Magnetic resonance imaging of the musculoskeletal system. Part 6. The Shoulder.

The role of magnetic resonance imaging in the diagnosis and treatment of patients with shoulder pain has increased remarkably in recent years, largely because of improved resolution of images and increased experience of musculoskeletal radiologists. In rotator cuff disease/impingement and instability, magnetic resonance imaging adds a new dimension to the clinical findings through the noninvasive visualization of either the pathology itself or frequently associated abnormalities. It is the associated abnormalities that are depicted in instability: glenoid irregularities, labral tears, capsular laxity, and Hill-Sachs deformities. Glenoid, labral, and Hill-Sachs abnormalities can be assessed with either magnetic resonance imaging or computed tomography arthrography. Magnetic resonance imaging has the advantages of noninvasiveness, multiplanar imaging capability and exquisite soft tissue contrast. In rotator cuff disease, magnetic resonance imaging depicts the status of the rotator cuff itself, revealing partial and full thickness tears, allowing an estimation of size and quality of tendon edges. Possible impingement sites can be identified. Primary instability with secondary impingement may be first suspected on magnetic resonance imaging. Postoperative complications, including recurrent tendon detachment, deltoid dehiscence, and infection, are clarified. Unsuspected but clinically important lesions, such as neoplasm, osteonecrosis, and ganglion with entrapment of the suprascapular nerve, each have characteristic magnetic resonance imaging appearances.