A direct comparison of MR images and thin-layer plastination of the shoulder in the apprehension-test position

Until now, patients with a shoulder instability being examined using magnetic resonance imaging have been placed in a position with the arm adducted or in the ABER position, as a result of the way conventional MR systems are built. Magnetic resonance systems with an open configuration have made it possible, for the first time, to examine patients in the apprehension-test position, which is a representative diagnostic position for anterior shoulder instability. This new examination position requires an exact understanding of layered imaging anatomy in order to clearly identify MR structures. The purpose of this study is to make possible a direct comparison of the respective abilities of MR cross-section imaging and thin-layer plastination to clearly identify all MR structures of the shoulder positioned in the apprehension-test position. The two shoulders of a body donor were separated and stored in special position supports in the apprehension-test position. The magnetic resonance examination was carried out using a vertically open 0.5-T MR system (Signa SP/i, General Electric Medical Systems, Milwaukee, WI). The following sequences were used: 2D GRE, TR 42.5 ms, TE 20 ms, layer width 3 mm, matrix 512x512, FOV 24 cm. The coronary und transversal MR cross-section segments were subsequently planned in conjunction with thin-layer plastination for both shoulders. Using a direct comparison of MR images with the corresponding thin-layer plastination, it was possible to clearly identify all MR structures.