Fig. 1.

Posterior approach of transversus abdominis plane (TAP) block. Note: a The patient was kept in semi-lateral position, the probe position and needle trajectory were displayed. The probe is placed posterior to the midaxillary line between the costal margin and the iliac crest. The needle is inserted in plane. b Corresponding ultrasound images. Posterior approach located in the end of transversus abdominis plane where TAP transmigrate into aponeurosis. The injection site is at the TAP between internal oblique and transversus abdominis posterior to the midaxillary line and near the aponeurosis. White dashed line: needle trajectory. Light blue area: the deposition site of local anesthetic. TA: transversus abdominis; IO: internal oblique; EO: external oblique