MR ARTHROGRAPHY OF THE SHOULDER - VARIANTS AND PITFALLS

Use of magnetic resonance arthrography to evaluate pathologic conditio ns of the shoulder is becoming widespread. However, normal anatomy or anatomic variations can cause interpretive errors. The most common var iations occur at the origins of the glenohumeral ligaments (GHLs) and the insertion of the joint capsule. Among the GHL variants, common ori gin of the superior and middle Ligaments is the most frequent followed by thinning, thickening, or absence of a Ligament, most often the mid dle one. Absence or thinning of one Ligament is sometimes associated w ith thickening of another or changes in the size and shape of the ante rior capsular recesses. Common normal variants of the labrum include f oramen sublabrum (detachment of the anterosuperior labrum from the gle noid margin) and the Buford complex (absence of the anterosuperior lab rum in association with a thick middle GHL). Pitfalls related to the a rthrographic technique include (a) visualization of a deep sulcus betw een the insertion of the long head of the biceps tendon and the superi or labrum and (b) an apparent type III capsular insertion due to overd istention of the capsule by injected contrast material.