Percutaneous auricular neuromodulation (nerve stimulation) for the treatment of pain following total knee arthroplasty: a randomized, double-masked, sham-controlled pilot study

Background Percutaneous auricular nerve stimulation (neuromodulation) is an analgesic technique involving the percutaneous implantation of multiple leads at various points on/around the ear followed by the delivery of electric current using an external pulse generator. A device is currently available within the USA cleared to treat symptoms from opioid withdrawal, and multiple reports suggest a possible postoperative analgesic effect. The current randomized, controlled pilot study was undertaken to (1) determine the feasibility and optimize the protocol for a subsequent definitive clinical trial and (2) estimate the treatment effect of auricular neuromodulation on postoperative pain and opioid consumption following total knee arthroplasty. Methods Within the recovery room following primary, unilateral, total knee arthroplasty, an auricular neuromodulation device (NSS-2 Bridge, Masimo, Irvine, California, USA) was applied using three percutaneous leads and one ground electrode. Participants were randomized to 5 days of either electrical stimulation or sham stimulation in a double-masked fashion. Participants were discharged with the stimulator in situ and removed the disposable devices at home. The dual primary treatment effect outcome measures were the cumulative opioid use (oral oxycodone) and the mean of the "average" daily pain measured with the Numeric Rating Scale for the first 5 postoperative days. Results During the first five postoperative days, oxycodone consumption in participants given active stimulation (n=15) was a median (IQR) of 4 mg (2-12) vs 13 mg (5-23) in patients given sham (n=15) treatment (p=0.039). During this same period, the average pain intensity in patients given active stimulation was a median (IQR) of 2.5 (1.5-3.3) vs 4.0 (3.6-4.8) in those given sham (p=0.014). Awakenings due to pain over all eight postoperative nights in participants given active stimulation was a median (IQR) of 5 (3-8) vs 11 (4-14) in those given sham (p<0.001). No device-related localized cutaneous irritation, systemic side effects, or other adverse events were identified. Conclusions Percutaneous auricular neuromodulation reduced pain scores and opioid requirements during the initial week after total knee arthroplasty. Given the ease of application as well as the lack of systemic side effects and reported complications, a definitive clinical trial appears warranted.