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JBR­BTR, 2007, 90: 377-383.


H-J. Van der Woude1, F M. Vanhoenacker2,3 . The impact of accurate imaging in the work-up of patients with glenohumeral instability is high. Results of imaging may directly influence the surgeon's strategy to perform an arthroscopic or open treatment for (recurrent) instability. Magnetic resonance (MR) imaging, and MR arthrography in particular, is the optimal technique to detect, localize and characterize injuries of the capsular-labrum complex. Besides T1-weighted sequences with fat suppression in axial, oblique sagital and coronal directions, an additional series in abduction and exoroation position is highly advocated. This ABER series optimally depicts abnormalities of the inferior capsular-labrum complex and partial undersurface tears of the spinatus tendons. Knowledge of different anatomical variants that may mimic labral tears and of variants of the classic Bankart lesion are useful in the analysis of shoulder MR arthrograms in patients with glenohumeral instability.

Key-words: Shoulder, MR -- Shoulder, dislocation.

Because of its remarkable degree of mobility, the glenohumeral joint is inherently prone to instability. Functional stability of the glenohumeral joint is maintained by both static and dynamic mechanisms. The static mechanisms include negative intraarticular pressure, adhesion and cohesion of articular surfaces, size, shape and orientation of the glenoid fossa and the capsulolabral complex. Dynamic mechanisms include the rotator cuff and the long biceps tendon (1). The leading cause of instability about the glenohumeral joint relates to previous dislocations resulting from trauma. Direction of dislocation can be anteriorly, which is by far most commonly encountered (95%), posteriorly, superiorly or inferiorly. These anteroinferior dislocations are usually associated with lesions of the anteroinferior bony glenoid margin (bony Bankart lesion), compression fracture of the superolateral humeral head (Hill-Sachs lesion), the anteroinferior labrum (Bankart lesion) with injury of the inferior glenohumeral ligament and/or stripping of the capsule and scapular periosteum. Non-traumatic shoulder instability may be caused by a congenital capsular hyperlaxity or hypoplasia of the glenoid. This may lead to multidirectional instability, which is often bilaterally encountered. The impact of accurate imaging in the work-up of patients with glenohumeral instability is high. Results of (magnetic resonance) imaging may directly influence the surgeon's strategy to perform an arthroscopic or open treatment for (recurrent) instability. Factors that are in favor of

Fig. 1. -- Hill-Sachs lesion. Axial MR arthrogram. There is a large bony impression on the posterolateral side of the humeral head (arrow), secondary to anterior shoulder dislocation. Bankart lesion anteriorly (short arrow).

Fig. 2. -- Bony erosion. Oblique sagittal MR arthrogram demonstrating flattening of the anterior glenoid, due to recurrent shoulder dislocations.

open treatment include a large bony Hill-Sachs defect (fig. 1), substantial bone erosion of the anterior glenoid rim (fig. 2), humeral avulsion of the glenohumeral ligament and hyperlaxity of the capsule. Magnetic resonance (MR) imaging, and MR arthrography in particular, is the optimal technique to detect, localize and characterize injuries of the capsularlabrumcomplex, and as such assists in determining the therapeutic strategy (2-18). Global anatomy The capsular complex provides the most important contribution to stabilization of the glenohumeral joint. The anterior capsular mechanism is composed of the fibrous capsule with reinforcements (the glenohumeral ligaments), the synovial

From: 1. Dept of Radiology Onze Lieve Vrouwe Gasthuis Amsterdam, The Netherlands, 2. Dept of Radiology AZ Sint-Maarten, Duffel-Mechelen, Belgium, 3. Dept of Radiology University Hospital Antwerp, Belgium Address for correspondence: Dr Henk-Jan Van der Woude, MD, PhD, Department of Radiology, Onze Lieve Vrouwe Gasthuis Amsterdam, PO Box 95500, 1090 HM Amsterdam, The Netherlands. E-mail: [email protected]

membrane, the fibrous glenoid labrum, the subscapularis muscle and tendon and periosteum of the scapula. The insertion of the anterior capsule is variable, depending on the proximity of the capsular origin to the glenoid margin; a more medial insertion on the glenoid (fig. 3) is probably associated with a higher rate of instability of the glenohumeral joint. The posterior capsular mechanism consists of the posterior capsule, the synovial membrane, posterior glenoid labrum and periosteum and posterosuperior rotator cuff tendons and muscles (1-5). The labrum (fig. 4) is a fibrous extension of the glenoid which deepens the fossa and as such attributes to increased stability. Moreover, it serves as anchoring structure for the superior, middle and inferior glenohumeral infoldings of the anterior capsule and the long biceps tendon (LBT) superiorly. Of the glenohumeral ligaments, the inferior glenohumeral ligament (IGHL), composed of an anterior and posterior band and axillary recess in between, contributes most in providing glenohumeral stability. From the


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Fig. 3. -- Type 3 anterior capsule. Axial MR arthrogram shows insertion of the anterior capsule far medial from the glenoid-labrum junction. Notice normal rounded shape of the anterior and posterior labrum.

Fig. 5. -- Relationship of labrum to SGHL and MGHL. Axial MR arthrogram. SGHL (long arrow) runs parallel to the coracoid and has a common origin with MGHL (short arrow) which runs more or less perpendicular to the SGHL. Notice normal triangular shaped anterior labrum (curved arrow).

portion. The intracapsular portion courses from a broad base on the superior labrum to the bicipital groove (fig. 6), surrounded by the coracohumeral ligament superiorly and SGHL anteriorly and inferiorly within the rotator interval. The tendon exits the joint anterosuperiorly at the anatomic neck of the humerus to enter the intertubercular sulcus. Near its exit point, the tendon is reinforced by the coracohumeral ligament superiorly, by the SGHL anteriorly and inferiorly and by slips from the subscapularis and supraspinatus tendons, whereas the transverse ligament reinforces the tendon in the intertubercular sulcus below this point of exit. Magnetic resonance (MR) imaging in glenohumeral instability Native (unenhanced) MR images, including axial, oblique coronal and oblique sagittal sequences are usually adequate to analyse rotator cuff abnormalities and can be used in more non-specific shoulder complaints. However, for the purpose of evaluating patients with glenohumeral instability, an MR arthrography protocol after intra-articular injection of a diluted Gd-DTPA mixturee, providing distention of the joint, is pivotal. This improves the diagnostic accuracy, particularly to appreciate delicate intra-articular structures, subtle labral abnormalities and undersurface margins of the rotator cuff tendons (2, 6, 7, 9, 10-17) (fig. 7). For this purpose, gadolinium is diluted 1:250, in order to optimize the paramagnetic effect on T1-weighted images. To obtain this concentration,

Fig. 4. -- Normal labrum. Oblique sagittal MR arthrogram shows a low signal fibrous extension of a normal pearshaped glenoid.

antero-posteroinferior labrum, the IGHL inserts on the inferior aspect of the anatomic neck of the humerus. The middle glenohumeral ligament (MGHL) shows a variable insertion on the anterosuperior glenoid. It passes the joint in an oblique inferior fashion, more or less parallel and posterior to the subscapularis tendon, insertion is on the lesser tuberosity. In approximately 30% of individuals, it is absent. A common origin with the superior glenohumeral ligament (SGHL) and/or LBT is not infrequently encountered (fig. 5). An other variable presentation is a cordlike thickening of the MGHL in absence of the anterosuperior labrum (Buford complex). The superior glenohumeral ligament has an origin immediately anterior to the labral-bicipital junction. It courses anteriorly and parallel with the coracoid process (fig. 5) and merges with the coracohumeral ligament in the rotator interval (1-8). The long biceps tendon has an intracapsular and an extracapsular



Fig. 6. -- Intra- and extraarticular course of long biceps tendon on oblique coronal MR arthrogram (A) and biceps anchor (arrow) on oblique sagittal MR arthrogram (B).

Fig. 7. -- Partial supraspinatus tear. MR arthrogram in ABER position. There is vertical and horizontal intratendinous leakage of contrast medium into supraspinatus tendon (arrow). Notice uninterrupted anteroinferior capsular-labrum complex (short arrow).



Fig. 8. -- The axial plane is perpendicular to the bony glenoid, to evaluate the capsulolabral structures.

Fig. 9. -- The oblique coronal scan plane is prescribed on an axial image parallel to the supraspinatus tendon.

2 mL Gadolinium DTPA is added to 250 ml of normal saline. Ten mL of this solution is mixed with 10 mL of 60% iodinated contrast material. Finally, 10-15 mL of the diluted gadolinium is injected into the shoulder joint under fluoroscopic guidance. Injection of air should be avoided, because this causes magnetic susceptibility artifacts. For imaging, patients should be optimally installed in supine position, with the arm extended and in slight exorotation. A dedicated phased array extremity shoulder coil should be centered on the lesser tuberosity. An MR arthrography protocol of the shoulder should include T1-weighted fast spin-echo series with fat-selective presaturation in axial, oblique coronal and oblique sagittal directions, using 3-4 mm slice thickness with a 0.5-1 mm interslice gap (figs 811). The axial series are oriented per-

pendicular to the glenoid and range from the acromio-clavicular joint to the level of the anatomic neck of the humerus. In this axial direction, the AC-joint can be evaluated, as well as anterior and posterior labrum, glenoid cartilage, biceps tendon and bicipital sulcus, the course of MGHL and SGHL and subscapularis tendon. The oblique coronal series are prescribed on an axial image, parallel to the supraspinatus tendon. As such, the rotator cuff can be evaluated, the morphology of the acromion and ACjoint, the superior biceps-labrumcomplex and the inferior capsularlabrum complex (2). The oblique sagittal series are oriented perpendicular to the coronal series and demonstrate an entire cross-section of the labrum, morphology of the glenoid and AC-joint, intra-articular course of the long biceps tendon and biceps anchor, rotator cuff components and gleno-

humeral ligaments. An additional T1weighted series with fat-saturation with the arm in abduction and exorotation (ABER) is highly advocated. Using this orientation, the inferior labral-ligamentous complex is optimally depicted as a consequence of stretching the inferior glenohumeral ligament. Moreover, due to relaxation of the supraspinatus tendon, small partial undersurface tears can be easily depicted. A (coronal) T2weighted fast spin-eco sequence can be performed in addition to assess bone abnormalities and potential extra-articular fluid collections (1-2). MR arthrography of the normal and pathologic capsular-labrumcomplex The anterior capsule has a variable insertion. The insertion of the posterior capsule is constantly located on the base of the labrum at its junction with the glenoid rim. The normal labrum, which is a fibrous extension of the capsule, has

Fig. 10. -- The oblique sagittal plane is prescribed on a coronal or axial image, perpendicular to the axis of the scapula, to evaluate the acromioclavicular joint and the coracoacromial arch.

Fig. 11. -- Axial sequence in ABER position.


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Fig. 13. -- Bankart lesion. Axial MR arthrogram shows detached labral tear (arrow) with disruption of the scapular periost and bony flattening of the anterior glenoid. Course of the MGHL parallel to the subscapularis tendon (short arrow). Fig. 12. -- Sublabral foramen. Axial MR arthrogram shows normal triangular shaped anterior labrum separated from the underlying superior part of the glenoid (arrow).

a low signal intensity on all sequences and has a variable morphology: it can be rounded, flattened, triangular or cleaved. The normal labrum is best evaluated on combined axial, oblique sagittal and coronal images. Usually, the posterior labrum is smaller and rounded. The anterior-superior labrum can be absent. This anatomical variation combined with a thickened bandlike MGHL is referred to as a Bufordcomplex and best appreciated on axial and oblique sagittal images. The sublabral foramen is a different variant, depicted on axial images, which reflects a normal fenestration of the anterior-superior labrum relative to the bony glenoid (fig. 12). These variations, and also the normal insertion of glenohumeral ligaments, should not be misinterpreted as labral tears. It should be noticed that isolated anteriorsuperior tears are very rare. A superior sublabral sulcus may be present on coronal images, which may mimic a so called SLAP (superior labrum anterior to posterior) lesion. The latter lesion usually has a lateral orientation with posterior extension relative to the biceps anchor. Therefore, contrast material extending to the ipsilateral shoulder should be considered a tear, whereas contrast medium undercutting the

labrum obliquely towards the patient's head is a normal finding. As mentioned previously, most lesions of the capsular-labrum complex occur anterior-inferiorly. Various direct or indirect signs on the MR arthrograms may indicate the diagnosis of a torn labrum. The labrum may be detached from the underlying glenoid with or without fragmentation, or absent; the labrum may show abnormal morphology and/or signal intensity (imbibition of contrast medium). Focal articular cartilage injury may accompany a torn labrum (1-11, 16, 17). In patients with complaints of glenohumeral instability, an MR arthrographic checklist may contain the following points of interest: Bone: presence or absence of an impaction fracture at the posterolateral surface of the humerus (Hill Sachs lesion, on axial images) and/ or an avulsion fracture at the anterior surface of the glenoid (bony Bankart lesion, axial and oblique sagittal images). Cartilage: presence or absence of defects, in particular on axial images. Labrum-capsular complex: should be judged in all directions, including ABER series. Biceps-labrum complex: best visualized on oblique coronal and sagittal images.

Rotator cuff: cuff lesions are not infrequently accompanying capsularlabrum lesions. Therefore, these lesions should be carefully excluded or confirmed on combined oblique coronal, sagittal and ABER images. Partial articular sided supraspinatus tears are optimally shown on the ABER provocative images. Corpora libera and synovitis: should be excluded on all present sequences. Several variations of anterior/ anterior-inferior labral injuries have been described, in order of decreasing frequency of incidence: The classic BANKART-lesion: represents an avulsed anterior labrum, with disruption of the scapular periost, with or without a bony avulsion of the inferior glenoid rim (fig. 13-15). The labrum along with the anterior band of the inferior glenohumeral ligament is displaced into the joint where it may have a floating appearance. Sometimes, a glenoid labrum ovoid mass (GLOM) may be identified, pathognomonic of a Bankart lesion (1-3, 7, 12, 13, 16, 18). ALPSA-lesion: represents anterior labral-ligamentous periosteal sleeve avulsion (figs 16-18). There is an anterior labral avulsion without disruption of the periost. In the acute phase, the periosteum remains attached to the labrum, which is pulled away by the anterior band of the inferior glenohumeral ligament complex and rotated in an inferome-



Fig. 14. -- Bankart lesion. Oblique sagittal MR arthrogram depicts avulsion of the anterior labrum together with the adherent anterior band of the inferior glenohumeral ligament (short arrow). Notice normal oblique course of the MGHL (arrow).

Fig. 16. -- ALPSA lesion. Axial MR\ arthrogram shows absence of the anterior labrum (which was displaced inferiorly).

Fig. 18. -- ALPSA lesion. Oblique sagittal MR arthrogram shows inferiorly displaced anterior labrum (arrow). There is a flattened bony erosion of the anterior glenoid.

Fig. 17. -- ALPSA lesion. Inferomedially displaced anterior labrum (arrow) on axial MR arthrogram.

Fig. 19. -- Perthes lesion. On axial MR arthrogram there is a near normal position of a rounded anterior labrum.

Fig. 15. -- Bankart lesion. Oblique coronal MR arthrogram without fat suppression shows avulsion of the inferior labrum. There is a physiologic sulcus between the superior labrum and glenoid (arrow).

dial direction. In the chronic phase the ALPSA lesion may heal due to synovialization, which results in a deformed and thickened labrum. ALPSA lesions can be depicted on either oblique coronal, sagittal or axial images. The rarely encountered POLPSA lesion is a posterior variant of the ALPSA lesion (19). Perthes lesion: represents a nondisplaced detachment of the anteriorinferior labrum, with intact though stripped periost (figs 19-21). These lesions may be difficult to visualize on standard axial MR images, because of the persistent partial attachment of the anterior labrum (fig. 19). By stressing the anterior inferior glenohumeral ligament in ABER position, detachment of the labrum with stripping of the periost can be easily depicted (fig. 20, 21).

GLAD-lesion: represents glenoidlabral articular disruption. This is best depicted on axial images. A labral tear is present together with an articular cartilaginous divot, which can be seen following acute forced adduction (Fig. 22). There is no associated capsuloperiosteal stripping (1, 20). HAGL-lesion: represents humeral avulsion of the glenohumeral ligament. This is a rare occasion where avulsion of the glenohumeral ligaments occurs at the ligamentous attachment site on the proximal humerus (Fig. 23). It is associated with recurrent anterior instability and more frequently encountered in older persons. Subscapularis tear may be present as well. The BHAGL represents the bony variant. A floating anterior inferior glenohumeral ligament (Floating AIGHL) can be regarded as a combined Bankart and HAGL lesion. Posterior labral tears, as a result of posterior dislocation, are rare (Fig. 24). A posterior labral tear may result in formation of a ganglioncyst, similar to the mechanism found in a meniscal cyst associated with a meniscal tear. In selected cases,

these cysts may be rather extensive and cause compression on the suprascapular nerve in the spinoglenoid notch, with subsequent atrophy of the supra- and infraspinatus muscles (1, 2).

Fig. 20. -- Perthes lesion. Due to stress provocation of the IGHL complex in ABER position the anterior labrum is detached with stripped but non disrupted scapular periost (arrow).


JBR­BTR, 2007, 90 (5)

Fig. 21. -- Perthes lesion. Subtle detachment of anteroinferior labrum in ABER position. Notice subluxation of the proximal humerus.

Fig. 23. -- HAGL lesion. Oblique coronal MR arthrogram showing the avulsion of the anterior band of the inferior glenohumeral complex.

Fig. 24. -- Posterior labral tear. Axial MR arthrogram demonstrates contrast medium interposition between posterior labrum and glenoid (short arrow). There is also an anterior labral injury (vertical arrow).

Fig. 22. -- GLAD lesion. MR arthrogram in ABER position. Abnormal configuration of the anterior labrum with detachment of articular cartilage fragment (arrow).


The superior labral anterior to posterior (SLAP) tears involve the superior portion of the labrum, with varying degrees of long biceps tendon involvement. Tears usually begin in the posterior-superior portion of the labrum and extend a variable distance anteriorly to the biceps-labral complex. Up to now, 12 variants of SLAP tears have been described, however, only the first four are present in any significant abundance. Type 1 (10%) represents a partial tear of the superior labrum with fibrillation of the biceps tendon and can usually only be diagnosed if there is significant imbibed contrast within the labrum. Type 2 (40%) represents a superior avulsion with tear of the anterior and posterior labrum (Fig. 25, 26). Type 3 is a bucket handle tear without involvement of the biceps.

Type 4 is a bucket handle tear that longitudinally extends into the biceps tendon. Accurate identification of the specific type of SLAP lesion can be extremely difficult, even with MR arthrography. An accurate description of the lesion and adequate communication with the referring clinician seems more important than the exact designation of a specific type. It is, however, important to differentiate lesions with avulsion of the biceps anchor from other lesions. The MR findings of a SLAP tear include the extension of contrast material between the labrum and the glenoid. A superior sulcus, which is a normal anatomic variant, should not be misinterpreted as a tear. A specific combination of anterior superior labral tear (SLAP lesion) and partial tear of the undersurface of the supraspinatus tendon has been described as a SLAC (superior labrum anterior cuff) lesion. Other lesions found in this group include the anterior part of the biceps anchor and the superior glenohumeral ligament (1-3, 9, 14, 21, 22). Internal impingement instability Symptomatic internal impingement of the shoulder is a particular mechanism of injury that has been described in various types of (throwing) sports. It may occur without (primary) or with (secondary) glenohumeral instability and capsular laxity. It can be subclassified into anterosuperior or posterosuperior impingement. In posterosuperior impingement (PSI), due to extreme combined abduction and exorotation of the shoulder (during the late cocking phase of throwing motions), the humeral head is thought to translate anteroinferiorly due to laxity of the

Fig 25. -- SLAP lesion type 2 on axial MR arthrogram.

Fig 26. -- SLAP lesion type 2 on oblique coronal MR arthrogram. Avulsion of the superior labrum (arrow), normal signal intensity of the long biceps tendon.

anterior IGHL. This allows contact between the greater tuberosity of the humerus with the posterosuperior glenoid and labrum, and with the deep undersurface of the rotator cuff. This contact can be a physiologic finding during overhead motion, however, as a result of repetitive impaction this may result in glenohumeral joint lesions at that particu-



Fig. 27. -- Posterosuperior internal impingement. MR arthrogram in ABER position. There is subtle contrast extension on articular side within supraspinatus tendon, subtle deformity of posterior labrum and irregularity of the greater tuberosity. Normal appearance of IGHL complex.

lar site, including labral degeneration, fraying and tears, paralabral cyst formation, articular-sided partial cuff tears, articular cartilage lesions and (reversible) posterosuperior humeral head cyst formation. Plain radiographs may show abnormalities of the greater tuberosity, including irregular margin, reactive sclerosis and/or geode formation. In this respect, a glenoid profile view, compared with the contralateral side may add to the diagnosis. MR arthrography is very useful to detect these PSI lesions, that can be very subtle and as such it assists in differentiation from other shoulder problems including rotator cuff injuries (Fig. 27). Identifying the most likely cause of shoulder pain may have serious consequences for further treatment. Again, imaging the shoulder in ABER apprehension position simulates the mechanism of injury and as such optimally depicts the posterosuperior glenohumeral joint. Rotator cuff tears in internal impingement are usually found on the deep surface of the posterior supraspinatus or supraspinatusinfraspinatus junction at about 1 cm from the greater tuberosity insertion. Tears are articular sided and typically small, depicted as small linear contrast extension in the tendon. These tears can be easily missed without ABER positioning, which allows contrast imbibition into a relaxed posterior superior rotator cuff. Frequently, subtle posterosuperior labral abnormalities can be appreci-

ated, demonstrated as contour irregularities and/or signal increase and impaction deformities at the posterior greater tuberosity. It has been suggested that glenohumeral internal rotation deficit and tightening of the posterior shoulder elements (capsule, cuff) may contribute to internal impingement. As such, thickening and scarring of the posterior capsule can be seen on MR images as well. Opposed to posterosuperior internal impingement, anterosuperior impingement is less frequently described. In these patients, shoulder pain is provoked by internal rotation and elevation. In anterosuperior internal impingement, MR arthrography may demonstrate partial-thickness articular-sided subscapularis tears, secondary to impingement along the anterior superior glenoid rim. At arthroscopy, partial subscapularis lesions can be encountered with or without pulley lesion, which reflects the combined humeral insertion of superior glenohumeral ligament and coracohumeral ligaments (2, 22-25). References

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