ESRA19-0419 Percutaneous electrical nerve block of acute pain in humans

Background and aims High-frequency electrical stimulation (HFES) delivered to a peripheral nerve through implanted electrodes can reduce chronic pain. However, surgical placement burdens the use of HFES for acute applications. We investigated the effects of HFES delivered percutaneously to a sensory nerve on acute pain elicited in able-bodied (AB) subjects, and on post-surgical pain in one subject within 24 hours of total knee arthroplasty (TKA). Methods High-frequency electrical stimulation (sinewave; 10 kHz; ≤ 25 mA) was delivered to the saphenous nerve at the adductor canal via a percutaneous lead in 5 AB and 1 TKA subjects. Acute pain sensations in AB subjects were elicited by transcutaneous electrical stimulation of the saphenous nerve at the ankle. Subjective sensations (11-point scale, with 3 corresponding to pain-threshold), pain scores (NRS), and muscle activity were recorded. The study was approved by Copernicus IRB. Results All subjects reported reduced pain scores in response to HFES. In able-bodied subjects, painful sensations were either completely abolished (N=4; figure 1a) or reduced (N=1; figure 1b). Post-surgical pain in the TKA subject was reduced from 6.5 to 2.5 on NRS. Pain scores in all 6 subjects returned to baseline values within seconds-to-minutes after the stimulation was terminated. High-frequency electrical stimulation did not elicit EMG activity or visible contractions of the thigh muscles. No serious adverse effects were reported. Conclusions Percutaneous high-frequency electrical stimulation of the saphenous nerve in the adductor canal can reversibly block acute pain sensations in humans, without causing co-excitation of nearby muscles.