Magnetic resonance imaging of the wrist.

Abstract

Magnetic resonance (MR) imaging has developed rapidly as a diagnostic tool in the evaluation of the wrist. In this article, the authors review simple high-resolution technique and appropriate surface coils to aid in wrist evaluation. Evaluation of the wrist is facilitated by an understanding of the anatomy of the carpal ligaments, the triangular fibrocartilage, and the carpal tunnel, and the anatomic features of the distal radioulnar joint. Triangular fibrocartilage tears, which represent an important cause of ulnar wrist pain, are well evaluated on MR. These appear as a linear band of increased signal on the short repetition time/echo time (TR/TE), proton density weighted spin echo, or gradient echo images. True tears should be differentiated from degenerative changes, which do not demonstrate increase in signal on T2 or T2* weighted images. With good technique, accuracies approaching 90% have been reported. MR is also useful in evaluating injuries of the interosseous ligaments and volar and dorsal radiocarpal ligaments and distal radioulnar joint instability. MR also has a role in evaluating the carpal tunnel syndrome. This is especially true with patients for whom symptoms suggest the diagnosis of carpal tunnel syndrome but for whom few objective findings exist. Findings suggestive of carpal tunnel syndrome include diffuse swelling of the median nerve, flattening of the median nerve at the level of the hamate, and increased signal of the median nerve on the long TR/TE images. MR is also indicated in avascular necrosis of the carpal bones and occult carpal fractures. MR is useful in evaluating bone tumors, particularly with regard to their extent. With the advent of more rapid scanning techniques, kinematic studies are feasible. For these, fast gradient echo techniques are employed and serial images are acquired during radial and ulnar deviation. These images may be helpful in observing integrity of intercarpal ligaments and evaluating dynamic instability. With proper attention to technique, and an understanding of wrist pathophysiology, MR is a valuable diagnostic tool.