MR imaging and MR arthrography of the postoperative shoulder: spectrum of normal and abnormal findings.

The postoperative shoulder may be evaluated with various imaging modalities, including radiography, ultrasonography, computed tomography, and magnetic resonance (MR) imaging, each of which has advantages and disadvantages. For optimal soft-tissue visualization, MR imaging and MR arthrography are widely used. Several factors, however, may decrease the accuracy of MR imaging in the evaluation of the postoperative shoulder. These factors include surgical distortions of native anatomy, changes in the signal intensity of tissues, and image degradation caused by metallic artifacts. To maximize the accuracy of MR imaging, the radiologist must select the most appropriate pulse sequences and techniques for the given anatomic structure and the suspected postoperative condition. To avoid magnetic susceptibility artifacts at MR imaging, inversion recovery may be used instead of fat saturation, and fast spin-echo sequences may be used instead of conventional spin-echo sequences or gradient-echo sequences. MR arthrography is most useful for optimal delineation of the rotator cuff, capsulolabral structures, and tendon defects. To achieve accurate image interpretation, the radiologist must be familiar with the arthroscopic and the open surgical techniques currently used to repair internal derangements of the glenohumeral joint, as well as with the typical imaging findings in each postoperative situation.