MR Arthrography of the Shoulder: Variants and Pitfalls1 Javier Beltran, MD Jenny Bencardino, MD Jose Mellado, MD Ze/iava S. Rosenberg, MD Robert D. Iris/i, MD Use of magnetic resonance arthrography to evaluate pathologic condi- tions of the shoulder is becoming widespread. However, normal anat- omy or anatomic variations can cause interpretive errors. The most common variations occur at the origins of the glenohumeral ligaments (GHLs) and the insertion of the joint capsule. Among the GHL variants, common origin of the superior and middle ligaments is the most fre- quent followed by thinning, thickening, or absence of a ligament, most often the middle one. Absence or thinning of one ligament is sometimes associated with thickening of another or changes in the size and shape of the anterior capsular recesses. Common normal variants of the labrum include foramen sublabrum (detachment of the anterosupenor labrum from the glenoid margin) and the Buford complex (absence of the an- terosuperior labrum in association with a thick middle GHL). Pitfalls re- lated to the arthrographic technique include (a) visualization of a deep sulcus between the insertion of the long head of the biceps tendon and the superior labrum and (b) an apparent type III capsular insertion due to overdistention of the capsule by injected contrast material. U INTRODUCTION The diagnostic accuracy of magnetic resonance (MR) arthrography of the shoulder may exceed that of conventional MR imaging of the shoulder. Intraarticular structures are better demonstrated if they are separated by means of capsular distention. Such separation can be achieved with intraarticular injection of contrast material (diluted gadopentetate dimeglumine) or saline or with preexisting joint fluid (joint effusion). The goal is to produce high contrast between the labrum, capsule, capsular recesses, glenohumeral ligaments (GHLs), and articular surface of the rotator cuff. It is essential Abbreviations: FDA Food and Drug Administration, GHL = glenohumeral ligament, 11th = institutional review board, SE = spin echo, SLAP = superior labral anterior and posterior Index terms: Gadolinium #{149} Shoulder, anatomy, 414.92 #{149} Shoulder, arthrography, 414.122 #{149} Shoulder, MR. 4 14.12143 RadloGraphies 1997; 17:1403-14 12 ‘From the I)epartmcnt of Radiology, Hospital forJoint Diseases, 301 E 17th St, New York, NY 10003. Recipient of a Cer- tificate of Merit award for a scientilIc exhibit at the 1996 RSNA scientific assembly. Receivedjanuary 23, 1997; revision requested March 17 and received April 4; accepted April 4. Address reprint requests toJ. Beltran. RSNA. 1997 See the commentary by Barr following this article. 1403