Special focus session. MR arthrography.

Direct magnetic resonance (MR) arthrography with injection of saline solution or diluted gadolinium can be useful for evaluating certain pathologic conditions in the joints. It is most helpful for outlining labral-ligamentous abnormalities in the shoulder and distinguishing partial-thickness from full-thickness tears in the rotator cuff, demonstrating labral tears in the hip, showing partial- and full-thickness tears of the collateral ligament of the elbow and delineating bands in the elbow, identifying residual or recurrent tears in the knee following meniscectomy, increasing the certainty of perforations of the ligaments and triangular fibrocartilage in the wrist, correctly identifying ligament tears in the ankle and increasing the sensitivity for ankle impingement syndromes, assessing the stability of osteochondral lesions in the articular surface of joints, and delineating loose bodies in joints. Indirect MR arthrography with intravenous administration of diluted gadolinium may be performed when direct arthrography is inconvenient or not logistically feasible. Although indirect MR arthrography has some disadvantages vis-à-vis direct MR arthrography, it does not require fluoroscopic guidance or joint injection and it is superior to conventional MR imaging in delineating structures when there is minimal joint fluid. In addition, vascularized or inflamed tissue will enhance with this method. Indirect MR arthrography can be used to rule in or diagnose abnormalities and to exclude abnormalities.