The purpose of this study was to analyze the scapular movement and the scapulo-humeral rhythm inthe rotator cuff tear. The condition of the rotator cuff in the second joint was also evaluated. There are few previous reports concerning these kinematics three dimensionally using an open MRI system. The subjects consisted of 15 rotator cuff tear patients and normal volunteers, respectively. The subjects were fixed to an open MRI and inclined with free motion around the scapula. MRI images were

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... n at the accurate scapular plane at every 30°arm-trunk angle from 30°in the supine position. Images in the coronal, transverse and sagittal planes and the 3D volume images were also taken. The scapular angles (the upward rotation angle, the medially tilting angle, the scapular downward tilting angle) were measured. The cuff condition in the second joint and the distance between the humeral head and the undersurface of the acromion (3D-AHI) were measured on the 3D analyzing software. The upward rotation angle tended to increase in theearly phase, and the medially tilting angle was not relatively constant in the rotator cuff tear patients compared with normal volunteers. The scapular downward tilting angle changed from anterior to posterior with elevation in the normal volunteers, but it did not change posteriorly in the cuff tear patients. There was a tendency for them to be narrowes in the second joint concerning those with the kinematics condition of the rotator cuff in both groups. The 3D-AHI had asmaller value in the cuff tear group, especially when it was at the minimum 90 degrees abduction position. A subacromial narrowing in the second joint is likely to happen during abduction in both groups. One of the reasons of a bad scaplo-humeral rhythm in the rotator cuff tear is due to a poor scapulo-thoracic movement.