Fig. 2

A 22-gauge spinal needle was used to complete the local anesthetic administration for the area behind the ligamentum flavum, which was confirmed at the lateral (a) and anterioposterior (d) plane. The spinal needle was placed at surface of the central area of the interlaminar space of L5/S1 along with the spinous process and then advanced until the sensation of loss-of-resistance occurred, which was confirmed at the lateral (b) and anterioposterior (e) plane. After gradient LA, routine PELD via the interlaminar approach was performed. The working channel was established, which was confirmed at the lateral (c) and anterioposterior (f) plane