Optimal Angle of Needle Insertion for Fluoroscopy‐Guided Transforaminal Epidural Injection of L 5

Background Unlike other sites, there is difficulty in performing TFESI at the L 5‐ S 1 level because the iliac crest is an obstacle to needle placement. Objective The objective of this study was to identify the optimal angle of fluoroscopy for insertion and advancement of a needle during L 5 TEFSI . Methods We conducted an observational study of patients undergoing fluoroscopy‐guided L 5 TFESI in the prone position. A total of 80 patients (40 men and 40 women) with radiating pain of lower limbs were enrolled. During TFESI , we measured the angle at which the L 5 vertebral body forms a rectangular shape and compared men and women. Then, we measured area of safe triangle in tilting angle of fluoroscopy from 15° to 35° and compared men and women. Results The mean cephalocaudal angle, where the vertebral body takes the shape of a rectangle, was 11.0° in men and 13.9° in women ( P  = 0.007). In men, the triangular area was maximal at 18.3 mm² with an oblique view angle of 25°. In women, the area was maximal at 23.6 mm² with an oblique view angle of 30°. At an oblique view angle of 30° and 35°, the area was significantly greater in women ( P  < 0.05). Conclusion When TFESI is performed at the L5 region in the prone position, placement of fluoroscopy at a cephalocaudal angle of 11.0° and an oblique angle of 25° in men and cephalocaudal angle of 13.9° and an oblique angle of 30° in women would be most reasonable.