Fig. 2

Mirrored L-shaped flap technique was designed for bilateral atresia (Each step is shown by Schematic diagram combined with real Endoscopic view). a Endoscopic view of the right nasal cavity showing the choanal atresia. b Endoscopic view of the left nasal cavity showing the choanal atresia. The red dashed line marks the incision made at the septal continue to nasal floor, reaching the lateral nasal wall. The long blue arrows mark the distance from the atretic plate to the septum incision, about 5–10 mm. c Elevation of the L-shaped septonasal flap and remove part of the pharyngeal face of the atresia plates by using a drill. d The thickened vomer and parts of the lateral bone were removed, widen the newly formed choana. e The septo-atretic flaps were fashioned by using the ear scissors. f The newly formed choana with the flap covering the lateral and inferior raw surface