Fig. 4

a Angles of approach (°) between the joint line portal and the perforation points 1–5 (Fig. 1). In none of the shoulders, a positive angle was obtained relative to the anterior edge of the supraspinatus tendon (perforation points 1). b Angles of approach (°) between the posterior edge portal and the perforation points 1–5. This portal showed the highest variability in relation to the posterior supraspinatus. c Angles of approach (°) between the intermediate portal and the perforation points 1–5. In 6 out of 7 of the shoulders through this portal, an angle of at least 10° could be obtained to the entire supraspinatus and infraspinatus tendons. Perforation points 1 and 2 were not reachable in 3 shoulders. d Angles of approach (°) between the anterior edge portal and the perforation points 1–5 (Fig. 1). In none of the shoulders, a positive angle could be obtained for the posterior edge of the infraspinatus (perforation point 5)