Randomized controlled trial comparing pudendal nerve block under ultrasound and fluoroscopic guidance

Although fluoroscopy is an established imaging modality for pudendal nerve block, ultrasound (US) technique allows physicians better visualization of anatomic structures. This study aimed to compare the effectiveness and safety between the US- and fluoroscopy-guided techniques.

A randomized, single-blind, split-plot design was used to conduct the study. Twenty-three patients undergoing bilateral pudendal nerve blocks received US-guided injections to either the left or right side, whereas the contralateral side received a fluoroscopic-guided injection in randomized sequence. Injections consisted of 4 mL of 0.5% bupivacaine and 40 mg methylprednisone. The primary outcome was the success of the block in the distribution of the pudendal nerve along the perineum, rated as either absent, moderate, or strong. Secondary outcomes were the time to administer the blocks, quality of visualization of anatomic structures using US and fluoroscopy, distance of the final US-guided needle position from the ischial spine, and incidence of adverse effects.

No differences in the degree of neural blockade were noted between US- or fluoroscopic-guided techniques for either temperature or pinprick blockade. Time to complete the procedure was significantly longer using US compared with fluoroscopy (219 [SD, 65] and 428 [SD, 151] secs, P < 0.0001). No significant differences were noted regarding the occurrence of adverse effects between the 2 techniques.

Ultrasound-guided pudendal nerve blockade is as accurate as fluoroscopically guided injections when performed by an experienced clinician. However, the former took a longer time to perform.