Needle tip position and epidural contrast spread pattern. After placement of the Tuohy needle in the dorsal epidural space via the ligamentum flavum, 0.5 mL of contrast dye (Iobrix 300, Iohexol; Taejoon Pharm, Seoul, Korea) was injected to determine the contrast dispersal pattern on the anteroposterior (AP; A) and lateral (B) fluoroscopic images. The position of the end of the needle was on the outside of the L5 traversing nerve root in the coronal plane (A) and in the dorsal epidural space in the sagittal plane (B). Then, the needle was gently advanced until it touched the posterior aspect of the proximal vertebral body or the annulus fibrosus of the intervertebral disc. It was observed that the final needle tip position rose from the inferior pedicle line to the mid-height of the pedicle on the AP (C) and lateral (D) fluoroscopic images. It was also confirmed that the contrast medium spread out along the L5 exiting nerve root and S1 traversing nerve root (C), as well as into the ventral epidural space (D). However, in paramedian interlaminar epidurography, the needle tip was 10°–15° inward and located inside the lateral margin of dural sac (E), and dorsal epidural contrast spread (F) was observed. In conventional transforaminal epidurography, ventral epidural contrast spread (F) and periradicular infiltration (E) were observed along the L5 exiting nerve root. After drug injection, periradicular infiltration (G) through the L5 exiting and S1 traversing nerve roots was noted and contrast dye was observed to spread from the ventral epidural space (H) in the craniocaudal direction on the AP (G) and lateral (H) fluoroscopic images.