Fig. 1

a First, an oblique sagittal cross-section across the tip of coracoid process was selected (blue line). b On a horizontal plane, a proximal slice depicting the obvious outline of the bicipital groove was selected to measure the radius and rotation angle (green line). The angle formed by the line from the central point to the bicipital groove and the vertical line was defined as rotation angle. c The white arrow indicates the supraspinatus central tendon, and the black arrow indicates the long head of the biceps tendon. From the anterior edge to the posterior edge of each tendon two straight lines (red line) are drawn. Inter-tendon distance was defined as distance (white line) between the midpoints of the two straight lines