M u s c u l o s k e l e t a l I m a g i n g • R ev i ew Beltran et al. Positional Maneuvers for Shoulder MRI and Ultrasound

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Musculoskeletal Imaging Review

Luis S. Beltran1 Ronald Adler 1 Taylor Stone1 Joseph Surace2,3 Javier Beltran2 Jenny T. Bencardino1 Beltran LS, Adler R, Stone T, Surace J, Beltran J, Bencardino JT

Keywords: abduction external rotation, flexion adduction internal rotation, MRI, positional imaging, ultrasound DOI:10.2214/AJR.15.14512 Received February 10, 2015; accepted after revision April 7, 2015. 1 Department of Radiology, NYU Langone Medical Center, 660 First Ave, Rm 218, New York NY 10016. Address correspondence to L. S. Beltran ([email protected]). 2 Department of Radiology, Maimonides Medical Center, New York, NY. 3 Present address: Schenectady Radiologists, ­Schenectady, NY.

WEB This is a web exclusive article. AJR 2015; 205:W244–W254 0361–803X/15/2053–W244 © American Roentgen Ray Society

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MRI and Ultrasound Imaging of the Shoulder Using Positional Maneuvers OBJECTIVE. The purpose of this article is to review the normal anatomy and pathologic conditions of the shoulder on the basis of the appearance on MR and ultrasound images obtained during performance of abduction external rotation and flexion adduction internal rotation positional maneuvers. CONCLUSION. Positional MRI and ultrasound are highly useful in evaluation of the shoulder. Knowledge of the normal appearance of anatomic structures and pathologic changes in nontraditional imaging planes is necessary to avoid pitfalls in interpretation.

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RI and ultrasound examinations of the shoulder are frequently performed in clinical practice. The use of positional imaging such as abduction and external rotation (ABER) and flexion in adduction and internal rotation (FADIR) to supplement standard imaging planes improves diagnostic accuracy for some lesions [1–5]. The FADIR position was introduced by Song et al. [5] in 2006 and was referred to as the ADIR position. Nevertheless, positional imaging often presents a diagnostic interpretation challenge because of the use of nonconventional imaging planes and positional distortion of the intraarticular and periarticular osseous and soft-tissue structures of the shoulder joint. It is important to have adequate knowledge of the normal and pathologic appearance of the shoulder anatomy in these positions to avoid pitfalls and errors in interpretation. This article reviews the imaging appearance of the glenohumeral structures obtained with the ABER and FADIR positional imaging techniques in MR arthrography and ultrasound. It includes a discussion of normal anatomic variants that mimic abnormalities that can be overlooked. Abduction and External Rotation Position Technique MR arthrography—The ABER position for MRI is achieved by instructing the patient to place the hand of the affected extremity behind the contralateral aspect of the

head or neck with the elbow flexed [6]. In this position, a surface flexible coil is placed on the affected shoulder, and a T1-weighted or gradient-recalled echo coronal localizer sequence is performed. An oblique axial imaging plane is prescribed through the glenohumeral joint along the long axis of the humerus. A stack of MR images from superior to inferior and medial to lateral through the glenohumeral joint and the surrounding softtissue structures is obtained (Fig. 1). During MR arthrography, a T1-weighted fat-suppressed MR sequence is typically performed to evaluate abnormal extension of contrast material into structures such as the labrum, joint capsule, and rotator cuff. At our institution, we typically perform this study with a 3-T MRI system with TR/TE of 825/24, slice thickness of 4 mm, and a 320 × 320 matrix. These parameters are sufficient to detect subtle pathologic changes, such as small tears of the anterior inferior labrum. Owing to the oblique axial imaging plane, the anterior inferior and posterior superior aspects of the glenohumeral joint can be visualized on a single image, which can be a source of confusion to an unaccustomed interpreter. It is therefore important to be familiar with the normal anatomy and variants related to positional distortion of the intraarticular and periarticular osseous and soft-tissue structures to avoid errors in interpretation. There are limitations to the ABER imaging technique. The rate of a patient’s inability or unwillingness to assume the ABER position because of shoulder pain or appre-

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Positional Maneuvers for Shoulder MRI and Ultrasound hension has been reported to be as high as 20% [1]. Furthermore, considerably more time must be allowed for the examination, even when performed by an experienced MRI technologist. Patient positioning and coil placement for ABER image acquisition add approximately 10 minutes to the routine MRI protocol [2]. Ultrasound—Sonographic scanning of the shoulder in ABER position can be performed with the patient seated on a swivel chair in front of and to the right of the ultrasound machine with the shoulder being evaluated closest to the sonographer (Fig. 2). The ABER position is achieved by asking the patient to place the palm of the affected extremity on the back of the head. Robinson et al. [7] used this technique by placing the ultrasound transducer in the transverse axis of the humeral shaft to evaluate the neurovascular structures in the quadrilateral space. Khoury et al. [8] suggested a different technique. They performed ultrasound evaluation of patients with engaging HillSachs lesions by placing the arm in 90° abduction and 90° external rotation using dynamic imaging. The procedure was performed with the assistance of an orthopedic surgery attending physician or resident, who applied a posteriorly directed force to the anterior humerus while the shoulder was positioned in 90° ABER. This maneuver is analogous to the relocation maneuver that is part of a routine physical examination of the shoulder [8]. Although the patient was supine, scanning was performed with the ultrasound transducer in the transverse axis of the humeral shaft in an axillary view with the shoulder in 90° of abduction. This approach afforded a coronal view of the glenohumeral joint, including the glenoid, humeral head, and part of the proximal humeral shaft. A Hill-Sachs lesion was described as focal flattening or convexity of the normal curved echogenic line of the humeral head. Dynamic scanning was performed from 0° of external rotation to maximal external rotation to assess for any change in the smooth contour of the humeral head during dynamic scanning while taking care to keep the humeral shaft in view [8]. Normal Anatomy and Variants MR arthrography—An important region to evaluate during ABER imaging is the anterior inferior labrum because this is often seen to better advantage in this plane than

in conventional planes. A normal anatomic variant that can mimic a pathologic condition is the pseudoredundant anteroinferior labrum in which there is a prominent anterior band of inferior glenohumeral ligament because of internal rotation in the axial plane, potentially mimicking an anterior inferior labral tear (Fig. 3). The superior labral bicipital complex, which consists of the superior labrum and the long head of the biceps tendon, can also be evaluated with ABER imaging (Fig. 4). A normal anatomic variant of the long head of the biceps tendon in the ABER position in which it has an accordion appearance in the proximal aspect of the intercondylar groove should not be mistaken for a biceps tear (Fig. 5). This finding rather represents the normal undulating appearance of the biceps tendon when the arm is placed in the ABER position, which relieves the normal tension placed on the tendon in the neutral position. Evaluation of the rotator cuff by ABER imaging can often be helpful to maximize the accuracy of conventional MR arthrography. In particular, on conventional coronal MR arthrograms, apparent undersurface fraying of the normal supraspinatus tendon at the interface with the rotator cable often is mistaken for a partial tear [9]. Contrast pooling along the superior joint recess during ABER imaging helps depict a smooth supraspinatus tendon undersurface and rotator cable interface (Fig. 6). Humeral head cysts can simulate small insertional rotator cuff tears because of the presence of volume-averaging artifact in conventional MRI planes. When these cysts are evaluated on ABER images, the fluid signal intensity is better defined as subcortical and not within the distal infraspinatus tendon substance [10] (Fig. 7). Ultrasound—A small number of publications have addressed use of the ABER position in ultrasound evaluation of the normal shoulder anatomy. Robinson et al. [7] found that 15 of 93 (16%) of healthy volunteers had asymptomatic occlusion or significant stenosis at Doppler ultrasound of the posterior circumflex humeral artery in the quadrilateral space with the arm in ABER position in the absence of shoulder problems. This finding in healthy subjects without symptoms has cast doubt on previous associations between compromise of this artery and the finding of quadrilateral space syndrome at MR angiography [11]. Stapleton et al. [12] performed a study to evaluate for changes in axillary artery diameter and peak systolic velocity in subjects with-

out symptoms during upper limb positioning with the arm in ABER, a position commonly used during physical examinations of athletes to assess for vascular abnormalities and referred to as the hyperabduction maneuver. Those investigators found statistically significant reductions in axillary artery diameter only during extreme (120°) abduction without shoulder symptoms. They therefore questioned the specificity of physical examination tests, such as the hyperabduction maneuver, and they also noted the necessity of interpreting test results in conjunction with other findings in the physical examination. Pathologic Findings MR arthrography—The clinical indications for performing additional ABER imaging in MR arthrography are, first, injuries to the anterior inferior glenohumeral joint and surrounding structures (including anterior shoulder instability) and evaluation of the postoperative labrum as for Bankart repair and, second, injuries to the posterosuperior glenohumeral joint and surrounding structures (including posterosuperior impingement) and delaminating articular surface tears of the supraspinatus and infraspinatus tendons. At our institution, ABER positioning is attempted in all shoulder MR arthrographic studies because these areas are frequently queried as sources of a patient’s symptoms. Anteroinferior abnormalities—Several studies [1–3] have shown that compared with conventional MRI planes, MR arthrography of the shoulder in the oblique axial imaging plane in the ABER position allows better visualization of normal anatomy and of pathologic conditions affecting the inferior glenohumeral ligament and anteroinferior labrum. In evaluating anterior inferior labral abnormalities, Cvitanic et al. [1] compared ABER against conventional MR arthrography for the detection of anterior inferior labral tears. They found higher sensitivity (89% vs 48%) and specificity (95% vs 91%) using ABER and maximized sensitivity (96%) and specificity (97%) when conventional and ABER MR images were reviewed together. In patients with anterior shoulder instability, injury to the glenohumeral joint and labrum from anterior shoulder dislocation has a characteristic appearance on images. Although conventional MRI positions are usually sufficient for accurate detection of such injuries, including Hill-Sachs impaction of the humeral head and Bankart injuries to the glenoid osseous rim and labrum, use of the

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Beltran et al. ABER position may assist in adding diagnostic information about the extent of the injury. The ABER technique is particularly useful for differentiating the different Bankart variants of labral pathologic entities in the anterior inferior labrum after anterior shoulder dislocation (Perthes, anterior labroligamentous periosteal sleeve avulsion, and Bankart lesions). The utility comes from the traction applied by the anterior band of the inferior glenohumeral ligament. In addition, this area is viewed en face in the oblique axial imaging plane without the confounding variable of volume-averaging artifacts that typically occur in conventional MRI planes. Patients with anterior shoulder instability due to ligamentous laxity sometimes do not present with bone and labral abnormalities, particularly if they have not experienced clinically significant trauma from a shoulder dislocation event, in which case the conventional MRI diagnosis can be quite challenging. On conventional MR arthrographic images with the arm in neutral position, the joint capsule is normally distended with contrast medium, making the diagnosis of a patulous joint capsule causing joint laxity challenging. Mosely and Overgaard [13] classified three types of anterior glenohumeral capsular insertions in relation to the labrum in patients with recurrent anterior shoulder dislocation. Type 1 corresponds to capsular insertion directly on the labrum. Type 2 is capsular insertion at the junction of the labrum and the glenoid. Type 3 is more medial insertion at the glenoid neck. However, patients without symptoms and with clinical laxity have been found to have type 2 and 3 capsular insertions on conventional MR arthrograms [14]. This finding may erroneously suggest a patulous anterior capsule if one is using only this classification system. Because the anterior glenohumeral joint capsule is stretched and therefore should be taut in healthy persons in the ABER position, use of this imaging position should assist in visualization of a truly patulous anterior inferior joint capsule associated with instability (Fig. 8). Additional research is necessary to confirm this hypothesis. At this time, we recommend that a patulous anterior inferior capsule on ABER images raise suspicion of possible anterior laxity of the glenohumeral joint. The finding, however, should be correlated with the clinical history and physical examination findings of the presence of anterior instability. In an assessment of atraumatic multidirectional instability of the shoulder, Schaeffeler et al. [15] evaluated several diagnostic signs

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and measurements of capsular redundancy at MR arthrography including ABER images and standard imaging planes. On ABER images, the presence of a layer of contrast medium between the humeral head and the anterior inferior glenohumeral ligament (AIGHL) (crescent sign) and a triangular space between the humeral head, AIGHL, and glenoid (triangle sign) were evaluated. Centering of the humeral head was measured as the shortest distance between the center of the humeral head and a line that perpendicularly bisected the glenoid fossa. Anterosuperior herniation of the rotator interval capsule and glenoid version were assessed in standard imaging planes. The crescent sign had sensitivity of 57%, 62%, and 48% for three observers and specificity of 100%, 100%, and 94% in the diagnosis of multidirectional instability. The triangle sign had sensitivity of 48%, 57%, and 48% and specificity of 94%, 94%, and 100%. The combination of both signs had sensitivity of 86%, 90%, and 81% and specificity of 94%, 94%, and 94%. The presence of a triangle sign had a statistically significant association with decentering of the humeral head. Measurements of rotator interval herniation, rotator interval width, and glenoid version were not significantly different between the two groups. The investigators concluded that combined assessment of redundancy signs on ABER MR arthrograms allows accurate differentiation between patients with atraumatic multidirectional instability and patients with clinically stable shoulders and that measurements in standard imaging planes are not useful. The utility of ABER imaging during MR arthrography in the postoperative evaluation of Bankart repair surgery has also been found. Sugimoto et al. [16] conducted a study with 30 patients who underwent suture-anchor Bankart repair. They found that MR arthrographic findings of reattachment of the AIGHL were significantly associated with arthroscopic findings of reestablishment of the capsulolabral complex (p < 0.01). They noted that ABER imaging was more sensitive than conventional MR arthrography in the detection of anterior labral detachment and torn AIGHL because maximum tension is applied to the AIGHL in the ABER position, more effectively depicting reattachment of the AIGHL to the glenoid rim. Humeral avulsion of the glenohumeral ligament (HAGL) is posttraumatic disruption of the inferior glenohumeral ligament from the anatomic neck of the humerus in which the

normal axillary recess complex of the joint capsule is disrupted on MR arthrograms. It can be visualized as the presence of contrast extravasation through the axillary recess along the medial margin of the proximal humeral shaft [17]. In addition to this diagnosis, there can often be spontaneous extravasation of contrast medium through the axillary recess in MR arthrography due to increased intraarticular pressure with an intact inferior glenohumeral ligament at surgery [18]. The diagnosis of a HAGL lesion with both conventional and arthrographic MRI can therefore be challenging. To our knowledge, the use of ABER positional MRI to improve detection of a HAGL lesion has not been studied in the literature. Nevertheless, at our institution we have found that in the appropriate clinical setting, ABER imaging can be helpful for confirming extravasation of contrast material through the axillary recess, which can also be seen in conventional MRI planes but with improved visualization of a torn inferior glenohumeral ligament (Fig. 9). Posterosuperior abnormalities—The conspicuity of subtle superior labral abnormalities can be increased on ABER images. Evaluation of the superior labrum for subtle pathologic conditions is often difficult because anatomic variants, such as a sublabral recess, are common and can mimic abnormalities. On ABER images, the presence of contrast imbibition and fraying of the superior labral substance can help confirm a labral tear and differentiate it from such normal variant anatomy. Posterior superior internal impingement of the shoulder is characterized by contact of the undersurface of the posterosuperior rotator cuff with the posterosuperior labrum when the arm is in the ABER position, in which the cuff can become pinched between the labrum and the greater tuberosity [19]. It typically occurs in professional throwing athletes and is attributed to repetitive overhead motion, most commonly in baseball pitchers, tennis players, javelin throwers, and swimmers. ABER is the ideal imaging plane not only for detecting associated abnormalities, including undersurface tearing of the rotator cuff and posterior superior labrum, but also for confirming abnormal contact between the cuff undersurface and the posterior superior glenoid in the ABER position (Fig. 10). Studies of the evaluation of posterior superior impingement have shown improved detection of undersurface tears of the posterior supraspinatus and anterior in-

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Positional Maneuvers for Shoulder MRI and Ultrasound fraspinatus tendons and the posterior superior labrum on ABER compared with conventional MR arthrographic images [20–22] and thickening of the posterior glenohumeral joint capsule in association with glenohumeral internal reduction deficit [23]. ABER positional imaging may also increase the conspicuity of pathologic findings in the posterior superior labrum because this area is imaged en face in the oblique axial imaging plane when this position is used, in contrast to conventional coronal and axial MRI, in which evaluation of this portion of the labrum is often confounded by volumeaveraging and magic angle artifacts. In addition to depicting labral and rotator cuff abnormalities, ABER imaging is also useful for evaluating the neurovascular structures around the glenohumeral joint. Mass lesions such as paralabral ganglion cysts in the scapular notch and spinoglenoid notch are often associated with labral tears and can cause mass effect with impingement on the adjacent suprascapular nerve, referred to as suprascapular nerve syndrome [24]. ABER imaging can assist in confirming the location of the cyst adjacent to the nerve and its communication with the labrum in a patient with a labral tear. In evaluation of the rotator cuff on conventional MR arthrograms, differentiating a high-grade partial articular-side tear (in which most of the tendon fibers are torn with only a thin rind of bursal-side fibers still intact) from a full-thickness tear can be challenging. Use of ABER imaging improves visualization of the undersurface fibers, improving diagnostic accuracy for this type of injury (Fig. 11). In an evaluation of partialthickness tears of the rotator cuff, Lee and Lee [25] compared ABER with the conventional coronal oblique MR arthrographic imaging plane. They found higher sensitivity for the detection of the horizontal components of undersurface rotator cuff tears on ABER images (100% vs 21%). They also classified the horizontal component of partial-thickness tears according to the shape and signal intensity of the articular surface of the cuff as it appeared on MR arthrograms (Fig. 12). Ultrasound—Khoury et al. [8] used ultrasound to evaluate patients with engaging HillSachs lesions. They placed the patient’s arm in 90° abduction and 90° external rotation and performed dynamic imaging as described earlier. Their hypothesis was that visualization of the Hill-Sachs lesion in this position, even if only partial, would signify that it was

an engaging lesion. Their results showed that in three of their nine patients with positive physical examination findings of unidirectional anterior glenohumeral instability, they were able to view the Hill-Sachs lesion with dynamic sonography using this approach. In these cases, the Hill-Sachs defect appeared either as an abrupt change in contour or focal irregularity along the lateral or posterolateral aspect of the humeral head (Fig. 13). Flexion, Adduction, and Internal Rotation Technique MR arthrography—Imaging of the shoulder in FADIR is a useful additional sequence in MR arthrography to evaluate normal anatomy and diagnose pathologic conditions in the posteroinferior glenohumeral joint [4, 26]. In this provocative position, the arm is placed across the chest with the hand on the contralateral shoulder and the palm facing outward [26]. A shoulder surface coil is placed on the shoulder, and T1-weighted fat-suppressed sequences in the FADIR position are performed in the axial plane, planned primarily in the coronal localizer sequence [26]. At our institution, FADIR imaging is not included in our routine MR arthrography protocol. However, if the appropriate clinical history or presentation of posterior shoulder instability is present, this additional sequence is recommended and may be performed as a replacement for the ABER sequence if there is no suspicion of anterior glenohumeral joint abnormalities, to better evaluate the posterior inferior joint. Ultrasound—For ultrasound in the FADIR position (Fig. 14), the patient is placed on a swivel chair and is asked to put the arm of the affected shoulder on the front of the chest over the contralateral shoulder with the palm of the hand facing toward the body [27]. Depending on the structure of interest, the ultrasound probe is placed either in the long or the transverse axis of the area of interest. A common indication for this position is evaluation of the infraspinatus tendon, in which the ultrasound probe is placed in the long axis of the infraspinatus tendon along the posterior aspect of the humeral head [27]. Another possible use of this position in ultrasound is to evaluate the subcoracoid bursa. In this case, the ultrasound probe is placed anteriorly over the shoulder in the transverse plane for evaluation of the subcoracoid bursa for pain and bursal fluid [28].

Anatomy and Variants A normal variant posterior inferior labral cleft at the 8-o’clock position in the posterior glenohumeral joint has been described [29]. The FADIR position may be useful for differentiating a real tear from this normal cleft [26]. Pathologic Findings MR arthrography—Chiavaras et al. [26] found in a retrospective review of nine patients with suspected pathologic changes in the posterior inferior labrum that use of the FADIR position helped to confirm, exclude, or better characterize a posterior inferior labral abnormality by increasing diagnostic confidence. Injury to the posterior inferior labrum in patients with posterior shoulder instability is less common than anterior inferior labral abnormalities, accounting for only 5% of cases of shoulder instability [30, 31]. Posterior shoulder instability is most often seen as the sequela of chronic repetitive injury associated with sports such as American football, weightlifting, and overhead sports, such as swimming and baseball, but is also less commonly seen after posterior dislocation or after direct impact to the shoulder without frank dislocation [26]. The clinical presentation of posterior shoulder instability can vary but typically is associated with poorly localized posterior shoulder pain. Some patients describe a sense of joint instability or looseness [30, 31]. In either presentation, the symptoms are exacerbated when the arm is in the FADIR position [30, 31]. Posterior shoulder instability is usually treated conservatively with physiotherapy and rehabilitation. It is treated surgically only when conservative therapy fails [31, 32]. In patients with clinical signs and symptoms of posterior shoulder instability, 95% successful outcome has been reported with surgical techniques designed to correct the labral and capsuloligamentous disorder causing the instability [33]. Therefore, optimal preoperative evaluation of this region using this positional MRI technique is helpful in surgical planning to correctly diagnose injury to this area. Posterior shoulder instability is associated with multiple structural abnormalities of the glenohumeral joint, including injury to the bone, muscles, labrum, and ligaments [4]. Many pathologic variants have been reported in the posterior inferior glenohumeral joint, including the reverse Bankart lesion, posterior periosteal sleeve avulsion, Kim lesion, and posterior glenolabral articular disrup-

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Beltran et al. tion [4]. Saupe et al. [34] found that in traumatic posterior shoulder dislocation, tears of the posterior inferior labrum occurred in as many as 60% of cases. Knowledge of the imaging appearance of these various lesions on conventional and provocative FADIR positional images is therefore important to guide appropriate lesion-specific treatment. In the FADIR position, the posterior band of the inferior glenohumeral ligament creates tension on the posterior inferior chondrolabral junction, allowing better delineation of chondrolabral separation tears [26] (Fig. 14). In addition, the absence of any separation at the chondrolabral junction may be useful to rule out a posteroinferior labral tear. A subtle concealed tear may also be more confidently diagnosed when this provocative maneuver reveals incomplete separation of the posterior inferior labrum with an intact posterior inferior glenohumeral ligament [4]. The FADIR position may also be useful for differentiating a displaceable tear from a healed tear filled with granulation tissue [26]. The use of the FADIR position to evaluate the rotator cuff and biceps tendon has not been extensively discussed in the literature. Chiavaras et al. [26] noted that contrast material preferentially pooled in the anterior glenohumeral joint recess during FADIR MR arthrography. This finding suggests that this technique may help in assessment of the undersurface of the subscapularis tendon and the contents of the biceps tendon sheath, including loose bodies, synovial thickening, and septation. Ultrasound—The FADIR position is commonly used during diagnostic ultrasound evaluation of the shoulder, particularly evaluations for tear of the infraspinatus tendon at the greater tuberosity insertion along the posterior aspect of the humeral head. The patient places the arm in front of the chest, and the examiner evaluates the infraspinatus tendon in the longitudinal plane [27]. Partial tears appear as hypoechoic partial defects in the tendon with some fibers remaining intact, whereas full-thickness tears appear as completed articular to bursal surface defects in the tendon, which can be associated with varying degrees of tendon retraction [27]. Calcifications can also be seen within the tendon in patients with calcific tendinosis, appearing on ultrasound images as echogenic foci with acoustic shadowing [27]. In a 2015 study [28], shoulder adduction, forward flexion, and internal rotation during ultrasound were found useful in the diagnosis of subcoracoid impingement in combina-

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tion with the findings of anterior shoulder pain and subcoracoid bursitis over the subcoracoid bursa in the anterior shoulder during this maneuver. Conclusion Positional imaging using ABER and FADIR during MRI and ultrasound can add diagnostic accuracy to the evaluation of the shoulder. However, correct interpretation of imaging studies requires familiarity with the peculiar arrangement of intraarticular and periarticular osseous and soft-tissue structures in these imaging planes. References 1. Cvitanic O, Tirman PF, Feller JF, Bost FW, ­Minter J, Carroll KW. Using abduction and external rotation of the shoulder to increase the sensitivity of MR arthrography in revealing tears of the anterior glenoid labrum. AJR 1997; 169:837–844 2. Choi JA, Suh SI, Kim BH, et al. Comparison between conventional MR arthrography and abduction and external rotation MR arthrography in revealing tears of the antero-inferior glenoid labrum. Korean J Radiol 2001; 2:216–221 3. Kwak SM, Brown RR, Trudell D, Resnick D. Glenohumeral joint: comparison of shoulder positions at MR arthrography. Radiology 1998; 208:375–380 4. Harish S, Nagar A, Moro J, Pugh D, Rebello R, O’Neill J. Imaging findings in posterior instability of the shoulder. Skeletal Radiol 2008; 37:693–707 5. Song HT, Huh YM, Kim S, et al. Anterior-inferior labral lesions of recurrent shoulder dislocation evaluated by MR arthrography in an adduction internal rotation (ADIR) position. J Magn Reson Imaging 2006; 23:29–35 6. Tirman PF, Bost FW, Steinbach LS, et al. MR arthrographic depiction of tears of the rotator cuff: benefit of abduction and external rotation of the arm. Radiology 1994; 192:851–856 7. Robinson DJ, Marks P, Schneider-Kolsky M. Occlusion and stenosis of the posterior circumflex humeral artery: detection with ultrasound in a normal population. J Med Imaging Radiat Oncol 2011; 55:479–484 8. Khoury V, Van Lancker HP, Martineau PA. Sonography as a tool for identifying engaging Hill-Sachs lesions: preliminary experience. J U ­ ltrasound Med 2013; 32:1653–1657 9. Gyftopoulos S, Bencardino J, Nevsky G, et al. Rotator cable: MRI study of its appearance in the intact rotator cuff with anatomic and histologic correlation. AJR 2013; 200:1101–1105 10. McMonagle JS, Vinson EN. MRI of the shoulder: rotator cuff. Appl Radiol 2012; 41:20–27 11. Mochizuki T, Isoda H, Masui T, et al. Occlusion of the posterior humeral circumflex artery: detec-

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Fig. 1—29-year-old man with right shoulder pain being evaluated for labral tear. Abduction and external rotation image acquisition. A, Coronal gradient-recalled echo scout localizer MR image shows prescribed sections (dashed lines). B, Oblique axial fat-suppressed T1-weighted MR arthrogram shows inferior glenohumeral ligament anterior band (open black arrow), normal posterior superior labrum (solid white arrow), normal anteroinferior labrum (dashed white arrow), and normal rotator cuff tendon (solid black arrow).

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Fig. 2—Abduction and external rotation (ABER) positioning. A, 30-year-old female volunteer. Photograph shows subject in ABER position with shoulder abducted 90° and externally rotated 90° and hand resting on head for comfort. B, 16-year-old boy with anterior shoulder pain and concern for superior labral tear. Ultrasound obtained with patient in ABER position after arthrographic injection into posterior glenohumeral joint shows infraspinatus tendon (white arrow) as it inserts on greater tuberosity (GT). Fluid (star) is within posterior aspect of glenohumeral joint and isoechoic triangular posterior labrum (black arrow) are evident. There is no fluid between labrum and shadowing osseous glenoid rim (G) or fluid imbibition within infraspinatus tendon indicating absence of a tear. Humeral head articular cartilage is visible as reflective surface between labrum and infraspinatus tendon insertion.

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Fig. 3—34-year-old man with left shoulder pain being evaluated for labral tear. Example of pseudoredundant anteroinferior labrum. A, Axial fat-suppressed T1-weighted MR arthrogram shows apparent prominence of anterior inferior labrum due to close apposition of anterior band of inferior glenohumeral ligament (arrow) due to internal rotation. B, Oblique axial T1-weighted MR arthrogram obtained in abduction and external rotation position shows prominence has resolved (arrow).

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B Fig. 4—16-year-old boy with recurrent shoulder dislocations and instability. Example of labral bicipital complex. A and B, Illustration (A) and oblique axial fatsuppressed T1-weighted MR arthrogram image obtained in abduction and external rotation position (B) show posterior superior labrum (open arrow), transverse ligament (white solid arrow), and long head of biceps tendon (black solid arrows). SSc = subscapularis muscle.

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Fig. 5—37-year-old man with remote left shoulder injury aggravated after weight-lifting being evaluated for labral tear. Example of biceps accordion appearance. A, Coronal fat-suppressed T1-weighted MR arthrogram in neutral position shows normal stretched appearance of long head of biceps tendon (arrow). B, Abduction and external rotation fat-suppressed T1-weighted MR arthrogram shows normal accordion appearance of long head of biceps tendon (arrow).

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Positional Maneuvers for Shoulder MRI and Ultrasound Fig. 6—30-year-old woman with left shoulder pain being evaluated for labral tear. Example of normal supraspinatus tendon. A, Coronal fat-suppressed T1-weighted MR arthrogram shows apparent undersurface fraying of supraspinatus tendon (solid arrow) at interface with rotator cable (dashed arrow). B, Abduction and external rotation fat-suppressed T1-weighted MR arthrogram shows normal smooth supraspinatus tendon undersurface (white solid arrow) in this region. Inferior glenohumeral ligament anterior band (open arrow) and posterior superior labrum (black solid arrow) are evident.

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B Fig. 7—37-year-old man with remote left shoulder injury aggravated after weight-lifting being evaluated for labral tear. Subcortical contrast medium–filled cysts volume average with adjacent infraspinatus tendon. A and B, Coronal (A) and oblique axial abduction and external rotation position (B) fat-suppressed T1weighted MR arthrograms show infraspinatus tendon (open arrow) and subcortical cysts (solid arrow).

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Fig. 8—28-year-old woman with chronic left shoulder pain and history of shoulder dislocation at age 14. Example of anterior inferior instability due to capsular laxity. A and B, Axial fat-suppressed T1-weighted (A) and oblique axial abduction and external rotation (B) MR images show patulous anterior inferior glenohumeral joint capsule (arrow). Arthroscopic evaluation revealed capsular redundancy and no displaced labral tear. Patient was treated with capsulorraphy.

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Fig. 9—20-year-old woman with humeral avulsion of inferior glenohumeral ligament after snowboarding trauma. A and B, Coronal (A) and oblique axial abduction and external rotation (ABER) (B) fat-suppressed T1-weighted MR arthrograms. ABER image confirms disruption of inferior glenohumeral ligament (white arrow), which is frayed and imbibes contrast medium and shows contrast extravasation (black arrow) along anterior aspect of proximal humeral shaft.

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B Fig. 10—24-year-old man with left shoulder pain from type II superior labral anteroposterior (SLAP) undersurface supraspinatus partial tear. A and B, Coronal (A) and oblique axial abduction and external rotation (B) fat-suppressed T1-weighted MR arthrograms show contact between torn posterosuperior labrum and torn supraspinatus tendon undersurface (black arrow) in setting of posterior superior internal impingement. White arrow indicates superior labrum.

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Fig. 11—26-year-old man with left shoulder pain undergoing evaluation for labral tear. Example of undersurface partial tear of supraspinatus tendon. A, Coronal fat-suppressed T1-weighted MR arthrogram shows nearly full-thickness articular-side tear of supraspinatus tendon (black arrow) with only thin rind of bursal surface fibers still intact. White arrows indicate associated circumferential tear of labrum. B, Abduction and external rotation image shows to better advantage intact bursa-side fibers (black arrow) at site of tear. White arrows indicate associated circumferential tear of labrum.

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Positional Maneuvers for Shoulder MRI and Ultrasound

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Fig. 12—Classification of partial rotator cuff tears. Illustrations (top) and corresponding oblique axial abduction and external rotation fat-suppressed T1-weighted MR arthrograms (bottom) of three patients with shoulder pain undergoing evaluation for rotator cuff tears. A = acromion, H = humerus, G = glenoid, C = flow of intraarticular contrast medium. (Reprinted with permission from Nomikos GC, Rafii M. Shoulder impingement syndromes. In: Pope T, Bloem HL, Beltran J, William B. Morrison WB, Wilson DJ, eds. Imaging of the musculoskeletal system. Philadelphia, PA: Saunders, 2008) A, 36-year-old man with type A horizontal partial-thickness intrasubstance tear (arrow) without articular surface abnormality. B, 22-year-old man with type B horizontal partial-thickness tear (arrow) with irregularity of articular surface. C, 35-year-old man with type C horizontal partial-thickness tear (arrow) with torn edge of articular surface (flap tear).

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Fig. 13—40-year-old man with recurrent left shoulder dislocations. A and B, Long-axis ultrasound images of posterior glenohumeral joint in minimal (A) and full (B) abduction and external rotation (ABER) show large impaction fracture (Hill-Sachs lesion) of posterosuperior humeral head (solid arrow). Fracture moves over glenoid (open arrow) in full ABER, which may imply engaging lesion. Ultrasound images were obtained after ultrasoundguided arthrographic injection, which accounts for fluid distention of joint (star). (Fig. 13 continues on next page)

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Fig. 13 (continued)—40-year-old man with recurrent left shoulder dislocations. C and D, Transaxial T1-weighted fat-suppressed MR arthrograms in neutral position (vertically flipped for orientation similar to ultrasound images) (C) and ABER (horizontally flipped) (D) show humeral head impaction fracture (arrow) translating over glenoid in ABER. Width of lesion is approximately same as glenoid diameter, consistent with engaging lesion.

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Fig. 14—Imaging in flexion, adduction, and internal rotation (FADIR) position. A, 30-year-old female volunteer. Photograph shows subject in FADIR position with shoulder flexed, adducted, and internally rotated with hand on contralateral elbow for comfort. Ultrasound probe is imaging posterior capsule in long axis in relation to infraspinatus tendon. B and C, 31-year-old man with left posterior labral tear. Long-axis ultrasound images of posterior glenohumeral joint at level of spinoglenoid notch in FADIR position just before (B) and after (C) ultrasound-guided intraarticular arthrographic injection show hypoechoic contrast imbibing within posterior chondrolabral junction separation and labral substance tear (solid arrow, C). Needle (open arrow) is placed from lateral approach. Placing patient in FADIR position produces traction on posterior labrum, making posterior labral tears more conspicuous. D, 31-year-old man with left posterior labral tear (same patient as in B and C). Transaxial T1-weighted fat-suppressed MR arthrographic obtained with patient in FADIR position (vertically flipped for orientation similar to ultrasound images) shows contrast material within posterior chondrolabral junction with irregular morphologic features of labral and chondral surface (arrow) confirming presence of labral tear.

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