Infection Rates of Electrical Leads Used for Percutaneous Neurostimulation of the Peripheral Nervous System

Randomized Placebo-Controlled Trial of 60-Day Percutaneous Peripheral Nerve Stimulation Treatment Indicates Relief of Persistent Postoperative Pain, and Improved Function After Knee Replacement

OBJECTIVES

Total knee arthroplasty (TKA) is an effective surgery for end-stage knee osteoarthritis, but chronic postoperative pain and reduced function affect up to 20% of patients who undergo such surgery. There are limited treatment options, but percutaneous peripheral nerve stimulation (PNS) is a promising nonopioid treatment option for chronic, persistent postoperative pain. The objective of the present study was to evaluate the effect of a 60-day percutaneous PNS treatment in a multicenter, randomized, double-blind, placebo-controlled trial for treating persistent postoperative pain after TKA.

MATERIALS AND METHODS

Patients with postoperative pain after knee replacement were screened for this postmarket, institutional review board-approved, prospectively registered (NCT04341948) trial. Subjects were randomized to receive either active PNS or placebo (sham) stimulation. Subjects and a designated evaluator were blinded to group assignments. Subjects in both groups underwent ultrasound-guided placement of percutaneous fine-wire coiled leads targeting the femoral and sciatic nerves on the leg with postoperative pain. Leads were indwelling for eight weeks, and the primary efficacy outcome compared the proportion of subjects in each group reporting ≥50% reduction in average pain relative to baseline during weeks five to eight. Functional outcomes (6-minute walk test; 6MWT and Western Ontario and McMaster Universities Osteoarthritis Index) and quality of life (Patient Global Impression of Change) also were evaluated at end of treatment (EOT).

RESULTS

A greater proportion of subjects in the PNS groups (60%; 12/20) than in the placebo (sham) group (24%; 5/21) responded with ≥50% pain relief relative to baseline (p = 0.028) during the primary endpoint (weeks 5-8). Subjects in the PNS group also walked a significantly greater distance at EOT than did those in the placebo (sham) group (6MWT; +47% vs -9% change from baseline; p = 0.048, n = 18 vs n = 20 completed the test, respectively). Prospective follow-up to 12 months is ongoing.

CONCLUSIONS

This study provides evidence that percutaneous PNS decreases persistent pain, which leads to improved functional outcomes after TKA at EOT.

Removal Forces of a Helical Microwire Structure Electrode

(1) Background: Medical devices, especially neuromodulation devices, are often explanted for a variety of reasons. The removal process imparts significant forces on these devices, which may result in device fracture and tissue trauma. We hypothesized that a device's form factor interfacing with tissue is a major driver of the force required to remove a device, and we isolated helical and linear electrode structures as a means to study atraumatic removal. (2) Methods: Ductile linear and helical microwire structure electrodes were fabricated from either Gold (Au) or Platinum-Iridium (Pt-Ir, 90-10). Removal forces were captured from synthetic gel models and following chronic implantation in rodent and porcine models. Devices were fully implanted in the animal models, requiring a small incision (<10 mm) and removal via tissue forceps. (3) Results: Helical devices were shown to result in significantly lower maximal removal forces in both synthetic gel and rodent studies compared to their linear counterparts. Chronically (1 yr.), the maximal removal force of helical devices remained under 7.30 N, for which the Platinum-Iridium device's tensile failure force was 32.90 ± 2.09 N, resulting in a safety factor of 4.50. (4) Conclusions: An open-core helical structure that can freely elongate was shown to result in reduced removal forces both acutely and chronically.

A review of prospective studies regarding percutaneous peripheral nerve stimulation treatment in the management of chronic pain

Conventionally, peripheral nerve stimulation (PNS) for treatment of chronic pain has involved a two-stage process: a short-term (e.g., 7 days) trial and, if significant pain relief is achieved, a permanent PNS system is implanted. A percutaneous PNS treatment is now available where a coiled lead may be implanted for up to 60 days with the goal of producing sustained relief. In the present review, published prospective trials using percutaneous PNS treatment were identified and synthesized. The collected evidence indicates that percutaneous PNS treatment for up to 60 days provides durable clinically significant improvements in pain and pain interference. Similar efficacy across diverse targets and etiologies supports the broad applicability for use within the chronic pain population using this nonopioid technology.

Literature Review: Mechanism, Indications, and Clinical Efficacy of Peripheral Nerve Stimulators in Lower Extremity Pain

PURPOSE OF REVIEW

Lower extremity pain is deemed by Center for Disease Control and Prevention (CDC) to be a significant source of chronic pain in adults. If not appropriately managed, patients are subjected to risks of prolonged musculoskeletal dysfunction, disruption to quality of life, and elevated healthcare expenditures. Peripheral nerve stimulation (PNS) has shown great potential in recent years demonstrating efficacy in multiple diagnoses ranging from acute post-surgical pain to complex regional pain syndrome (CRPS). This study seeks to delineate efficacy of peripheral neuromodulation in the context of chronic lower extremity pain.

RECENT FINDINGS

Prevailing clinical studies demonstrate evidence levels ranging from II to V (Oxford Centre of Level of Evidence) in lower limb PNS, attaining positive outcomes in pain scores, opioid use, and quality of life measures. Nerves most frequently targeted are the sciatic and femoral nerves with post-amputation pain and CRPS most commonly investigated for efficacy. PNS is a promising therapeutic modality demonstrated to be effective for a variety of nociceptive and neuropathic pain conditions in the lower extremity. PNS offers chronic pain physicians a powerful tool in the multi-modal management of lower limb chronic pain.

Latest Advances in Regional Anaesthesia

Training and expertise in regional anaesthesia have increased significantly in tandem with increased interest over the past two decades. This review outlines the most recent advances in regional anaesthesia and focuses on novel areas of interest including fascial plane blocks. Pharmacological advances in the form of the prolongation of drug duration with liposomal bupivacaine are considered. Neuromodulation in the context of regional anaesthesia is outlined as a potential future direction. The growing use of regional anaesthesia outside of the theatre environment and current thinking on managing the rebound plane after regional block regression are also discussed. Recent relevant evidence is summarised, unanswered questions are outlined, and priorities for ongoing investigation are suggested.

Reconnecting the Hand and Arm to the Brain: Efficacy of Neural Interfaces for Sensorimotor Restoration After Tetraplegia

BACKGROUND AND OBJECTIVES

Paralysis after spinal cord injury involves damage to pathways that connect neurons in the brain to peripheral nerves in the limbs. Re-establishing this communication using neural interfaces has the potential to bridge the gap and restore upper extremity function to people with high tetraplegia. We report a novel approach for restoring upper extremity function using selective peripheral nerve stimulation controlled by intracortical microelectrode recordings from sensorimotor networks, along with restoration of tactile sensation of the hand using intracortical microstimulation.

METHODS

A 27-year-old right-handed man with AIS-B (motor-complete, sensory-incomplete) C3-C4 tetraplegia was enrolled into the clinical trial. Six 64-channel intracortical microelectrode arrays were implanted into left hemisphere regions involved in upper extremity function, including primary motor and sensory cortices, inferior frontal gyrus, and anterior intraparietal area. Nine 16-channel extraneural peripheral nerve electrodes were implanted to allow targeted stimulation of right median, ulnar (2), radial, axillary, musculocutaneous, suprascapular, lateral pectoral, and long thoracic nerves, to produce selective muscle contractions on demand. Proof-of-concept studies were performed to demonstrate feasibility of using a brain-machine interface to read from and write to the brain for restoring motor and sensory functions of the participant's own arm and hand.

RESULTS

Multiunit neural activity that correlated with intended motor action was successfully recorded from intracortical arrays. Microstimulation of electrodes in somatosensory cortex produced repeatable sensory percepts of individual fingers for restoration of touch sensation. Selective electrical activation of peripheral nerves produced antigravity muscle contractions, resulting in functional movements that the participant was able to command under brain control to perform virtual and actual arm and hand movements. The system was well tolerated with no operative complications.

CONCLUSION

The combination of implanted cortical electrodes and nerve cuff electrodes has the potential to create bidirectional restoration of motor and sensory functions of the arm and hand after neurological injury.

Sustained Relief of Complex Regional Pain Syndrome (CRPS) Pain Following a 60-Day Peripheral Nerve Stimulation: A Report of Three Cases

Patients who present to pain clinics with complex regional pain syndrome (CRPS) typically have debilitating pain, including hyperalgesia and allodynia, and additional substantial quality-of-life concerns related to the motor and autonomic-related symptoms of CRPS. Present treatments for CRPS such as neuropathic pain medications and sympathetic blocks are often unsatisfactory for managing symptoms. The present cases highlight the use of a 60-day percutaneous peripheral nerve stimulation (PNS) treatment for three patients with CRPS Type I affecting the foot. In all three patients, the tibial and common peroneal nerves were targeted separately at the popliteal fossa with two percutaneous leads each placed a remote distance (~1 cm) from the target nerve under ultrasound guidance. All three patients reported substantial pain relief and resolution of autonomic symptoms (e.g., swelling, edema, erythema), with sustained relief lasting 8-10 months in two patients, and 34 months (as of this writing) in the third patient. There were no medical complications. These three cases suggest that 60-day PNS is a safe and efficacious treatment for CRPS.

Transdermal wires for improved integration in vivo

Alternative engineering approaches have led the design of implants with controlled physical features to minimize adverse effects in biological tissues. Similar efforts have focused on optimizing the design features of percutaneous VAD drivelines with the aim to prevent infection, omitting however a thorough look on the implant-skin interactions that govern local tissue reactions. Here, we utilized an integrated approach for the biophysical modification of transdermal implants and their evaluation by chronic sheep implantation in comparison to the standard of care VAD drivelines. We developed a novel method for the transfer of breath topographical features on thin wires with modular size. We examined the impact of implant's diameter, surface topography, and chemistry on macroscopic, histological, and physical markers of inflammation, fibrosis, and mechanical adhesion. All implants demonstrated infection-free performance. The fibrotic response was enhanced by the increasing diameter of implants but not influenced by their surface properties. The implants of small diameter promoted mild inflammatory responses with improved mechanical adhesion and restricted epidermal downgrowth, in both silicone and polyurethane coated transdermal wires. On the contrary, the VAD drivelines with larger diameter triggered severe inflammatory reactions with frequent epidermal downgrowth. We validated these effects by quantifying the infiltration of macrophages and the level of vascularization in the fibrotic zone, highlighting the critical role of size reduction for the benign integration of transdermal implants with skin. This insight on how the biophysical properties of implants impact local tissue reactions could enable new solutions on the transdermal transmission of power, signal, and mass in a broad range of medical devices.

The Emerging Role of Peripheral Nerve Stimulation in Postoperative Analgesia

PURPOSE OF REVIEW

Though peripheral nerve stimulation has long been utilized in the field of chronic pain management, its use in acute pain management in the postoperative period is relatively novel and warrants further consideration.

RECENT FINDINGS

In the postsurgical period, peripheral nerve stimulation may offer an additional low-risk, opioid-sparing analgesic option, which is particularly pertinent in the setting of the ongoing opioid epidemic, as inadequate postsurgical analgesia has been shown to increase the risk of developing persistent or chronic postsurgical pain. In this review, we discuss the current literature that illustrate the emerging role of peripheral nerve stimulation as an effective treatment modality in the postoperative period for the management of acute pain, as various studies have recently been conducted evaluating the feasibility of utilizing percutaneous peripheral nerve stimulation as an adjunct in postsurgical analgesia. Nonetheless, future studies are necessary to continue to elucidate the short- and long-term impacts of peripheral nerve stimulation use in acute postsurgical analgesia.

Safety of Scrambler Therapy: A Systematic Review of Complications and Adverse Effects

OBJECTIVE

The objective was to qualitatively synthesize all reported cases of complications, adverse effects, side effects, or harms arising from the use of scrambler therapy (ST).

METHODS AND DESIGN

A systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. The PubMed, Embase, Scopus, Web of Science, United States National Library of Medicine clinical trials registry, and Cochrane Central Register of Controlled Trials databases were searched from database inception to December 10, 2021. Case reports/series, abstracts, retrospective studies, and prospective studies (e.g., open-label trials, randomized controlled trials) pertaining to ST and any description of a complication, adverse effect, side effect, or harm were screened. The search protocol was developed a priori and registered via the International Prospective Register of Systematic Reviews (PROSPERO ID: CRD42021291838).

RESULTS

A total of six RCTs, 19 prospective open-label trials, and 11 case series / case reports met the inclusion criteria, comprising 1,152 total patients. Two patients experienced contact dermatitis, and one patient reported minor ecchymosis that resolved without intervention. This yielded a composite complication rate of 0.26% (3/1,152). There were zero reported serious adverse events.

CONCLUSIONS

When used in accordance with the treatment protocols described by the United States Food and Drug Administration and device manual, ST is associated with a reported composite complication rate that is orders of magnitude lower than those of invasive neuromodulation devices. ST neuromodulation is a safe alternative for patients who cannot undergo invasive neuromodulation device implantation because of either risk or preference.

Mechanism of Action of Peripheral Nerve Stimulation for Chronic Pain: A Narrative Review

The use of stimulation of peripheral nerves to test or treat various medical disorders has been prevalent for a long time. Over the last few years, there has been growing evidence for the use of peripheral nerve stimulation (PNS) for treating a myriad of chronic pain conditions such as limb mononeuropathies, nerve entrapments, peripheral nerve injuries, phantom limb pain, complex regional pain syndrome, back pain, and even fibromyalgia. The ease of placement of a minimally invasive electrode via percutaneous approach in the close vicinity of the nerve and the ability to target various nerves have led to its widespread use and compliance. While most of the mechanism behind its role in neuromodulation is largely unknown, the gate control theory proposed by Melzack and Wall in the 1960s has been the mainstay for understanding its mechanism of action. In this review article, the authors performed a literature review to discuss the mechanism of action of PNS and discuss its safety and usefulness in treating chronic pain. The authors also discuss current PNS devices available in the market today.

No more tears from surgical site infections in interventional pain management

As the field of interventional pain management (IPM) grows, the risk of surgical site infections (SSIs) is increasing. SSI is defined as an infection of the incision or organ/space that occurs within one month after operation or three months after implantation. It is also common to find patients with suspected infection in an outpatient clinic. The most frequent IPM procedures are performed in the spine. Even though primary pyogenic spondylodiscitis via hematogenous spread is the most common type among spinal infections, secondary spinal infections from direct inoculation should be monitored after IPM procedures. Various preventive guidelines for SSI have been published. Cefazolin, followed by vancomycin, is the most commonly used surgical antibiotic prophylaxis in IPM. Diagnosis of SSI is confirmed by purulent discharge, isolation of causative organisms, pain/tenderness, swelling, redness, or heat, or diagnosis by a surgeon or attending physician. Inflammatory markers include traditional (C-reactive protein, erythrocyte sedimentation rate, and white blood cell count) and novel (procalcitonin, serum amyloid A, and presepsin) markers. Empirical antibiotic therapy is defined as the initial administration of antibiotics within at least 24 hours prior to the results of blood culture and antibiotic susceptibility testing. Definitive antibiotic therapy is initiated based on the above culture and testing. Combination antibiotic therapy for multidrug-resistant Gram-negative bacteria infections appears to be superior to monotherapy in mortality with the risk of increasing antibiotic resistance rates. The never-ending war between bacterial resistance and new antibiotics is continuing. This article reviews prevention, diagnosis, and treatment of infection in pain medicine.

The American Society of Pain and Neuroscience (ASPN) Evidence-Based Clinical Guideline of Interventional Treatments for Low Back Pain

Introduction

Painful lumbar spinal disorders represent a leading cause of disability in the US and worldwide. Interventional treatments for lumbar disorders are an effective treatment for the pain and disability from low back pain. Although many established and emerging interventional procedures are currently available, there exists a need for a defined guideline for their appropriateness, effectiveness, and safety.

Objective

The ASPN Back Guideline was developed to provide clinicians the most comprehensive review of interventional treatments for lower back disorders. Clinicians should utilize the ASPN Back Guideline to evaluate the quality of the literature, safety, and efficacy of interventional treatments for lower back disorders.

Methods

The American Society of Pain and Neuroscience (ASPN) identified an educational need for a comprehensive clinical guideline to provide evidence-based recommendations. Experts from the fields of Anesthesiology, Physiatry, Neurology, Neurosurgery, Radiology, and Pain Psychology developed the ASPN Back Guideline. The world literature in English was searched using Medline, EMBASE, Cochrane CENTRAL, BioMed Central, Web of Science, Google Scholar, PubMed, Current Contents Connect, Scopus, and meeting abstracts to identify and compile the evidence (per section) for back-related pain. Search words were selected based upon the section represented. Identified peer-reviewed literature was critiqued using United States Preventive Services Task Force (USPSTF) criteria and consensus points are presented.

Results

After a comprehensive review and analysis of the available evidence, the ASPN Back Guideline group was able to rate the literature and provide therapy grades to each of the most commonly available interventional treatments for low back pain.

Conclusion

The ASPN Back Guideline represents the first comprehensive analysis and grading of the existing and emerging interventional treatments available for low back pain. This will be a living document which will be periodically updated to the current standard of care based on the available evidence within peer-reviewed literature.

Infection of a Retained Peripheral Nerve Stimulation Lead: A Case Report

Percutaneous peripheral nerve stimulation is used to provide analgesia for weeks or even months. While infection of any percutaneously implanted object is a concern, it is exceedingly rare for helically coiled leads, with a reported incidence of less than 1 infection for every 32,000 indwelling days. We now report an infected helically coiled lead requiring sedation for extraction and complicated by lead fracture during removal, leaving a remnant in situ. The infection was successfully treated with oral antibiotics. We speculate on the cause of this infection and propose steps to prevent this complication, including the avoidance of sling-to-lead insertion site overlap.

Extending Perioperative Analgesia with Ultrasound-Guided, Percutaneous Cryoneurolysis, and Peripheral Nerve Stimulation (Neuromodulation)

The use of regional anesthesia is key to a successful approach to improving postoperative analgesia, which involves local anesthetic deposition either around peripheral nerves or within a fascial plane. Unfortunately, the realistic duration even with continuous peripheral nerve blocks usually does not match the duration of surgical pain, comprising a major limitation. Here, the use of 2 interventional modalities-ultrasound-guided percutaneous cryoneurolysis and peripheral nerve stimulation-is discussed, both of which may be used to treat acute and subacute pain and may therefore have a positive impact on the incidence and severity of chronic pain development.

Real-world evidence of sustained improvement following 60-day peripheral nerve stimulation treatment for pain: a cross-sectional follow-up survey

Objective: This study presents real-world data from a cross-sectional follow-up survey of patients who previously received 60-day peripheral nerve stimulation (PNS) treatment for pain. Materials & methods: A survey including validated pain and other related outcome measures was distributed to patients who previously underwent implantation of temporary PNS leads for 60-day PNS treatment. Results: Among survey respondents who were at least 3 months from the start of treatment, most reported sustained clinically significant improvements in pain and/or quality of life, with the length of follow-up at the time of survey completion ranging from 3 to 30 months. Conclusion: These real-world data support recent prospective studies indicating that 60-day percutaneous PNS provides significant and sustained relief across a wide range of pain conditions.

60-Day PNS Treatment May Improve Identification of Delayed Responders and Delayed Non-Responders to Neurostimulation for Pain Relief

Objective

Conventional neurostimulation typically involves a brief (eg, ≤10-day) trial to assess presumed effectiveness prior to permanent implantation. Low trial conversion rates and high explant rates due to inadequate pain relief highlight the need for improved patient identification strategies. The development of a 60-day percutaneous peripheral nerve stimulation (PNS) system enables evaluation of outcomes following an extended temporary treatment period of up to 60 days, that may obviate or validate the need for permanent implant. The present study provides the first real-world evidence regarding patient response throughout a 60-day PNS treatment period.

Methods

Anonymized data listings were compiled from patients who underwent implantation of temporary percutaneous leads and opted-in to provide real-world data to the device manufacturer during routine interactions with device representatives throughout the 60-day treatment.

Results

Overall, 30% (222/747) of patients were early responders (≥50% pain relief throughout treatment). Another 31% (231/747) of patients initially presented as non-responders but surpassed 50% pain relief by the end of treatment. Conversely, 32% (239/747) of patients were non-responders throughout treatment. An additional 7% (55/747) of patients initially presented as responders but fell below 50% relief by the end of the treatment period.

Conclusion

An extended, 60-day PNS treatment may help identify delayed responders, providing the opportunity for sustained relief and improving access to effective PNS treatment. Compared to a conventionally short trial of ≤10 days, a longer 60-day PNS treatment may also help reduce explant rates by identifying delayed non-responders unlikely to benefit long-term. These scenarios support the importance of an extended 60-day temporary PNS stimulation period to help inform stepwise treatment strategies that may optimize outcomes and cost-effectiveness.

Cancer Pain Management-New Therapies

PURPOSE OF REVIEW

Despite the rapid advance in anti-cancer treatment in recent years, the treatment to cancer-related pain remains largely unchanged. One systemic review has shown that approximately 32% of patient with cancer-related pain were undertreated. While in patients responding to strong opioids, long-term use of opioids will lead to many undesired side effects such as constipation, tolerance, and addiction. The goals of this review are to re visit the current algorism of cancer pain management and bring attention to the emerging interventional pain management techniques.

RECENT FINDINGS

Peripheral nerve stimulation (PNS) has been successfully used to treat certain types of chronic non-cancer pain with long-term analgesic effect. PNS has also brought some promising results in treating localized cancer-related pain in a pilot study. More studies are needed to advance the novel and safe treatment of cancer-related pain. Incorporating interventional techniques such as PNS properly can optimize the current treatment strategy and improve outcomes.

Peripheral nerve stimulation for the management of acute and subacute post-amputation pain: a randomized, controlled feasibility trial

Introduction & aim: Temporary (60-day) percutaneous peripheral nerve stimulation (PNS) has demonstrated effectiveness for the treatment of chronic post-amputation pain, and this pilot study aims to evaluate the feasibility of temporary percutaneous PNS for the treatment of acute post-amputation pain. Patients & methods: Sixteen veterans undergoing lower extremity amputation received PNS and standard medical therapy or standard medical therapy alone. Results: The PNS group reported greater reductions in average phantom limb pain, residual limb pain and daily opioid consumption, and there were fewer participants taking opioids through 3 months post-amputation. Conclusion: This pilot study suggests that PNS is feasible in the acute postoperative period following lower limb amputation and may provide a non-pharmacologic analgesic therapy that lowers pain scores and reduces opioid consumption, and thus warrants further investigation.

Percutaneous Neuromodulation of the Brachial Plexus and Sciatic Nerve for the Treatment of Acute Pain Following Surgery: Secondary Outcomes From a Multicenter, Randomized, Controlled Pilot Study

OBJECTIVES

We recently reported that percutaneous peripheral nerve stimulation (PNS or "neuromodulation") decreased pain and opioid consumption within the first two weeks following ambulatory surgery. However, the anatomic lead locations were combined for the analysis, and benefits for each location remain unknown. We therefore now report the effects of percutaneous PNS for brachial plexus and sciatic nerve leads separately.

MATERIALS AND METHODS

Before surgery, leads were implanted percutaneously to target the brachial plexus (N = 21) for rotator cuff repair or sciatic nerve (N = 40) for foot/ankle surgery, followed by a single injection of local anesthetic. Postoperatively, subjects were randomized in a double masked fashion to 14 days of electrical stimulation (N = 30) or sham/placebo (N = 31) using an external pulse generator. The primary outcome of interest was opioid consumption and pain scores evaluated jointly. Thus, stimulation was deemed effective if superior on either outcome and at least noninferior on the other.

RESULTS

For brachial plexus leads, during the first seven postoperative days pain measured with the numeric rating scale in participants given active stimulation was a median [interquartile range ] of 0.8 [0.5, 1.6] versus 3.2 [2.7, 3.5] in patients given sham (p < 0.001). For this same group, opioid consumption in participants given active stimulation was 10 mg [5, 20] versus 71 mg [35, 125] in patients given sham (p = 0.043). For sciatic nerve leads, pain scores for the active treatment group were 0.7 [0, 1.4] versus 2.8 [1.6, 4.6] in patients given sham (p < 0.001). During this same period, participants given active stimulation consumed 5 mg [0, 30] of opioids versus 40 mg [20, 105] in patients given sham (p = 0.004). Treatment effects did not differ statistically between the two locations.

CONCLUSIONS

Ambulatory percutaneous PNS of both the brachial plexus and sciatic nerve is an effective treatment for acute pain free of systemic side-effects following painful orthopedic surgery.

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

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.

EDITOR’S PERSPECTIVE

Treatment of chronic axial back pain with 60-day percutaneous medial branch PNS: Primary end point results from a prospective, multicenter study

Background

The objective of this prospective, multicenter study is to characterize responses to percutaneous medial branch peripheral nerve stimulation (PNS) to determine if results from earlier, smaller single‐center studies and reports were generalizable when performed at a larger number and wider variety of centers in patients recalcitrant to nonsurgical treatments.

Materials & Methods

Participants with chronic axial low back pain (LBP) were implanted with percutaneous PNS leads targeting the lumbar medial branch nerves for up to 60 days, after which the leads were removed. Participants were followed long‐term for 12 months after the 2‐month PNS treatment. Data collection is complete for visits through end of treatment with PNS (primary end point) and 6 months after lead removal (8 months after start of treatment), with some participant follow‐up visits thereafter in progress.

Results

Clinically and statistically significant reductions in pain intensity, disability, and pain interference were reported by a majority of participants. Seventy‐three percent of participants were successes for the primary end point, reporting clinically significant (≥30%) reductions in back pain intensity after the 2‐month percutaneous PNS treatment (n = 54/74). Whereas prospective follow‐up is ongoing, among those who had already completed the long‐term follow‐up visits (n = 51), reductions in pain intensity, disability, and pain interference were sustained in a majority of participants through 14 months after the start of treatment.

Conclusion

Given the minimally invasive, nondestructive nature of percutaneous PNS and the significant benefits experienced by participants who were recalcitrant to nonsurgical treatments, percutaneous PNS may provide a promising first‐line neurostimulation treatment option for patients with chronic axial back pain.

Ultrasound-Guided Percutaneous Peripheral Nerve Stimulation: A Pragmatic Effectiveness Trial of a Nonpharmacologic Alternative for the Treatment of Postoperative Pain

BACKGROUND

Percutaneous peripheral nerve stimulation (PNS) is an analgesic modality involving the insertion of a lead through an introducer needle followed by the delivery of electric current after needle withdrawal. This modality has been used extensively to treat chronic pain, but only small series have been published involving postoperative pain. The ultimate objective of this study is to determine the postoperative effects of percutaneous PNS following moderately to severely painful ambulatory surgery within a real-world clinical practice setting. The primary hypothesis is that surgical pain and opioid consumption during the initial 7 days after surgery will be reduced by percutaneous PNS compared with usual and customary analgesia (dual primary outcome measures).

DESIGN

A multicenter pragmatic effectiveness trial. We are randomizing participants having painful orthopedic surgical procedures of the upper and lower extremity to receive 14 days of either 1) electrical stimulation or 2) sham in a double-masked fashion. End points are being assessed at various time points over 12 postoperative months.

SUMMARY

The postoperative experience will be much improved if percutaneous PNS provides potent analgesia while concurrently decreasing opioid requirements following painful surgery. Because this modality can be administered for up to 60 days at home, it may provide postoperative analgesia that outlasts surgical pain yet has relatively few risks and, unlike opioids, has no systemic side effects or potential for abuse, addiction, and overdose. Percutaneous PNS has the potential to revolutionize postoperative analgesia as it has been practiced for the past century. This study will inform key stakeholders regarding an evidence-based nonpharmacologic approach to the management of postoperative pain.

Mechanism of Action of Peripheral Nerve Stimulation

PURPOSE OF REVIEW

The number of applications for peripheral nerve stimulation (PNS) in the pain management field is ever-growing. With the increasing number of clinical applications for peripheral nerve stimulation, the purpose of this article is to review the mechanism of action surrounding PNS, the recent literature from January 2018 to January 2021, and pertinent clinical outcomes.

RECENT FINDINGS

The authors searched articles identified from PubMed (January 2018-January 2021), Cochrane Central Register of Controlled Trials databases (January 2018-January 2021), and Scopus (January 2018-January 2021) databases, and manually searched references of identified publications. Broad MeSH terms and Boolean operators were queried in each search, including the following terms and their respective synonyms: peripheral nerve stimulation, mechanism of action, biochemical pathway, and pain pathway. 15 consensus articles were selected for in-depth review and inclusion for qualitative analysis. PNS may activate and modulate higher central nervous system (CNS) centers, including the dorsal lateral prefrontal cortex, somatosensory cortex, anterior cingulate cortex, and parahippocampal areas. Neuromodulatory effects from PNS may also extend into the spinal columns. Also, PNS may lead to changes in endogenous neurotransmitters and affect the plasticity of NMDA pathways.

A review of the StimRouter® peripheral neuromodulation system for chronic pain management

The StimRouter® peripheral nerve stimulation system created by Bioness, Inc., (CA, USA) is US FDA-approved for the treatment of peripheral mononeuropathy refractory to conservative medical management. StimRouter is a minimally invasive system that utilizes a subcutaneously implanted lead with integrated anchor and electrodes, and an external pulse generator to produce peripheral neuromodulation and achieve pain relief. Multiple published clinical trials reviewed here have shown the StimRouter system to have a high margin of safety, differentiating it from other existing peripheral neuromodulation systems requiring open surgical electrode placement and implantable pulse generators. These studies have also shown the StimRouter system to be efficacious in the treatment of multiple peripheral mononeuropathies; improving patient pain, activity levels and quality of life. StimRouter represents a feasible option for management of chronic peripheral mononeuropathy.

Correct Sciatic Nerve Management to Apply Ultrasound-Guided Percutaneous Neuromodulation in Patients With Chronic Low Back Pain: A Pilot Study

BACKGROUND

The objectives of this study were to evaluate the effects of an ultrasound (US)-guided percutaneous neuromodulation (PNM) intervention on the sciatic nerve, regarding pain, hip range of motion (ROM), balance, and functionality in patients with chronic low back pain (LBP); and to determine the optimal anatomical location of sciatic nerve stimulation to obtain therapeutic benefits in such patients.

MATERIALS AND METHODS

Thirty patients with chronic LBP were recruited and divided randomly into three groups. All patients received a single percutaneous electrical stimulation intervention on the sciatic nerve, with a different anatomical application location for each group (proximal, middle, and distal). Level of pain, hip passive ROM, dynamic balance, and Oswestry disability index were analyzed. All variables were calculated before the intervention, immediately postintervention, 48 hours and one week after the intervention, except the LBP questionnaire (before, and 48 hours and one week after the intervention).

RESULTS

All interventions decreased the level of pain and increased the ROM, balance, and functionality. Besides, these therapeutic effects were maintained during one week, regardless of the anatomical location of application.

CONCLUSIONS

The choice of an anatomical location of application of the US-guided PNM on the sciatic nerve by the physiotherapist does not influence the improvement of pain, ROM, balance, and function in patients with chronic LBP.

Percutaneous Peripheral Nerve Stimulation of the Medial Branch Nerves for the Treatment of Chronic Axial Back Pain in Patients After Radiofrequency Ablation

OBJECTIVE

Lumbar radiofrequency ablation is a commonly used intervention for chronic back pain. However, the pain typically returns, and though retreatment may be successful, the procedure involves destruction of the medial branch nerves, which denervates the multifidus. Repeated procedures typically have diminishing returns, which can lead to opioid use, surgery, or implantation of permanent neuromodulation systems. The objective of this report is to demonstrate the potential use of percutaneous peripheral nerve stimulation (PNS) as a minimally invasive, nondestructive, motor-sparing alternative to repeat radiofrequency ablation and more invasive surgical procedures.

DESIGN

Prospective, multicenter trial.

METHODS

Individuals with a return of chronic axial pain after radiofrequency ablation underwent implantation of percutaneous PNS leads targeting the medial branch nerves. Stimulation was delivered for up to 60 days, after which the leads were removed. Participants were followed up to 5 months after the start of PNS. Outcomes included pain intensity, disability, and pain interference.

RESULTS

Highly clinically significant (≥50%) reductions in average pain intensity were reported by a majority of participants (67%, n = 10/15) after 2 months with PNS, and a majority experienced clinically significant improvements in functional outcomes, as measured by disability (87%, n = 13/15) and pain interference (80%, n = 12/15). Five months after PNS, 93% (n = 14/15) reported clinically meaningful improvement in one or more outcome measures, and a majority experienced clinically meaningful improvements in all three outcomes (i.e., pain intensity, disability, and pain interference).

CONCLUSIONS

Percutaneous PNS has the potential to shift the pain management paradigm by providing an effective, nondestructive, motor-sparing neuromodulation treatment.

Peripherally Induced Reconditioning of the Central Nervous System: A Proposed Mechanistic Theory for Sustained Relief of Chronic Pain with Percutaneous Peripheral Nerve Stimulation

Peripheral nerve stimulation (PNS) is an effective tool for the treatment of chronic pain, although its efficacy and utilization have previously been significantly limited by technology. In recent years, purpose-built percutaneous PNS devices have been developed to overcome the limitations of conventional permanently implanted neurostimulation devices. Recent clinical evidence suggests clinically significant and sustained reductions in pain can persist well beyond the PNS treatment period, outcomes that have not previously been observed with conventional permanently implanted neurostimulation devices. This narrative review summarizes mechanistic processes that contribute to chronic pain, and the potential mechanisms by which selective large diameter afferent fiber activation may reverse these changes to induce a prolonged reduction in pain. The interplay of these mechanisms, supported by data in chronic pain states that have been effectively treated with percutaneous PNS, will also be discussed in support of a new theory of pain management in neuromodulation: Peripherally Induced Reconditioning of the Central Nervous System (CNS).

Acute postoperative pain management with percutaneous peripheral nerve stimulation: the SPRINT neuromodulation system

INTRODUCTION

Ultrasound-guided percutaneous peripheral nerve stimulation (PNS) may be used to treat acute postoperative pain for various types of surgeries. This modality avoids several limitations of traditional local anesthetic-based peripheral nerve blocks including avoidance of motor blockade and sensory deficits.

AREAS COVERED

In this review, we discuss the use of SPRINT (SPR Therapeutics, Cleveland, OH) neuromodulation system in the setting of acute postoperative pain management.

EXPERT OPINION

PNS is a novel modality in regional anesthesia that has much promise in reducing overall opioid use after surgery. Placement of PNS is very similar to that of catheter-based regional anesthesia techniques. Ultrasound is used to guide the percutaneously placed introducer needle in proximity to the target nerve. There are several benefits of PNS over catheter-based approaches, including: 1) avoidance of motor or sensory blockade; 2) no medication bag required to be carried; and 3) electric leads may be kept in situ safely for up to 60 days. While several proof-of-concept studies have been published highlighting its use in various types of surgeries, large high-quality randomized controlled trials are still needed.

Cryoneurolysis and Percutaneous Peripheral Nerve Stimulation to Treat Acute Pain

Two regional analgesic modalities currently cleared by the U.S. Food and Drug Administration hold promise to provide postoperative analgesia free of many of the limitations of both opioids and local anesthetic-based techniques. Cryoneurolysis uses exceptionally low temperature to reversibly ablate a peripheral nerve, resulting in temporary analgesia. Where applicable, it offers a unique option given its extended duration of action measured in weeks to months after a single application. Percutaneous peripheral nerve stimulation involves inserting an insulated lead through a needle to lie adjacent to a peripheral nerve. Analgesia is produced by introducing electrical current with an external pulse generator. It is a unique regional analgesic in that it does not induce sensory, motor, or proprioception deficits and is cleared for up to 60 days of use. However, both modalities have limited validation when applied to acute pain, and randomized, controlled trials are required to define both benefits and risks.

A Review of Peripheral Nerve Stimulation Techniques Targeting the Medial Branches of the Lumbar Dorsal Rami in the Treatment of Chronic Low Back Pain

OBJECTIVES

The lumbar medial branch nerve has historically been a focus for ablative techniques in the treatment of chronic low back pain (CLBP) of facetogenic origin. Recent developments in the field of neuromodulation have been employed to target these nerves for analgesia and/or functional restoration in broader populations of CLBP patients. The objective of this article was to provide an introductory review of procedural techniques and devices employed for peripheral nerve stimulation (PNS) of the lumbar medial branch of the dorsal ramus for the treatment of CLBP.

METHODS

A literature search via PubMed.gov was performed through September 2019 with key words focusing on peripheral nerve stimulation for chronic low back pain. This was refined to include only those articles that focused specifically on stimulation of the lumbar medial branch of the dorsal ramus. References within selected articles and unpublished data currently in the peer review process were also utilized.

RESULTS

Ninety articles from PubMed.gov were obtained. Two approaches to PNS of the medial branch of the dorsal ramus were identified.

CONCLUSIONS

Our review of the current literature regarding techniques for neuromodulation of the medial branch of the dorsal ramus revealed two dominant methods: a temporarily implanted percutaneous coiled-lead approach and a permanently implanted system. The two techniques share some similarities, such as targeting the medial branch of the dorsal ramus, and also have some differences, such as indwelling time, stimulation parameters, duration of treatment, image guidance, and degrees of invasiveness, but they are both demonstrating promising results in clinical trials.

Percutaneous Peripheral Nerve Stimulation for the Treatment of Chronic Pain Following Amputation

Introduction

Chronic pain and reduced function are significant problems for Military Service members and Veterans following amputation. Peripheral nerve stimulation (PNS) is a promising therapy, but PNS systems have traditionally been limited by invasiveness and complications. Recently, a novel percutaneous PNS system was developed to reduce the risk of complications and enable delivery of stimulation without surgery.

Materials and Methods

Percutaneous PNS was evaluated to determine if stimulation provides relief from residual and phantom limb pain following lower-extremity amputation. PNS leads were implanted percutaneously to deliver stimulation to the femoral and/or sciatic nerves. Patients received stimulation for up to 60 days followed by withdrawal of the leads.

Results

A review of recent studies and clinical reports found that a majority of patients (18/24, 75%) reported substantial (≥50%) clinically relevant relief of chronic post-amputation pain following up to 60 days of percutaneous PNS. Reductions in pain were frequently associated with reductions in disability and pain interference.

Conclusions

Percutaneous PNS can durably reduce pain, thereby enabling improvements in quality of life, function, and rehabilitation in individuals with residual or phantom limb pain following amputation. Percutaneous PNS may have additional benefit for Military Service members and Veterans with post-surgical or post-traumatic pain.

Visual Feedback Control of a Rat Ankle Angle Using a Wirelessly Powered Two-Channel Neurostimulator

Peripheral nerve disconnections cause severe muscle atrophy and consequently, paralysis of limbs. Reinnervation of denervated muscle by transplanting motor neurons and applying Functional Electrical Stimulation (FES) onto peripheral nerves is an important procedure for preventing irreversible degeneration of muscle tissues. After the reinnervation of denervated muscles, multiple peripheral nerves should be stimulated independently to control joint motion and reconstruct functional movements of limbs by the FES. In this study, a wirelessly powered two-channel neurostimulator was developed with the purpose of applying selective FES to two peripheral nerves—the peroneal nerve and the tibial nerve in a rat. The neurostimulator was designed in such a way that power could be supplied wirelessly, from a transmitter coil to a receiver coil. The receiver coil was connected, in turn, to the peroneal and tibial nerves in the rat. The receiver circuit had a low pass filter to allow detection of the frequency of the transmitter signal. The stimulation of the nerves was switched according to the frequency of the transmitter signal. Dorsal/plantar flexion of the rat ankle joint was selectively induced by the developed neurostimulator. The rat ankle joint angle was controlled by changing the stimulation electrode and the stimulation current, based on the Proportional Integral (PI) control method using a visual feedback control system. This study was aimed at controlling the leg motion by stimulating the peripheral nerves using the neurostimulator.

Percutaneous Peripheral Nerve Stimulation for Chronic Low Back Pain: Prospective Case Series With 1 Year of Sustained Relief Following Short-Term Implant

Introduction

Percutaneous peripheral nerve stimulation (PNS) provides an opportunity to relieve chronic low back pain and reduce opioid analgesic consumption as an alternative to radiofrequency ablation and permanently implanted neurostimulation systems. Traditionally, the use of neurostimulation earlier in the treatment continuum has been limited by its associated risk, invasiveness, and cost.

Methods

Percutaneous PNS leads (SPRINT MicroLead) were placed bilaterally to target the medial branches of the dorsal rami nerves under image guidance. The percutaneous leads were connected to miniature wearable stimulators (SPRINT PNS System) for the 1‐month therapy period, after which the leads were removed. Pain and disability were assessed long‐term up to 12 months after lead removal.

Results

Substantial, clinically significant reductions in average pain intensity (≥50% reduction as measured by the Brief Pain Inventory Short Form) were experienced by a majority of subjects (67%) at end of treatment compared to baseline (average 80% reduction among responders; P < 0.05, analysis of variance; n = 9). Twelve months after the end of PNS treatment, a majority of subjects who completed the long‐term follow‐up visits experienced sustained, clinically significant reductions in pain and/or disability (67%, n = 6; average 63% reduction in pain intensity and 32‐point reduction in disability among responders). No serious or unanticipated adverse events were reported.

Conclusions

This study challenges the long‐held notion that a positive trial of PNS should be followed by a permanent implant in responders. Percutaneous PNS may serve as an effective neurostimulation therapy for patients with chronic low back pain and should be considered earlier in the treatment continuum as a motor‐sparing means of avoiding opioids, denervation, and permanently implanted neurostimulation systems.

Percutaneous 60-day peripheral nerve stimulation implant provides sustained relief of chronic pain following amputation: 12-month follow-up of a randomized, double-blind, placebo-controlled trial

INTRODUCTION

Peripheral nerve stimulation (PNS) has historically been used to treat chronic pain, but generally requires implantation of a permanent system for sustained relief. A recent study found that a 60-day PNS treatment decreases post-amputation pain, and the current work investigates longer-term outcomes out to 12 months in the same cohort.

METHODS

As previously reported, 28 traumatic lower extremity amputees with residual and/or phantom limb pain were randomized to receive 8 weeks of PNS (group 1) or 4 weeks of placebo followed by a crossover 4 weeks of PNS (group 2). Percutaneous leads were implanted under ultrasound guidance targeting the femoral and sciatic nerves. During follow-up, changes in average pain and pain interference were assessed using the Brief Pain Inventory-Short Form and comparing with baseline.

RESULTS

Significantly more participants in group 1 reported ≥50% reductions in average weekly pain at 12 months (67%, 6/9) compared with group 2 at the end of the placebo period (0%, 0/14, p=0.001). Similarly, 56% (5/9) of participants in group 1 reported ≥50% reductions in pain interference at 12 months, compared with 2/13 (15%, p=0.074) in group 2 at crossover. Reductions in depression were also statistically significantly greater at 12 months in group 1 compared with group 2 at crossover.

CONCLUSIONS

This work suggests that percutaneous PNS delivered over a 60-day period may provide significant carry-over effects including pain relief, potentially avoiding the need for a permanently implanted system while enabling improved function in patients with chronic pain.

TRIAL REGISTRATION NUMBER

NCT01996254.

Percutaneous Peripheral Nerve Stimulation for Pain Reduction and Improvements in Functional Outcomes in Chronic Low Back Pain

Chronic low back pain represents one of the most common sources of disability and a significant healthcare burden for the U.S. military. Present treatments for chronic back pain are often ineffective, poorly tolerated, invasive, destructive, and/or associated with complications and lead to the progression to invasive surgical procedures. There have been multiple calls for the development of a minimally invasive system that is effective without the risks or complications of existing surgical therapies, which could prevent the need for surgery and the recurrence of pain. The goal of this study was to evaluate a novel, minimally invasive approach using a percutaneous peripheral nerve stimulation (PNS) system designed to provide pain relief without surgery, to reduce complications, and provide a less-invasive treatment option. In nine subjects, percutaneous PNS improved participants' function, as evidenced by clinically and statistically significant reductions in pain, disability, and pain interference. Subjects also experienced reductions in opioid and non-opioid analgesic medication usage and reported improvements in quality of life with treatment. There were no serious or unanticipated adverse events. These results demonstrate the potential of percutaneous PNS as a non-surgical therapy to treat chronic back pain without opioids.

Percutaneous Peripheral Nerve Stimulation to Control Postoperative Pain, Decrease Opioid Use, and Accelerate Functional Recovery Following Orthopedic Trauma

Orthopedic trauma is a significant military problem, causing several of the most disabling conditions with high rates of separation from duty and erosion of military readiness. The objective of this report is to summarize the findings of case series of a non-opioid therapy-percutaneous peripheral nerve stimulation (PNS) - and describe its potential for postoperative analgesia, early opioid cessation, and improved function following orthopedic trauma. Percutaneous PNS has been evaluated for the treatment of multiple types of pain, including two case series on postoperative pain following total knee replacement (n = 10 and 8, respectively) and a case series on postamputation pain (n = 9). The orthopedic trauma induced during TKR is highly representative of multiple types of orthopedic trauma sustained by Service members and frequently produces intense, prolonged postoperative pain and extended opioid use following surgery. Collectively, the results of these three clinical studies demonstrated that percutaneous PNS can provide substantial pain relief, reduce opioid use, and improve function. These outcomes suggest that there is substantial potential for the use of percutaneous PNS following orthopedic trauma.

Peripheral nerve blocks for postoperative analgesia: From traditional unencapsulated local anesthetic to liposomes, cryoneurolysis and peripheral nerve stimulation

Peripheral nerve blocks (PNBs) using local anesthetics either via single injection or continuous perineural catheter have been the mainstay for regional anesthesia and are a vital component of postoperative multimodal opioid-sparing pain management. There are some limitations to PNBs, however, mainly its limited duration of action, but also risk of catheter-associated infection and dislodgements. Furthermore, local anesthetic-based blocks can induce sensory deficits and motor weakness, possibly increasing the risk of falling and/or decreasing the ability to participate in postoperative rehabilitation. In this review, we first discuss various local anesthetic-based PNB techniques for major surgery and then review newer modalities, including liposome bupivacaine, cryoanalgesia, and peripheral nerve stimulation; all of which may offer advantages over single and continuous local anesthetic-based PNBs.

Percutaneous peripheral nerve stimulation for acute postoperative pain

Peripheral nerve stimulation or peripheral neuromodulation is a modality utilized for decades to manage chronic pain. There have been recent studies published describing its use in managing acute surgical pain for orthopedic surgery. The postoperative acute pain associated with several types of surgeries often outlasts the analgesia duration provided by single and continuous peripheral nerve blocks. Ultrasound-guided percutaneous peripheral nerve stimulation has the potential to provide much longer analgesia for acute pain while avoiding some limitations associated with local anesthetic-based peripheral nerve blocks. We summarize the current devices used in published studies to demonstrate feasibility with a focus on acute pain control.

Percutaneous peripheral nerve stimulation for the treatment of chronic neuropathic postamputation pain: a multicenter, randomized, placebo-controlled trial

BACKGROUND AND OBJECTIVES

Chronic neuropathic pain is a common challenging condition following amputation. Recent research demonstrated the feasibility of percutaneously implanting fine-wire coiled peripheral nerve stimulation (PNS) leads in proximity to the sciatic and femoral nerves for postamputation pain. A multicenter, double-blinded, randomized, placebo-controlled study collected data on the safety and effectiveness of percutaneous PNS for chronic neuropathic pain following amputation.

METHODS

Twenty-eight lower extremity amputees with postamputation pain were enrolled. Subjects underwent ultrasound-guided implantation of percutaneous PNS leads and were randomized to receive PNS or placebo for 4 weeks. The placebo group then crossed over and all subjects received PNS for four additional weeks. The primary efficacy endpoint evaluated the proportion of subjects reporting ≥50% pain reduction during weeks 1-4.

RESULTS

A significantly greater proportion of subjects receiving PNS (n=7/12, 58%, p=0.037) demonstrated ≥50% reductions in average postamputation pain during weeks 1-4 compared with subjects receiving placebo (n=2/14, 14%). Two subjects were excluded from efficacy analysis due to eligibility changes. Significantly greater proportions of PNS subjects also reported ≥50% reductions in pain (n=8/12, 67%, p=0.014) and pain interference (n=8/10, 80%, p=0.003) after 8 weeks of therapy compared with subjects receiving placebo (pain: n=2/14, 14%; pain interference: n=2/13, 15%). Prospective follow-up is ongoing; four of five PNS subjects who have completed 12-month follow-up to date reported ≥50% pain relief.

CONCLUSIONS

This work demonstrates that percutaneous PNS therapy may provide enduring clinically significant pain relief and improve disability in patients with chronic neuropathic postamputation pain.

TRIAL REGISTRATION NUMBER

NCT01996254.

Ultrasound-guided percutaneous peripheral nerve stimulation: neuromodulation of the suprascapular nerve and brachial plexus for postoperative analgesia following ambulatory rotator cuff repair. A proof-of-concept study

BACKGROUND AND OBJECTIVES

Percutaneous peripheral nerve stimulation (PNS) is an analgesic modality involving the insertion of a lead through an introducing needle followed by the delivery of electric current. This modality has been reported to treat chronic pain as well as postoperative pain following knee and foot surgery. However, it remains unknown if this analgesic technique may be used in ambulatory patients following upper extremity surgery. The purpose of this proof-of-concept study was to investigate various lead implantation locations and evaluate the feasibility of using percutaneous brachial plexus PNS to treat surgical pain following ambulatory rotator cuff repair in the immediate postoperative period.

METHODS

Preoperatively, an electrical lead (SPR Therapeutics, Cleveland, Ohio) was percutaneously implanted to target the suprascapular nerve or brachial plexus roots or trunks using ultrasound guidance. Postoperatively, subjects received 5 min of either stimulation or sham in a randomized, double-masked fashion followed by a 5 min crossover period, and then continuous stimulation until lead removal postoperative days 14-28.

RESULTS

Leads (n=2) implanted at the suprascapular notch did not appear to provide analgesia, and subsequent leads (n=14) were inserted through the middle scalene muscle and placed to target the brachial plexus. Three subjects withdrew prior to data collection. Within the recovery room, stimulation did not decrease pain scores during the first 40 min of the remaining subjects with brachial plexus leads, regardless of which treatment subjects were randomized to initially. Seven of these 11 subjects required a single-injection interscalene nerve block for rescue analgesia prior to discharge. However, subsequent average resting and dynamic pain scores postoperative days 1-14 had a median of 1 or less on the Numeric Rating Scale, and opioid requirements averaged less than 1 tablet daily with active stimulation. Two leads dislodged during use and four fractured on withdrawal, but no infections, nerve injuries, or adverse sequelae were reported.

CONCLUSIONS

This proof-of-concept study demonstrates that ultrasound-guided percutaneous PNS of the brachial plexus is feasible for ambulatory shoulder surgery, and although analgesia immediately following surgery does not appear to be as potent as local anesthetic-based peripheral nerve blocks, the study suggests that this modality may provide analgesia and decrease opioid requirements in the days following rotator cuff repair. Therefore, it suggests that a subsequent, large, randomized clinical trial with an adequate control group is warranted to further investigate this therapy in the management of surgical pain in the immediate postoperative period. However, multiple technical issues remain to be resolved, such as the optimal lead location, insertion technique, and stimulating protocol, as well as preventing lead dislodgment and fracture.

TRIAL REGISTRATION NUMBER

NCT02898103.

Ultrasound-Guided Percutaneous Peripheral Nerve Stimulation: Neuromodulation of the Sciatic Nerve for Postoperative Analgesia Following Ambulatory Foot Surgery, a Proof-of-Concept Study

BACKGROUND AND OBJECTIVES

Percutaneous peripheral nerve stimulation (PNS) is an analgesic modality involving the insertion of a lead through an introducing needle followed by the delivery of electric current. This modality has been reported to treat chronic pain as well as postoperative pain the day following knee surgery. However, it remains unknown if this analgesic technique may be used in ambulatory subjects following foot procedures beginning within the recovery room immediately following surgery, and with only short series of patients reported to date, the only available data are derived from strictly observational studies. The purposes of this proof-of-concept study were to demonstrate the feasibility of using percutaneous sciatic nerve PNS to treat postoperative pain following ambulatory foot surgery in the immediate postoperative period and provide the first available data from a randomized controlled study design to provide evidence of analgesic effect.

METHODS

Preoperatively, an electrical lead (SPRINT; SPR Therapeutics, Inc, Cleveland, Ohio) was percutaneously inserted posterior to the sciatic nerve between the subgluteal region and bifurcation with ultrasound guidance. Following hallux valgus osteotomy, subjects received 5 minutes of either stimulation or sham in a randomized, double-masked fashion followed by a 5-minute crossover period and then continuous stimulation until lead removal on postoperative days 14 to 28.

RESULTS

During the initial 5-minute treatment period, subjects randomized to stimulation (n = 4) experienced a downward trajectory in their pain over the 5 minutes of treatment, whereas those receiving sham (n = 3) reported no such change until their subsequent 5-minute stimulation crossover. During the subsequent 30 minutes of stimulation, pain scores decreased to 52% of baseline (n = 7). Three subjects (43%) used a continuous popliteal nerve block for rescue analgesia during postoperative days 0 to 3. Overall, resting and dynamic pain scores averaged less than 1 on the numeric rating scale, and opioid use averaged less than 1 tablet daily with active stimulation. One lead dislodged, 2 fractured during use, and 1 fractured during intentional withdrawal.

CONCLUSIONS

This proof-of-concept study demonstrates that percutaneous sciatic nerve PNS is feasible for ambulatory foot surgery and suggests that this modality provides analgesia and decreases opioid requirements following hallux valgus procedures. However, lead dislodgement and fracture are concerns.

CLINICAL TRIAL REGISTRATION

This study was registered at Clinicaltrials.gov, identifier NCT02898103.

Novel Methodologies in Regional Anesthesia for Knee Arthroplasty

Maximizing analgesia is critical following joint arthroplasty because postoperative pain is a major barrier to adequate physical therapy. Continuous peripheral nerve blocks have been the mainstay for acute pain management in this population; however, this and similar techniques are limited by their duration of action. Cryoneurolysis and peripheral nerve stimulation are two methodologies used for decades to treat chronic pain. With the advent of portable ultrasound devices and percutaneous administration equipment, both procedures may now be suitable for treatment of acute pain. This article reviews these two modalities and their application to joint arthroplasty.

Ultrasound-Guided Percutaneous Peripheral Nerve Stimulation: Neuromodulation of the Femoral Nerve for Postoperative Analgesia Following Ambulatory Anterior Cruciate Ligament Reconstruction: A Proof of Concept Study

Objectives

The purpose of this prospective proof of concept study was to investigate the feasibility of using percutaneous peripheral nerve stimulation of the femoral nerve to treat pain in the immediate postoperative period following ambulatory anterior cruciate ligament reconstruction with a patellar autograft.

Materials and Methods

Preoperatively, an electrical lead (SPRINT, SPR Therapeutics, Inc., Cleveland, OH, USA) was percutaneously implanted with ultrasound guidance anterior to the femoral nerve caudad to the inguinal crease. Within the recovery room, subjects received 5 min of either stimulation or sham in a randomized, double‐masked fashion followed by a 5‐min crossover period, and then continuous active stimulation until lead removal postoperative Day 14–28. Statistics were not applied to the data due to the small sample size of this feasibility study.

Results

During the initial 5‐min treatment period, subjects randomized to stimulation (n = 5) experienced a slight downward trajectory (decrease of 7%) in their pain over the 5 min of treatment, while those receiving sham (n = 5) reported a slight upward trajectory (increase of 4%) until their subsequent 5‐min stimulation crossover, during which time they also experienced a slight downward trajectory (decrease of 11% from baseline). A majority of subjects (80%) used a continuous adductor canal nerve block for rescue analgesia (in addition to stimulation) during postoperative Days 1–3, after which the median resting and dynamic pain scores remained equal or less than 1.5 on the numeric rating scale, respectively, and the median daily opioid consumption was less than 1.0 tablet.

Conclusions

This proof of concept study demonstrates that percutaneous femoral nerve stimulation is feasible for ambulatory knee surgery; and suggests that this modality may be effective in providing analgesia and decreasing opioid requirements following anterior cruciate ligament reconstruction. clinicaltrials.gov: NCT02898103.

A Feasibility Study of Percutaneous Peripheral Nerve Stimulation for the Treatment of Postoperative Pain Following Total Knee Arthroplasty

INTRODUCTION

The objective of the present feasibility study was to investigate the use of a new treatment modality-percutaneous peripheral nerve stimulation (PNS)-in controlling the often severe and long-lasting pain following total knee arthroplasty (TKA).

METHODS

For patients undergoing a primary, unilateral TKA, both femoral and sciatic open-coil percutaneous leads (SPR Therapeutics, Cleveland, OH) were placed up to seven days prior to surgery using ultrasound guidance. The leads were connected to external stimulators and used both at home and in the hospital for up to six weeks total.

RESULTS

In six of seven subjects (86%), the average of daily pain scores across the first two weeks was <4 on the 0-10 Numeric Rating Scale for pain. A majority of subjects (four out of seven; 57%) had ceased opioid use within the first week (median time to opioid cessation for all subjects was six days). Gross sensory/motor function was maintained during stimulation, enabling stimulation during physical therapy and activities of daily living. At 12 weeks following surgery, six of seven subjects had improved by >10% on the Six-Minute Walk Test compared to preoperative levels, and WOMAC scores improved by an average of 85% compared to before surgery. No falls, motor block, or lead infections were reported.

CONCLUSIONS

This feasibility study suggests that for TKA, ultrasound-guided percutaneous PNS is feasible in the immediate perioperative period and may provide analgesia without the undesirable systemic effects of opioids or quadriceps weakness induced by local anesthetics-based peripheral nerve blocks.