Fig. 2
From: Full-endoscopic foraminoplasty for highly down-migrated lumbar disc herniation
a Anteroposterior (AP) fluoroscopic view showing the needle tip located at the exterior margin of the superior articular process. b Lateral fluoroscopic view showing the needle tip located at the tip of the superior articular process. c AP view showing the working cannula located at the exterior margin of the superior articular process. d Lateral fluoroscopic view showing the working cannula located at the tip of the superior articular process