Glenohumeral instability: evaluation using MR ... - Springer Link

Skeletal Radiol (1999) 28:365–382 © International Skeletal Society 1999

Steve Shankman Jenny Bencardino Javier Beltran

Received: 24 February 1999 Revision requested: 19 April 1999 Revision received: 12 May 1999 Accepted: 13 May 1999 S. Shankman, M.D. · J. Beltran, M.D. (✉) Department of Radiology, Maimonides Md Ctr, 4802 10th Ave, Brooklyn, NY 11219, USA J. Bencardino, M.D. Department of Radiology, Long Island Jewish Md Ctr, 270-05 76th Ave, New Hyde Park, NY 11040, USA

R E V I E W A RT I C L E

Glenohumeral instability: evaluation using MR arthrography of the shoulder

Abstract In the setting of glenohumeral instability or when internal derangement of the shoulder joint is suspected, MR arthrography has been demonstrated to be an accurate diagnostic imaging technique. Knowledge of the complex anatomy of the shoulder and its variations is essential in order to maximize diagnostic accuracy.

Introduction Direct MR arthrography is an emerging technique that combines the exquisite soft tissue contrast resolution of MR imaging with the intra-articular injection of a gadolinium solution [1, 2]. Routine MR imaging of the shoulder has been proven efficacious in the examination of the rotator cuff tendons in those patients with impingement syndrome. However, MR arthrography has multiple advantages over conventional MR imaging when used in the setting of glenohumeral instability and suspected internal derangement of the shoulder [3, 4]. This technique provides controlled distension of the joint space with better assessment of the complex glenohumeral intraarticular structures and their abnormalities [5–7]. Accurate depiction of the glenohumeral ligaments, glenoid labrum, joint capsule and intra-articular portion of the long head of the biceps tendons has been made possible using MR arthrography [8, 9]. Additionally, multiple normal anatomic variations of the glenohumeral joint previously described on anatomic and arthroscopic examinations have been correlated on MR arthrographic images in previous reports [10–12]. Awareness of the normal anatomy by the radiologist avoids misinterpretation of these varia-

Key words Shoulder MR arthrography · Glenohumeral instability · Normal variants

tions with disease. As the understanding and treatment of shoulder instability and internal derangement have advanced, MR arthrography has emerged as the technique best suited for preoperative diagnosis [4, 5, 7]. However, the acceptance of this technique by the radiology and the orthopedic communities is not universal. Increased cost, invasiveness, cumbersome scheduling and legal considerations may deter the more wide spread use of MR arthrography [13, 14].

Technique Under fluoroscopic guidance a 20–22 gauge needle is placed within the glenohumeral joint using standard arthrographic technique [7]. Alternatively, the needle can be positioned under sonographic guidance [15], MR imaging guidance [16, 17], or without imaging using anatomic landmarks [18]. When using fluoroscopy, needle position is verified with the injection of 1–3 cm3 of 60% diatrizoate meglumine [19]. A gadolinium/saline solution (0.1 ml gadoentetate dimeglumine, 20 ml normal saline) is then injected. Results on a cadaveric study indicated that 15 ml appears to be the optimal amount of injected solution for

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Table 1 MR imaging techniques Fat-suppressed T1-weighted axial (SE 600–800/15–20 TR/TE) Fat-suppressed T1-weighted oblique sagittal (SE 600–800/15–20 TR/TE) Fat-suppressed T1-weighted oblique coronal (SE 600–800/15–20 TR/TE) T2-weighted fast spin echo oblique coronal (SE 3500/90 TR/TE) Optional: Oblique sagittal T1-weighted with the arm in the abduction–external rotation position (ABER) and using a flexible coil placed over the axilla Shoulder surface coil 16–18 cm FOV 256×256 or 256×192 matrix 3 mm slice thickness interleaved or 4 mm thick with 1 mm gap

MR arthrography [20]. Care should be taken not to inject air because resultant artifacts may simulate joint bodies or bicipital abnormalities [21]. Following the intra-articular injection of contrast material, the patient is escorted to the MR suite. There should be limited arm motion. The study is performed no later than 45 min following the injection to prevent absorption of contrast and loss of distension [19, 20]. Axial, oblique sagittal and coronal as well as abduction external rotation views are included in the MR imaging protocol [22, 23]. T1weighted images with and without fat suppression are of paramount importance on MR arthrography [24]. Extraarticular fat and gadolinium have similar signal intensities on T1-weighted images. Fat suppression techniques accurately demonstrate extra-articular accumulation of contrast material. Chemical shift, truncation and motionrelated artifacts are also minimized using selective fat saturation sequences. However, it is also recommended to include in the protocol at least one T2-weighted sequence in order to visualize extra-articular fluid collections or masses. The examination is obtained using a dedicated shoulder coil and the parameters listed in Table 1. If the study is performed on a low field magnet, alternative techniques to fat-suppressed T1-weighted sequences should be used, such as gradient echo T1*- and T2*-weighted images [25]. Saline has been advocated for use as a contrast agent [26, 27]. The main advantage is reduction in the cost of the test. However, the disadvantages outweigh this benefit [28]. Saline has identical signal intensity to natural fluid which makes it impossible to discriminate pre-existing fluid from injected saline. Furthermore, it does not allow for such contrast T1-weighted images where the anatomic detail is greater [28].

Normal anatomy Despite the better delineation of the intracapsular structures of the shoulder with MR arthrography, an appreciation of its complex anatomy and normal anatomic varia-

Table 2 normal features and variants of the labral-ligamentous complex (GHL glenohumeral ligament) Superior GHL Absent (10% of cases) Originates with biceps tendon Originates distinct from biceps tendon Originates with middle GHL Normally thin Occasionally thick Middle GHL Absent (27% of cases) Originates with superior GHL, with inferior GHL, or alone Distal insertion in capsule instead of lesser tubercle Normally thin Cord-like middle GHL (Buford complex) Double middle GHL Redundant middle GHL Position related to degree of rotation Inferior GHL Anterior band normally thicker than posterior band Posterior band occasionally thicker than anterior band Rough-looking at its origin in humeral neck Labrum Normal sulcus under anterosuperior labrum Foramen sublabrum (fenestration) Pseudo-SLAP lesion Absence of anterosuperior labrum (Buford complex) Capsular recesses Axillary pouch simulates loose bodies Variations of subscapular recess Enlarged subscapular recess when middle GHL is absent Variations in insertion of anterior capsule Variations in insertion of posterior capsule Bicipital sheath usually fills with contrast

tions is essential [6, 10, 12]. The arthrographic technique itself may also contribute to potential diagnostic pitfalls [21]. Table 2 summarizes the normal variants and pitfalls documented in the literature and/or encountered in our experience. The superior glenohumeral ligament The superior glenohumeral ligament (GHL) extends from the superior glenoid margin, just anterior to the origin of the long head of the biceps tendon, to the fovea capitis line just superior to the lesser tuberosity, where it blends with the coracohumeral ligament (Fig. 1) [29]. On arthroscopic examination this ligament is found in 97% of patients [29]. Palmer et al. [4] identified the superior GHL in 98% of 48 patients undergoing MR arthrography of the shoulder. It may originate with the long head of the biceps tendon (Fig. 2) alone, or with the middle GHL [8, 10]. The superior GHL is normally thin, but it can become quite thick, in which case the middle GHL may be absent or underdeveloped (Fig. 3).

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Fig. 1A, B Normal anatomy. A Drawing (anterior view) shows ligaments of the glenohumeral joint. The coracohumeral ligament (CL) extends from the base of the coracoid process to the greater tuberosity. The superior glenohumeral ligament (SGHL) extends from the anterosuperior margin of the glenoid fossa to the humeral neck, above the lesser tuberosity. The middle GHL (MGHL) extends from the anterosuperior glenoid fossa to the lesser tuberosity. The inferior GHL (IGHL) extends from the inferior margin of the glenoid fossa to the inferior aspect of the humeral neck. The long head of the biceps tendon (LHBT) inserts in the superior margin of the glenoid fossa and labrum. B Drawing (lateral view) shows the glenoid fossa outlined by the labrum. Note the insertions of the LHBT and GHLs in the labrum. The subscapular recess opens into the anterior aspect of the capsule, between the su-

perior GHL (SGHL) and the tendon of the subscapularis muscle, but many variations have been described. If the middle GHL (MGHL) is absent, a large opening to the subscapular recess may be seen. Rarely, more than one recess can be found. Note the anterior (curved arrow) and posterior (open arrow) bands of the inferior GHL (IGHL). (Reprinted with permission from [7]) Fig. 2A, B Superior GHL originating with the biceps tendon. A Axial MR arthrogram (SE 650/15) shows the superior GHL (white arrow) originating with the long head of the biceps tendon (arrow). B Oblique sagittal MR arthrogram (SE 650/15) shows the superior GHL (long arrow) in continuity with the biceps tendon (filled arrow). The middle GHL (open arrow) also originates from the biceps tendon. (Reprinted with permission from [10])

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The middle glenohumeral ligament The middle GHL shows the greatest variation of all the glenohumeral ligaments [29]. It is absent in up to 30% of cases in cadaver dissections and it was not identified in 12% of patients surveyed with MR arthrography (Fig. 4) [4, 10]. It arises most frequently from the anterior superior aspect of the labrum and it may originate with the superior GHL, either alone or with the inferior GHL. It inserts at the humerus at the base of the lesser tuberosity, although it also can blend with the capsule before reaching the tuberosity. As it passes anterior to the glenoid labrum, a labral tear or displaced fragment may be simulated on axial images if contiguous slices are not examined [10, 30]. Occasionally the middle GHL is very thick and cord-like, and may be associated with a normally absent anterosuperior labrum, the so-called Buford complex (Fig. 5) [31]. Williams et al. [32] noted this variation in 1.5% of their 200 arthroscopic cases. In cases of Buford complex, axial MR images obtained at the level of the superior half of the glenoid depict the cross-section of the thickened middle GHL close to the glenoid margin with an absent labrum, simulating a labral tear (Fig. 5). Identification of the thick middle GHL in the oblique sagittal images helps in avoiding this pitfall [10]. Rare cases of double middle GHL have been described [14]. In this case, oblique sagittal MR images demonstrate a double parallel line and axial images show a U-shaped structure, which may simulate a labral ”cleft” or tear (Fig. 6). Sometimes the middle GHL is redundant, running medial to the labrum where the capsule is well distended [19]. It should be noted that the position of the middle GHL is closely related to the degree of rotation of the arm during scanning [10]. With the arm in external rotation the middle GHL becomes stretched and it blends with the capsule [23]. The inferior glenohumeral ligament

The labrum The glenoid labrum may demonstrate multiple variations in size and configuration [33, 34]. Anteriorly it is often rounded and posteriorly triangular. It may have clefts or be crescentic, thin, or even absent [30, 35]. Very frequently, articular cartilage is present between the labrum and the glenoid cortex, predominantly at the superior half of the joint. This interface can simulate a labral tear on axial or oblique coronal images (Fig. 9) [8, 10, 11, 12, 36]. Another variation is a synovial recess interposed between the glenoid rim and the labral-bicipital complex [34]. This recess may fill with contrast material on MR arthrographic images (Fig. 13). This variant has been denominated pseudo-SLAP due to its potential misinterpretation as a Superior Labrum Anterior to Posterior (SLAP) lesion [8, 10]. In general, SLAP tears are oriented laterally, whereas the synovial recess usually follows a medial orientation (Fig. 10) [10]. Frequently encountered in the anterosuperior labral region is the so-called foramen sublabrum or labral fenestration [9, 26, 37]. This represents a normal complete detachment of the anterosuperior labrum from the glenoid rim, with no clinical significance. This variant can easily be misinterpreted as a labral tear (Fig. 11). It should be noted that isolated tears of this region of the labrum are very rare [7]. As previously mentioned, the anterosuperior labrum may also be absent, and in this situation, there is an associated thick, cord-like middle glenohumeral ligament [32]. Capsular recesses Synovial folds of the axillary recess may become quite prominent, simulating loose bodies or intra-articular deFig. 5A–C Buford complex. A Drawing (lateral view) shows the Buford complex. Note the absence of the anterosuperior labrum (arrowheads). MGL middle GHL. B Axial MR arthrogram (SE 650/15) shows absence of the anterosuperior labrum (long arrow); the posterior labrum is normal (curved arrow). The middle GHL (short arrow) is unusually thick. C Oblique sagittal MR arthrogram (SE 650/15) shows a thick middle GHL (arrow). Absence of the anterosuperior labrum is also evident (arrowheads). (Reprinted with permission from [10]) Fig. 6A, B Double middle GHL. A Axial MR arthrogram (SE 650/15) shows a normal anterior labrum (open arrow) and two ligamentous structures (filled arrows) in its vicinity that correspond to a double middle GHL. B Oblique sagittal MR arthrogram (SE 650/15) shows a double middle GHL (black arrows) arising from the superior bicipital-labral complex and blending with the capsule behind the subscapular muscle (white arrow). (Reprinted with permission from [10])

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The inferior GHL complex is composed of an anterior band, a posterior band and an axillary recess of the capsule between these bands [29]. The anterior band extends from the anterior-inferior aspect of the labrum to the region of the surgical neck of the humerus. The posterior band extends from the posterior-inferior aspect of the labrum to the surgical humeral neck. The anterior band is usually thicker than the posterior band, although the opposite situation may exist. The insertion of the axillary recess, along with the anterior and posterior bands at the neck of the humerus creates a jagged appearance on axial MR images (Fig. 7) [4, 10]. With the arm held in abduction and external rotation (ABER position), the anterior band of the inferior GHL becomes taut and it can be visualized in its entirety (Fig. 8) [23]. The inferi-

or GHL is identified in 91% of cases using MR arthrography [8].

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Fig. 3 Thick superior GHL. Oblique sagittal MR arthrogram (SE 650/15) shows a thick superior GHL (open arrow) below the coracohumeral ligament (filled arrow). Note the thin middle GHL extending inferiorly from the undersurface of the superior GHL. (Reprinted with permission from [10]) Fig. 4 Absent middle GHL. Oblique sagittal MR arthrograms (SE 650/15) (left image obtained medial to the right image) show absence of the middle GHL. Normal superior (short arrow) and inferior (long arrow) GHLs are present. Marked distension of the subscapular recess is noted (*). (Reprinted with permission from [10])

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Fig. 7A, B Rough-looking inferior GHL at its origin in the humeral neck. A Axial arthrogram (SE 650/15) shows the origin of the inferior GHL as irregular tendinous slips (arrowheads). B Oblique sagittal MR arthrogram (SE 650/15) shows the fan-shaped insertion of the inferior GHL in the humeral neck (arrowheads). The anterior and posterior bands are indicated by the most anterior and posterior arrowheads, respectively. (Reprinted with permission from [10])

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bris on axial and oblique coronal MR images (Fig. 12) [10]. The subscapularis recess is a normal extension of the capsule under the coracoid process, above the superior margin of the subscapularis muscle. It may present may variations, depending on the configuration of the glenohumeral ligaments. An absent middle GHL is often associated with a large subscapular recess (Fig. 4). Variations of the anterior capsular insertions at the scapula have been described. In type I, the capsule inserts at the glenoid margin, in type II it inserts at the glenoid neck and in type III the insertion is more medial, at the scapula [6]. In general it is agreed that type III insertions are often associated with anterior instability. When performing MR arthrography, the capsule is overdistended and this produces a false appearance of type III insertion (Fig. 13). A similar effect can be seen at the posterior capsular recess (Fig. 14). It is important to remember that the anterior capsular recess appears more redundant with the arm held in internal rotation and the posterior capsular recess appears more redundant with the arm held in external rotation.

Glenohumeral instability

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The shoulder is the most commonly dislocated major joint in the body. The discrepancy between the small size of the glenoid fossa and the large size of the humeral head provides the glenohumeral joint with the largest

Fig. 8A–C ABER position. A Oblique sagittal MR arthrogram along the longitudinal axis of the humerus shows a normal glenohumeral joint in the ABER position. Note the stretched anterior band of the inferior GHL (straight filled arrow) attached to the anteroinferior labrum (curved arrow) and humeral neck (arrowhead). Note also the supraspinatus tendon inserting into the greater tuberosity (open arrow). B MR arthrogram shows the shoulder in the ABER position in a patient with posterosuperior glenoid impingement syndrome. There is impaction at the level of the humeral head (open arrow), poor definition, abnormal high signal intensity of the anteroinferior labrum (curved arrow) and marked irregularity of the inferior margin of the supraspinatus tendon (arrowhead); straight arrow = posterior superior glenoid. C MR arthrogram shows the shoulder in the ABER position in a patient with multidirectional instability. There is a tear of the anterior labrum (curved arrow), an attenuated labrum (straight arrow) and an intra-articular loose body (arrowhead). (Reprinted with permission from [7]) Fig. 9 Articular cartilage–superior labral interface. Oblique coronal MR arthrogram (SE 650/15) demonstrates bright articular cartilage (curved arrow) adjacent to the superior labrum (*) creating an interface (arrow) that may be confused with partial labral detachment Fig. 10 Pseudo-SLAP lesion. Oblique coronal T1-weighted MR arthrogram (550/15) shows a small sulcus (arrowhead) between the superior labrum (white arrow) and biceps tendon (black arrow). This synovial recess points medially, towards the glenoid rim, and should not be misinterpreted as a type II SLAP lesion (see Fig. 25B)

Table 3 Stabilizing mechanisms of the glenohumeral joint Passive stabilizing mechanisms Size, shape and tilt of the glenoid fossa Negative intracapsular pressure Adhesion and cohesion of the two articular surfaces Ligamentous and capsular structures Glenoid labrum Bony restraints (acromion, coracoid process) Active stabilizing mechanisms Long head of the biceps tendon Rotator cuff muscles

mobility among the human articulations [29]. This also makes this joint particularly vulnerable for dislocation. The stability of the glenohumeral joint is maintained by “passive” and “active” mechanisms depending on whether or not muscle energy is required (Table 3). It is currently believed that the glenohumeral ligaments, particularly the inferior one, are the major passive stabilizers of the joint and that the glenoid labrum functions more as a site of ligamentous attachment than by providing increased depth to the glenoid fossa and hence stability as previously believed [29, 38]. The strong union between the collagen fibers of the glenohumeral ligaments and the glenoid labrum is more resistant to injury than the union between the bony glenoid and the labrum itself. Labral tears associated with glenohumeral instability are therefore usually secondary to avulsion rather than impaction. Because the superior glenohumeral ligaments and middle glenohumeral ligaments are often underdeveloped or absent, it is believed that they play a minor role in the stability of the joint (Fig. 1) [38, 39]. In general, shoulder instability can be classified into two types: atraumatic or traumatic instability (Table 4). The reported accuracy of nonenhanced MR imaging for the detection of labral tears has been mixed. Garneau et al. [40] reported a sensitivity of 44% in 26 patients. On the other hand, Legan et al. [37] reported a sensitivity of 95% in a group of 88 patients. More recently, Gusner et al. [41], reporting on a series of 103 patients studied using a high-resolution technique, found a sensitivity and specificity of MR imaging for anterior, superior and posterior labral tears of 100%/95%, 86%/100% and 74%/95% respectively. The accuracy of nonenhanced MR imaging for the evaluation of the glenohumeral ligaments has not been reported. Studies evaluating the accuracy of nonenhanced MR imaging in the investigation of SLAP lesions have been limited. Smith et al. [42] reported a retrospective assessment, with four of six cases predicting superior labral tear. The preoperative reports, however, made a correct diagnosis in only one case. Monu et al. [43] reported similar results in a retrospective analysis. Cartland et al. [44] showed 100% correlation between MR imaging and the surgical findings in a retrospective

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Fig. 13 Variation of the anterior capsular recess. Axial MR arthrogram (SE 650/15) shows a large anterior capsular recess (*). When the joint is overdistended, the anterior capsular insertion may appear to be stripped away from the glenoid margin (arrow). (Reprinted with permission from [10])

Fig. 14 Variation of the posterior capsular recess. Axial MR arthrogram (SE 650/15) shows a mildly distended posterior capsular recess (*) that is related to the degree of capsular distension. The capsular insertion is actually in the posterior labrum (arrow)

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Fig. 11A–C Foramen sublabrum or anterior fenestration. A Drawing (lateral view) shows the foramen sublabrum (arrowheads). L anterior labrum. B Axial MR arthrogram (SE 650/15) shows a normal middle GHL (short arrow), a normal anterior labrum (white arrow) and a small fenestration between the anterior labrum and the anterior margin of the glenoid rim (long arrow). This variant should not be misinterpreted as complete detachment of the labrum. C Oblique sagittal MR arthrogram (SE 650/15) of a patient without a middle GHL shows the fenestration as a small pocket of contrast material (short arrow) extending under the anterior labrum (long arrow) Fig. 12A, B Pseudo-loose bodies of the axillary pouch. Axial MR arthrogram (SE 650/15) (A) and oblique coronal MR arthrogram (SE 2200/90) (B) show synovial folds within the axillary pouch that simulate loose bodies (arrows). (Reprinted with permission from [10])

study. No mention, however, was made of the original preoperative diagnosis. Recently, Yoneda et al. [45] reported a sensitivity of 41%, specificity of 86% and accuracy of 63% using conventional MR imaging for the diagnosis of SLAP lesions of the shoulder. Several studies have emerged citing the accuracy of direct MR arthrography. Chandnani et al. [3] compared imaging techniques and reported 96% sensitivity of MR arthrography, compared with 93% and 73% sensitivity for MR imaging and CT arthrography respectively, in a group of 28 patients. Palmer et al. [4] showed 91% sensitivity and 93% specificity in 48 patients using MR arthrography. The accuracy of MR arthrography for the evaluation of the glenohumeral ligaments specifically was reported by Chandnani et al. [5] in a series of 46 patients with arthroscopic correlation. Lesions of the superior, middle and inferior glenohumeral ligaments were depicted with a sensitivity and specificity of 100%/94%, 89%/88% and 88%/100% respectively. Bencardino et al. [46] studied 158 patients referred for MR arthrography of the shoulder. Fifty-one of these patients underwent arthroscopy or open surgery. There was an overall sensitivity of 89%, specificity of 91% and accuracy of 90% in the diagnosis of SLAP lesions in this prospective study. Anterior glenohumeral instability Restraints to anterior translation of the humeral head are provided by the capsule and glenohumeral ligaments (GHLS) as indicated above [29, 38]. The labrum tears as it is avulsed by the GHLs at the time of injury. Anteroinferior labral tear Anteroinferior dislocation is the most frequent cause of anterior glenohumeral instability [3, 37]. A single event creates a constellation of lesions, which leads to other episodes of dislocation or subluxation. The lesions that may result during an anteroinferior dislocation are:

Table 4 Clinical classification of shoulder instability Atraumatic instability Constitutionally lax shoulder Multidirectional Bilateral Treated with physical therapy and rehabilitation Traumatic instability Unidirectional Anterior dislocation may be the initial event Often requires surgical management Anterior dislocation: abduction, extension and external rotation forces Posterior dislocation: axial loading in adduction or violent muscle contracture Inferior dislocation: hyperabduction (luxatio erecta)

1. Anteroinferior labral tear (Fig. 15). 2. Tear of the inferior GHL and/or capsular-periosteal stripping. 3. Fracture of the anterior-inferior glenoid margin (Fig. 18). 4. Compression fracture of the superior lateral aspect of the humeral head (Hill-Sachs lesion) [4]. The classic Bankart lesion is a combination of 1 and 2. Arthroscopy and MR arthrography show the Bankart lesion as a fragment of labrum attached to the anterior band of the inferior GHL and to the ruptured scapular periosteum, “floating” in the anteroinferior aspect of the glenohumeral joint (Fig. 15). Extensive bone and soft tissue damage and persistent instability may lead to multidirectional instability, resulting in episodes of posterior dislocation [48]. A number of variants of anteroinferior labral tears have been described. The anterior labroligamentous periosteal sleeve avulsion (ALPSA) refers to a tear of the anterior inferior labrum, with associated capsuloperiosteal stripping [49]. The torn labrum is rotated medially and a small cleft or separation can be seen between the glenoid margin and the labrum (Fig. 16B). Contrary to the Bankart lesion, the ALPSA lesion can heal, leaving a deformed and redundant labrum (Fig. 16C). The glenoid labral articular disruption (GLAD) represents a tear of the anterior labrun, attached to a fragment of articular cartilage, without associated capsuloperiosteal stripping (Fig. 17) [50, 51]. Extensive anterior labral tear The second most frequent location of labral lesions is the anterior aspect of the labrum extending from the base of the biceps tendon insertion to the insertion of the inferior GHL, involving also the insertions of the superior GHL and middle GHL (Fig. 19). In a series of 45 patients, Palmer et al. [4] reported nine of 27 labral tears having this distribution.

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15A–D. Anteroinferior labral tear. A Drawing shows the classic Bankart lesion: detachment of the anteroinferior capsulolabral complex and scapular periosteum. B Drawing of the anterior labrum (AL) (axial view) shows the periosteum (P), capsuloligamentous complex (CLC) and articular cartilage of the glenoid fossa (C). C Drawing shows a Bankart lesion. Note the anterior labrum (AL), capsuloligamentous complex, and torn periosteum (P). D Axial fat-suppressed T1-weighted (SE 650/15) MR arthrogram shows the classic Bankart lesion. Note the torn fragment of the anterior labrum (straight arrow). Note also the cleft between the glenoid margin and an irregular structure (curved arrow) that represents the detached capsule and periosteum. (A, B and C reprinted with permission from [7])

Glenohumeral ligament tear

A tear limited to the anterosuperior aspect of the labrum with or without (Fig. 20) associated ligamentous lesions (superior GHL and middle GHL) is often associated with lesions of the insertion of the long head of the biceps tendon (LHBT) [46]. Isolated anterosuperior labral tears without clinical evidence of instability and without a previous episode of dislocation can produce shoulder pain [39]. This condition is found in the throwing athlete. The patient complains of pain and a sensation of instability when throwing (“functional instability”). Care should be taken not to confuse an anterosuperior labral tear with a normal anterosuperior sublabral foramen (Fig. 11) [10]. Periosteal detachment and irregularity of the torn labrum along with clinical history and symptoms may help differentiate the two conditions.

Tears of the GHLs can occur without associated labral tear (Fig. 21). Humeral avulsions of the glenohumeral ligaments (HAGL) are less often seen than classic Bankart lesions but these may also cause anterior shoulder instability. The torn GHL appears thick, wavy and irregular, with increased signal intensity on MR examination (Fig. 22) [52].

Fig. 18A, B Fracture of the anteroinferior glenoid margin. A Drawing shows an anteroinferior glenoid margin fracture (osseous Bankart lesion) (arrow). B Axial fat-suppressed T1-weighted MR arthrogram depicts a detached anteroinferior labrum (white arrow) associated with small avulsion fragments from the anterior inferior glenoid rim (black arrow). (A reprinted with permission from [7])

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Anterosuperior labral tear

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Fig. 16A–C Anterior labroligamentous periosteal sleeve avulsion (ALPSA) lesion. A Drawing shows the ALPSA lesion. The anteroinferior labrum is torn and internally rotated, and capsuloperiosteal stripping is present (arrow). B Axial MR arthrogram through the inferior labrum shows an acute ALPSA lesion: a labral tear with periosteal separation (straight white arrow). Note the cleft (curved arrow) and the torn labrum (straight arrow). C Axial MR arthrogram through the inferior labrum shows a chronic ALPSA lesion. Abnormal thickening and flattening of the labrum (arrow) resulted from healing with synovial fibrous tissue between the labrum and glenoid margin. (A reprinted with permission from [7]) Fig. 17A, B Glenoid labral articular disruption (GLAD) lesion. A Drawing shows a GLAD lesion. Note the separation of the anterior labrum along with a fragment of articular cartilage (arrow). B Axial fat-suppressed T1-weighted MR arthrogram shows detachment of anterior labrum (*) along with a fragment of articular cartilage consistent with GLAD lesion (straight arrow). Note the subscapular recess (curved arrow) distended with contrast material. (A reprinted with permission from [7])

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Fig. 19 A, B Extensive anterior labral tear. A Drawing shows an extensive tear of the anterior labrum from the insertion of the middle GHL to the inferior glenoid margin. B oblique sagittal MR arthrogram shows massive detachment of the anterior labrum from the glenoid fossa (arrowheads) extending from the 1 to 6 o’clock position (A reprinted with permission from [7]) Fig. 20A, B Anterosuperior labral tear. A Drawing shows a tear of the anterosuperior labrum at the insertion of the middle GHL (arrow). B Axial MR arthrogram at the level of the superior labrum shows the anterior labrum detached from the glenoid margin (straight arrow) with stripping of the periosteum (arrowhead). Note the intact middle GHL (curved arrow). (A and B reprinted with permission from [7]) Fig. 21A, B Tear of the middle GHL. A Oblique sagittal MR arthrogram shows a detached, thick and irregular middle GHL (arrow) with a small fragment of the anterior labrum. B Oblique coronal MR arthrogram shows the middle GHL floating within the contrast-material-distended anterior capsular space (arrow). (A reprinted with permission from [7])

Posterior glenohumeral instability Posterior shoulder dislocation more often occurs as a result of a violent muscle contraction, by electrical shock or seizures. After the acute episode of dislocation, the arm frequently remains locked in adduction and internal

rotation [29]. Posterior instability caused by repeated microtrauma, without frank dislocation, may cause persistent shoulder pain in young athletes. Abduction, flexion and internal rotation are the mechanisms involved in these cases (swimming throwing and punching). This may also be associated with posterior capsular laxity.

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Fig. 22A, B Humeral avulsion of the inferior glenohumeral ligament (IGHL). A Oblique coronal T2-weighted (SE 2500/90) image through the anterior band of the IGHL demonstrates irregularity and fraying at its humeral insertion (arrow) consistent with partial avulsion injury. B Axial T1-weighted MR arthrogram confirms the presence of fraying and partial avulsion tear involving the anterior band of the IGHL (arrow) Fig. 23A, B Posterior labral tear. A Drawing shows a tear of the posterior labrum (arrow). B Axial fat-suppressed T1-weighted (SE 650/20) MR arthrogram shows a tear of the posterior labrum (straight arrow). There is also a paralabral cyst (*) filled with gadolinium solution adjacent to the tear. (A reprinted with permission from [7])

The following lesions may result during posterior dislocations or in cases of repeated microtrauma [53].

Superior labral anterior to posterior lesions (SLAP)

1. Posterior labral tear (Fig. 23). 2. Posterior capsular stripping or laxity. 3. Fracture, erosion or sclerosis and ectopic bone formation of the posterior glenoid. 4. Vertical impacted fracture of the anterior aspect of the humeral head (reverse Hill-Sachs, McLaughlin fracture).

SLAP lesions are defined as superior labral tears oriented in the anterior to posterior direction (Fig. 24). Snyder et al. [54] described and classified SLAP lesions into four types based on arthroscopic findings. In Snyder et al.’s series, type I lesions were defined as fraying of the free edge of the superior labrum, type II (Fig. 25) consisted of an avulsion of the labral-bicipital complex from the glenoid, type III (Fig. 26) was a bucket-handle tear of the superior labrum with an intact biceps anchor and type IV (Fig. 27) lesions represented a bucket-handle tear of the superior labrum with extension into the fibers of the biceps tendon. Maffet and collaborators [55] added three more types to this classification. Type V is an anteroinferior Bankart lesion that extends superiorly involving the biceps tendon anchor. Type IV is defined as an unstable radial or flap tear associated with separation

Posterosuperior glenoid impingement syndrome refers to the shoulder pain induced by placing the arm in abduction and external rotation. This condition has been described in the throwing athlete and some degree of anterior instability may be present. This position causes anterior subluxation of the humerus with impingement of the humeral head against the posterosuperior labrum with associated damage to the rotator cuff and humeral head (Fig. 8B) [48].

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Fig. 25A, B Type II SLAP lesion. A Axial fat-suppressed T1-weighted iamges show complete separation of the superior labrum from the glenoid rim (curved arrow). Anterior labrum (*). B Oblique coronal fat-suppressed T1-weighted MR arthrogram demonstrates detachment of the bicipital labral complex (*) and contrast interface interposed between the labrum and glenoid rim (arrow). This interface points laterally, away from the glenoid rim

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Fig. 26A, B Type III SLAP lesion. A Detachment and inferior displacement of the superior labrum consistent (open arrows) with a bucket-handle tear is demonstrated on these oblique coronal fatsuppressed T1-weighted (SE 600/20) images. The biceps tendon insertion is preserved (*). B Oblique sagittal fat-suppressed T1weighted image depicts inferior displacement of superior labral free edge (arrow) within the joint space. The medial aspect of the superior labrum remains attached to the superior glenoid rim (*)

Fig. 24A–I Types of SLAP lesion. A Drawing shows a type I lesion. There is a partial tear of the long head of the biceps tendon (LHBT) at the labral insertion. The labrum is normal. B Drawing shows a type II lesion. The LHBT and the anterosuperior labrum are detached from the glenoid margin. C Drawing shows a type III lesion. There is a bucket-handle tear of the labrum with a fragment displaced inferiorly. D Drawing shows a type IV lesion. There is a bucket-handle tear of the labrum with a longitudinal tear of the LHBT. E Type V lesion consists of an anteroinferior Bankart lesion that extends superiorly involving the biceps tendon anchor. F Type VI is characterized by an unstable radial or flap tear of superior labrum. G Drawing shwos a type VII tear extending beneath the middle GHL. H Superior labral tear involving extensively the posterior labrum. I Extensive concentric detachment of the labrum. (A, B, C and D reprinted with permission from [7])

of the biceps anchor and type VII (Fig. 28) is characterized by an extension of the SLAP lesion beneath the middle GHL. Two other types have been incorporated into the classification: type VIII (Fig. 29) represents a superior labral tear extending posteriorly with extensive detachment of the posterior labrum and type IX is complete concentric avulsion of the labrum from the genoid rim [56]. SLAP lesions may result from compression forces to the shoulder (28%), usually after a fall onto an outstretched arm or from traction on the arm (22%), either secondary to a sudden pull on the arm or as a result of repetitive overhead use (25%) [57]. Physical examination is often unreliable in diagnosing SLAP lesions [54]. Occasionally, if the lesion involves the biceps tendon insertion, stress maneuvers may reveal glenohumeral instability. Surgical treatment with either debridement or reattachment of the superior labrum is based on the compromise of the biceps anchor [56, 57]. Therefore, special attention must be paid to determining the integrity of the biceps tendon for preoperative planning [33, 34]. The

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Fig. 27 Type IV SLAP tear. Contrast material dissecting into the fibers of the long head of the biceps tendon (arrow) is demonstrated on this oblique sagittal T1-weighted (SE 650/20) image Fig. 28 Type VII SLAP tear. Oblique sagittal fat-suppressed T1weighted image demonstrates fraying and irregularity of the middle GHL (arrow) representing extension of SLAP lesion (curved arrow) into this structure Fig. 29 Type VIII SLAP tear. Oblique sagittal fat-suppressed MR arthrogram depicts a superior labral tear (arrow) extending into the posterior labrum causing complete separation of this structure from the glenoid rim (open arrow) Fig. 30 Paralabral cyst located within the suprascapular notch. Oblique coronal T1-weighted image shows a type II SLAP tear (curved arrow) associated with a contrast-filled cystic structure (*) within the suprascapular notch consistent with a communicating paralabral cyst

differential diagnosis of superior labral lesions from labral-bicipital variants is crucial to avoiding unnecessary surgical procedures [10, 12, 36]. MR arthrography may demonstrate the following signs: (a) contrast material extending superiorly into the glenoid attachment of the LHBT on oblique coronal images, (b) irregularity of the insertion of the LHBT on oblique coronal and oblique sagittal images, (c) accumulation of contrast material between the labrum and glenoid fossa on axial images, (d) detachment and displacement of the superior labrum on oblique sagittal and oblique coronal images, and (e) a fragment of the labrum displayed inferiorly between the glenoid fossa and humeral head. Paralabral cysts can be associated with superior labral tears, frequently located in the suprascapular notch where they may cause nerve entrapment syndrome (Fig. 30) [58, 59].

In a recent series, SLAP lesions were found in 36% of a patient population with clinical history of instability or chronic shoulder pain that had MR arthrography prior to arthroscopy or open surgery [46]. Thirty-two percent of the lesions were type I (Fig. 27), 47% type II (Fig. 28), 5% type III (Fig. 29) and 16% type IV (Fig. 30). SLAP lesions were associated with partial tear of the rotator cuff tendon in 42% of cases. Other associated lesions included frayed or lax inferior glenohumeral ligament, chondral lesions, loose bodies, Bankart lesion, HillSachs lesion, complete rotator cuff tear and posterior labral tear [46, 60].

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