Published online December 13, 2005, 10.1148/rg.e23
RadioGraphics 2006;26:e23
© RSNA, 2006
US of the Shoulder: Rotator Cuff and Non–Rotator Cuff Disorders1
Athanasios Papatheodorou, MD,
Panagiotis Ellinas, MD,
Fotios Takis, MD,
Antonios Tsanis, MD,
Ioannis Maris, MD and
Nikolaos Batakis, MD, PhD
1 From the Departments of Radiology (A.P., P.E., F.T., A.T., N.B.) and Orthopedics (I.M.), Hellenic Red Cross Hospital, 1 Athanasaki St, GR-115 26, Athens, Greece. Presented as an education exhibit at the 2004 RSNA Annual Meeting. Received May 19, 2005; revision requested August 2; revision received September 22; accepted October 6. All authors have no financial relationship to disclose.
Address correspondence to A.P. (e-mail: athpapatheodorou{at}yahoo.gr).
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Abstract
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Ultrasonography (US) has been shown to be an effective imaging modality in the evaluation of both rotator cuff and non–rotator cuff disorders, usually serving in a complementary role to magnetic resonance imaging of the shoulder. US technique for shoulder examination depends on patient positioning, scanning protocol for every tendon and anatomic part, and dynamic imaging.
The primary US signs for rotator cuff supraspinatus tendon tears are tendon nonvisualization for complete tears, focal tendon defect for full-thickness tears, a hypoechoic defect of the articular side of the tendon for an articular-side partial-thickness tear, and flattening of the bursal surface of the tendon for a bursal-side partial-thickness tear. Secondary US signs such as cortical irregularity of the greater tuberosity and joint and subacromial-subdeltoid bursal fluid are helpful when correlated with the primary signs. Tendon degeneration, tendinosis, and intrasubstance tear are demonstrated as internal heterogeneity.
Long-head biceps tendon abnormalities include instability, acute or chronic tear, and tendinosis. The acromioclavicular joint is assessed for dislocation, fluid collection, cysts, and bone erosions. Other non–rotator cuff disorders include synovial disorders such as adhesive capsulitis and synovial osteochondromatosis; degenerative disorders such as osteoarthritis, amyloid arthropathy, hemarthrosis, and chondrocalcinosis; infectious disorders such as septic arthritis and bursitis; and space-occupying lesions.
Movies: http://radiographics.rsnajnls.org/cgi/content/full/e23/DC1
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LEARNING OBJECTIVES
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After reading this article and taking the test the reader will be able to
- Describe the normal sonographic anatomy of the rotator cuff and non–rotator cuff.
- Understand the technique of US examination of the shoulder.
- Identify the sonographic appearance of both rotator and non–rotator cuff abnormalities.
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Introduction
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High-resolution real-time ultrasonography (US) has been shown to be a successful imaging modality for both rotator cuff (1) and non–rotator cuff disorders (2). Advances in technology have substantially improved US image quality, producing spatial resolution exceeding that obtained with magnetic resonance (MR) imaging without the use of special coils and imaging parameters (3). Also, sonography is inexpensive, fast, and offers dynamic capabilities for examining the patient in multiple scanning planes and specific arm positions or movements, in addition to having the ability to focus the examination on the precise region of maximum discomfort (4).
Non–rotator cuff disorders affecting the long head biceps tendon, glenohumeral joint and bursae, acromioclavicular joint, humeral head cartilage and subcutaneous tissues may mimic rotator cuff disorders and should also be assessed during US examination of the shoulder. It has been estimated that US is underused for non–rotator cuff disorders (2).
MR imaging is currently considered the reference standard for imaging of shoulder disorders. The strength of MR imaging lies in its potential for assessing sonographically inaccessible areas such as bone, labral cartilage, deep parts of various ligaments, capsule, and areas obscured by bone (5).
US is suitable for examination when shoulder disorders are localized and predominantly superficial (5). US usually serves in a complementary role to MR imaging, and there are potential benefits from the combined use of these two modalities (5). The strength of US lies in its extreme sensitivity in identification of calcium deposits, its dynamic nature, its ability to guide interventional procedures, and its ability to perform in the presence of postoperative metallic hardware and pacemakers or in claustrophobic patients.
We discuss the various types of rotator cuff and non–rotator cuff disorders that can be sonographically diagnosed. Normal shoulder anatomy, US examination technique, and US imaging findings are described.
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Anatomy
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Rotator Cuff
The rotator cuff consists of four muscles and their tendons: subscapularis, supraspinatus, infraspinatus, and teres minor (6,7). The subscapularis muscle arises from the subscapular fossa; its fibers extend anteriorly to the glenohumeral joint, and its tendon inserts in the lesser tuberosity of the humerus. The supraspinatus muscle originates from the supraspinatus fossa of the scapula and passes under the acromioclavicular joint; its tendon inserts in the anterior portion of the greater tuberosity of the humerus (8). The infraspinatus muscle arises from the infraspinatus fossa of the scapula, and its tendon inserts in the posterior portion of the greater tuberosity, touching the posterior aspect of the supraspinatus tendon. The teres minor muscle originates from the lateral border of the scapula and inserts in the posterior aspect of the humeral head, posteroinferiorly to the infraspinatus tendon.
Non–Rotator Cuff
The non–rotator cuff structures include several tendons, ligaments, and bursae in the shoulder area. The 9–10-cm long tendon of the long head of the biceps muscle (LHBT) arises from the supraglenoid tubercle and the superior glenoid labrum, courses over the top of the humeral head intraarticularly but extrasynovially, and goes down into the bicipital groove between the greater and lesser tuberosities (9). The LHBT sheath communicates with the synovial joint. The LHBT is retained in its proper position by the combined action of the coracohumeral ligament, superior glenohumeral ligament, transverse humeral ligament, and the tendon of the pectoralis major muscle (2). A shallow (less than 3 mm deep) and flattened groove predisposes to LBHT instability.
The rotator interval is a triangular region through which the LHBT travels from its intraglenohumeral joint course toward the bicipital groove (10). The base of the triangle is the coracoid process, and the superior and inferior sides are formed by the supraspinatus and subscapularis tendons, respectively. It houses the coracohumeral ligament and capsule overlying the LHBT (11).
The glenohumeral joint capsule extends from the glenoid rim to the humeral neck. This capsule normally contains no US-detectable fluid (2). The fibrocartilaginous labrum surrounds the glenoid rim. Because of capsular laxity, certain synovial redundant spaces become prominent when the joint contains an effusion: the axillary pouch lying below the teres minor, the posterior recess lying deep to the infraspinatus tendon, the anterior recess lying next to the anterior labrum, and the superior subscapularis recess lying anterior to the superior surface of the subscapularis tendon (12). A large area below the deltoid muscle is covered by the subacromial-subdeltoid bursa. This bursa extends below the acromion from the coracoid process to the greater tuberosity. It communicates potentially with the subcoracoid bursa, which lies deep to the tendon of the short head of the biceps, next to the coracoid (9,13).
The acromioclavicular joint is made up of a fibrocartilaginous articular disk of highly variable size and with a weak capsule, thickened superiorly and inferiorly. Three ligaments are crucial to the stability of the acromioclavicular joint: the coracoacromial and coracoclavicular ligaments, the later consisting of two components, conoid and trapezoid ligaments, which attach to the undersurface of the clavicle (14). The normal width of the joint space is 3. 5 mm ± 0. 9, on average. A slight amount of fluid may be found in asymptomatic individuals (14).
The spinoglenoid notch lies below the lateral border of the scapular spine, and the suprascapular nerve and accompanying artery enter through it.
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US Technique
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A high-frequency (5–12 MHz) linear array scan head should always be used. Harmonics, extended field of view, and new image optimization techniques are desirable (8,15). Modern transducers give a spatial resolution of less than 1 mm and produce excellent diagnostic images (16). Normal tendons appear hyperechoic relative to adjacent muscles and demonstrate an internal fibrillar structure.
The examination begins with the patient sitting on a rotating stool at a slightly lower level than that of the examiner. US images include but are not limited to longitudinal and transverse or coronal planes relative to the shoulder tendons (17). Both shoulders are examined, starting with the less- or nonsymptomatic side (17). The application of graded pressure with the scan head and the focusing of the examination at the site of maximum discomfort are essential for obtaining the correct diagnosis.
The tendon of the long head of the biceps is visualized within the bicipital groove (Videos 1a, 1b) (Figs 1, 2). The patient is examined with his or her forearm pronated on the thigh (6). The osseous anatomy of the groove and its depth and the tendon’s stability during external rotation of the patient’s arm, which accentuates the subluxation of the tendon, are assessed. Inferiorly, and anteromedially to the LHBT, lies the tendon of the pectoralis major (Fig 3). The intraarticular portion of the tendon is examined with posterior extension of the patient’s arm, with the elbow flexed and the palm of the hand placed over the posterior iliac crest. In this position, the rotator interval is wide open and the LHBT is flattened, stretching just below the coracohumeral ligament, which is seen as a flat echogenic band measuring 2–3 mm in thickness (Fig 4).
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Figure 2. Biceps tendon, transverse view. The biceps tendon (arrows) lies within the bicipital groove, between the lesser (LT) and greater (GT) tuberosities and below the deltoid muscle.
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Figure 4. Rotator interval, transverse view. The echogenic biceps tendon (BT) lies below the coracohumeral ligament (CHL, arrows) and between the supraspinatus (SS) and subscapularis (SSC) tendons.
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The subscapularis tendon is examined in orthogonal planes with the patient’s arm in passive external rotation (Videos 2a, 2b) (Fig 5).
The coracoid process is visualized in a medial position, and the superior subscapularis recess and the subcoracoid and subdeltoid bursae are assessed for the possibility of fluid collection (Fig 6). Deep settings of the transducer or a lower-frequency (3.5 MHz) probe are sometimes required (2).
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Figure 6. Subscapularis tendon and coracoid process, longitudinal view. The coracoid process (C) lies anteriorly to the subscapularis tendon. Fluid (arrow) is seen in the subcoracoid bursa.
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Next, the supraspinatus tendon is examined, with the patient’s arm flexed at the elbow and directed posteriorly, and with the palm of the hand placed over the posterior iliac crest. One should always remember that the axis of the tendon is at 45° between the sagittal and coronal planes. The tendon is generally echogenic, with an internal fibrillar pattern; its superior surface is convex, and it tapers as it inserts in the greater tuberosity (6). The greater tuberosity has a smooth surface (Videos 3a, 3b) (Fig 7).
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Figure 7. Supraspinatus tendon, longitudinal view. The tendon is seen as an echogenic band superior to the humeral head, with a convex upper surface; it tapers toward the greater tuberosity. The arrow indicates a hypoechogenic area due to tendon anisotropy.
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The subacromial-subdeltoid bursa also extends into this area (Fig 8).
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Figure 8. Subacromial-subdeltoid bursa, longitudinal view. The subdeltoid bursa (arrows) is seen as a thin hypoechoic line superior to the supraspinatus tendon. The echogenic line superior to the bursa represents subdeltoid fat.
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The patient’s bent arm is next placed in front of his or her chest, and the infraspinatus and teres minor tendons are visualized from a posterior approach (8) (Videos 4a, 4b) (Fig 9).
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Figure 9. Infraspinatus tendon, longitudinal view. The infraspinatus tendon (arrows) lies superior to the posterosuperior aspect of the humeral head. Double arrows outline the glenoid labrum.
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The supraspinatus and infraspinatus tendons are interwoven. On the transverse view the anterior 1.5 cm of the complex represents the supraspinatus tendon, while the posterior 1.5 cm represents the infraspinatus tendon (Fig 10).
The posterior fibrocartilaginous labrum is visualized as a triangular hyperechoic structure superior to the glenoid rim (Fig 9). The posterolateral part of the humeral head is examined in the transverse plane and normally has no bone defects (2).
The axillary pouch and posterior recess of the glenohumeral joint capsule are evaluated from a posterior transverse approach with a deep setting of the transducer, below the inferior edge of the teres minor tendon and deep to the infraspinatous tendon, respectively (2). With a posterior approach, the spinoglenoid notch is examined during external-internal rotation of the extended arm (Videos 5a, 5b). The acromioclavicular joint and the acromion are examined in longitudinal and transverse planes, with the transducer placed exactly over them and with a liberal amount of transmission gel applied (Videos 6a, 6b) (Fig 11).
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Figure 11. Acromioclavicular joint, longitudinal view. The acromioclavicular joint is the area between the acromion (A) and clavicle (C). The superior aspect of the joint capsule is seen as a hypoechoic band above the joint.
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The area of the coracoclavicular and coracoacromial ligaments is evaluated from an anterior approach (14) (Videos 7a, 7b) (Fig 12).
Finally, a dynamic examination is performed during lateral passive elevation of the arm, with the transducer placed above the acromion. Normally, the subacromial-subdeltoid bursa is thin, and the supraspinatus tendon slides smoothly inferior to the acromion (16) (Videos 8a, 8b).
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US Findings of Rotator Cuff Disorders
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Rotator cuff abnormalities represent a spectrum ranging from tendinosis to massive tear. Tendinosis is tendon degeneration without clinical or histologic signs of inflammatory response. The tendon shows a diffuse heterogeneous hypoechogenicity (17) (Fig 13).
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Figure 13. Supraspinatus tendon, longitudinal view. The tendon demonstrates a heterogeneous echogenicity without any focal area representative of a tear. This pattern may indicate tendinosis or intrasubstance tear (17).
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Most rotator cuff tears occur at the site of insertion of the supraspinatus tendon in the greater tuberosity, but tendon fiber may deteriorate either locally (a partial tear becoming complete) or involve multiple shoulder tendons (8,18) (Figs 14–16).
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Figure 14. Subscapularis tendon, longitudinal view. This patient has multiple torn tendons. There is a complete subscapularis tendon tear. The area between the humerus and coracoid (C) is empty.
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A partial-thickness supraspinatus tendon tear extends either to the articular or bursal surface of the tendon (19). A bursal-side partial-thickness tear produces flattening of the bursal surface, with loss of the superior convexity of the tendon. An articular-side partial-thickness tear appears as a distinct hypoechoic or mixed hyper-hypoechoic defect of the articular surface (20) (Fig 17).
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Figure 17. Supraspinatus tendon, longitudinal view. An articular-side partial-thickness tear appears as a distinct hypoechoic defect (arrow) at the tendon’s articular surface, abutting the articular cartilage.
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A cortical bone irregularity of the greater tuberosity is a sensitive sign of an articular-side partial-thickness tear (16) (Fig 18).
The primary US sign for a full-thickness tear is a focal tendon defect or focal tendon nonvisualization (Figs 19–21).
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Figure 19. Supraspinatus tendon, longitudinal view. Hypoechoic fluid fills a full-thickness tear of the supraspinatus tendon (arrows), with loss of the normal outward convexity of the tendon at this site.
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A full-thickness tear should be demonstrated in both orthogonal planes. Secondary US signs are bone irregularity of the greater tuberosity and the presence of fluid in the joint (Figs 22,23) and the bursae (Figs 24–27).
Another secondary sign is the cartilage interface or uncovered cartilage sign (a hyperechoic interface created between joint fluid and the hyaline cartilage of the uncovered humeral head) (7,20) (Fig 28).
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Figure 28. Supraspinatus tendon, transverse view. A gap in the mass of the tendon contain anechoic joint fluid and represents a full-thickness tear. The uncovered cartilage sign is the hyperechoic interface between the joint fluid and the cartilage covering the humeral head. There is also loss of the normal outward convexity of the supraspinatus tendon and dipping of the deltoid muscle.
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These secondary signs are more often present in patients with tendon tear than in patients without tear (6). A complete or massive supraspinatus tendon tear is characterized by nonvisualization and retraction of the tendon, with the deltoid muscle abutting the humeral head (Figs 29,30).
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Figure 29. Supraspinatus tendon, longitudinal view. Massive supraspinatus tendon tear with tendon nonvisualization and joint fluid collection. The stump of the supraspinatus tendon (arrows) is retracted.
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Figure 30. Supraspinatus tendon, transverse view. A massive supraspinatus tendon tear is seen. Owing to the pressure applied with the transducer, the deltoid muscle lies atop the humeral head.
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A possible pitfall is the misinterpretation of the deltoid muscle or the thickened synovium as supraspinatus tendon (Fig 31).
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Figure 31. Supraspinatus tendon, longitudinal view. A thickened hypoechoic synovium (which lacks an internal fibrillar pattern), and not the supraspinatus tendon, lies atop the humeral head.
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Essential information for the orthopedic surgeon includes characterization of the tear, the dimensions and location of the tear, and the amount of tendon retraction on the longitudinal view (8). In patients with supraspinatus tendon repair or semitotal arthroplasty, US must to rule out the presence of recurrent tear (Fig 32).
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Figure 32. Supraspinatus tendon, longitudinal view. A recurrent massive tear of the supraspinatus tendon is seen in a patient who underwent surgery for repair of a partially torn supraspinatus tendon. Note the uncovered cartilage sign and the presence of synovial proliferation and debris above the humeral head cartilage.
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Postoperative changes in the greater tuberosity that represent the supraspinatus tendon reimplantation trough are a common finding (8) (Fig 33).
Calcific tendinitis is a common disorder caused by deposition of calcium hydroxyapatite crystals in various shoulder tendons. The cause is considered to be dystrophic, and all tendons can be affected, although the most common site is within the supraspinatus tendon near its insertion. It is believed that the calcifications become symptomatic when the calcium undergoes resorption (21). At US, calcium deposits may have a fluffy appearance, with echogenic foci without posterior shadowing, or may appear as typical discrete, well-circumscribed calcifications with posterior shadowing (Figs 34– 36).
US is very sensitive for detecting even tiny calcium deposits. Sometimes calcifications are massive, obscuring adjacent anatomic structures (16,20,22) (Fig 37).
US-guided fine-needle puncture and lavage has been proposed as an effective treatment prior to possible surgery (23,24).
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US Findings of Non–Rotator Cuff Disorders
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LHBT
Biceps tendinosis (tendon degeneration without inflammatory cells) is present in patients with a rotator cuff tear. US is relatively insensitive for this condition; the LHBT is seen as normal in size and echotexture (25). Rarely, the tendon is enlarged, appears diffusely hypoechoic, and shows tendon sheath effusion and increased vascularity with color Doppler (2,6,8) (Figs 38–40).
Tendon rupture occurs either in an acute or chronic setting. Acute rupture results in nonvisualization of the tendon within the bicipital groove and biceps muscle contraction with bulbous appearance. Chronic rupture results in partial nonvisualization of the upper portion of the tendon, whereas the lower portion adheres within the groove. Thus, it is important to examine the entire length of the bicipital groove (2) (Figs 41, 42).
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Figure 42. LHBT, transverse view. Chronic rupture results in partial nonvisualization of the tendon within the bicipital groove. The bicipital groove is filled with echogenic scar tissue that simulates a normal tendon; nonetheless, the characteristic fibrillar pattern of a tendon is not seen.
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LHBT subluxation is looked for during external rotation of the patient’s arm. Occasionally, the dislocated tendon may be difficult to identify because of its deep location, and thorough transverse scanning technique is required (Fig 43–45).
An empty bicipital groove becomes filled with echogenic scar tissue that simulates a normal LHBT, although the characteristic fibrillar pattern of the tendon is not seen (6).
Glenohumeral Joint
US is sensitive for the detection of osseous abnormalities that are sequelae of shoulder instability. A Hill-Sachs lesion appears as a defect of the posterosuperior aspect of the humeral head, and it occurs when there is recurrent anterior shoulder dislocation (2) (Fig 46).
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Figure 46. Infraspinatus tendon, longitudinal view. Patient had history of recurrent anterior shoulder instability. A bone defect at the posterosuperior aspect of the humeral head (Hill-Sachs lesion) is seen.
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An avulsion fracture of the greater tuberosity may be caused by sudden retraction of the supraspinatus tendon. The tuberosity fragment deforms the cortical bone, and the supraspinatus tendon is thickened and retracted (2) (Figs 47, 48).
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Figure 47. Supraspinatus tendon, longitudinal view. The avulsed bone fragment (arrows) originating from the greater tuberosity (GRT) protrudes superiorly, and the supraspinatus tendon (SS) is slightly retracted.
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Acromioclavicular Joint
The acromioclavicular joint connects the distal clavicle end with the anterior edge of the acromion and is made up of a highly variable fibrocartilaginous disk and a capsule. The superior and inferior acromioclavicular ligaments represent a thickening of the superior and inferior aspects of the capsule (26). The ligaments that are vital to the integrity of the acromioclavicular joint are the coracoacromial ligament and the coracoclavicular ligament, with trapezoid and conoid components attaching at the undersurface of the clavicle (15). US is helpful in evaluating the superior aspect of the acromioclavicular joint. By using a sagittal plane and the gap between clavicle and acromion as a window, it is possible to image the joint space. Joint fluid is a rare finding in normal shoulders. Bone erosion, fluid, cysts, and hypertrophic changes represent degenerative changes (Figs 49, 50).
Joint width is 3. 5 cm ± 0. 9 on average (27). Comparing the contralateral acromioclavicular joint is always useful. In acute dislocation, the distal end of the clavicle is dislocated superiorly, and a hematoma or inhomogeneity in the area of the coracoclavicular ligament may be a sign of ligamentous injury (28) (Figs 51, 52).
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Figure 52. Coracoclavicular ligament, longitudinal view. In a patient with a recent clavicular dislocation, a small fluid collection (double arrows) in the middle portion of the coracoclavicular ligament (arrow) represents acute ligamentous injury (CL = clavicle, COR = coracoid).
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In chronic clavicular dislocation with ligamentous injuries, elevation of the distal clavicle end, increase in the coracoid-clavicle distance, and possible degenerative calcifications at the site of the ruptured coracoclavicular ligament may be present (Fig 53).
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Figure 53. Coracoclavicular ligament, longitudinal view. Increased coracoclavicular distance (CL = clavicle, C = coracoid) is a result of an old traumatic clavicular dislocation. Dystrophic calcifications (arrow) at the site of the ruptured ligament are seen.
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An os acromiale is an acromial epiphysis caused by failure of the acromial ossification center to fuse properly. It occurs in 1%–8% of the population; though it is usually asymptomatic, it may become symptomatic by narrowing the space available for the supraspinatus tendon. In this case, a useful US sign is a "double" acromioclavicular joint, describing the acromion–os acromiale and os acromiale–clavicle joints (29) (Fig 54).
Other Abnormalities
Synovial disorders. —
Primary synovial osteochondromatosis is a benign monoarticular disorder characterized by proliferation and metaplastic transformation of the synovium, with formation of multiple cartilaginous nodules (30). Men are affected twice as commonly as women. The shoulder is an uncommon site for chondral bodies; knee, elbow, and hip joints the most common sites. Patients present with mild pain, shoulder swelling, and limitation of motion (31). Intraarticular nodules may contain cartilage, cartilage and bone, or mature bone (32). In 70% of patients, calcifications are present. US findings consist of multiple small, uniform in size, echogenic nodules within the joint or bursae or along the LHBT sheath. When calcifications are present, characteristic posterior shadowing is seen (28) (Figs 55–57).
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Figure 56. Longitudinal view parallel to the LHBT. Primary osteochondromatosis. Multiple well-defined calcified nodules of uniform size aligned parallel to the LHBT (not shown) are seen.
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Figure 57. Radiograph of the shoulder, anteroposterior view. Primary osteochondromatosis. Multiple osteocartilaginous nodules of uniform size cluster inferiorly to the humeral head.
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Synovial osteochondromatosis may be associated with small joint effusions and secondary ostearthritic changes (32). Secondary osteochondromatosis is characterized by the presence of larger (varying in size) and less numerous intraarticular loose bodies due to trauma, aseptic osteonecrosis, and degenerative arthropathy (33). Adhesive capsulitis (frozen shoulder) is a condition characterized by pain and severely restricted joint movements (2). Capsular thickening and bursal adhesions with reduced articular volume may also be present. Dynamic scanning of the sliding pattern of the supraspinatus tendon beneath the acromion during lateral passive elevation of the arm is helpful. Suggestive findings for adhesive capsulitis are abnormal tendon bulging instead of a smoothly sliding tendon beneath the acromion (34).
Degenerative disorders. —
US findings for degenerative osteoarthritis include the presence of intraarticular loose bodies, buttressing osteophyte formation around the h
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Abstract
LEARNING OBJECTIVES
