Fig. 2

a Illustration of the anatomic landmarks used to define the coordinate system on each scapula. b Definition of glenoid version and inclination around Friedman’s line. (Abbreviations: P, most proximal point on the scapula body; M, most medial point on the medial spine; D, most distal point on the scapula body; C, glenoid center of surface (approximated through an ellipsoid); G, glenoid center of rotation (approximated through a least square spherical fit); H, humeral head center(approximated through a least squares spherical fit))