Ultrasound Does Not Improve the Success Rate of a Deep Peroneal Nerve Block at the Ankle

Abstract

The deep peroneal nerve is 1 of 5 nerves anesthetized when performing an ankle block. Multiple techniques of blocking the deep peroneal nerve have been described, but little evidence exists to delineate the efficacy of any one technique. We hypothesized that ultrasound would increase both the success rate and the quality of a deep peroneal nerve block at the ankle. Eighteen healthy volunteers participated in this randomized, controlled, prospective study. Each subject was randomly assigned to receive an ultrasound-guided deep peroneal nerve block of either the right or the left ankle. The deep peroneal nerve on the opposite side was blocked using a conventional landmark technique. Subjects were blinded to the technique used. All blocks were preformed with 5 mL of 3% 2-chloroprocaine. We evaluated both sensory and motor blocks at 10-min intervals for 60 mins. Blocks were maximal in both groups at 20 to 30 mins. There was a statistically significant difference in temperature sensation and motor function at 10 mins favoring the ultrasound group. There was no statistical difference in motor function, temperature, or pinprick sensation between 20 and 60 mins. The use of ultrasound seems to improve the onset of deep peroneal nerve block at the ankle but does not improve the overall quality of the block.