Pictorial ReviewNormal anatomy and common labral lesions at MR arthrography of the shoulder
Introduction
MR arthrography of the shoulder is the most accurate established imaging method for demonstrating abnormalities of the glenoid labrum and associated structures.1, 2, 3, 4, 5 Tears of the labrum, capsule or glenohumeral ligaments can lead to pain, catching, “popping” or instability. The glenohumeral joint allows a great range of movement and therefore is prone to instability and pain. The supporting structures, namely the joint capsule, glenoid labrum, glenohumeral ligaments, biceps tendon and biceps anchor, constitute a complex network of anatomy. There is increasing awareness of labral and ligamentous pathology, and knowledge of this anatomy is crucial to the diagnosis of abnormalities at magnetic resonance (MR) arthrography.2, 4, 6 We present the normal anatomy of the glenoid labrum, biceps anchor and glenohumeral ligaments, together with their normal variants, and then describe common labral-ligamentous lesions.
Section snippets
The glenoid labrum
The glenoid labrum is a fibro-cartilaginous structure that increases the depth of the glenoid fossa and provides an anchoring structure for the glenohumeral ligaments and the long head of the biceps (LHB) tendon. It has superior, inferior, anterior and posterior portions, with variations (Figure 1, Figure 2, Figure 3).7, 8, 9, 10, 11 By convention, the anterior, inferior, posterior and superior labrum can be described in their position as on a clock face, at 3, 6, 9 and 12 o'clock,
Common labral-ligamentous pathology
MR arthrography has been shown to be the most accurate imaging method for tears of the glenoid labrum and glenohumeral ligaments, with specificities and sensitivities of up to 93% and 96%, respectively, for labral tears, and 91% and 100%, respectively, for the glenohumeral ligaments.1, 30, 31 When purely SLAP tears were evaluated by Bencardino, an overall specificity and an overall sensitivity of 89% and 91%, respectively, were achieved.12
Conclusion
Direct MR arthrography is an accurate, minimally invasive investigation for the painful or unstable shoulder. A grasp of normal anatomy and the range of normal variants is essential in understanding the many possible lesions. The anterior labrum, anterior capsule, anterior band of the glenohumeral ligament and superior labrum should be thoroughly evaluated. If a superior labral tear is present, involvement of the long head of the biceps tendon or glenohumeral ligaments should be reported.
Acknowledgement
We thank J. Giglia for her help in image preparation.
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