抄録
Background: The purpose of this study was to assess the movement of rotator cuff in internal and external rotation of the shoulder, by MRI.
Methods: Subjects were twenty-one volunteer who had no shoulder problems (11 males, 10 females). The average age at the time of investigation was 28.7 years old. All scans were done on a GE Signa MRI 1.5T scanner. A linear shoulder coil was used. We used Fast Imaging Employing Steady state Acquisition (FIESTA) images of MRI to assess rotator cuff movement (TR: 4.6msec, TE: Min Full 2.1msec, Flip Angle:20 degree, Bandwidth:+62.5, Matrix:256x224, NEX:1.0, FOV:28x28, Slice Thickness: 6.0mm). An axial scout scan at the middle of the smaller tuberosity of humerus was done. Subjects reciprocated their shoulder from maximum internal rotation to maximum external rotation in 20 seconds in drooping position. We assessed congruity, rotation angle and cross-section ratio of muscles. The cross-section ratio of subscapularis and infraspinatus at maximum internal and external rotation, and neutral position were compared.
Results: All cases kept congruity of the glenohumeral joint during rotation. Internal and external rotation angles were 45.3 ± 27.2 degrees and 55.4 ± 22.3 degrees, respectively. The subscapularis ratio of neutral to external rotation, and to internal rotation were 1.10 ± 0.10, 0.94 ± 0.11, respectively, and the infraspinatus ratios were 0.95 ± 0.09, 1.02 ± 0.08, respectively.
Discussion: FIESTA was able to shoot the rotator cuff movements with vivid clarity. In concentric contraction of subscapularis and infraspinatus, the cross-section area that was parallel to the direction of muscle fibers became significantly smaller than the area in eccentric contraction. FIESTA was able to assess rotator cuff function.
