Figure 1: llustrations of selective nerve root blocks (SLNRBs) in an oblique position (A) and in a prone position (B) (A) in the lumbar spine; the positional relation between the superior articular process of the caudal vertebral body and the target vertebral body is aligned. Because the nerve root is located anterior to the caudal superior articular process, caudal to the pedicle of the vertebral arch, and cranial to the inferior border of the vertebral body, the needle is advanced incrementally toward the nerve root. When radiating pain is induced, contrast material is injected and contrast enhancement is confirmed. The region of the safe triangle, which is composed of the inferior border of the pedicle, the anterior border of the nerve root, and the lateral border of the vertebral body, is widely used as the needle-tip injection site, where the analgesic effect of SLNRB without radiating pain is anticipated. (B) In the lumbar spine, a block needle is inserted toward the transverse process base. Thereafter, the block needle is retracted slightly, and the needle is advanced as if it is sliding along the inferior border of the transverse process. Assuming that there is another virtual pedicle of the vertebral arch caudal to the actual pedicle of the vertebral arch, the needle is advanced to the outer half. When radiating pain is induced, the contrast material is injected, and the nerve root is confirmed as contrast enhanced.