DOI: 10.1148/radiol.2323021239
(Radiology 2004;232:725-726.)
© RSNA, 2004
The "J" Sign1
Christian L. Carlson, MD, MS
1 From the Department of Radiology, Brooke Army Medical Center, 3851 Roger Brooke Dr, Fort Sam Houston, TX 78234-6200. Received September 24, 2002; revision requested December 3; revision received February 20, 2003; accepted March 13. Address correspondence to the author (e-mail: christian.carlson@cen.amedd.army.mil).
Index terms: Ligaments, injuries, 414.439 • Shoulder, injuries, 414.439, 414.481 • Signs in Imaging
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APPEARANCE
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The "J" sign refers to the J-shaped appearance of the right inferior glenohumeral ligament as seen with oblique coronal conventional magnetic resonance (MR) imaging and MR arthrography (Figure).
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Oblique coronal fat-suppressed T2-weighted MR image (2,500/60, repetition time msec/echo time msec) of right shoulder in patient with humeral avulsion of the glenohumeral ligament (HAGL) lesion demonstrates J-shaped appearance of inferior glenohumeral ligament (curved arrow) and extravasation of joint fluid (arrowhead) around the humeral detachment and between the medial aspect of the humerus and the tip of the "J." Note also a humeral head bone bruise from anterior dislocation.
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EXPLANATION
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The "J" sign indicates HAGL (1,2). The inferior glenohumeral ligament normally attaches to the glenoid labrum medially and to the anatomic neck of the humerus laterally, just below the articular margin of the humeral head. The inferior glenohumeral ligament is composed of an axillary pouch that is situated between an anterior and a posterior band (3). Fluid distention of the glenohumeral joint secondary to effusion or gadolinium-based contrast material gives the inferior glenohumeral ligament a U-shaped appearance. Avulsion of the inferior glenohumeral ligament from the neck of the humerus allows the detached end of the anterior or posterior band to fall inferiorly, thus transforming the U-shaped appearance of the inferior glenohumeral ligament into a J-shaped appearance. A left humeral avulsion of the glenohumeral ligament forms a mirror image of the "J" sign, which is called the reverse "J" sign. Loss of integrity of the inferior glenohumeral ligament allows extravasation of effusion or contrast material around the free end of the detached ligament (1,2).
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DISCUSSION
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The inferior glenohumeral ligament–labral complex is the main anterior stabilizer of the shoulder when the arm is at 90° abduction, and it prevents anterior dislocation during external rotation (4). In a biomechanic study of the tensile properties of the inferior glenohumeral ligament, the location and frequency of failure along the ligament were 40% (19 of 48 cases) at the glenoid, 35% (17 of 48 cases) in the midsubstance, and 25% (12 of 48 cases) at the humeral attachment (5). The mechanism that results in HAGL is traumatic hyperabduction and external rotation of the arm (6). The HAGL lesion is most commonly found in anterior shoulder dislocations (6–8).
HAGL lesions have a male predominance of 92% (60 of 65 patients) (1,6–10). The mean age of patients with the lesion is 28.1 years (age range, 12–54 years) (1,6–10), which is slightly greater than the mean age (23.0 years) of patients with anterior shoulder instability in the absence of the lesion (7). In the three largest clinical series to date, the prevalence of the HAGL lesion as a cause of anterior glenohumeral instability has ranged from 2% (six of 307 patients) to 7.5% (41 of 547 patients) to 9.4% (six of 64 patients) (1,7,8). The HAGL lesions have occurred as a result of different activities: rugby, snow or water skiing, surfing, football, basketball, volleyball, ice hockey, diving, wrestling, pugil stick training, and boxing (1,6–9). Of note, seven of the 65 patients (11%) in whom HAGL lesions were diagnosed had undergone prior orthopedic surgery (1,6–10).
The clinical presentation is usually an adult male with either an acute anterior dislocation that has been reduced or a history of anterior shoulder instability following an initial traumatic dislocation. Signs and symptoms may include pain and tenderness in the anterior aspect of the shoulder, patient apprehension in abduction and lateral rotation, decreased external rotation, a sensation of the shoulder shifting out of joint, crepitus, or generalized laxity (1,6,7,9).
The clinical differential diagnosis of anterior instability includes Bankart lesions, anterior labroligamentous periosteal sleeve avulsions, glenolabral articular disruption lesions, and HAGL lesions (2,10–13). The HAGL lesion is one of the causes of anterior shoulder instability and predisposes patients to recurrent subluxation and dislocation. Forty-two of 65 patients (65%) with HAGL lesions have associated abnormalities including (in descending order of frequency) rotator cuff tears, Bankart lesions, Hill-Sachs lesions, and other lesions (1,6–10).
Because HAGL lesions may be overlooked during arthroscopy or open stabilization, preoperative radiologic evaluation can be invaluable in diagnosing the lesion. Radiography demonstrates only the variant bony HAGL lesion, which is best seen on the Garth view (15° oblique in the anterior plane of the shoulder) (10). MR imaging is essential in facilitating the preoperative detection of HAGL lesions and most associated injuries. The presence of a joint effusion or the use of MR arthrography is necessary for aiding in the detection of HAGL lesions on MR images (1,2). Bui-Mansfield et al (1) reported that the oblique coronal, fat-suppressed, T2-weighted sequence best demonstrates the J-shaped appearance of the detached inferior glenohumeral ligament and extravasated joint fluid across the humeral detachment.
Management of the HAGL lesion depends on the presence of associated injuries and may consist of either conservative therapy or surgical repair (10). However, most orthopedists advocate either arthroscopic or open surgical repair (6–9).
In conclusion, the HAGL lesion is an uncommon but important cause of anterior instability of the shoulder. On MR arthrograms or conventional MR images, the HAGL lesion has a J-shaped appearance known as the "J" sign. The majority of patients with a HAGL lesion demonstrate concomitant associated injuries (1,6–10).
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ACKNOWLEDGMENTS
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The author thanks Liem T. Bui-Mansfield, MD, for the use of the figure and for his assistance in reviewing the manuscript.
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FOOTNOTES
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Author stated no financial relationship to disclose.
The opinions and assertions contained herein are those of the author and should not be construed as official or as representing the opinions of the Department of the Army or the Department of Defense.
A trainee (resident or fellow) wishing to submit a manuscript for Signs in Imaging should first write to the Editor for approval of the sign to be prepared, to avoid duplicate preparation of the same sign.
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REFERENCES
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- Stoller DW. MR arthrography of the glenohumeral joint. Radiol Clin North Am 1997; 35:97-116.[Medline]
- O’Brien SJ, Neves MC, Arnoczky SP, et al. The anatomy and histology of the inferior glenohumeral ligament complex of the shoulder. Am J Sports Med 1990; 18:449-456.[Abstract/Free Full Text]
- Turkel SJ, Panio MW, Marshall JL, Girgis FG. Stabilizing mechanisms preventing anterior dislocation of the glenohumeral joint. J Bone Joint Surg Am 1981; 63:1208-1217.[Abstract/Free Full Text]
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- Rowe CR, Patel D, Southmayd WW. The Bankart procedure: a long-term end result. J Bone Joint Surg Am 1978; 60:1-16.[Abstract/Free Full Text]
- Neviaser TJ. The anterior labroligamentous periosteal sleeve avulsion lesion: a cause of anterior instability of the shoulder. Arthroscopy 1993; 9:17-21.[Medline]
- Neviaser TJ. The GLAD lesion: another cause of anterior shoulder pain. Arthroscopy 1993; 9:22-23.[Medline]
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