Percutaneous Peripheral Nerve Stimulation (Neuromodulation) for Postoperative Pain: A Randomized, Sham-controlled Pilot Study

Abstract

Background: Percutaneous peripheral nerve stimulation is an analgesic technique involving the percutaneous implantation of a lead followed by the delivery of electric current using an external pulse generator. Percutaneous peripheral nerve stimulation has been used extensively for chronic pain, but only uncontrolled series have been published for acute postoperative pain. The current multicenter study was undertaken to (1) determine the feasibility and optimize the protocol for a subsequent clinical trial and (2) estimate the treatment effect of percutaneous peripheral nerve stimulation on postoperative pain and opioid consumption.

Methods: Preoperatively, an electrical lead was percutaneously implanted to target the sciatic nerve for major foot/ankle surgery (e.g., hallux valgus correction), the femoral nerve for anterior cruciate ligament reconstruction, or the brachial plexus for rotator cuff repair, followed by a single injection of long-acting local anesthetic along the same nerve/plexus. Postoperatively, participants were randomized to 14 days of either electrical stimulation (n = 32) or sham stimulation (n = 34) using an external pulse generator in a double-masked fashion. The dual primary treatment effect outcome measures were (1) cumulative opioid consumption (in oral morphine equivalents) and (2) mean values of the "average" daily pain scores measured on the 0 to 10 Numeric Rating Scale within the first 7 postoperative days.

Results: During the first 7 postoperative days, opioid consumption in participants given active stimulation was a median (interquartile range) of 5 mg (0 to 30) versus 48 mg (25 to 90) in patients given sham treatment (ratio of geometric means, 0.20 [97.5% CI, 0.07 to 0.57]; P < 0.001). During this same period, the average pain intensity in patients given active stimulation was a mean ± SD of 1.1 ± 1.1 versus 3.1 ± 1.7 in those given sham (difference, -1.8 [97.5% CI, -2.6 to -0.9]; P < 0.001).

Conclusions: Percutaneous peripheral nerve stimulation reduced pain scores and opioid requirements free of systemic side effects during at least the initial week after ambulatory orthopedic surgery.

Figure 1.

CONSORT diagram.

Figure 2.

Joint hypothesis testing of total opioid consumption and pain score primary outcomes during the Initial 7-days postoperatively. The plot of mean difference of BPI average pain score (Upper Panel) and the Ratio of Geometric Means of Total Opioid Consumption (Lower Panel). The mean difference (97.5% CI) of pain score on stimulation vs. sham (placebo) was estimated from a repeated measures linear mixed model with an autoregressive correlation structure, adjusting for baseline BPI average pain score and imbalanced surgical location. The ratio of geometric means of total opioid consumption were each estimated using a multivariable linear regression model adjusting for imbalanced surgical location. The stimulation was superior on pain and total opioid consumption (both superiority test p < 0.001) compared to the placebo group.

Figure 3.

Effects of 14 days of percutaneous peripheral nerve stimulation on pain. Pain severity is indicated using a numeric rating scale (Panels A and B) the Defense and Veterans Pain Rating Scale (Panel C) with 0 equal to no pain and 10 being the worst imaginable pain. For scores during the initial 7 postoperative days, P values were estimated from repeated measures linear mixed effects model with an autoregressive correlation structure, adjusting for baseline scores and imbalanced surgical location; for postoperative day 11 and 15, P values were estimated from Wilcoxon rank sum test stratified by surgical location; for month 1, P values were estimated from multivariable linear regression models adjusting for baseline scores and surgical location. Data expressed as median (dark horizontal bars) with 25^th–75^th (box), 10^th–90^th (whiskers), mean (diamonds), and outliers (circles).

Figure 4.

Effects of 14 days of percutaneous peripheral nerve stimulation on opioid consumption (oral morphine equivalents). For the opioid consumption within 24 hours at each time point, P values were estimated from Wilcoxon rank test (skewed data) stratified by surgical location. Data expressed as median (dark horizontal bars) with 25^th–75^th (box), 10^th–90^th (whiskers), mean (diamonds), and outliers (circles).

Figure 5.

Effects of 14 days of percutaneous peripheral nerve stimulation on the Brief Pain Inventory interference domain. Pain interference indicated using a numeric rating scale of 0–70, with 0 and 70 equal to no and maximal interference, respectively. During postoperative days 3 and 7, P values were estimated from repeated measures linear mixed model with an autoregressive correlation structure, adjusting for baseline values and imbalanced surgical location; for postoperative day 15, P values were estimated from Wilcoxon rank test (skewed data) stratified by surgical location; for 1 month, P values were estimated from multivariable linear regression models adjusting for baseline values and surgical location. Data expressed as pain’s interference on either the total or of each of the 7 components (higher scores = more interference) demarked as median (dark horizontal bars) with 25^th–75^th (box), 10^th–90^th (whiskers), mean (diamonds), and outliers (circles).