DOI: 10.1148/rg.232025100
(Radiographics. 2003;23:381-401.)
© RSNA, 2003
US of the Shoulder: Non–Rotator Cuff Disorders1
Carlo Martinoli, MD,
Stefano Bianchi, MD,
Nicolò Prato, MD,
Francesca Pugliese, MD,
Maria Pia Zamorani, MD,
Maura Valle, MD and
Lorenzo E. Derchi, MD
1 From the Cattedra "R" di Radiologia-DICMI, Università di Genova, Largo Rosanna Benzi 8, 16132 Genoa, Italy (C.M., F.P., L.E.D.); the Department of Radiology, Hôpital Cantonal Universitaire, Geneva, Switzerland (S.B., M.P.Z.); the Department of Radiology, Ospedale San Carlo, Genoa, Italy (N.P.); and the Department of Radiology, Istituto Giannina Gaslini, Genoa, Italy (M.V.). Recipient of a Cum Laude award for an education exhibit at the 2001 RSNA scientific assembly. Received May 20, 2002; revision requested June 13 and received July 26; accepted August 1. Address correspondence to C.M. (e-mail: martinoli@zeus.newnetworks.it).
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Abstract
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The most common indication for shoulder ultrasonography (US) is the diagnosis of rotator cuff disease. However, there is a spectrum of non–rotator cuff abnormalities that are amenable to US examination, including instability of the biceps tendon, glenohumeral joint, and acromioclavicular joint; arthropathies and bursites (inflammatory diseases, degenerative and infiltrative disorders, infections); nerve entrapment syndromes; and space-occupying lesions. Many of these conditions may be overlooked clinically or can even mimic rotator cuff tears, and US can help redirect the diagnosis if a complete shoulder examination rather than a simple rotator cuff assessment is performed. In addition, US can be remarkably helpful in guiding either needle aspiration procedures or local injection therapy in patients with synovial processes. Although radiography, magnetic resonance (MR) imaging, and computed tomographic and MR arthrography are effective modalities for the evaluation of non–rotator cuff disorders, US is both less costly and less invasive and will likely be used more frequently in this setting as experience increases. Once adequate radiographs have been obtained to exclude apparent bone disorders, high-resolution US should be the first-line imaging modality in the assessment of non–rotator cuff disorders of the shoulder, assuming the study is performed with high-end equipment by an experienced examiner.
© RSNA, 2003
Index Terms: Shoulder, anatomy, 41.92 • Shoulder, arthritis, 41.71, 41.772 • Shoulder, dislocation, 41.42 • Shoulder, injuries, 41.481 • Shoulder, US, 41.1298
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LEARNING OBJECTIVES FOR TEST 3
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After reading this article and taking the test, the reader will be able to:
- Identify the main US findings in non–rotator cuff abnormalities of the shoulder.
- Describe the proper technique for imag- ing non–rotator cuff disorders.
- Discuss the utility of US in evaluating these pathologic conditions.
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SUPPLEMENTAL MATERIAL
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Movie clips to supplement this article are available online at radiographics.rsnajnls.org/cgi/content/full/23/2/381/DC1.
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Introduction
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The shoulder is one of the anatomic areas that is most commonly evaluated with musculoskeletal ultrasonography (US). When performed with appropriate equipment by skilled operators, US is widely recognized as a means of accurately assessing rotator cuff disease, with a sensitivity and specificity as high as 90%–95% in the assessment of both partial- and full-thickness tears (1,2). Nevertheless, radiologists as a whole are poorly informed regarding the contributions that US can make in the assessment of non–rotator cuff abnormalities such as instability problems, synovial joint diseases, and nerve entrapment syndromes. Only a few US studies have been conducted to evaluate these conditions, and most of these studies describe only a limited number of cases or lack a standard of reference. Thus, US probably remains underused in this context. Other imaging modalities such as magnetic resonance (MR) imaging and computed tomographic (CT) and MR arthrography will probably remain the modalities of choice for diagnosing most non–rotator cuff disorders: With these modalities, image acquisition is less operator dependent and evaluation of anatomic relationships and soft-tissue structures (eg, capsule, labrum, bone) is intuitively easier and can be more readily performed. However, high-resolution US is quick, noninvasive, and inexpensive and has specific advantages over MR imaging. These advantages, which include the capacity for higher resolution and for examining tissues in both static and dynamic states with the patient in different positions, warrant the wider use of US in the evaluation of non–rotator cuff disorders.
In this article, we review the major types of non–rotator cuff abnormalities that can be diagnosed with US, with emphasis on musculoskeletal anatomy, US technique, and main US findings. Because of the wide range and heterogeneity of these abnormalities, we arbitrarily grouped them into instability problems, arthropathies and bursites, nerve entrapment syndromes, and space-occupying lesions.
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Instability Problems
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Because of its wide range of motion, the shoulder is susceptible to dislocations, subluxations, and lesions related to chronic stress in the surrounding soft tissues. Regardless of the type of abnormality or instability pattern, a combination of different osseous and soft-tissue restraints such as the ligaments, tendons, labrum, and capsule have increasingly received recognition either as stabilizers or as structures that sustain secondary damage in these situations. The main shoulder structures that can be evaluated with US in patients with instability problems are the long head of the biceps tendon (LBT), the glenohumeral joint (GHJ), and the acromioclavicular joint (ACJ).
Biceps Tendon
Because of its curvilinear course and its reflection over the humeral head, the LBT is prone to medial displacement, especially during powerful contraction of the biceps muscle or maximal external rotation. The tendon is retained in its proper anatomic location by the conformation of the humeral biceps sulcus and by various tendinous and ligamentous structures encountered at three different levels along its course. From cranial to caudal, these structures are the coracohumeral ligament (CHL) and superior glenohumeral ligament, the transverse humeral ligament (THL), and the tendon of the pectoralis major muscle.
The LBT enters the GHJ through the rotator cuff interval, the space between the subscapularis and supraspinatus tendons. The rotator cuff interval also houses the CHL, which courses above the LBT and then bifurcates, blending with the adjacent cuff tendons and the underlying joint capsule (Fig 1a). The anterior band of the CHL joins with the superior glenohumeral ligament to form a strong sling, commonly referred to as the reflection pulley, which inserts into the lesser tuberosity and stabilizes the LBT before the LBT enters the bicipital groove, thus protecting it against anterior shearing stress (3–5). High-resolution US can depict the CHL. Proper positioning is achieved when the patient extends the lower arm posteriorly by placing the palm of the hand on the superior aspect of the iliac wing with the elbow flexed and directed toward midline. This position causes maximal opening of the rotator cuff interval. The intraarticular portion of the LBT flattens as it is stretched against the humeral cartilage, and the CHL is tightened between the subscapularis and supraspinatus tendons. The CHL appears as a thick, homogeneously echogenic band of tissue that covers the LBT; it measures 2–3 mm in thickness and can be differentiated from the LBT because it is less anisotropic (Fig 1b). Its deep margin is delineated by a thin hypoechoic layer that bulges anteriorly from the deep edge of the supraspinatus tendon, possibly representing an interface between this ligament and the joint capsule. Although US cannot help detect the superior glenohumeral ligament, depiction of a normal-appearing CHL with absence of intraarticular fluid around the LBT almost always indicates an intact rotator cuff interval. When the CHL is torn, the intraarticular portion of the LBT may appear surrounded by fluid (possibly on both sides) and elevated from the humeral cartilage (Fig 1c). In such cases, the LBT may exhibit increased mediolateral motion during rotational movements (see Movie 1 at radiographics.rsnajnls.org/cgi/content/full/23/2/381/DC1). Chronic microtraumas can lead to early degeneration of the LBT and fissures in the inferior aspect of the tendon. Disruption of the superior border of the subscapularis tendon is almost invariably associated with these lesions (6).
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Figure 1a. Rotator cuff interval. (a) Schematic illustrates the relationship of the CHL (green) to the subscapularis (SubS) and supraspinatus (SS) tendons. The ligament forms the roof of the intraarticular portion of the biceps tendon (orange). (b) Corresponding transverse 12-5-MHz US image demonstrates the flattened, echogenic intraarticular portion of the biceps tendon (arrow) anterior to the supraspinatus tendon (SS). The CHL (*) is seen as an echogenic band of tissue superficial to the biceps tendon. A thin hypoechoic layer (arrowheads) bulges from the deep edge of the supraspinatus tendon and intervenes between the ligament and the biceps tendon, a finding that may represent the capsular interface. (c) Transverse 12-5-MHz US image obtained in a 42-year-old man with a surgically confirmed lesion in the rotator cuff interval that involved the CHL and the fibers of the superior capsule shows hypoechoic fluid surrounding an intact biceps tendon (arrow). Note the absence of the CHL. SS = supraspinatus tendon.
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Figure 1b. Rotator cuff interval. (a) Schematic illustrates the relationship of the CHL (green) to the subscapularis (SubS) and supraspinatus (SS) tendons. The ligament forms the roof of the intraarticular portion of the biceps tendon (orange). (b) Corresponding transverse 12-5-MHz US image demonstrates the flattened, echogenic intraarticular portion of the biceps tendon (arrow) anterior to the supraspinatus tendon (SS). The CHL (*) is seen as an echogenic band of tissue superficial to the biceps tendon. A thin hypoechoic layer (arrowheads) bulges from the deep edge of the supraspinatus tendon and intervenes between the ligament and the biceps tendon, a finding that may represent the capsular interface. (c) Transverse 12-5-MHz US image obtained in a 42-year-old man with a surgically confirmed lesion in the rotator cuff interval that involved the CHL and the fibers of the superior capsule shows hypoechoic fluid surrounding an intact biceps tendon (arrow). Note the absence of the CHL. SS = supraspinatus tendon.
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Figure 1c. Rotator cuff interval. (a) Schematic illustrates the relationship of the CHL (green) to the subscapularis (SubS) and supraspinatus (SS) tendons. The ligament forms the roof of the intraarticular portion of the biceps tendon (orange). (b) Corresponding transverse 12-5-MHz US image demonstrates the flattened, echogenic intraarticular portion of the biceps tendon (arrow) anterior to the supraspinatus tendon (SS). The CHL (*) is seen as an echogenic band of tissue superficial to the biceps tendon. A thin hypoechoic layer (arrowheads) bulges from the deep edge of the supraspinatus tendon and intervenes between the ligament and the biceps tendon, a finding that may represent the capsular interface. (c) Transverse 12-5-MHz US image obtained in a 42-year-old man with a surgically confirmed lesion in the rotator cuff interval that involved the CHL and the fibers of the superior capsule shows hypoechoic fluid surrounding an intact biceps tendon (arrow). Note the absence of the CHL. SS = supraspinatus tendon.
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The THL is in distal continuity with the CHL and is composed of the most superficial fibers of the subscapularis tendon. The THL bridges the lesser and greater tuberosities, thereby transforming the bicipital sulcus into an osteofibrous tunnel (Fig 2a). However, the THL is weak, and its role in stabilizing the LBT just distal to its exit from the rotator cuff interval is not considered important unless the CHL is torn (5,6). Careful scanning with the transducer placed in a transverse position over the tuberosities is required to recognize the instability of the LBT at the humeral groove. The normal THL can be seen as a thin echogenic layer that overlies the bicipital sulcus (Fig 2b). In the proximal groove, an LBT that rests against the medial wall of the sulcus is a normal finding. The tendon is referred to as subluxated when it is perched over the tip of the lesser tuberosity and as dislocated when it lies on the outer slope of the groove (7,8). The LBT does not undergo medial subluxation or dislocation out of the bicipital groove when the CHL is intact, even with subscapularis tendon tear (6). On the other hand, if the CHL is torn but the subscapularis tendon is intact, the LBT can become dislocated superficial to the tendon (Fig 3a, 3b; see also Movie 2 at radiographics.rsnajnls.org/cgi/content/full/23/2/381/DC1) (5,6). The most common condition, however, is tearing of both the subscapularis tendon and the CHL (Fig 3c, 3d). In such cases, the disruption of the subscapularis tendon may allow the LBT to slip medially over the lesser tuberosity within the GHJ (see Movie 3 at radiographics.rsnajnls.org/cgi /content/full/23/2/381/DC1). Scanning with the patient’s arm in external rotation can accentuate the subluxation of the LBT and further increase sensitivity to this condition. In acute dislocation, the US diagnosis is based on the absence of the LBT within the groove and its detection in a more medial position (8). Occasionally, the dislocated LBT may be difficult to identify due to its location deep within the GHJ. Transverse imaging at a more distal level can allow visualization of the LBT surrounded by a hypoechoic effusion; then, the tendon can be followed upward to its intraarticular portion. Difficulties may also arise in long-standing dislocations, in which the empty groove may be filled with echogenic fibrous scar tissue that mimics a normally positioned LBT (Fig 3c) (9). Scanning the entire length of the groove longitudinally to look for the fibrillar pattern of the LBT, which is not seen in scar tissue, may help increase the examiner’s confidence (1). In intermittent instability, a "to-and-fro" medial displacement of the tendon out of the groove is reported during maximal external and internal rotation of the arm (10). The entire length of the humeral groove should also be examined with transverse imaging to determine the osseous anatomy of the groove (11). In fact, a congenital shallow intertubercular sulcus (<3 mm deep) with a flat medial wall intrinsically predisposes to LBT instability (Fig 3a).
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Figure 2a. Biceps tendon groove. (a) Schematic illustrates how the biceps tendon (orange) is located between the greater tuberosity (GT) and the lesser tuberosity (LT) and covered by the THL (green). G = glenoid region of the scapula, SubS = subscapularis tendon. (b) Corresponding transverse 12-5-MHz US image demonstrates the THL (arrowheads) as a thin echogenic layer that overlies the biceps tendon (arrow). The bone groove has a normal size and shape. GT = greater tuberosity, LT = lesser tuberosity, SubS = subscapularis tendon.
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Figure 2b. Biceps tendon groove. (a) Schematic illustrates how the biceps tendon (orange) is located between the greater tuberosity (GT) and the lesser tuberosity (LT) and covered by the THL (green). G = glenoid region of the scapula, SubS = subscapularis tendon. (b) Corresponding transverse 12-5-MHz US image demonstrates the THL (arrowheads) as a thin echogenic layer that overlies the biceps tendon (arrow). The bone groove has a normal size and shape. GT = greater tuberosity, LT = lesser tuberosity, SubS = subscapularis tendon.
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Figure 3a. Biceps tendon dislocation. (a, b) Intact subscapularis tendon in a 27-year-old man with biceps tendon instability. Transverse 12-5-MHz US image (a) and corresponding gradient-recalled-echo (GRE) MR image (repetition time msec/echo time msec/flip angle = 400/12/90°) (b) demonstrate the biceps tendon (arrow) displaced superficial to the intact subscapularis tendon (* in a). Note that the intertubercular sulcus (arrowheads in a) is obtuse. (c, d) Full-thickness tear of the subscapularis tendon in a 58-year-old man with impingement syndrome. On a transverse 12-5-MHz US image (c) and corresponding GRE MR image (550/15/25°) (d), the torn subscapularis tendon (* in c) is retracted from its normal attachment point on the lesser tuberosity, and the biceps tendon (arrow) is dislocated medially out of the groove (arrowheads in c).
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Figure 3b. Biceps tendon dislocation. (a, b) Intact subscapularis tendon in a 27-year-old man with biceps tendon instability. Transverse 12-5-MHz US image (a) and corresponding gradient-recalled-echo (GRE) MR image (repetition time msec/echo time msec/flip angle = 400/12/90°) (b) demonstrate the biceps tendon (arrow) displaced superficial to the intact subscapularis tendon (* in a). Note that the intertubercular sulcus (arrowheads in a) is obtuse. (c, d) Full-thickness tear of the subscapularis tendon in a 58-year-old man with impingement syndrome. On a transverse 12-5-MHz US image (c) and corresponding GRE MR image (550/15/25°) (d), the torn subscapularis tendon (* in c) is retracted from its normal attachment point on the lesser tuberosity, and the biceps tendon (arrow) is dislocated medially out of the groove (arrowheads in c).
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Figure 3c. Biceps tendon dislocation. (a, b) Intact subscapularis tendon in a 27-year-old man with biceps tendon instability. Transverse 12-5-MHz US image (a) and corresponding gradient-recalled-echo (GRE) MR image (repetition time msec/echo time msec/flip angle = 400/12/90°) (b) demonstrate the biceps tendon (arrow) displaced superficial to the intact subscapularis tendon (* in a). Note that the intertubercular sulcus (arrowheads in a) is obtuse. (c, d) Full-thickness tear of the subscapularis tendon in a 58-year-old man with impingement syndrome. On a transverse 12-5-MHz US image (c) and corresponding GRE MR image (550/15/25°) (d), the torn subscapularis tendon (* in c) is retracted from its normal attachment point on the lesser tuberosity, and the biceps tendon (arrow) is dislocated medially out of the groove (arrowheads in c).
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Figure 3d. Biceps tendon dislocation. (a, b) Intact subscapularis tendon in a 27-year-old man with biceps tendon instability. Transverse 12-5-MHz US image (a) and corresponding gradient-recalled-echo (GRE) MR image (repetition time msec/echo time msec/flip angle = 400/12/90°) (b) demonstrate the biceps tendon (arrow) displaced superficial to the intact subscapularis tendon (* in a). Note that the intertubercular sulcus (arrowheads in a) is obtuse. (c, d) Full-thickness tear of the subscapularis tendon in a 58-year-old man with impingement syndrome. On a transverse 12-5-MHz US image (c) and corresponding GRE MR image (550/15/25°) (d), the torn subscapularis tendon (* in c) is retracted from its normal attachment point on the lesser tuberosity, and the biceps tendon (arrow) is dislocated medially out of the groove (arrowheads in c).
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Farther distal to the humeral tuberosities, the main stabilizing structure of the LBT is the tendon of the pectoralis major muscle. This flattened tendon crosses anterior to the myotendinous junction of the LBT and inserts into the lateral lip of the intertubercular groove. At US, the pectoralis major tendon is identified dorsal to the deltopectoral groove (Fig 4). Rupture of this tendon is quite uncommon and occurs at either the myotendinous or teno-osseous junction (12). In complete tears, US findings include either a wavy appearance or nonvisualization of the tendon, depending on the site of the tear (Fig 5). The presence of hypoechoic fluid in the tendinous bed related to hematoma can help in making the diagnosis. The LBT and its myotendinous junction are surrounded by fluid and may appear elevated from the humerus.
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Figure 4a. Pectoralis major tendon. (a) Schematic illustrates the relationship of the pectoralis major tendon (green) to the myotendinous junction of the biceps (B). The biceps muscle and biceps tendon are shown in red and orange, respectively. (b) Corresponding transverse 12-5-MHz US image obtained distal to the humeral tuberosities shows the pectoralis major tendon (arrowheads), which crosses the myotendinous junction of the biceps tendon (B) on its anterior aspect to insert onto the humeral shaft (H).
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Figure 4b. Pectoralis major tendon. (a) Schematic illustrates the relationship of the pectoralis major tendon (green) to the myotendinous junction of the biceps (B). The biceps muscle and biceps tendon are shown in red and orange, respectively. (b) Corresponding transverse 12-5-MHz US image obtained distal to the humeral tuberosities shows the pectoralis major tendon (arrowheads), which crosses the myotendinous junction of the biceps tendon (B) on its anterior aspect to insert onto the humeral shaft (H).
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Figure 5a. Pectoralis major tendon tear in a 37-year-old man who presented with pain after attempting to catch a heavy object. (a) Clinical photograph shows a palpable defect (arrow) in the anterior wall of the left axilla. (b) Transverse extended-field-of-view 12-5-MHz US image reveals hypoechoic fluid that fills the bed of the ruptured pectoralis major tendon (arrowheads). Note the medial retraction of the belly of the pectoralis major muscle (PM) and the anterior displacement of the myotendinous junction of the biceps tendon (B), which appears to be surrounded by fluid. D = deltoid muscle, H = humerus, Pm = pectoralis minor muscle.
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Figure 5b. Pectoralis major tendon tear in a 37-year-old man who presented with pain after attempting to catch a heavy object. (a) Clinical photograph shows a palpable defect (arrow) in the anterior wall of the left axilla. (b) Transverse extended-field-of-view 12-5-MHz US image reveals hypoechoic fluid that fills the bed of the ruptured pectoralis major tendon (arrowheads). Note the medial retraction of the belly of the pectoralis major muscle (PM) and the anterior displacement of the myotendinous junction of the biceps tendon (B), which appears to be surrounded by fluid. D = deltoid muscle, H = humerus, Pm = pectoralis minor muscle.
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Glenohumeral Joint
US is generally not appropriate for the evaluation of patients with GHJ instability. However, a scanning technique for documenting the presence, direction, and extent of glenohumeral translation has been described in patients with posterior shoulder subluxation or dislocation (13). With the examiner standing behind the patient, transverse scans should be obtained over the posterior GHJ to measure the distance between the dorsal rim of the bony glenoid and the tip of the humeral head. In voluntary subluxation, the patient is examined in different positions (neutral, 90° flexion, abduction, external rotation), including the position in which the patient perceives that the shoulder has become subluxated. The measured glenohumeral distances are compared for the affected shoulder and the healthy one: Differences greater than 20 mm indicate dislocation, whereas differences of 12 to 18 mm indicate subluxation (Fig 6).
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Figure 6a. Posterior GHJ instability in a 17-year-old girl with posterior voluntary subluxation. IS = infraspinatus tendon, L = posterior labrum. (a) Transverse 12-5-MHz US image obtained over the posterior right shoulder during subluxation shows that the humeral head (HH) is more exposed and posterior to the level of the bony glenoid (G) (dotted line). (b) US image obtained after reduction of the subluxation shows the humeral head (HH) and the glenoid (G) in exact apposition.
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Figure 6b. Posterior GHJ instability in a 17-year-old girl with posterior voluntary subluxation. IS = infraspinatus tendon, L = posterior labrum. (a) Transverse 12-5-MHz US image obtained over the posterior right shoulder during subluxation shows that the humeral head (HH) is more exposed and posterior to the level of the bony glenoid (G) (dotted line). (b) US image obtained after reduction of the subluxation shows the humeral head (HH) and the glenoid (G) in exact apposition.
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An attempt can also be made with US to detect a variety of instability injuries that affect the glenoid labrum and the bone. The fibrocartilaginous labrum can be visualized at US as a triangular, homogeneously hyperechoic structure that caps the bony rim of the glenoid (14). A thin (<2-mm) hypoechoic zone at the base of the labrum is a normal finding. The anterior labrum is best scanned with curved-array transducers and low frequencies (as low as 5 MHz) with an anterior or axillary transverse approach performed either with the patient’s arm in adducted position or with the patient supine and the arm abducted 90° with the elbow flexed (15). The posterior labrum is easily evaluated with posterior transverse scans of the GHJ at the level of the infraspinatus tendon; in contrast, the superior labrum is very difficult to see. Changes in the shape of the labrum can be observed in different rotations of the arm. A more pointed appearance is noted when traction is exerted on the labrum by the capsule (during external rotation for the anterior labrum). In general, the labrum is visualized more easily when it is surrounded by joint effusion. In anterior shoulder instability, the main criteria for anterior labral tear are an enlarged (>2-mm) hypoechoic zone at the base of the labrum, a truncated shape or absence of the labrum, and abnormal motility of the labrum at dynamic imaging, whereas an altered labral echogenicity seems to represent an inaccurate finding (15,16). On the other hand, a small, altered labrum indicates degenerative changes (15,17). In selected groups of young patients with acute traumatic or recurrent anterior shoulder dislocation, US is reported to have a sensitivity of 88%–95% and a specificity of 67%–100% in the diagnosis of labral tears (15). We believe that US has a promising role in the evaluation of the labrum, particularly in excluding labral tears when the labrum appears normal. Despite having limitations in the assessment of the anterior glenoid, US may occasionally demonstrate fragmentation of the anteroinferior rim, a finding that represents a Bankart lesion, as a V-shaped bone defect over the anterior aspect of the glenoid (15).
US is more reliable in the detection of other osseous injuries that accompany GHJ instability, such as Hill-Sachs and McLaughlin fractures and avulsions of the tuberosities. Hill-Sachs deformity is an osteochondral compression fracture located on the posterolateral humeral head that occurs in anterior shoulder dislocation. The fracture is created when the posterolateral humeral head strikes the anteroinferior glenoid rim during dislocation. US has a reported sensitivity of 91%–100%, a specificity of 89%–100%, and an accuracy of 84%–94% in detecting this lesion (18–20). The posterolateral shoulder should be examined in a transverse plane. A Hill-Sachs lesion appears as a shallow wedge-shaped defect of the hyperechoic bony contour of the humeral head at the point where the infraspinatus inserts into the greater tuberosity (Fig 7). The size and shape of the fracture can easily be assessed with US. It is important not to confuse a Hill-Sachs lesion with either the surface erosions of the humeral head secondary to rotator cuff tendinopathy, which are usually smaller and more superficial, or the more caudal normal depression of the humeral neck (2). A similar impaction fracture of the anterior surface of the humeral head, commonly referred to as trough fracture or McLaughlin fracture, is encountered in posterior GHJ dislocations. In such cases, US can demonstrate a bone defect on the anterolateral surface of the humeral head deep to the subscapularis tendon.
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Figure 7a. Hill-Sachs lesion in a 47-year-old man with recurrent anterior shoulder instability. (a) Transverse 12-5-MHz US image obtained over the posterior shoulder reveals a wide, deep, and irregular grooved defect (arrows) of the humeral head (HH). IS = infraspinatus muscle. (b) Radiograph helps confirm the presence of a Hill-Sachs lesion (arrow).
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Figure 7b. Hill-Sachs lesion in a 47-year-old man with recurrent anterior shoulder instability. (a) Transverse 12-5-MHz US image obtained over the posterior shoulder reveals a wide, deep, and irregular grooved defect (arrows) of the humeral head (HH). IS = infraspinatus muscle. (b) Radiograph helps confirm the presence of a Hill-Sachs lesion (arrow).
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Avulsions of the tuberosities can also be encountered in shoulder instability. Greater tuberosity fractures may arise from an acute distraction avulsion injury caused by the supraspinatus tendon. When undisplaced, these fractures appear as a break or step-off deformity of cortical bone at the notch between the humeral head and the greater tuberosity or at the junction of the humeral shaft and the anatomic neck of the humerus, thereby suggesting an elevated fragment (21). The uplifted fragment may be angled or overlapping, and the contiguous portion of the supraspinatus tendon appears abnormally thickened and heterogeneous due to edema and contusion (Fig 8). Visualization of a well-demarcated defect on the surface of the greater tuberosity can help avoid misdiagnosis as calcifying tendinitis. Avulsions of the lesser tuberosity can also be found in posterior shoulder dislocations as a result of subscapularis traction (Fig 9). However, conventional radiographs are necessary to confirm these findings.
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Figure 8a. Avulsion fracture of the greater tuberosity in a 32-year-old man with anterior shoulder instability. (a, b) Longitudinal (a) and transverse (b) 12-5-MHz US images demonstrate interruption of the continuity of the humeral surface (arrowheads in b) and a small fragment of bone (arrow) displaced superiorly into the supraspinatus tendon (SS). (c) Radiograph helps confirm the presence of an avulsion fracture (arrow).
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Figure 8b. Avulsion fracture of the greater tuberosity in a 32-year-old man with anterior shoulder instability. (a, b) Longitudinal (a) and transverse (b) 12-5-MHz US images demonstrate interruption of the continuity of the humeral surface (arrowheads in b) and a small fragment of bone (arrow) displaced superiorly into the supraspinatus tendon (SS). (c) Radiograph helps confirm the presence of an avulsion fracture (arrow).
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Figure 8c. Avulsion fracture of the greater tuberosity in a 32-year-old man with anterior shoulder instability. (a, b) Longitudinal (a) and transverse (b) 12-5-MHz US images demonstrate interruption of the continuity of the humeral surface (arrowheads in b) and a small fragment of bone (arrow) displaced superiorly into the supraspinatus tendon (SS). (c) Radiograph helps confirm the presence of an avulsion fracture (arrow).
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Figure 9a. Avulsion fracture of the lesser tuberosity in a 54-year-old woman with posterior shoulder instability. (a) Transverse 12-5-MHz US image obtained over the anterior shoulder shows a large fleck of bone (arrows) avulsed from the humeral head (HH). Note the deep defect (arrowheads) on the anterior surface of the humerus and the continuity of the avulsed bone with the subscapularis tendon (*). (b) Corresponding GRE MR image (500/15/20°) shows the avulsed bone fragment (arrows), the humeral defect (arrowheads), and the subscapularis tendon (*).
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Figure 9b. Avulsion fracture of the lesser tuberosity in a 54-year-old woman with posterior shoulder instability. (a) Transverse 12-5-MHz US image obtained over the anterior shoulder shows a large fleck of bone (arrows) avulsed from the humeral head (HH). Note the deep defect (arrowheads) on the anterior surface of the humerus and the continuity of the avulsed bone with the subscapularis tendon (*). (b) Corresponding GRE MR image (500/15/20°) shows the avulsed bone fragment (arrows), the humeral defect (arrowheads), and the subscapularis tendon (*).
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Acromioclavicular Joint
Subluxation or dislocation of the ACJ may be a source of shoulder pain that is often confused for a rotator cuff tear because of the proximity of this joint to the tendons of the rotator cuff. US is more sensitive than conventional radiography in detecting low-grade sprains. In such cases, the superior capsule and ligament may become prominent, and the joint cavity appears widened and distended by hematoma or fluid (Fig 10). When the ACJ is more severely injured, an upward displacement of the distal end of the clavicle can be appreciated. In high-grade dislocations, a hypoechoic hematoma in the soft tissues between the clavicle and the coracoid process may be considered as an indirect sign of injured coracoclavicular ligaments.
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Figure 10a. Mild ACJ sprain in a 42-year-old woman with posttraumatic shoulder pain. Coronal (a) and sagittal (b) 13-10-MHz US images reveal a widened, echogenic joint space (arrowheads). A = acromion, C = clavicle.
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Figure 10b. Mild ACJ sprain in a 42-year-old woman with posttraumatic shoulder pain. Coronal (a) and sagittal (b) 13-10-MHz US images reveal a widened, echogenic joint space (arrowheads). A = acromion, C = clavicle.
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Although US is not routinely used in screening for ACJ separation, some attempts have been made with this modality to quantify acute and chronic ACJ instability of varying severity according to the radiographic scale described by Tossy et al (22). The width of the joint is measured with a coronal approach and compared with that of the contralateral ACJ. Measurements should be taken with the patient letting the arms hang down and holding a 10-kg weight in each hand. An acromioclavicular index (AC index) is then calculated by dividing the ACJ width on the normal side by that on the injured side. In Tossy-I injury, the ACJ width was no more than 6 mm and the AC index was 1.0; patients with Tossy-II instability had a mean ACJ width of 10.2 mm on the injured side and an AC index of 0.5; and patients with Tossy-III instability and an indication for surgery had a mean ACJ width of 22.3 mm on the injured side and an AC index of less than 0.25 (23). Additional measurements of the coracoclavicular distance may increase diagnostic confidence.
Osteolysis of the clavicle may occur from several weeks to several years after the ACJ trauma. This process is self-limiting, with gradual reparative changes occurring over a period of 4–6 months (24). At US, the resorption of the clavicular tip manifests as irregular cortical erosions associated with joint space widening, joint effusion, and soft-tissue swelling, whereas the acromion remains intact (Fig 11). Clavicular osteolysis should be included in the differential diagnosis when a patient experiences chronic pain or soft-tissue swelling beyond the acute phase of the injury.
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Figure 11a. Posttraumatic osteolysis of the clavicle in a 25-year-old man with a 6-month history of posttraumatic pain and tenderness over the ACJ. (a) Coronal 10-5-MHz US image demonstrates irregular erosion (arrowheads) of the distal end of the clavicle (C). A = acromion. (b) Radiograph helps confirm the presence of osteolysis (arrow).
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Figure 11b. Posttraumatic osteolysis of the clavicle in a 25-year-old man with a 6-month history of posttraumatic pain and tenderness over the ACJ. (a) Coronal 10-5-MHz US image demonstrates irregular erosion (arrowheads) of the distal end of the clavicle (C). A = acromion. (b) Radiograph helps confirm the presence of osteolysis (arrow).
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Arthropathies and Bursites
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US is commonly used to examine synovial disorders. Knowledge of the soft-tissue anatomy and of the technique for examining the main synovial recesses and bursae around the shoulder girdle, particularly the recesses of the GHJ and the subacromial-subdeltoid (SA-SD) bursa, is essential for the US examiner to avoid misdiagnoses and pitfalls in the interpretation of pathologic findings.
The GHJ capsule extends from the boundaries of the labrum and glenoid rim to the neck of the humerus. To allow a wide range of arm movements, the capsule is lax and redundant. In normal states, the joint space is a potential space that is not visible at US; when the joint space contains effusions, US may delineate fluid in the dependent axillary pouch and in three main synovial recesses: the posterior and anterior recesses and the sheath of the LBT. Fluid in the axillary pouch is evaluated on posterior transverse scans obtained below the inferior edge of the teres minor muscle. The transducer is moved upward, and the posterior recess is then examined deep to the infraspinatus tendon. Changes in the appearance of a fluid collection in this recess can be appreciated when the arm is externally rotated, which reduces the tension on the posterior structures. Increased fluid in the posterior recess splays the infraspinatus tendon and creates a hypoechoic crescent around the posterior labrum (Fig 12a). Evaluation of the anterior recess is more complex due to the deep location of the recess and often requires a lower-frequency curvilinear array probe and careful scanning technique. When fluid is present, it can be appreciated on transverse scans as a hypoechoic halo that surrounds the labrum. An opening in the anterior capsule creates a communication between the joint and the superior subscapularis recess. This small recess has a saddle shape; it originates between the anterior neck of the scapula and the subscapularis tendon, overlying and then descending anterior to the superior tendon edge. The superior subscapularis recess does not usually extend beyond the tip of the coracoid process unless a large, intraarticular effusion causes considerable distention of the joint cavity. Sagittal scans can better depict this recess if it is distended by fluid. The superior subscapularis recess should not be confused with the larger subcoracoid bursa, which extends more caudally and does not normally communicate with the GHJ but may communicate with the SA-SD bursa (25). The subcoracoid bursa extends deep to the conjoint tendon of the short head of the biceps and the coracobrachial muscle and may contain a large amount of fluid in cases of anterior rotator cuff tears. It is best examined by scanning just inferior and medial to the coracoid process with the patient’s arm adducted. Furthermore, the synovial membrane extrudes at the level of the rotator cuff interval to form the LBT sheath. This sheath surrounds the LBT down to approximately 4 cm beyond the distal end of the bicipital groove. Because the LBT sheath is merely an extension of the joint cavity, joint effusion can lead to fluid in the sheath. Fluid as a result of an isolated biceps tendinitis is rare.
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Figure 12. Fluid collections in the SA-SD bursa. (a) Transverse 12-5-MHz US image obtained over the posterior shoulder reveals a bursal fluid collection (*) overlying the infraspinatus tendon (IS). Note the coexistent joint effusion in the posterior recess ( ) deep to the infraspinatus tendon. G = glenoid, HH = humeral head. (b) Coronal 12-5-MHz US image obtained over the lateral shoulder shows a bursal fluid collection (*) just inferior to the greater tuberosity (GT) and distal to the insertion of the supraspinatus tendon (SS). (c) Transverse 12-5-MHz US image obtained over the anterior shoulder demonstrates a bursal fluid collection (*) that extends superficial to the bicipital groove. Note the lack of fluid in the underlying biceps tendon sheath (arrow), a finding that reflects the absence of communication between the SA-SD bursa and the GHJ. GT = greater tuberosity, LT = lesser tuberosity.
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Figure 12. Fluid collections in the SA-SD bursa. (a) Transverse 12-5-MHz US image obtained over the posterior shoulder reveals a bursal fluid collection (*) overlying the infraspinatus tendon (IS). Note the coexistent joint effusion in the posterior recess () deep to the infraspinatus tendon. G = glenoid, HH = humeral head. (b) Coronal 12-5-MHz US image obtained over the lateral shoulder shows a bursal fluid collection (*) just inferior to the greater tuberosity (GT) and distal to the insertion of the supraspinatus tendon (SS). (c) Transverse 12-5-MHz US image obtained over the anterior shoulder demonstrates a bursal fluid collection (*) that extends superficial to the bicipital groove. Note the lack of fluid in the underlying biceps tendon sheath (arrow), a finding that reflects the absence of communication between the SA-SD bursa and the GHJ. GT = greater tuberosity, LT = lesser tuberosity.
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Figure 12. Fluid collections in the SA-SD bursa. (a) Transverse 12-5-MHz US image obtained over the posterior shoulder reveals a bursal fluid collection (*) overlying the infraspinatus tendon (IS). Note the coexistent joint effusion in the posterior recess () deep to the infraspinatus tendon. G = glenoid, HH = humeral head. (b) Coronal 12-5-MHz US image obtained over the lateral shoulder shows a bursal fluid collection (*) just inferior to the greater tuberosity (GT) and distal to the insertion of the supraspinatus tendon (SS). (c) Transverse 12-5-MHz US image obtained over the anterior shoulder demonstrates a bursal fluid collection (*) that extends superficial to the bicipital groove. Note the lack of fluid in the underlying biceps tendon sheath (arrow), a finding that reflects the absence of communication between the SA-SD bursa and the GHJ. GT = greater tuberosity, LT = lesser tuberosity.
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In adhesive capsulitis ("frozen shoulder"), a clinical syndrome characterized by pain and severely restricted joint movement, thickening and fibrosis of the joint capsule and synovium lead to reduced articular volume capacity. Although US cannot depict adhesions or help measure the restriction of the joint cavity, the diagnosis may be suggested at dynamic scanning by either restriction of sliding movements of the supraspinatus tendon underneath the acromion during arm abduction or persistent visualization of the supraspinatus tendon during lateral elevation of the arm (26). Minimal synovial inflammation may be an associated finding.
The SA-SD bursa covers a large area of the shoulder. It extends medially to the coracoid process and anteriorly to cover the bicipital groove, whereas its lateral and inferior boundary is more variable and extends to approximately 3 cm below the greater tuberosity (27). The normal synovial membrane of the bursa cannot be visualized at US. The SA-SD bursa appears as a 2-mm-thick complex consisting of an inner layer of hypoechoic fluid between two layers of hyperechoic peribursal fat (28). Fluid collections tend to accumulate in the most dependent portions of the bursa and, more commonly, along the lateral edge of the greater tuberosity, producing a typical "teardrop" appearance (Fig 12b) (28). Small amounts of fluid can go unnoticed if this portion of the bursa is not examined or if fluid is squeezed away by exerting excessive pressure with the probe. More abundant fluid collections fill the bursa anterior to the bicipital groove and must not be confused with intraarticular fluid contained within the LBT sheath (Fig 12c).
Inflammatory Diseases
Rheumatoid arthritis usually involves not only the GHJ, but also the ACJ and the synovial bursae around the shoulder. US has been shown to reveal synovitis in the early stages of disease, when no radiographic changes are yet evident, as well as to help differentiate between synovial hypertrophy and effusions (Fig 13) (29,30). In a selected group of patients with symptomatic disease, US assessment of synovitis has shown SA-SD bursitis to be the most common finding, occurring in up to 69% of cases, followed by GHJ involvement in 58% and biceps tendinitis in 57% (31). Overall, no correlation was observed between these findings and either duration or stage of disease according to radiographic criteria for the evaluation of hand or wrist joints. A quantitative assessment of synovitis may be attempted by measuring the widest distance between the humeral head and the joint capsule in the axillary pouch and posterior recesses (29,31). It may be difficult to distinguish fluid from the pannus in the posterior recess because graded compression does not always squeeze the fluid away owing to increased intraarticular pressure. Color and power Doppler US may be used to assess the activity of the inflammatory process by depicting hyperemic flow within the synovial tissue (29). However, the reliability of these findings seems inadequate for objective assessment, especially when color Doppler US is used to evaluate response to therapy. It is possible that US contrast agent will have a role in this setting. Along with synovium, US is able to reveal bone erosions, which usually appear as cortical defects filled with hypoechoic pannus (30). Loss of definition and thinning of the articular cartilage can be demonstrated in advanced disease as well. Because it allows clear visualization of the needle tip, US is excellent for imaging-guided synovial needle biopsy as well as for intraarticular injection of corticosteroids, thereby avoiding the risks of inadvertent intratendinous steroid injection. US-guided needle placement is more accurate and less painful than needle placement without US guidance. US has also been used to investigate the structures involved by the inflammatory process in polymyalgia rheumatica (32–34). Most studies report that bursitis is seen considerably less frequently than GHJ synovitis (14%–16% versus 57%–66% of cases, respectively) in this disease (32,33).
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Figure 13a. Rheumatoid arthritis in a 62-year-old woman with long-standing disease. (a) Transverse 12-5-MHz US image obtained over the posterior shoulder reveals a hypoechoic soft-tissue mass that represents synovial pannus within the posterior recess (arrowheads). In addition, there is a defect (arrow) of the posterior humeral head (HH), a finding that represents erosion. G = glenoid. (b) Corresponding GRE MR image (500/15/20°) demonstrates the soft-tissue mass (arrowheads).
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Figure 13b. Rheumatoid arthritis in a 62-year-old woman with long-standing disease. (a) Transverse 12-5-MHz US image obtained over the posterior shoulder reveals a hypoechoic soft-tissue mass that represents synovial pannus within the posterior recess (arrowheads). In addition, there is a defect (arrow) of the posterior humeral head (HH), a finding that represents erosion. G = glenoid. (b) Corresponding GRE MR image (500/15/20°) demonstrates the soft-tissue mass (arrowheads).
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Degenerative and Infiltrative Disorders
Degenerative osteoarthritis of the GHJ is most often associated with chronic massive disruption of the rotator cuff. US findings include bone changes related to the superior subluxation of the humerus, formation of osteophytes along the inferior margin of the humeral head, bone spurring in the tuberosities and at the bicipital groove, and joint effusion. Superior humeral subluxation may be identified at coronal US as a reduced acromiohumeral distance. The humeral head shows loss of the hypoechoic layer of articular cartilage and bone irregularities; the greater tuberosity has a smooth appearance and blends with the humeral epiphysis. In these circumstances, detection of the bicipital groove can be problematic. Reduced thickness of the acromion may also be observed. The subluxation of the humerus may lead to secondary damage of the inferior ACJ capsule and passage of joint fluid through the ACJ, producing a cyst in the soft tissues at the superior aspect of the shoulder ("geyser sign"), a finding that may be considered pathognomonic for long-standing massive rotator cuff tears (Fig 14) (26). During passive movements of the arm or exertion of pressure on the cyst with the probe, debris may be seen moving to and fro across the ACJ. In shoulder osteoarthritis, the progressive disintegration of the articular surfaces leads to the formation and release of intraarticular loose bodies which, once freed into the joint cavity, can progressively worsen the damage to the joint surfaces. Osteochondral loose bodies usually remain trapped in the most dependent portions of the GHJ, such as the axillary pouch and the LBT sheath (Fig 15). Most of these loose bodies appear as hyperechoic areas with posterior acoustic shadowing. In some cases, however, a thin layer of hypoechoic cartilage may be seen overlying the echogenic interface of the subchondral bone (35). The size and position of a fragment can be reliably evaluated with US, but the exact number of fragments cannot always be established.
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Figure 14a. ACJ cyst in a 68-year-old man with a chronic rotator cuff tear. (a) Clinical photograph demonstrates a soft-tissue mass (arrow) that arises over the ACJ. (b) Coronal 12-5-MHz US image reveals a cystic mass (arrowheads) that arises from the ACJ. A = acromion, C = clavicle.
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Figure 14b. ACJ cyst in a 68-year-old man with a chronic rotator cuff tear. (a) Clinical photograph demonstrates a soft-tissue mass (arrow) that arises over the ACJ. (b) Coronal 12-5-MHz US image reveals a cystic mass (arrowheads) that arises from the ACJ. A = acromion, C = clavicle.
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Figure 15a. Intraarticular loose body in a 45-year-old woman. (a) Longitudinal 12-5-MHz US image of the shoulder obtained at the level of the sheath of the LBT (arrowheads) demonstrates a loose body (arrow) surrounded by anechoic fluid in the synovial space. (b) Corresponding radiograph shows the fragment with a typical laminated concentric appearance (arrow).
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Figure 15b. Intraarticular loose body in a 45-year-old woman. (a) Longitudinal 12-5-MHz US image of the shoulder obtained at the level of the sheath of the LBT (arrowheads) demonstrates a loose body (arrow) surrounded by anechoic fluid in the synovial space. (b) Corresponding radiograph shows the fragment with a typical laminated concentric appearance (arrow).
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Other conditions that lead to the rapid development of joint destruction with deposition of calcium apatite crystals cannot be specifically identified in patients with rotator cuff osteoarthritis. On the other hand, US is sensitive in depicting the deposition of pyrophosphate crystals in the cartilage of the humeral head in patients with chondrocalcinosis (36). These crystals appear as a blurry hyperechoic line that runs parallel to the cartilage surface. In patients with calcifying tendinitis, the calcific deposit may extrude either into the bone or within the SA-SD bursa. Intraosseous calcific material can be visualized as a 
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Abstract
LEARNING OBJECTIVES FOR TEST...
