Shoulder MR arthrography: How, why, when

MR imaging is a powerful tool in the diagnosis and follow-up of patients with various shoulder pathologies. Attention to anatomic detail is paramount in obtaining diagnostic accuracy. Age and symptomatology should guide the choice of conventional MR imaging, indirect MR arthrography, or direct MR arthrography. The advantages and disadvantages of each technique have been discussed herein. Tables 1 and 2 compare recent publications that have used direct, indirect, or nonenhanced MR imaging in an attempt to identify glenoid labral lesions or rotator cuff tears, respectively. Nonenhanced MR imaging is much simpler to perform; with increasing acuity as to normal variants and pitfalls, it remains the mainstay in diagnosing rotator cuff pathology. Its sensitivity in identifying capsulolabral lesions may be limited, particularly in the absence of native joint effusion. The accuracy of indirect MR arthrography is similar to that of direct MR arthrography except for one population group. Box 1 lists the various indications for each of the three MR techniques. Based on a meta-analysis, the authors believe that direct MR arthrography should be reserved for young athletes (less than 40 years old) who present with instability or chronic injuries. This group of patients seems to benefit most from direct MR arthrography because they tend to have smaller labral tears in greater number and frequency. Additionally, the accompanying rotator cuff pathology tends to occur in atypical locations. Nonenhanced MR imaging may be sufficiently accurate in patients aged more than 40 years who have trauma or instability, in AC joint evaluation, and in other causes of shoulder pain, such as neoplasm, cervical spine disease, vascular disease, and neural disease. Indirect MR arthrography has a high diagnostic accuracy in the evaluation of pathologic versus normal anatomic variant labral lesions, paralabral cysts, and biceps anchors; in the postoperative evaluation of the labrum or rotator cuff; and the evaluation of partial rotator cuff tears, chronic recurrent instability, and inflammatory arthropathy.