Fig. 3

Radiological measurements at MRI. a Acromiohumeral distance measurements, b Humeral migration measurements, c Upper migration index formula and measurements. a AHD was defined as the distance between the lowest border of the acromion and the humeral head's highest point. b HM value, the humeral head center, was determined by drawing a tangent circle to the humeral head's boundaries. Then, the glenoid fossa was determined by the line drawn between the superior and inferior most edges of the glenoid, and then the center of the glenoid fossa was marked on this line. A second line was drawn from the center of the humeral head perpendicular to the glenoid fossa line, and the intersection point was marked. The distance between the intersection point and the center of the glenoid fossa was recorded as the HM. If the center of the glenoid fossa was inferior to the intersection point, the HM was recorded as a negative value. If it was superior, then the HM took a positive value. c The UMI, where the distance between the center of the humeral head to the acromion’s undersurface was divided by the humeral head’s radius, as described by Hirooka et all