensitivity and 96%–98% specificity for detection of tendon subluxation or dislocation (7,8,16).
Figure 4.
Normal right shoulder anatomy in a 28-year-old woman. Arthroscopic image from a posterior viewing portal shows the typical origin of the LHBT from the supraglenoid tubercle and superior labrum. The tendon courses anteriorly toward the bicipital groove. An anterior portal was also established through the rotator interval, between the anterior margin of the SST and the superior margin of the SubST. HH = humeral head.
Biceps Tendinosis and Tenosynovitis.—At clinical examination, patients with LHBT disease present with vague anterior shoulder pain (17) or pain induced by focal palpation of the bicipital groove. The underlying causes of LHBT disease are grouped into the following general categories: tendinopathy, instability, anchor injury, and multifactorial combination of causes. Although primary tendinosis can occur within the extracapsular intertubercular portion of the tendon, it is rare, and the majority of cases of biceps tendinosis are secondary to a coexisting shoulder anomaly (18). Inflammatory and degenerative causes of biceps tendinosis are typically related to chronic repetitive overuse due to traction and friction forces on the tendon. This results in predominantly noninflammatory histologic changes to the tendon architecture (ie, tendinosis), including fibrosis, mucopolysaccharide deposition, and collagen disorganization, which commonly occur at the distal bicipital groove and near the LHBT origin at the superior glenoid labrum (8,18,19).
Although inflammation involving the LHBT itself is rare, inflammation of the synovial sheath surrounding the tendon (ie, tenosynovitis) is common. Tenosynovitis commonly occurs with chronic repetitive mechanical microtrauma and is related to the constrained path of the tendon within the bicipital groove (20). It can also be seen with predisposing inflammatory conditions such as inflammatory arthropathy or infection.
Overall, US is less accurate for detection of “nontear” abnormalities of the LHBT such as tendinosis and tenosynovitis than it is for detection of tear-related abnormalities and tendon subluxation and dislocation (8). However, changes related to underlying tendinosis should be documented when they are present; they appear as tendon thickening and enlargement, with geographic areas of hypoechoegenicity and loss of the normal fibrillar tendon architecture, which are due in part to edema and fibroblast proliferation (Fig 5a, 5b) (8,21).
Figure 5a.
(a–d) Biceps tendinosis, subluxation, and partial tear in a 76-year-old woman with chronic left shoulder pain. (a) Short-axis power Doppler US image of the proximal left LHBT at the entrance to the bicipital groove shows pronounced tendon thickening with geographic areas of hypoechogenicity (arrow), consistent with tendinosis. (b) Corresponding oblique axial fat-suppressed proton-density–weighted MR image of the left shoulder shows pronounced enlargement and heterogeneity of the left LHBT. There is medial subluxation and a focal abnormal increase in signal intensity (solid arrow) within the tendon substance, consistent with partial tearing. There is also tendinosis and tearing of the superior SubST fibers (dashed arrow). (The tear is incompletely shown.) A large glenoid cyst also is present. (c) Short-axis US image of the left LHBT obtained more distally shows medial subluxation of the tendon (solid arrow), which is perched on the lesser tuberosity (LT). The tendon is heterogeneous in appearance, with a focal area of thinning and attenuation (dashed arrow) that corresponds to the partial tendon tear. (d) Corresponding oblique axial fat-suppressed proton-density–weighted MR image of the left shoulder shows medial subluxation of the LHBT (solid arrow), focal thinning, and an abnormal increase in signal intensity (dashed arrow), which correspond to areas of partial tearing. (e) In a companion case, arthroscopic image from a posterior viewing portal in a 54-year-old man with chronic left shoulder pain shows a dislocated LHBT with associated laxity and partial tearing. GL = glenoid, HH = humeral head.
Figure 5b.
(a–d) Biceps tendinosis, subluxation, and partial tear in a 76-year-old woman with chronic left shoulder pain. (a) Short-axis power Doppler US image of the proximal left LHBT at the entrance to the bicipital groove shows pronounced tendon thickening with geographic areas of hypoechogenicity (arrow), consistent with tendinosis. (b) Corresponding oblique axial fat-suppressed proton-density–weighted MR image of the left shoulder shows pronounced enlargement and heterogeneity of the left LHBT. There is medial subluxation and a focal abnormal increase in signal intensity (solid arrow) within the tendon substance, consistent with partial tearing. There is also tendinosis and tearing of the superior SubST fibers (dashed arrow). (The tear is incompletely shown.) A large glenoid cyst also is present. (c) Short-axis US image of the left LHBT obtained more distally shows medial subluxation of the tendon (solid arrow), which is perched on the lesser tuberosity (LT). The tendon is heterogeneous in appearance, with a focal area of thinning and attenuation (dashed arrow) that corresponds to the partial tendon tear. (d) Corresponding oblique axial fat-suppressed proton-density–weighted MR image of the left shoulder shows medial subluxation of the LHBT (solid arrow), focal thinning, and an abnormal increase in signal intensity (dashed arrow), which correspond to areas of partial tearing. (e) In a companion case, arthroscopic image from a posterior viewing portal in a 54-year-old man with chronic left shoulder pain shows a dislocated LHBT with associated laxity and partial tearing. GL = glenoid, HH = humeral head.
Figure 5e.
(a–d) Biceps tendinosis, subluxation, and partial tear in a 76-year-old woman with chronic left shoulder pain. (a) Short-axis power Doppler US image of the proximal left LHBT at the entrance to the bicipital groove shows pronounced tendon thickening with geographic areas of hypoechogenicity (arrow), consistent with tendinosis. (b) Corresponding oblique axial fat-suppressed proton-density–weighted MR image of the left shoulder shows pronounced enlargement and heterogeneity of the left LHBT. There is medial subluxation and a focal abnormal increase in signal intensity (solid arrow) within the tendon substance, consistent with partial tearing. There is also tendinosis and tearing of the superior SubST fibers (dashed arrow). (The tear is incompletely shown.) A large glenoid cyst also is present. (c) Short-axis US image of the left LHBT obtained more distally shows medial subluxation of the tendon (solid arrow), which is perched on the lesser tuberosity (LT). The tendon is heterogeneous in appearance, with a focal area of thinning and attenuation (dashed arrow) that corresponds to the partial tendon tear. (d) Corresponding oblique axial fat-suppressed proton-density–weighted MR image of the left shoulder shows medial subluxation of the LHBT (solid arrow), focal thinning, and an abnormal increase in signal intensity (dashed arrow), which correspond to areas of partial tearing. (e) In a companion case, arthroscopic image from a posterior viewing portal in a 54-year-old man with chronic left shoulder pain shows a dislocated LHBT with associated laxity and partial tearing. GL = glenoid, HH = humeral head.
Tenosynovitis has variable appearances at US and may appear as anechoic fluid (out of proportion to joint fluid); hypoechoic synovial hypertrophy surrounding the tendon, with associated debris; or echogenic synovial hypertrophy, with associated increased signal at Doppler US. On power Doppler US images, increased flow within an abnormally thickened tendon sheath represents synovial proliferation.
US can also be used to guide corticosteroid injections in the setting of symptomatic tendinosis or tenosynovitis. However, care should be taken to identify tendon tearing, as corticosteroid injection can increase the risk for tear propagation or rupture. When injecting a corticosteroid, care should also be taken to identify and avoid the anterior circumflex humeral artery branch within the bicipital groove.
Biceps Tendon Rupture and Tearing.—Proximal LHBT tears and ruptures typically occur in the setting of preexisting tendinosis and progressive tendon degeneration. Tendon rupture usually occurs spontaneously in individuals older than 50 years, with little to no antecedent trauma (18,22). Rupture may manifest in conjunction with pain and a palpable retracted muscle belly, the so-called “pop-eye” sign (18). US findings of rupture include complete disruption of the LHBT fibers in association with a fluid gap and “empty” bicipital groove, with or without associated tendon retraction (Fig 6, Movie 3). The proximal tendon stump may retract into the groove entrance, articular space, or rotator interval.
Figure 6a.
Biceps tendon rupture in a 29-year-old man who felt a “pop” while lifting weights. This patient had sustained a right biceps tendon rupture previously and subsequently underwent biceps tendon repair. (a) Short-axis US image in the expected region of the right LHBT shows an “empty” fluid-filled biceps tendon sheath (arrow). (b) Long-axis US image in the same region shows the extracapsular tendon rupture, with retraction of the distal tendon stump (dashed arrow) and a fluid-filled gap (solid arrows). (c) Arthroscopic image of the right shoulder from a posterior viewing portal shows the intracapsular portion of the LHBT rupture near the tendon anchor. The proximal tendon stump (arrow) has a frayed and irregular appearance. AP = anterior portal, GL = glenoid, HH = humeral head.
Figure 6b.
Biceps tendon rupture in a 29-year-old man who felt a “pop” while lifting weights. This patient had sustained a right biceps tendon rupture previously and subsequently underwent biceps tendon repair. (a) Short-axis US image in the expected region of the right LHBT shows an “empty” fluid-filled biceps tendon sheath (arrow). (b) Long-axis US image in the same region shows the extracapsular tendon rupture, with retraction of the distal tendon stump (dashed arrow) and a fluid-filled gap (solid arrows). (c) Arthroscopic image of the right shoulder from a posterior viewing portal shows the intracapsular portion of the LHBT rupture near the tendon anchor. The proximal tendon stump (arrow) has a frayed and irregular appearance. AP = anterior portal, GL = glenoid, HH = humeral head.
Figure 6c.
Biceps tendon rupture in a 29-year-old man who felt a “pop” while lifting weights. This patient had sustained a right biceps tendon rupture previously and subsequently underwent biceps tendon repair. (a) Short-axis US image in the expected region of the right LHBT shows an “empty” fluid-filled biceps tendon sheath (arrow). (b) Long-axis US image in the same region shows the extracapsular tendon rupture, with retraction of the distal tendon stump (dashed arrow) and a fluid-filled gap (solid arrows). (c) Arthroscopic image of the right shoulder from a posterior viewing portal shows the intracapsular portion of the LHBT rupture near the tendon anchor. The proximal tendon stump (arrow) has a frayed and irregular appearance. AP = anterior portal, GL = glenoid, HH = humeral head.
Movie 3.
LHBT rupture in a 65-year-old woman. Short-axis cine capture US image shows complete absence of the proximal LHBT from the distal groove. There is retraction of the LHBT distally. Areas of heterogeneous anechoic and hypoechoic material at the myotendinous junction represent edema and hemorrhage.
It has been reported that partial LHBT tears can be challenging to detect with US (7,8) and MR imaging (23). Partial tears that can be seen on US images commonly occur at the entrance to the bicipital groove and may propagate distally, whereas proximal intracapsular tears—that is, those that occur with superior labral tears—may extend into the biceps anchor and are best evaluated arthroscopically. Focal intrasubstance tears may manifest in conjunction with isolated pain and appear as anechoic clefts in the tendon substance on US images or as focal fluid high-signal-intensity clefts on MR images (Fig 7) (24). Thinning and fraying of the tendon also may be apparent at US.
Figure 7a.
Focal split tear of the biceps tendon in a 43-year-old man with anterosuperior right shoulder pain. (a) Short-axis US image of the right LHBT shows a longitudinal split tear (arrow). With transducer palpation in this area, the patient reported reproduction of his typical pain. (b) Corresponding oblique axial fat-suppressed proton-density–weighted MR image of the right shoulder shows a longitudinal split tear involving the LHBT, with an abnormal high-signal-intensity cleft (arrow).
Figure 7b.
Focal split tear of the biceps tendon in a 43-year-old man with anterosuperior right shoulder pain. (a) Short-axis US image of the right LHBT shows a longitudinal split tear (arrow). With transducer palpation in this area, the patient reported reproduction of his typical pain. (b) Corresponding oblique axial fat-suppressed proton-density–weighted MR image of the right shoulder shows a longitudinal split tear involving the LHBT, with an abnormal high-signal-intensity cleft (arrow).
Biceps Tendon Subluxation and Dislocation.—The most common site of LHBT subluxation and dislocation is the entrance to or within the proximal bicipital groove. Subluxation and dislocation are typically seen in conjunction with destabilizing rotator interval injuries and are commonly preceded by tearing of the SubST. Subluxation and dislocation also occur in conjunction with SST tears and injury to the coracohumeral ligament or superior glenohumeral ligament (25). The LHBT may be displaced anterior to, posterior to, or within the substance of the SubST. US and MR images show partial (subluxation) or complete (dislocation) displacement of the tendon from the bicipital groove—often with associated biceps tendinosis or tearing. The tendon may also appear flattened or perched on the adjacent lesser tuberosity (Fig 5c, 5d). Real-time dynamic US of the LHBT is particularly advantageous in confirming the diagnosis.
Figure 5c.
(a–d) Biceps tendinosis, subluxation, and partial tear in a 76-year-old woman with chronic left shoulder pain. (a) Short-axis power Doppler US image of the proximal left LHBT at the entrance to the bicipital groove shows pronounced tendon thickening with geographic areas of hypoechogenicity (arrow), consistent with tendinosis. (b) Corresponding oblique axial fat-suppressed proton-density–weighted MR image of the left shoulder shows pronounced enlargement and heterogeneity of the left LHBT. There is medial subluxation and a focal abnormal increase in signal intensity (solid arrow) within the tendon substance, consistent with partial tearing. There is also tendinosis and tearing of the superior SubST fibers (dashed arrow). (The tear is incompletely shown.) A large glenoid cyst also is present. (c) Short-axis US image of the left LHBT obtained more distally shows medial subluxation of the tendon (solid arrow), which is perched on the lesser tuberosity (LT). The tendon is heterogeneous in appearance, with a focal area of thinning and attenuation (dashed arrow) that corresponds to the partial tendon tear. (d) Corresponding oblique axial fat-suppressed proton-density–weighted MR image of the left shoulder shows medial subluxation of the LHBT (solid arrow), focal thinning, and an abnormal increase in signal intensity (dashed arrow), which correspond to areas of partial tearing. (e) In a companion case, arthroscopic image from a posterior viewing portal in a 54-year-old man with chronic left shoulder pain shows a dislocated LHBT with associated laxity and partial tearing. GL = glenoid, HH = humeral head.
Figure 5d.
(a–d) Biceps tendinosis, subluxation, and partial tear in a 76-year-old woman with chronic left shoulder pain. (a) Short-axis power Doppler US image of the proximal left LHBT at the entrance to the bicipital groove shows pronounced tendon thickening with geographic areas of hypoechogenicity (arrow), consistent with tendinosis. (b) Corresponding oblique axial fat-suppressed proton-density–weighted MR image of the left shoulder shows pronounced enlargement and heterogeneity of the left LHBT. There is medial subluxation and a focal abnormal increase in signal intensity (solid arrow) within the tendon substance, consistent with partial tearing. There is also tendinosis and tearing of the superior SubST fibers (dashed arrow). (The tear is incompletely shown.) A large glenoid cyst also is present. (c) Short-axis US image of the left LHBT obtained more distally shows medial subluxation of the tendon (solid arrow), which is perched on the lesser tuberosity (LT). The tendon is heterogeneous in appearance, with a focal area of thinning and attenuation (dashed arrow) that corresponds to the partial tendon tear. (d) Corresponding oblique axial fat-suppressed proton-density–weighted MR image of the left shoulder shows medial subluxation of the LHBT (solid arrow), focal thinning, and an abnormal increase in signal intensity (dashed arrow), which correspond to areas of partial tearing. (e) In a companion case, arthroscopic image from a posterior viewing portal in a 54-year-old man with chronic left shoulder pain shows a dislocated LHBT with associated laxity and partial tearing. GL = glenoid, HH = humeral head.
Superior Examination
Pertinent Anatomy
AC Joint.—The AC joint is a synovial (ie, diarthrodial) joint that articulates the flat or concave acromion with the convex distal clavicle. The AC, coracoacromial, and coracoclavicular ligaments and overlying fibrous joint capsule provide static stabilization of the joint. The anterior deltoid, trapezius, and serratus anterior muscles provide dynamic stabilization (26).
US Technique and Imaging Appearance of the Normal Anatomy
The AC joint is imaged with the patient seated in the upright position and the arm in resting adduction. The transducer is placed along the long axis of the clavicle and then moved laterally to profile the joint space (Fig 8). The equivalent MR imaging plane is the oblique coronal plane. On US images, only the superficial aspect of the joint is seen well, and it has an overlying hypoechoic joint capsule flanked by the hyperechoic bone acoustic landmarks of the distal clavicle and acromion. The fibrocartilaginous disk may be seen as a thin linear hyperechoic structure in the center of the joint (27).
Figure 8.
Right: Computer-generated three-dimensional image of the superior region of the shoulder shows the positioning of the transducer for evaluation of the AC joint. The transducer is oriented along the long axis of the clavicle, perpendicular to the AC joint. Left: Corresponding long-axis (relative to the clavicle) US (top) and oblique coronal T2-weighted fat-suppressed (T2 FS) MR (bottom) images of the AC joint were obtained in two healthy volunteers. A = acromion, C = clavicle.
Although the normal width of the AC joint varies according to the imaging modality, at US, the normal width is approximately 3–4 mm and decreases with age (28). A 2–3-mm difference between the AC joint width on one side and that on the other side is considered abnormal in the appropriate clinical setting and when accompanied by correlative patient symptoms (26). If there is concern regarding joint instability, dynamic imaging of the joint can be performed with the patient’s arm initially in a neutral adducted position. The elbow should then be bent and crossed over the chest, with the hand touching the opposite shoulder. Stress imaging with the patient holding weights—akin to stress radiographic examinations—has also been described (29).
Common Indications and Diseases
The AC joint is a potential source of anterosuperior shoulder pain in the setting of age-related or posttraumatic joint degeneration, acute trauma, or other infectious and inflammatory processes, and AC joint disease may be mistaken for common symptomatic RC disease clinically. Common clinical indications for evaluation of the AC joint include osteoarthritis (including posttraumatic injury), acute AC joint trauma (ie, separation or dislocation), synovitis, synovial cyst, osteolysis, and needle guidance for joint aspiration or corticosteroid injection.
The primary role of AC joint US is to evaluate for capsular hypertrophy and distension. US findings can be used effectively to rule out joint inflammation—regardless of whether the anomaly is degenerative, infectious, or inflammatory. A capsule-to-bone distance of less than 3 mm effectively rules out synovial hypertrophy and joint effusion (28). In addition, although US is not primarily used in the setting of trauma, it is more sensitive than radiography for the identification of grade I AC joint injuries, which appear as soft-tissue swelling and capsular distension on US images. The US findings of more severe traumatic AC joint injuries are similar to the radiographic findings (Fig 9) (27,29,30).
Figure 9a.
AC joint separation in a 68-year-old man with shoulder pain after a fall onto an outstretched hand. (a) Anteroposterior radiograph of the right shoulder shows abnormal widening of the right AC joint (double-headed arrow), superior displacement of the clavicle (arrow), and widening of the coracoclavicular interval. (b) Long-axis (relative to the clavicle) neutral-position US image of the right AC joint shows marked abnormal widening of the right AC joint (double-headed arrow)—to 2.2 cm—and associated capsular distension (arrows). The asymptomatic left AC joint (not shown) was normal in appearance and 0.3 cm in width. A = acromion, C = clavicle.
Figure 9b.
AC joint separation in a 68-year-old man with shoulder pain after a fall onto an outstretched hand. (a) Anteroposterior radiograph of the right shoulder shows abnormal widening of the right AC joint (double-headed arrow), superior displacement of the clavicle (arrow), and widening of the coracoclavicular interval. (b) Long-axis (relative to the clavicle) neutral-position US image of the right AC joint shows marked abnormal widening of the right AC joint (double-headed arrow)—to 2.2 cm—and associated capsular distension (arrows). The asymptomatic left AC joint (not shown) was normal in appearance and 0.3 cm in width. A = acromion, C = clavicle.
Anterolateral Examination
Pertinent Anatomy
Supraspinatus Tendon of the Rotator Cuff.—The RC forms a confluent tendon that facilitates shoulder movement and plays a principal role in active glenohumeral joint stability. Of the four RC tendons, the SST is primarily implicated in symptomatic RC disease. The supraspinatus muscle originates from the supraspinatus fossa of the scapula and is responsible for shoulder abduction. The results of cadaveric studies delineating RC anatomy have shown that the normal SST consistently and reproducibly courses laterally from the supraspinatus fossa, blends with the IST, and inserts onto the anteromedial aspect of the superior facet of the greater tuberosity (31,32). The SST footprint (ie, osseous insertion site) on the greater tuberosity has a triangular configuration (32).
Subacromial-Subdeltoid Bursa.—The normal SASD bursa is a synovial lined potential space (in healthy individuals) composed of synovial tissue, connective tissue, and fat. The SASD bursa is the largest bursa in the body and is situated between the RC and coracoacromial arch (subacromial bursa) and between the RC and deltoid muscle (subdeltoid bursa) (33). The SASD bursa overlies the bicipital groove anteriorly and extends to the coracoid process medially and to variable distances laterally below the greater tuberosity (34). The primary functions of the SASD bursa are to facilitate motion of the RC and dissipate the friction caused by complex shoulder movements.
US Technique and Imaging Appearance of the Normal Anatomy
Special patient positioning is required for examination of the SST owing to the anatomic relationships between the SST and the acromion and the resultant shadowing that is produced if these structures are imaged with the arm and shoulder in a neutral position. One method of evaluating the SST involves having the patient’s arm hyperextended and internally rotated, with the elbow flexed and the dorsal aspect of the hand placed along the low midline of the back. This is referred to as the Crass position (Fig 10a) (35). Another commonly used position that can be included alternatively in the standard examination is that with the elbow flexed and the volar aspect of the hand placed along the ipsilateral iliac wing in a “hand-in-back-pocket” configuration. This is referred to as the modified Crass, or Middleton, position. These positions bring the SST out from underneath the acromion, approximately 45° anteriorly from the coronal plane, and allow optimal imaging of the RC. The Middleton position facilitates visualization of the anterior part of the SST.
Figure 10a.
Anatomy of the normal SST and US technique. (a) Computer-generated three-dimensional image shows the Crass position that can be used to evaluate the SST. The patient’s arm is hyperextended and internally rotated, the elbow is flexed, and the dorsal aspect of the hand is placed along the low midline of the back. (b–d) Normal anatomy with correlative US and MR imaging findings. GL = glenoid, GT = greater tuberosity, HH = humeral head, SS m. = supraspinatus muscle. (b) Right: Computer-generated three-dimensional image of the anterolateral region of the shoulder shows the positioning of the transducer for evaluation of the SST. Left: Corresponding long-axis US (top) and oblique coronal T2-weighted fat-suppressed (T2 FS) MR (bottom) images were obtained in healthy volunteers. The normal SST has a distinct “bird’s beak” appearance. (c) Long-axis US (top left), oblique coronal T1-weighted MR (bottom left), and standard oblique coronal T2-weighted fat-suppressed (T2 FS) MR (right) images in healthy volunteers show correlative US and MR imaging findings of the long-axis anatomy of the SST. The T1-weighted MR image was obtained with the volunteer in the modified Crass (Middleton) position within the magnet for illustrative purposes. (d) Short-axis US (top left), oblique axial T1-weighted MR (bottom left), and standard oblique sagittal (Obl Sag) T2-weighted fat-suppressed (T2 FS) MR (right) images obtained in healthy volunteers show correlative US and MR imaging findings of the short-axis anatomy of the SST. The T1-weighted MR image was obtained with the volunteer in the modified Crass (Middleton) position within the magnet for illustrative purposes.
At US, the LHBT at the rotator interval is an anatomic landmark that is helpful for identifying the leading edge of the SST, which can be seen just posterior to the LHBT. The SST is then examined in long (Fig 10b) and short axis (Movie 4). The equivalent long- and short-axis MR imaging planes are the oblique coronal and oblique sagittal planes, respectively (Fig 10c, 10d). The normal tendon is hyperechoic, with a convex surface and uniform fibrillar appearance, and is often described as having a bird’s beak appearance. The examination should be performed with gentle toggling of the transducer to eliminate anisotropy, given the curvilinear course and convex contour of the tendon as it travels circumferentially around the humeral head. The deep tendon fibers, which have a steepened course as they insert near the footprint–articular surface junction, deserve particular attention. In addition, the proximal and medial regions of the SST adjacent to the acromion should be evaluated for tendinosis or tear.
Figure 10b.
Anatomy of the normal SST and US technique. (a) Computer-generated three-dimensional image shows the Crass position that can be used to evaluate the SST. The patient’s arm is hyperextended and internally rotated, the elbow is flexed, and the dorsal aspect of the hand is placed along the low midline of the back. (b–d) Normal anatomy with correlative US and MR imaging findings. GL = glenoid, GT = greater tuberosity, HH = humeral head, SS m. = supraspinatus muscle. (b) Right: Computer-generated three-dimensional image of the anterolateral region of the shoulder shows the positioning of the transducer for evaluation of the SST. Left: Corresponding long-axis US (top) and oblique coronal T2-weighted fat-suppressed (T2 FS) MR (bottom) images were obtained in healthy volunteers. The normal SST has a distinct “bird’s beak” appearance. (c) Long-axis US (top left), oblique coronal T1-weighted MR (bottom left), and standard oblique coronal T2-weighted fat-suppressed (T2 FS) MR (right) images in healthy volunteers show correlative US and MR imaging findings of the long-axis anatomy of the SST. The T1-weighted MR image was obtained with the volunteer in the modified Crass (Middleton) position within the magnet for illustrative purposes. (d) Short-axis US (top left), oblique axial T1-weighted MR (bottom left), and standard oblique sagittal (Obl Sag) T2-weighted fat-suppressed (T2 FS) MR (right) images obtained in healthy volunteers show correlative US and MR imaging findings of the short-axis anatomy of the SST. The T1-weighted MR image was obtained with the volunteer in the modified Crass (Middleton) position within the magnet for illustrative purposes.
Figure 10c.
Anatomy of the normal SST and US technique. (a) Computer-generated three-dimensional image shows the Crass position that can be used to evaluate the SST. The patient’s arm is hyperextended and internally rotated, the elbow is flexed, and the dorsal aspect of the hand is placed along the low midline of the back. (b–d) Normal anatomy with correlative US and MR imaging findings. GL = glenoid, GT = greater tuberosity, HH = humeral head, SS m. = supraspinatus muscle. (b) Right: Computer-generated three-dimensional image of the anterolateral region of the shoulder shows the positioning of the transducer for evaluation of the SST. Left: Corresponding long-axis US (top) and oblique coronal T2-weighted fat-suppressed (T2 FS) MR (bottom) images were obtained in healthy volunteers. The normal SST has a distinct “bird’s beak” appearance. (c) Long-axis US (top left), oblique coronal T1-weighted MR (bottom left), and standard oblique coronal T2-weighted fat-suppressed (T2 FS) MR (right) images in healthy volunteers show correlative US and MR imaging findings of the long-axis anatomy of the SST. The T1-weighted MR image was obtained with the volunteer in the modified Crass (Middleton) position within the magnet for illustrative purposes. (d) Short-axis US (top left), oblique axial T1-weighted MR (bottom left), and standard oblique sagittal (Obl Sag) T2-weighted fat-suppressed (T2 FS) MR (right) images obtained in healthy volunteers show correlative US and MR imaging findings of the short-axis anatomy of the SST. The T1-weighted MR image was obtained with the volunteer in the modified Crass (Middleton) position within the magnet for illustrative purposes.
Figure 10d.
Anatomy of the normal SST and US technique. (a) Computer-generated three-dimensional image shows the Crass position that can be used to evaluate the SST. The patient’s arm is hyperextended and internally rotated, the elbow is flexed, and the dorsal aspect of the hand is placed along the low midline of the back. (b–d) Normal anatomy with correlative US and MR imaging findings. GL = glenoid, GT = greater tuberosity, HH = humeral head, SS m. = supraspinatus muscle. (b) Right: Computer-generated three-dimensional image of the anterolateral region of the shoulder shows the positioning of the transducer for evaluation of the SST. Left: Corresponding long-axis US (top) and oblique coronal T2-weighted fat-suppressed (T2 FS) MR (bottom) images were obtained in healthy volunteers. The normal SSThas a distinct “bird’s beak” appearance. (c) Long-axis US (top left), oblique coronal T1-weighted MR (bottom left), and standard oblique coronal T2-weighted fat-suppressed (T2 FS) MR (right) images in healthy volunteers show correlative US and MR imaging findings of the long-axis anatomy of the SST. The T1-weighted MR image was obtained with the volunteer in the modified Crass (Middleton) position within the magnet for illustrative purposes. (d) Short-axis US (top left), oblique axial T1-weighted MR (bottom left), and standard oblique sagittal (Obl Sag) T2-weighted fat-suppressed (T2 FS) MR (right) images obtained in healthy volunteers show correlative US and MR imaging findings of the short-axis anatomy of the SST. The T1-weighted MR image was obtained with the volunteer in the modified Crass (Middleton) position within the magnet for illustrative purposes.
Movie 4.
Computer-generated animation demonstrates the US examination technique used to evaluate the SST on the long and short axes.
The SASD bursa is identified by placing the transducer along the long axis of the humerus, lateral to the greater tuberosity (33). The SASD bursa appears as a thin uniform 1–2-mm hypoechoic bursal line between hyperechoic peribursal fat, resulting in a layered “tram-track” appearance.
Dynamic US of the SST is then performed to evaluate possible subacromial impingement (Fig 11, Movie 5). The patient is initially examined while in resting adduction. The transducer is placed over the anterolateral region of the shoulder, parallel to the humeral shaft. The proximal end of the transducer overlies the acromion for visualization of the SST and the SASD bursa. With the patient’s thumb pointing toward the floor and the arm flexed approximately 45°, the arm is slowly abducted while the transducer remains fixed in place. The SST and overlying SASD bursa normally glide smoothly and freely along an arc beneath the acromion. Any compression or mass effect of the acromion on the SST and/or SASD bursa induced by dynamic abduction should be documented with cine imaging. In addition, any pain caused by the dynamic maneuver should be documented.
Figure 11.
Right: Computer-generated three-dimensional image shows the positioning of the transducer for dynamic evaluation of the anterolateral region of the shoulder for possible impingement. The transducer is positioned along the anterolateral region of the shoulder. Left: Corresponding long-axis neutral-position (top) and abduction (bottom) US images were obtained in a healthy volunteer. The normal SST and SASD bursa glide freely beneath the acromion; with abduction, they are obscured by osseous shadowing. HH = humeral head.
Movie 5.
Short-axis cine capture US image in a healthy 36-year-old female volunteer during dynamic abduction-position evaluation of the SST. The SST and overlying SASD bursa glide smoothly and freely along an arc beneath the acromion.
Common Indications and Diseases
RC and SASD bursal anomalies are principal causes of shoulder pain. Evaluation of the RC is the most common indication for shoulder US in patients older than 40 years (36). The spectrum of SST anomalies evaluated with US includes SST tear (full- and partial-thickness tears), SST tendinopathy (ie, tendinosis and tendinitis), subacromial impingement, and calcific tendinitis.
RC Tendinopathy and Tear.—The causes of RC tendinopathy and tearing are multifactorial and related to a combination of intrinsic, extrinsic, genetic, and environmental factors (2). The results of studies evaluating RC tear prevalence in symptomatic and asymptomatic populations suggest that RC tears occur in the setting of tendon degeneration and/or tendinopathy and increase in prevalence with age (37–39). Hand dominance and history of trauma also are implicated (40). The histopathologic changes of intrinsic tendinopathy and degeneration that predispose the RC to tearing include tendon thinning, disorganization of underlying collagen fiber architecture, myxoid degeneration, hyaline degeneration, chondroid metaplasia, vascular proliferation, and fat infiltration (41). The extrinsic mechanisms related to RC tears include impingement syndromes involving the coracoacromial arch (42) and acute traumatic injuries (macrotrauma).
On US images, the appearance of RC tendinopathy is similar to that seen in other tendons and includes tendon thickening and enlargement that may progress and appear as areas of focal or diffuse hypoechogenicity and loss of the normal fibrillar tendon architecture, with or without hyperemia (43). A potential pitfall is that discriminating between tendinopathy and discrete tendon tears may be difficult.
When performed by experienced individuals, US and MR imaging have equivalent high sensitivity and specificity in the diagnosis of full- and partial-thickness RC tears (5,44–47). In a meta-analysis comparing MR imaging, MR arthrography, and US, de Jesus et al (4) found that although MR arthrography was more sensitive and specific than both US and MR imaging for the diagnosis of full- and partial-thickness RC tears, there was no statistically significant difference between US and MR imaging. The historic variability in the performance and accuracy of US in the detection of RC tears is probably related to a combination of inexperience and technology-limiting factors (48); however, these have improved with training and modern high-resolution US systems. Implementation of a standard shoulder US examination protocol will further improve the performance of this modality by decreasing variability.
Full-Thickness RC Tear.—Full-thickness RC tears extend through the entire thickness of the tendon substance, from the articular surface to the bursal surface (Fig 12). Most RC tears involve the SST and occur 13–17 mm posterior to the LHBT, near the confluence of the SST and IST (49). These tears should be evaluated in both the short and long axis and characterized as focal or full-width (ie, complete) tears. RC tears should be described in terms of their location and dimensions in the short (eg, anterior, middle, or posterior SST fibers) and long (eg, involving the footprint, musculotendinous junction, etc) axis of the tendon. Tears can also be described according to their shape (eg, crescent, L-shaped, etc) and extent. Tear size (ie, short- and long-axis dimensions) and associated findings such as tendon retraction should also be documented, although characterization may be more challenging in the setting of large and massive RC tears (50). The preferred nomenclature (eg, full thickness, full width, complete) may vary from institution to institution, depending on the referral base and provider preference.
Figure 12a.
Full-thickness SST tear in a 63-year-old man with persistent right shoulder pain after sustaining a right shoulder injury while bench pressing. (a) Long-axis US image of the right SST shows a full-thickness tear, with complete tendon disruption (double-headed arrow) extending from the bursal surface to the articular surface and associated depression of the overlying bursa (arrows) caused by transducer pressure. (b) Oblique coronal T2-weighted MR image of the right shoulder obtained 4 months later shows progression of the SST tear, with tendon discontinuity (solid arrow) and retraction (dashed arrow).
Figure 12b.
Full-thickness SST tear in a 63-year-old man with persistent right shoulder pain after sustaining a right shoulder injury while bench pressing. (a) Long-axis US image of the right SST shows a full-thickness tear, with complete tendon disruption (double-headed arrow) extending from the bursal surface to the articular surface and associated depression of the overlying bursa (arrows) caused by transducer pressure. (b) Oblique coronal T2-weighted MR image of the right shoulder obtained 4 months later shows progression of the SST tear, with tendon discontinuity (solid arrow) and retraction (dashed arrow).
On US images, full-thickness RC tears appear as hypoechoic or anechoic tendon defects that extend through the entire tendon, from the humeral articular surface to the SASD bursa. The corresponding T2-weighted MR imaging finding is a tendon defect with high signal intensity extending from the articular surface to the bursal surface. Findings of massive tears—defined as tears greater than 5 cm in width and/or involving two or more tendons—include nonvisualization of the tendon and depression of the deltoid muscle into the tendon defect (51).
With regard to chronicity, acute full-thickness RC tears commonly involve the middle substance of the tendon, with associated joint or bursal effusion. Chronic full-thickness RC tears are more commonly associated with tendon retraction or nonvisualization and are less commonly associated with joint or bursal effusion (Fig 13) (52). A potential pitfall is mistaking the overlying deltoid muscle for an intact tendon, since the muscle sits on top of the “bare” humeral head in the setting of a chronic full-thickness RC tear.
Figure 13a.
Chronic full-thickness SST tear in a 52-year-old man with chronic right shoulder pain. (a) Long-axis US image of the right SST shows a chronic-appearing full-thickness SST tear. There are no intact fibers inserting onto the irregular-appearing greater tuberosity (double-headed arrow). There is granulation tissue and scarring (solid arrow) in the expected region of the SST and slight depression of the overlying bursa (dashed arrow) into the defect caused by transducer pressure. (b) Oblique coronal T2-weighted MR image of the right shoulder shows a chronic-appearing full-thickness, full-width SSTtear, with tendon discontinuity (solid white arrow) and associated granulation tissue and scarring (red arrow). There is a small tendon stump (dashed arrow) at the greater tuberosity insertion site. (c) Short-axis US image of the right SST shows the chronic-appearing full-thickness tear involving the entire SST. Again, there are no intact SST fibers (double-headed arrow). (d) Double oblique sagittal T2-weighted MR image of the right shoulder confirms the full-thickness SST tear. There is abnormal fluid signal intensity at the expected site of the SST insertion, with no intact fibers (arrow). (e) Arthroscopic image of the right shoulder from a posterior viewing portal shows the full-thickness SST tear (arrows), which exposes the SASD bursa, with associated scarring.
Figure 13b.
Chronic full-thickness SST tear in a 52-year-old man with chronic right shoulder pain. (a) Long-axis US image of the right SST shows a chronic-appearing full-thickness SST tear. There are no intact fibers inserting onto the irregular-appearing greater tuberosity (double-headed arrow). There is granulation tissue and scarring (solid arrow) in the expected region of the SST and slight depression of the overlying bursa (dashed arrow) into the defect caused by transducer pressure. (b) Oblique coronal T2-weighted MR image of the right shoulder shows a chronic-appearing full-thickness, full-width SSTtear, with tendon discontinuity (solid white arrow) and associated granulation tissue and scarring (red arrow). There is a small tendon stump (dashed arrow) at the greater tuberosity insertion site. (c) Short-axis US image of the right SST shows the chronic-appearing full-thickness tear involving the entire SST. Again, there are no intact SST fibers (double-headed arrow). (d) Double oblique sagittal T2-weighted MR image of the right shoulder confirms the full-thickness SST tear. There is abnormal fluid signal intensity at the expected site of the SST insertion, with no intact fibers (arrow). (e) Arthroscopic image of the right shoulder from a posterior viewing portal shows the full-thickness SST tear (arrows), which exposes the SASD bursa, with associated scarring.
Figure 13c.
Chronic full-thickness SST tear in a 52-year-old man with chronic right shoulder pain. (a) Long-axis US image of the right SST shows a chronic-appearing full-thickness SST tear. There are no intact fibers inserting onto the irregular-appearing greater tuberosity (double-headed arrow). There is granulation tissue and scarring (solid arrow) in the expected region of the SST and slight depression of the overlying bursa (dashed arrow) into the defect caused by transducer pressure. (b) Oblique coronal T2-weighted MR image of the right shoulder shows a chronic-appearing full-thickness, full-width SSTtear, with tendon discontinuity (solid white arrow) and associated granulation tissue and scarring (red arrow). There is a small tendon stump (dashed arrow) at the greater tuberosity insertion site. (c) Short-axis US image of the right SST shows the chronic-appearing full-thickness tear involving the entire SST. Again, there are no intact SST fibers (double-headed arrow). (d) Double oblique sagittal T2-weighted MR image of the right shoulder confirms the full-thickness SST tear. There is abnormal fluid signal intensity at the expected site of the SST insertion, with no intact fibers (arrow). (e) Arthroscopic image of the right shoulder from a posterior viewing portal shows the full-thickness SST tear (arrows), which exposes the SASD bursa, with associated scarring.
Figure 13d.
Chronic full-thickness SST tear in a 52-year-old man with chronic right shoulder pain. (a) Long-axis US image of the right SST shows a chronic-appearing full-thickness SST tear. There are no intact fibers inserting onto the irregular-appearing greater tuberosity (double-headed arrow). There is granulation tissue and scarring (solid arrow) in the expected region of the SST and slight depression of the overlying bursa (dashed arrow) into the defect caused by transducer pressure. (b) Oblique coronal T2-weighted MR image of the right shoulder shows a chronic-appearing full-thickness, full-width SSTtear, with tendon discontinuity (solid white arrow) and associated granulation tissue and scarring (red arrow). There is a small tendon stump (dashed arrow) at the greater tuberosity insertion site. (c) Short-axis US image of the right SST shows the chronic-appearing full-thickness tear involving the entire SST. Again, there are no intact SST fibers (double-headed arrow). (d) Double oblique sagittal T2-weighted MR image of the right shoulder confirms the full-thickness SST tear. There is abnormal fluid signal intensity at the expected site of the SST insertion, with no intact fibers (arrow). (e) Arthroscopic image of the right shoulder from a posterior viewing portal shows the full-thickness SST tear (arrows), which exposes the SASD bursa, with associated scarring.
Figure 13e.
Chronic full-thickness SST tear in a 52-year-old man with chronic right shoulder pain. (a) Long-axis US image of the right SST shows a chronic-appearing full-thickness SST tear. There are no intact fibers inserting onto the irregular-appearing greater tuberosity (double-headed arrow). There is granulation tissue and scarring (solid arrow) in the expected region of the SST and slight depression of the overlying bursa (dashed arrow) into the defect caused by transducer pressure. (b) Oblique coronal T2-weighted MR image of the right shoulder shows a chronic-appearing full-thickness, full-width SST tear, with tendon discontinuity (solid white arrow) and associated granulation tissue and scarring (red arrow). There is a small tendon stump (dashed arrow) at the greater tuberosity insertion site. (c) Short-axis US image of the right SST shows the chronic-appearing full-thickness tear involving the entire SST. Again, there are no intact SST fibers (double-headed arrow). (d) Double oblique sagittal T2-weighted MR image of the right shoulder confirms the full-thickness SST tear. There is abnormal fluid signal intensity at the expected site of the SST insertion, with no intact fibers (arrow). (e) Arthroscopic image of the right shoulder from a posterior viewing portal shows the full-thickness SST tear (arrows), which exposes the SASD bursa, with associated scarring.
Secondary indirect signs of RC tears include cortical irregularity of the greater tuberosity footprint, the “cartilage interface” sign, glenohumeral joint effusion, herniation of the SASD bursa and deltoid muscle, and SASD bursal effusion (53–55). Cortical irregularity and joint effusion have the highest sensitivity, specificity, and positive and negative predictive values for the detection of full-thickness SST tears at US (53). The cartilage interface sign is a curvilinear hyperechoic line paralleling the hypoechoic hyaline cartilage of the humeral head at the interface of the hyaline cartilage and the abnormal hypoechoic tendon. It is the result of increased through transmission related to changes in acoustic impedance when there is articular surface–sided tendon disease, and it is most pronounced with RC tears (Fig 14). A potential pitfall is that a normal thin hyaline cartilage interface can be seen with intact RCs, particularly in thinner individuals. Applying gentle transducer pressure over the deltoid muscle can increase the conspicuity of nonretracted tears.
Figure 14a.
(a, b) Full-thickness SST tear in a 62-year-old woman with right shoulder pain after sustaining a fall 3 months earlier. (a) Long-axis US image of the right SST shows a full-thickness SST tear with a tendon stump (solid white arrow), and the cartilage interface sign (dashed arrow) with a thin curvilinear hyperechoic line parallel to the hyaline cartilage. There is also an associated fluid gap (red arrow). (b) Oblique coronal T2-weighted MR image of the right shoulder shows a full-thickness SST tear, with no intact fibers at the greater tuberosity insertion (solid white arrow). There is associated retraction (dashed arrow) and a fluid gap, as well as a correlative finding (red arrow) that corresponds to the cartilage interface sign seen on the US image. (c) In a companion case, an arthroscopic image of the right shoulder from a posterior viewing portal was obtained in a 55-year-old woman who sustained right shoulder trauma that resulted in a full-thickness SST tear. The tear and associated tendon gapping (double-headed arrow) are seen. There is also associated SST retraction (arrow) nearly to the level of the glenoid and exposure of the underlying humeral head (HH).
Figure 14b.
(a, b) Full-thickness SST tear in a 62-year-old woman with right shoulder pain after sustaining a fall 3 months earlier. (a) Long-axis US image of the right SST shows a full-thickness SST tear with a tendon stump (solid white arrow), and the cartilage interface sign (dashed arrow) with a thin curvilinear hyperechoic line parallel to the hyaline cartilage. There is also an associated fluid gap (red arrow). (b) Oblique coronal T2-weighted MR image of the right shoulder shows a full-thickness SST tear, with no intact fibers at the greater tuberosity insertion (solid white arrow). There is associated retraction (dashed arrow) and a fluid gap, as well as a correlative finding (red arrow) that corresponds to the cartilage interface sign seen on the US image. (c) In a companion case, an arthroscopic image of the right shoulder from a posterior viewing portal was obtained in a 55-year-old woman who sustained right shoulder trauma that resulted in a full-thickness SST tear. The tear and associated tendon gapping (double-headed arrow) are seen. There is also associated SST retraction (arrow) nearly to the level of the glenoid and exposure of the underlying humeral head (HH).
Figure 14c.
(a, b) Full-thickness SST tear in a 62-year-old woman with right shoulder pain after sustaining a fall 3 months earlier. (a) Long-axis US image of the right SST shows a full-thickness SST tear with a tendon stump (solid white arrow), and the cartilage interface sign (dashed arrow) with a thin curvilinear hyperechoic line parallel to the hyaline cartilage. There is also an associated fluid gap (red arrow). (b) Oblique coronal T2-weighted MR image of the right shoulder shows a full-thickness SST tear, with no intact fibers at the greater tuberosity insertion (solid white arrow). There is associated retraction (dashed arrow) and a fluid gap, as well as a correlative finding (red arrow) that corresponds to the cartilage interface sign seen on the US image. (c) In a companion case, an arthroscopic image of the right shoulder from a posterior viewing portal was obtained in a 55-year-old woman who sustained right shoulder trauma that resulted in a full-thickness SST tear. The tear and associated tendon gapping (double-headed arrow) are seen. There is also associated SST retraction (arrow) nearly to the level of the glenoid and exposure of the underlying humeral head (HH).
Partial-Thickness RC Tear.—Partial-thickness RC tears involve a portion of the tendon thickness (ie, articular surface or bursal surface). They appear as focal hypoechoic regions involving the articular (Fig 15) or bursal (Fig 16) surface of the tendon or as mixed hypo- and hyperechoic foci within the critical zone of the tendon (51,56). When evaluating possible partial-thickness RC tears with US, toggling of the transducer should be performed to eliminate anisotropy, which again can mimic tendinopathy or a partial-thickness articular surface–sided tear. Secondary findings of partial-thickness RC tears include cortical irregularity—or “pitting”—at the tendon insertion (Fig 15a) and transducer pressure–induced depression of the SASD bursa into the tear defect, which is seen with bursal surface–sided tears (Fig 17).
Figure 15a.
Partial-thickness articular surface SST tear in a 57-year-old man with right shoulder pain. (a) Short-axis US image of the right SST shows disruption of the SST along the articular surface, with anechoic tendon disruption (solid white arrow) and intact overlying bursal fibers (dashed arrow). Cortical irregularity (red arrows) is a secondary finding in the setting of articular surface tear. (b) Double oblique sagittal T2-weighted MR image of the right shoulder shows abnormal signal intensity (solid arrow) along the articular surface of the SST, with intact overlying bursal fibers (dashed arrow).
Figure 16a.
Partial-thickness bursal surface SST tear in an 84-year-old woman with chronic right shoulder pain. (a) Long-axis US image of the right SST shows a proximal partial-thickness bursal surface tear, as evidenced by a focal defect in the bursal fibers (arrow). This finding highlights the importance of examining the proximal and medial regions of the SST. There were also areas of articular surface tearing involving the distal anterior region of the SST (not shown). (b) Oblique coronal T2-weighted MR image shows a focal area of abnormal high signal intensity (arrow) within the bursal fibers of the SST. There were also areas of articular surface tearing involving the distal anterior region of the SST (not shown).
Figure 17.
Partial-thickness bursal surface tear in a 46-year-old man with bilateral shoulder pain. Short-axis US image of the left SST shows irregular disruption of the SST bursal surface fibers (solid arrow), with anechoic tendon disruption and transducer pressure–induced depression of the bursa into the defect (dashed arrow). The articular surface fibers (arrowhead) are intact.
Figure 15b.
Partial-thickness articular surface SST tear in a 57-year-old man with right shoulder pain. (a) Short-axis US image of the right SST shows disruption of the SST along the articular surface, with anechoic tendon disruption (solid white arrow) and intact overlying bursal fibers (dashed arrow). Cortical irregularity (red arrows) is a secondary finding in the setting of articular surface tear. (b) Double oblique sagittal T2-weighted MR image of the right shoulder shows abnormal signal intensity (solid arrow) along the articular surface of the SST, with intact overlying bursal fibers (dashed arrow).
Figure 16b.
Partial-thickness bursal surface SST tear in an 84-year-old woman with chronic right shoulder pain. (a) Long-axis US image of the right SST shows a proximal partial-thickness bursal surface tear, as evidenced by a focal defect in the bursal fibers (arrow). This finding highlights the importance of examining the proximal and medial regions of the SST. There were also areas of articular surface tearing involving the distal anterior region of the SST (not shown). (b) Oblique coronal T2-weighted MR image shows a focal area of abnormal high signal intensity (arrow) within the bursal fibers of the SST. There were also areas of articular surface tearing involving the distal anterior region of the SST (not shown).
Subacromial Impingement.—Dynamic evaluation for possible subacromial impingement involving the SST and SASD bursa is important when examining the painful shoulder. Providing a rationale for treatment with anterior acromioplasty, Neer (42) proposed that impingement syndromes involving the coracoacromial arch are associated with as many as 95% of RC tears. Physical examination tools such as the Neer test, Hawkins-Kennedy test, and painful arc signs have been used to assess possible impingement and implicate the acromion as the underlying cause of impingement; however, the value and diagnostic accuracy of these tests have been debated (57).
Positive findings for soft-tissue subacromial impingement at dynamic US evaluation include impaired gliding, soft-tissue compression, bursal fluid pooling, and bursal thickening (Fig 18) (58). Osseous impingement is observed when there is upward migration of the humeral head that impedes movement under the acromion. Ultimately, the imaging findings should be interpreted in conjunction with the patient’s symptoms. US grading systems have been devised on the basis of the clinical presentation, dynamic examination findings (eg, soft-tissue or osseous impingement), and associated RC tears (58,59).
Figure 18a.
Subacromial impingement and partial-thickness SST tears in a 44-year-old man with right anterior shoulder pain, which worsened with swimming and boxing. (a) Long-axis US image obtained at dynamic examination of the right shoulder in the abducted position shows bunching and distension of the SASD bursa (solid arrows), as well as bunching of the SST fibers (dashed arrow). A = acromion, GT = greater tuberosity. (b) Long-axis US image of the right SST shows associated deep partial-thickness SST tears with articular surface–sided (solid white arrow) and bursal surface–sided (dashed arrow) components and cortical irregularity (arrowhead).
Figure 18b.
Subacromial impingement and partial-thickness SST tears in a 44-year-old man with right anterior shoulder pain, which worsened with swimming and boxing. (a) Long-axis US image obtained at dynamic examination of the right shoulder in the abducted position shows bunching and distension of the SASD bursa (solid arrows), as well as bunching of the SST fibers (dashed arrow). A = acromion, GT = greater tuberosity. (b) Long-axis US image of the right SST shows associated deep partial-thickness SST tears with articular surface–sided (solid white arrow) and bursal surface–sided (dashed arrow) components and cortical irregularity (arrowhead).
Calcific Tendinitis.—Calcific tendinitis is a dynamic process characterized by calcium hydroxyapatite crystal deposition that most commonly affects the RC in patients aged 30–50 years (60). Although the exact pathogenesis of this condition remains unknown, it is probably multifactorial—likely being related to degeneration, reactive change, predisposing medical conditions, and genetics (60). Uhthoff et al (61) proposed that calcific tendinitis occurs in multiple stages—namely, the precalcific, calcific (including formative and resorptive phases), and postcalcific stages—and that pain primarily occurs during the resorptive phase. The SST is the most commonly affected tendon of the RC, and hydroxyapatite deposition occurs approximately 10 mm from the SST insertion on the greater tuberosity, although any portion of the RC—and even the LHBT and SASD—can be involved.
US is useful for detecting and localizing the characteristic calcifications seen with calcific tendinitis, and its capability to guide therapeutic needle placement and lavage for symptomatic calcific tendinitis represents a unique advantage (62,63). RC calcifications appear as fluffy or well-defined hyperechoic deposits within the tendon, with or without associated posterior acoustic shadowing (Fig 19a). Color Doppler US may be helpful in differentiating the formative phase from the resorptive phase, with an increased color Doppler signal being associated with the resorptive phase (64). At MR imaging, the calcium deposits are hypointense, and they may show associated blooming and surrounding intratendinous high signal intensity, representing edema, on T2-weighted images (Fig 19b).
Figure 19a.
Calcific tendinitis in a 33-year-old man with a multiple-year history of right shoulder pain. (a) Long-axis US image of the right SST shows fluffy oval echogenic hydroxyapatite deposits (arrows) in the SST. These deposits were targeted for US-guided lavage. (b) Oblique coronal T2-weighted MR image of the right shoulder shows hypointense calcific hydroxyapatite deposits (solid arrows) in the SST, with surrounding edema (dashed arrow), which is compatible with associated inflammatory change in the setting of calcific tendinitis.
Figure 19b.
Calcific tendinitis in a 33-year-old man with a multiple-year history of right shoulder pain. (a) Long-axis US image of the right SST shows fluffy oval echogenic hydroxyapatite deposits (arrows) in the SST. These deposits were targeted for US-guided lavage. (b) Oblique coronal T2-weighted MR image of the right shoulder shows hypointense calcific hydroxyapatite deposits (solid arrows) in the SST, with surrounding edema (dashed arrow), which is compatible with associated inflammatory change in the setting of calcific tendinitis.
Subacromial-Subdeltoid Bursa.—Other conditions that can affect the SASD bursa include bursal reaction or effusion secondary to underlying RC disease, and infectious or inflammatory SASD bursitis. Van Holsbeeck and Strouse (33) dichotomized SASD bursal distension into communicating and noncommunicating forms with respect to the glenohumeral joint. As more than 90% of patients with RC tears have concomitant abnormal SASD bursal distension (33), the most common cause of communicating bursal distension is RC tear.
Examples of noncommunicating SASD bursal distension include reactive bursitis that occurs with subacromial impingement, hemorrhagic bursitis in the setting of direct trauma, inflammatory bursitis in inflammatory arthropathy, and infectious or septic bursitis in the setting of immune compromise or intravenous drug use. Hydroxyapatite deposition or calcific SASD bursitis (Fig 20) also may occur.
Figure 20a.
Calcific SASD bursitis in a 53-year-old man with right shoulder pain, in whom a calcified mass was seen on recently obtained radiographs (not shown). (a) Long-axis US image of the right SASD shows a large echogenic calcified hydroxyapatite excrescence (solid arrows) within the SASD bursa. There is adjacent bursal thickening (dashed arrow). (b) Oblique coronal T2-weighted MR image of the right shoulder shows the large hypointense calcified hydroxyapatite excrescence (solid arrows) within the SASD bursa, with surrounding high signal intensity (dashed arrow), which is compatible with associated inflammatory change.
Figure 20b.
Calcific SASD bursitis in a 53-year-old man with right shoulder pain, in whom a calcified mass was seen on recently obtained radiographs (not shown). (a) Long-axis US image of the right SASD shows a large echogenic calcified hydroxyapatite excrescence (solid arrows) within the SASD bursa. There is adjacent bursal thickening (dashed arrow). (b) Oblique coronal T2-weighted MR image of the right shoulder shows the large hypointense calcified hydroxyapatite excrescence (solid arrows) within the SASD bursa, with surrounding high signal intensity (dashed arrow), which is compatible with associated inflammatory change.
SASD bursal effusion appears as teardrop-shaped bursal distension. The collection may consist of simple anechoic fluid or have varying complexity, depending on the underlying mechanism (eg, dependent internal echoes in the setting of hemorrhage, or complex fluid, debris, and septa in the setting of infection) (Fig 21a). A common pitfall is that the SASD bursal collection may be isoechoic to the deltoid muscle and lead to a false-negative diagnosis. The T2-weighted MR imaging correlate for bursal effusion is fluid signal intensity in the SASD bursa. Power Doppler US images may show increased signal when there is acute inflammation, which is seen as enhancement on contrast-enhanced MR images (Fig 21b). US can also be used to guide needle placement for either aspiration in cases of infectious bursitis or corticosteroid injection in the setting of impingement-related reactive bursitis.
Figure 21a.
Infectious SASD bursitis in a 35-year-old woman with a history of renal transplantation who presented with bacteremia, left shoulder pain, and swelling. (a) Short-axis color Doppler US image shows a complex SASD bursal fluid collection with septa (solid arrow) and associated bursal thickening (dashed arrow). There is also pronounced hyperemia at the margins of the SASD bursa and in the adjacent deltoid muscle. (b) Oblique coronal contrast-enhanced T1-weighted fat-suppressed MR image of the left shoulder shows a complex thick-walled, peripherally enhancing SASD bursa collection (arrow), which is compatible with abscess.
Figure 21b.
Infectious SASD bursitis in a 35-year-old woman with a history of renal transplantation who presented with bacteremia, left shoulder pain, and swelling. (a) Short-axis color Doppler US image shows a complex SASD bursal fluid collection with septa (solid arrow) and associated bursal thickening (dashed arrow). There is also pronounced hyperemia at the margins of the SASD bursa and in the adjacent deltoid muscle. (b) Oblique coronal contrast-enhanced T1-weighted fat-suppressed MR image of the left shoulder shows a complex thick-walled, peripherally enhancing SASD bursa collection (arrow), which is compatible with abscess.
Posterior Examination
Pertinent Anatomy
Infraspinatus Tendon of the Rotator Cuff.—The infraspinatus muscle originates from the infraspinatus fossa of the scapula and is responsible for external rotation of the shoulder. The IST (Figs 22, 23) courses superolaterally from the infraspinatus fossa and blends with the SST fibers near its insertion. The IST footprint has a trapezoidal configuration and reproducibly inserts onto the anterolateral portion of the superior facet of the greater tuberosity and along the entirety of the middle facet (31,32).
Figure 22.
Left: Computer-generated three-dimensional image of the posterior region of the shoulder shows the transducer positioned in the oblique axial plane for evaluation of the glenohumeral (GH) joint and labrum. Right: Corresponding long-axis US (top) and oblique axial proton-density–weighted fat-suppressed (PD FS) MR (bottom) images obtained in healthy volunteers. The MR image is flipped vertically for direct comparison with the US image. GL = glenoid, HH = humeral head.
Figure 23.
Left: Computer-generated three-dimensional image of the posterior region of the shoulder shows the transducer positioned slightly more medially in the oblique axial plane for evaluation of the SGN. Right: Corresponding long-axis US (top) and oblique axial proton-density–weighted fat-suppressed (PD FS) MR (bottom) images obtained in healthy volunteers. The MR image is flipped vertically for direct comparison with the US image. GL = glenoid, HH = humeral head.
Teres Minor Tendon of the Rotator Cuff.—The teres minor muscle originates from the superolateral border of the scapula and, along with the IST, functions to externally rotate the humerus. The teres minor tendon courses laterally to insert onto the inferior facet of the greater tuberosity and is the most posterior RC tendon insertion. It has an important role in shoulder functionality and patient satisfaction after debridement and decompression for massive RC tears (65).
Glenohumeral Joint and SGN.—The glenohumeral joint is a synovial “ball-and-socket”–type joint that is formed by the articulation of the humeral head with the glenoid process of the scapula. The peripheral glenoid rim is surrounded by a thick fibrocartilaginous glenoid labrum, which serves to deepen the articulation and stabilize the joint. The SGN is located along the posterosuperior aspect of the scapula, at the convergence of the acromion, scapular spine, and anatomic neck of the scapula. It is a connection between the supraspinatus and infraspinatus fossae.
US Technique and Imaging Appearance of the Normal Anatomy
For US evaluation of the posterior shoulder, one begins by orienting the transducer along the posterior region of the shoulder in a plane similar to the axial plane at MR imaging, with the patient’s arm in neutral resting adduction and the palm supinated on the lap. The posterior glenohumeral joint and posterior labrum can be visualized from this transducer position. The transducer is then moved medially along the scapular spine and slightly rotated to best visualize the SGN.
Evaluation of the posterior shoulder musculature begins with assessment of the supraspinatus muscle, which is identified on the basis of its position above the scapular spine, deep to the trapezius muscle. The transducer orientation along the long axis of the supraspinatus muscle belly is equivalent to the oblique coronal MR imaging plane, and the short axis of the supraspinatus muscle is equivalent to the oblique sagittal MR imaging plane. Next, the infraspinatus muscle is identified below the scapular spine. This muscle is readily identified on the basis of its triangular shape and by following its course to its insertion onto the greater tuberosity. With the transducer in the short-axis plane of the infraspinatus muscle, the teres minor muscle can be identified by moving the transducer inferiorly while maintaining the same transducer orientation (66).
At US, normal muscles have a pennate pattern, are hypoechoic, and have linear hyperechoic septa (Fig 24). To evaluate muscle bulk and find evidence of fatty atrophy, each muscle is evaluated along its length in short and long axis. An extended field of view that includes the short axis of both the SST and the IST facilitates comparison for evaluation of fatty atrophy. Right versus left comparisons of the short-axis (ie, cross-sectional) area of the SST and/or IST muscle also may be useful.
Figure 24.
Normal supraspinatus musculature in a 45-year-old woman. Short-axis US images used to compare the left and right supraspinatus muscles show symmetric muscle bulk. The muscles have a normal hypoechoic appearance, with linear hyperechoic septa and a normal pennate pattern.
Common Indications and Diseases
Common indications for evaluation of the shoulder include RC tear (IST, teres minor tendon), RC muscle bulk and atrophy, SGN cyst, glenohumeral joint degeneration, glenohumeral joint synovitis, and percutaneous needle guidance (eg, for SGN cyst aspiration or US-guided corticosteroid injection).
RC Tear and Muscle Atrophy.—RC tears involving the IST are similar in appearance to the described RC tears involving the SST. Assessment of the RC musculature is important because fatty atrophy in the setting of RC tear is a negative prognostic factor in the subsequent RC repair (67–69), and US and MR imaging have comparable diagnostic performance in the detection of RC atrophy (70). Muscular atrophy can also be seen with non–tear-related conditions such as shoulder denervation syndromes.
On US images, muscle atrophy appears as increased echogenicity relative to that of the adjacent normal deltoid or trapezius muscle, with loss of the normal muscle architecture (ie, contour, intramuscular tendons, and pennate pattern) (Fig 25). Various US grading schemes have been devised using these changes as imaging markers (70,71).
Figure 25.
Fatty atrophy of the supraspinatus muscle in a 54-year-old woman with long-standing right anterior shoulder pain. Long-axis US images were obtained to compare the affected right supraspinatus muscle (S) with the unaffected left supraspinatus muscle. Right image shows the characteristic US findings of muscular atrophy in the setting of a full-thickness full-width SST tear. These findings include size asymmetry (right side smaller than left side), increased echogenicity (arrow), and loss of the normal muscle architecture compared with the architecture of the adjacent trapezius muscle (T).
SGN and Posterior Labrum.—Evaluation of the SGN and posterior labrum is performed to evaluate possible paralabral or ganglion cysts (Fig 26). On US images, these cysts appear as anechoic or hypoechoic masses (Fig 26a). The corresponding MR imaging findings are single or multilobulated fluid signal intensity masses at the SGN (Fig 26b). Identification of an SGN cyst should prompt complete MR imaging evaluation of the adjacent labrum in the appropriate clinical setting since these cysts are associated with posterior-superior labral tears and capsulolabral injury, and MR imaging and MR arthrography are more accurate than US for characterizing underlying labral disease (72). Depending on the size and extent of the cyst, entrapment neuropathy may ensue owing to compression of the suprascapular nerve. Isolated involvement of the infraspinatus muscle suggests nerve compression at the SGN, whereas supraspinatus and infraspinatus muscle involvement suggests extension into the suprascapular notch (73). Although US can be used to direct needle placement for SGN cyst aspiration (74), management of the underlying labral tears is likely to be required for durable treatment.
Figure 26a.
(a, b) SGN cyst in a 28-year-old man with left shoulder pain and a posterior-superior labral tear. (a) Long-axis US image obtained over the left posterior region of the shoulder shows a large multilobulated hypoechoic cyst (thin arrows), with low-level echoes occupying the SGN (dashed line). (b) Oblique axial T2-weighted MR image (flipped vertically) of the left shoulder shows a multilobulated paralabral cyst (solid arrow) at the SGN in conjunction with a posterior-superior labral tear (dashed arrow). (c) In a companion case, the arthroscopic image obtained in a 52-year-old man with chronic shoulder pain and an SGN cyst shows a large cyst (arrows) in the setting of a posterior labral tear. GL = glenoid.
Figure 26b.
(a, b) SGN cyst in a 28-year-old man with left shoulder pain and a posterior-superior labral tear. (a) Long-axis US image obtained over the left posterior region of the shoulder shows a large multilobulated hypoechoic cyst (thin arrows), with low-level echoes occupying the SGN (dashed line). (b) Oblique axial T2-weighted MR image (flipped vertically) of the left shoulder shows a multilobulated paralabral cyst (solid arrow) at the SGN in conjunction with a posterior-superior labral tear (dashed arrow). (c) In a companion case, the arthroscopic image obtained in a 52-year-old man with chronic shoulder pain and an SGN cyst shows a large cyst (arrows) in the setting of a posterior labral tear. GL = glenoid.
Figure 26c.
(a, b) SGN cyst in a 28-year-old man with left shoulder pain and a posterior-superior labral tear. (a) Long-axis US image obtained over the left posterior region of the shoulder shows a large multilobulated hypoechoic cyst (thin arrows), with low-level echoes occupying the SGN (dashed line). (b) Oblique axial T2-weighted MR image (flipped vertically) of the left shoulder shows a multilobulated paralabral cyst (solid arrow) at the SGN in conjunction with a posterior-superior labral tear (dashed arrow). (c) In a companion case, the arthroscopic image obtained in a 52-year-old man with chronic shoulder pain and an SGN cyst shows a large cyst (arrows) in the setting of a posterior labral tear. GL = glenoid.
Glenohumeral Joint.—Evaluation of the posterior shoulder may also reveal the causes of symptomatic glenohumeral joint disease—namely, osteoarthritis or synovitis. Although US is not a primary modality for evaluating glenohumeral degenerative joint disease, the characteristic findings of severe degenerative joint disease may be evident, including severe joint space narrowing, bulky osteophytosis, and cortical irregularity. Shoulder US findings should always be correlated with shoulder radiographic findings. Degenerative tearing of the posterior labrum and echogenic joint bodies or debris may also be seen. These changes should be noted, as severe glenohumeral degenerative joint disease has important negative implications for surgical outcomes in the setting of RC tear (69).
Last, power Doppler US may have clinical value in the diagnosis of synovial proliferation and inflammatory changes that are indicative of synovitis, such as that seen with early rheumatoid arthritis, before cartilage degeneration and erosive disease (75). Changes of synovitis appear as anechoic effusion or synovial thickening involving the posterior and axillary joint recesses, with an associated increase in power Doppler flow.
Conclusion
US is an important and complementary imaging tool for the evaluation of the superficial soft-tissue structures of the shoulder. The advantages of performing US, including patient satisfaction, low cost, accessibility, real-time dynamic assessment, and needle guidance, have helped to drive the recent increase in its use. As more radiologists are looking to implement shoulder US into their clinical practices, comfort in performing standardized shoulder US examinations and familiarity with the types of diseases that are best evaluated using US are imperative for the delivery of high-quality patient care. To facilitate these objectives, we have used a standardized shoulder US examination framework (ASAP [anterior, superior, anterolateral, and posterior]) to review the basic shoulder US technique, normal shoulder anatomy, common indications for US of the painful shoulder, and characteristic US appearances of common shoulder anomalies, with multimodality correlation. Using a standardized approach to shoulder US will aid radiologists, sonographers, and technologists in overcoming the barriers to implementing shoulder US in clinical practice and help to promote high-quality diagnostic imaging.
For this journal-based SA-CME activity, the authors S.E.S. and K.S.L. have provided disclosures (see “Disclosures of Conflicts of Interest”); all other authors, the editor, and the reviewers have disclosed no relevant relationships.
K.S.L. supported by the RSNA Research & Education Foundation (2013–2015 RSNA Research Scholar Grant RSCH1317) and the National Institutes of Health (UL1TR000427).
Disclosures of Conflicts of Interest.—: S.E.S. Activities related to the present article: disclosed no relevant relationships. Activities not related to the present article: edited textbook for Elsevier. Other activities: disclosed no relevant relationships. K.S.L. Activities related to the present article: received royalties from Elsevier and nonfinancial support from SuperSonic Imagine and Arthrex. Activities not related to the present article: disclosed no relevant relationships. Other activities: disclosed no relevant relationships.
Abbreviations:
- AC
- acromioclavicular
- IST
- infraspinatus tendon
- LHBT
- long head of the biceps tendon
- RC
- rotator cuff
- SASD
- subacromial-subdeltoid
- SST
- supraspinatus tendon
- SubST
- subscapularis tendon
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