Fig. 1From: Learning curve for biportal endoscopic posterior cervical foraminotomy determined using the cumulative summation testSkin incisions of biportal full-endoscopic posterior cervical foraminotomy (BE-PCF) (A, B). In BE-PCF, two skin incisions of 0.7 cm are made 2 cm apart around the “V”-point. Blue line, facet joint medial border; red line, incision site; and yellow circle, “V”-pointBack to article page