Maximal Analgesic Effect Attained by the Use of Objective Neurophysiological Measurements With Closed-Loop Spinal Cord Stimulation.

OBJECTIVES: Spinal cord stimulation (SCS) has been challenged by the lack of neurophysiologic data to guide therapy optimization. Current SCS programming by trial-and-error results in suboptimal and variable therapeutic effects. A novel system with a physiologic closed-loop feedback mechanism using evoked-compound action potentials enables the optimization of physiologic neural dose by consistently and accurately activating spinal cord fibers. We aimed to identify neurophysiologic dose metrics and their ranges that resulted in clinically meaningful treatment responses. MATERIALS AND METHODS: Subjects from 3 clinical studies (n = 180) with baseline back and leg pain ≥60 mm visual analog scale and physical function in the severe to crippled category were included. Maximal analgesic effect (MAE) was operationally defined as the greatest percent reduction in pain intensity or as the greatest cumulative responder score (minimal clinically important differences [MCIDs]) obtained within the first 3 months of SCS implant. The physiologic metrics that produced the MAE were analyzed. RESULTS: We showed that a neural dose regimen with a high neural dose accuracy of 2.8µV and dose ratio of 1.4 resulted in a profound clinical benefit to chronic pain patients (MAE of 79 ± 1% for pain reduction and 12.5 ± 0.4 MCIDs). No differences were observed for MAE or neurophysiological dose metrics between the trial phase and post-implant MAE visit. CONCLUSION: For the first time, an evidence-based neural dose regimen is available for a neurostimulation intervention as a starting point to enable optimization of clinical benefit, monitoring of adherence, and management of the therapy.

The Neurostimulation Appropriateness Consensus Committee (NACC)®: Recommendations for the Mitigation of Complications of Neurostimulation.

INTRODUCTION: The International Neuromodulation Society convened a multispecialty group of physicians based on expertise and international representation to establish evidence-based guidance on the mitigation of neuromodulation complications. This Neurostimulation Appropriateness Consensus Committee (NACC)® project intends to update evidence-based guidance and offer expert opinion that will improve efficacy and safety. MATERIALS AND METHODS: Authors were chosen on the basis of their clinical expertise, familiarity with the peer-reviewed literature, research productivity, and contributions to the neuromodulation literature. Section leaders supervised literature searches of MEDLINE, BioMed Central, Current Contents Connect, Embase, International Pharmaceutical Abstracts, Web of Science, Google Scholar, and PubMed from 2017 (when NACC last published guidelines) to October 2023. Identified studies were graded using the United States Preventive Services Task Force criteria for evidence and certainty of net benefit. Recommendations are based on the strength of evidence or consensus when evidence was scant. RESULTS: The NACC examined the published literature and established evidence- and consensus-based recommendations to guide best practices. Additional guidance will occur as new evidence is developed in future iterations of this process. CONCLUSIONS: The NACC recommends best practices regarding the mitigation of complications associated with neurostimulation to improve safety and efficacy. The evidence- and consensus-based recommendations should be used as a guide to assist decision-making when clinically appropriate.

Pacific Spine and Pain Society (PSPS) Evidence Review of Surgical Treatments for Lumbar Degenerative Spinal Disease: A Narrative Review.

INTRODUCTION: Interventional treatment options for the lumbar degenerative spine have undergone a significant amount of innovation over the last decade. As new technologies emerge, along with the surgical specialty expansion, there is no manuscript that utilizes a review of surgical treatments with evidence rankings from multiple specialties, namely, the interventional pain and spine communities. Through the Pacific Spine and Pain Society (PSPS), the purpose of this manuscript is to provide a balanced evidence review of available surgical treatments. METHODS: The PSPS Research Committee created a working group that performed a comprehensive literature search on available surgical technologies for the treatment of the degenerative spine, utilizing the ranking assessment based on USPSTF (United States Preventative Services Taskforce) and NASS (North American Spine Society) criteria. RESULTS: The surgical treatments were separated based on disease process, including treatments for degenerative disc disease, spondylolisthesis, and spinal stenosis. CONCLUSIONS: There is emerging and significant evidence to support multiple approaches to treat the symptomatic lumbar degenerative spine. As new technologies become available, training, education, credentialing, and peer review are essential for optimizing patient safety and successful outcomes.

Prospective Six-Month Analysis of Multiarea Burst Spinal Cord Stimulation: Correlating Intraoperative Neuromonitoring With Postoperative Programming and Clinical Outcomes.

INTRODUCTION: DeRidder burst spinal cord stimulation (SCS) has shown superior relief from overall pain to traditional tonic neurostimulation therapies and a reduction in back and leg pain. However, nearly 80% of patients have two or more noncontiguous pain areas. This affects the ability to effectively program stimulation and deliver long-term efficacy of the therapy. Multiple DeRidder burst region programming is an option to treat multisite pain by interleaving stimulation at multiple areas along the spinal cord. Previous intraoperative neuromonitoring studies have shown that DeRidder burst stimulation provides broader myotomal coverage at a lower recruitment threshold. The goal of this study is to correlate intraoperative electromyogram (EMG) threshold and postsynaptic excitability with postoperative paresthesia thresholds and optimal burst stimulation programming. MATERIALS AND METHODS: Neuromonitoring was performed during permanent implant of SCS leads in ten patients diagnosed with chronic intractable back and/or leg pain. Each patient underwent the surgical placement of a Penta Paddle electrode through laminectomy at the T8-T11 spinal levels. Subdermal electrode needles were placed into lower extremity muscle groups, in addition to the rectus abdominis muscles, for EMG recording. Evoked responses were compared across multiple trials of burst stimulation in which the number of independent burst areas was varied. After intraoperative data collection, all patients were programmed with single- and multiarea DeRidder burst. Intermittent dosing was delivered at 30:90, 120:360, 120:720, and 120:1440 (seconds ON/OFF) intervals. Numerical rating scale (NRS) and Patient Global Impression of Change scores were evaluated at one, two, three, four, and six months after permanent implant. RESULTS: The thresholds for EMG recruitment after DeRidder burst differed across all patients owing to anatomical and physiological variations. After a 30-second dose of stimulation, the average decrease in thresholds was 1.25 mA for two-area and 0.9 mA for four-area DeRidder burst. Furthermore, a 30-second dose of multisite DeRidder burst produced a 0.25 mA reduction in the postoperative paresthesia thresholds. Across all patients, the baseline NRS score was 6.5 ± 0.5, and the NRS score after single or multiarea DeRidder burst therapy was 2.87 ± 1.50. Eight of ten patients reported a ≥50% decrease in their pain scores through the six-month follow-up visit. Pain outcomes using intermittent multiarea stimulation with longer OFF times (120:360, 120:720, 120:1440) were comparable to those using single-area DeRidder burst at 30:90 up to six months after implant with patient preference being two-area DeRidder burst. CONCLUSIONS: This study aims to evaluate the use of intraoperative neuromonitoring to optimize stimulation programming for multisite pain and correlate it with postoperative programming and efficacy. These results suggest that multisite programming can be used to further customize DeRidder burst stimulation to each individual patient and improve outcomes and quality of life for patients receiving SCS therapy for multisite pain.

Neurophysiological outcomes that sustained clinically significant improvements over 3 years of physiologic ECAP-controlled closed-loop spinal cord stimulation for the treatment of chronic pain.

INTRODUCTION: A novel, spinal cord stimulation (SCS) system with a physiologic closed-loop (CL) feedback mechanism controlled by evoked compound action potentials (ECAPs) enables the optimization of physiologic neural dose and the accuracy of the stimulation, not possible with any other commercially available SCS systems. The report of objective spinal cord measurements is essential to increase the transparency and reproducibility of SCS therapy. Here, we report a cohort of the EVOKE double-blind randomized controlled trial treated with CL-SCS for 36 months to evaluate the ECAP dose and accuracy that sustained the durability of clinical improvements. METHODS: 41 patients randomized to CL-SCS remained in their treatment allocation and were followed up through 36 months. Objective neurophysiological data, including measures of spinal cord activation, were analyzed. Pain relief was assessed by determining the proportion of patients with ≥50% and ≥80% reduction in overall back and leg pain. RESULTS: The performance of the feedback loop resulted in high-dose accuracy by keeping the elicited ECAP within 4µV of the target ECAP set on the system across all timepoints. Percent time stimulating above the ECAP threshold was >98%, and the ECAP dose was ≥19.3µV. Most patients obtained ≥50% reduction (83%) and ≥80% reduction (59%) in overall back and leg pain with a sustained response observed in the rates between 3-month and 36-month follow-up (p=0.083 and p=0.405, respectively). CONCLUSION: The results suggest that a physiological adherence to supra-ECAP threshold therapy that generates pain inhibition provided by ECAP-controlled CL-SCS leads to durable improvements in pain intensity with no evidence of loss of therapeutic effect through 36-month follow-up.

Early Functional Outcomes in Low Back Pain Subjects with a Novel Interspinous Fusion Device: REFINE Study 6-Month Results.

Purpose: Lumbar interlaminar decompression with interspinous fixation is an established safe and effective treatment for spinal stenosis. Early maintenance of improvements in pain intensity and function are critical for durability of symptom relief. The purpose of this study was to investigate the efficacy of minimally invasive treatments for low back pain during the early period after treatment and their utility in setting the course for longer term success. Patients and Methods: This study utilized patient evaluations at 3- and 6-months following treatment and is part of an actively enrolling, institutional review board (IRB) approved, single-arm, multicenter, prospective, open-label 12-month study. Clinical efficacy was assessed primarily using the change from baseline in Oswestry Disability Index (ODI), Visual Analog Scale (VAS) of the back and leg pain during walking and standing, and Zurich Claudication Questionnaire (ZCQ), and secondarily using the Patient Global Impression of Change (PGIC) and Patient-Reported Outcomes Measurement Information System (PROMIS) 29 v2.1. The safety endpoints were the adverse events and reoperations or revisions at the index level(s). Results: At 6-month post-op, 76%, 62%-64%, and 64% of patients demonstrated clinical meaningful, and statistically significant improvement in their pain as defined by ZCQ, VAS (back and leg), and ODI, respectively. In addition, 78% of patients noted improvement in PGIC. Two procedure-related adverse events were noted which fully resolved without surgical intervention. Conclusion: This 6-month interim analysis at 42% enrollment of patients was conducted to determine prolonged safety and efficacy of the interspinous fusion device. Our analysis showed a sustained improvement in clinical efficacy, and safety endpoints, when compared to the 3-months evaluations, across both interventional pain and neurosurgery specialties.

ECAP-controlled closed-loop versus open-loop SCS for the treatment of chronic pain: 36-month results of the EVOKE blinded randomized clinical trial.

INTRODUCTION: The evidence for spinal cord stimulation (SCS) has been criticized for the absence of blinded, parallel randomized controlled trials (RCTs) and limited evaluations of the long-term effects of SCS in RCTs. The aim of this study was to determine whether evoked compound action potential (ECAP)-controlled, closed-loop SCS (CL-SCS) is associated with better outcomes when compared with fixed-output, open-loop SCS (OL-SCS) 36 months following implant. METHODS: The EVOKE study was a multicenter, participant-blinded, investigator-blinded, and outcome assessor-blinded, randomized, controlled, parallel-arm clinical trial that compared ECAP-controlled CL-SCS with fixed-output OL-SCS. Participants with chronic, intractable back and leg pain refractory to conservative therapy were enrolled between January 2017 and February 2018, with follow-up through 36 months. The primary outcome was a reduction of at least 50% in overall back and leg pain. Holistic treatment response, a composite outcome including pain intensity, physical and emotional functioning, sleep, and health-related quality of life, and objective neural activation was also assessed. RESULTS: At 36 months, more CL-SCS than OL-SCS participants reported ≥50% reduction (CL-SCS=77.6%, OL-SCS=49.3%; difference: 28.4%, 95% CI 12.8% to 43.9%, p<0.001) and ≥80% reduction (CL-SCS=49.3%, OL-SCS=31.3%; difference: 17.9, 95% CI 1.6% to 34.2%, p=0.032) in overall back and leg pain intensity. Clinically meaningful improvements from baseline were observed at 36 months in both CL-SCS and OL-SCS groups in all other patient-reported outcomes with greater levels of improvement with CL-SCS. A greater proportion of patients with CL-SCS were holistic treatment responders at 36-month follow-up (44.8% vs 28.4%), with a greater cumulative responder score for CL-SCS patients. Greater neural activation and accuracy were observed with CL-SCS. There were no differences between CL-SCS and OL-SCS groups in adverse events. No explants due to loss of efficacy were observed in the CL-SCS group. CONCLUSION: This long-term evaluation with objective measurement of SCS therapy demonstrated that ECAP-controlled CL-SCS resulted in sustained, durable pain relief and superior holistic treatment response through 36 months. Greater neural activation and increased accuracy of therapy delivery were observed with ECAP-controlled CL-SCS than OL-SCS. TRIAL REGISTRATION NUMBER: NCT02924129.

Congress of Neurological Surgeons Systematic Review and Evidence-Based Guidelines for Occipital Nerve Stimulation for the Treatment of Patients With Medically Refractory Occipital Neuralgia: Update.

BACKGROUND: The Guidelines Task Force conducted a systematic review of the relevant literature on occipital nerve stimulation (ONS) for occipital neuralgia (ON) to update the original 2015 guidelines to ensure timeliness and accuracy for clinical practice. OBJECTIVE: To conduct a systematic review of the literature and update the evidence-based guidelines on ONS for ON. METHODS: The Guidelines Task Force conducted another systematic review of the relevant literature, using the same search terms and strategies used to search PubMed and Embase for relevant literature. The updated search included studies published between 1966 and January 2023. The same inclusion/exclusion criteria as the original guideline were also applied. Abstracts were reviewed, and relevant full text articles were retrieved and graded. Of 307 articles, 18 were retrieved for full-text review and analysis. Recommendations were updated according to new evidence yielded by this update . RESULTS: Nine studies were included in the original guideline, reporting the use of ONS as an effective treatment option for patients with medically refractory ON. An additional 6 studies were included in this update. All studies in the original guideline and this current update provide Class III evidence. CONCLUSION: Based on the availability of new literature, the current article is a minor update only that does not result in modification of the prior recommendations: Clinicians may use ONS as a treatment option for patients with medically refractory ON.

Cost-utility Analysis of Evoke Closed-loop Spinal Cord Stimulation for Chronic Back and Leg Pain.

OBJECTIVES: The effectiveness of Evoke closed-loop spinal cord stimulation (CL-SCS), a novel modality of neurostimulation, has been demonstrated in a randomized controlled trial (RCT). The objective of this cost-utility analysis was to develop a de novo economic model to estimate the cost-effectiveness of Evoke CL-SCS when compared with open-loop SCS (OL-SCS) for the management of chronic back and leg pain. METHODS: A decision tree followed by a Markov model was used to estimate the costs and outcomes of Evoke CL-SCS versus OL-SCS over a 15-year time horizon from the UK National Health Service perspective. A "high-responder" health state was included to reflect improved levels of SCS pain reduction recently reported. Results are expressed as incremental cost per quality-adjusted life year (QALY). Deterministic and probabilistic sensitivity analysis (PSA) was conducted to assess uncertainty in the model inputs. RESULTS: Evoke CL-SCS was estimated to be the dominant treatment strategy at ~5 years postimplant (ie, it generates more QALYs while cost saving compared with OL-SCS). Probabilistic sensitivity analysis showed that Evoke CL-SCS has a 92% likelihood of being cost-effective at a willingness to pay threshold of £20,000/QALY. Results were robust across a wide range of scenario and sensitivity analyses. DISCUSSION: The results indicate a strong economic case for the use of Evoke CL-SCS in the management of chronic back and leg pain with or without prior spinal surgery with dominance observed at ~5 years.

Anticipating and preventing complications in spinal cord stimulator implantation.

INTRODUCTION: Spinal cord stimulation is considered a minor elective procedure. The inherent goal is to provide safe, reliable, effective treatment with mitigation of known potential risk of adverse events. AREAS COVERED: This is a comprehensive literature review evaluating the most prevalent complications encountered with SCS implantation. EXPERT OPINION: SCS-related complications are uncommon. The authors offer clinical insight and feel the best practice is to have strategies employed to avoid complications, and we assist clinicians and surgeons in appropriately identifying and treating potential complications. There is a focus on appropriate patient selection, adherence to evidence-based guidelines and best practice recommendations.

Regional Coverage Differences With Single- and Multi-Area Burst Spinal Cord Stimulation for Treatment of Chronic Pain.

INTRODUCTION: Burst spinal cord stimulation (SCS) has shown superior relief from overall pain and a reduction in back and leg pain compared with traditional tonic neurostimulation therapies. However, nearly 80% of patients have two or more noncontiguous pain areas. This can provide challenges in effectively programming stimulation and long-term therapy efficacy. Multiarea DeRidder Burst programming is a new option to treat multisite pain by delivering stimulation to multiple areas along the spinal cord. This study aimed to identify the effect of intraburst frequency, multiarea stimulation, and location of DeRidder Burst on the evoked electromyography (EMG) responses. MATERIALS AND METHODS: Neuromonitoring was performed during permanent implant of SCS leads in nine patients diagnosed with chronic intractable back and/or leg pain. Each patient underwent the surgical placement of a Penta Paddle electrode via laminectomy at the T8-T10 spinal levels. Subdermal electrode needles were placed into lower extremity muscle groups, in addition to the rectus abdominis muscles, for EMG recording. Evoked responses were compared across multiple trials of burst stimulation in which the number of independent burst areas were varied. RESULTS: The thresholds for EMG recruitment with DeRidder Burst differed across patients owing to anatomic and physiological variations. The average threshold to evoke a bilateral EMG response using single site DeRidder Burst was 3.2 mA. Multisite DeRidder Burst stimulation on up to four stimulation programs evoked a bilateral EMG response at a threshold of 2.5 mA (∼23% lower threshold). DeRidder Burst stimulation across four electrode pairs resulted in more proximal recruitment (vastus medialis and tibialis anterior) than did stimulation across two pairs. It also resulted in more focal coverage of areas across multiple sites. CONCLUSIONS: Across all patients, multisite DeRidder Burst provided broader myotomal coverage than did traditional DeRidder Burst. Multisite DeRidder Burst stimulation provided focal recruitment and differential control of noncontiguous distal myotomes. Energy requirements were also lower when multisite DeRidder Burst was used.

Clinical Longevity of 106,462 Rechargeable and Primary Cell Spinal Cord Stimulators: Real World Study in the Medicare Population.

INTRODUCTION: Spinal cord stimulators (SCS) are available with either primary cell (PC) or rechargeable cell (RC) batteries. Although RC systems are proposed to have a battery longevity upward of nine years, in comparison with four years for PC systems, there are few studies of longevity of SCS in the real world. MATERIALS AND METHODS: This was an observational, nonrandomized, retrospective study of Medicare beneficiaries who received neurostimulator implants in the outpatient hospital. This study used Medicare fee-for-service claims data from 2013 to 2020. The clinical longevity of the implantable pulse generator (IPG), defined as the duration from implant until removal for any reason, was compared between PC and RC devices. Life distribution analysis was used to approximate device lifespan. The secondary analysis separated removals into explant or replacements. The statistics were adjusted for relevant clinical covariates. RESULTS: A total of 25,856 PC and 79,606 RC systems were included in the study. At seven years after implant, 53.8% of PC IPGs and 55.0% of RC IPGs remained in use. The life distribution modeling analysis projected a median lifespan of 8.2 years for PC and 9.0 years for RC devices. The rate of explant was lower for PC devices (19.2%) than for RC devices (22.0%, hazard ratio (HR) = 0.96, p = 0.082), whereas the rate of replacements was higher for PC devices (33.7%) than for RC devices (29.5%, HR = 1.31, p < 0.001). An analysis of the battery type used in device replacements showed an increasing adoption of PC devices over time. CONCLUSIONS: This large, retrospective, real-world analysis of Medicare claims data demonstrated that the clinical longevity of neurostimulator devices is similar for PC and RC batteries. In the past, clinicians may have defaulted to RC devices based on the assumption that they provided extended battery life. Considering this longevity data, clinicians should now consider the choice between PC and RC devices based on other individual factors pertinent to the patient experience and not on purported longevity claims.

A Prospective, Observational, Open-Label, Non-Randomized, Multicenter Study Measuring Functional Outcomes in a Novel Interspinous Fusion Device in Subjects with Low Back Pain: REFINE Study.

INTRODUCTION: Lumbar degenerative disease and the accompanying pain and dysfunction affect a significant number of patients in the USA and around the world. As surgery and innovation are moving towards minimally invasive treatments, this study looks to explore interspinous fixation as a standalone posterior approach to treat lumbar degenerative disc disease in the presence of neurogenic claudication and spinal stenosis. METHODS: This study was approved by an institutional review board (IRB) and is actively enrolling in a single-arm, multicenter, prospective, open-label fashion. Patients are followed with reporting at 3 months, and 12 months for primary endpoint analysis of efficacy and safety based on improved composite endpoints relative to baseline, with success defined as greater than 20 mm back pain reduction in Visual Analog Scale 100 mm (VAS) while standing or walking, greater than 20 mm leg pain reduction in VAS while standing or walking, Zurich Claudication Questionnaire (ZCQ) improvement of 0.5 or greater in two or three domains, Oswestry Disability Index (ODI) improvement of a least 10 points and no reoperations or revisions at the index level(s). Secondary endpoints included a multidimensional assessment in the Patient-Reported Outcomes Measurement Information System (PROMIS) 29 v2.1 and Patient Global Impression of Change (PGIC). RESULTS: In this interim 3-month analysis, 82% of patients reported they were improved from the procedure, while 65% of patients demonstrated clinical meaningful improvement in their pain and function, as defined by the VAS, ODI, and ZCQ. There was only one adverse event and no complications were identified at last clinic research follow-up visit. CONCLUSIONS: This interim analysis of the first 20% of the enrolled patients out to 3 months was to determine safety of the procedure and report on adverse events, acknowledging the heterogeneity of surgical specialty. Further follow-up and greater numbers are needed as the study is ongoing. TRIAL REGISTRATION: ClinicalTrials.gov identifier, NCT05504499.

Transfixation of the Sacroiliac Joint: Biomechanical Stability of a Dual-Implant Minimally Invasive Procedure.

BACKGROUND: Despite minimally invasive techniques for sacroiliac joint fixation, clinical challenges remain. The investigators hypothesized the studied technique will transfix the sacroiliac joint to a level comparable to the intact sacroiliac joint. OBJECTIVES: The study objective was to determine the dynamic stability of a square inter-joint implant using a triangular notch in opposing bone segments spanning the joint space. STUDY DESIGN: Stability was assessed by measuring micromotion using contralaterally placed transducers spanning the sacroiliac joint of a specimen during cyclic loading. SETTING: A porcine in-vitro model was equipped with micromotion transducers on the intact and surgically implanted sacroiliac joint. Cyclic loading was applied on the L4 vertebra and the recorded micromotion data at each sacroiliac joint was analyzed. METHODS: Porcine specimens from L3 to the sacrum including the pelvic ring were used to biomechanically evaluate the implantation technique. A novel technique consisting of a square inter-joint implant was placed so as to create a triangular stabilization notch within adjacent boney components of the sacroiliac joint. Displacement transducers were placed across implanted and contralateral porcine sacroiliac joint. Specimens were subjected to compressive loading between -10N and -100N followed by bending/rotation between 0.4Nm and 4.0Nm. Tests were conducted at 0.5Hz for 200 cycles. For each loading mode, transducer deflections (or rotations) were averaged at five-cycle intervals. Student's t-tests were used to compare fitted parameters between implanted and intact sacroiliac joint. RESULTS: In compression, implanted SIJ displayed reduced deflection compared to intact sacroiliac joint (P < 0.0001). In bending/rotation, initial rotation for the intact sacroiliac joint was increased compared to implanted sacroiliac joint (P < 0.0001). The computed Half-Life parameter represents the number of cycles at which the initial rotation decreases by 50% and was found to be statistically reduced for implanted sacroiliac joint as compared to intact sacroiliac joint. LIMITATIONS: The use of porcine specimens resulted in uniform and good quality bone purchase. Further study may be required to evaluate the technique in older patients where bone quality is reduced. CONCLUSIONS: Compared to the intact sacroiliac joint, the implant and procedure in this study demonstrated decreased motion under cyclic compression. Under rotation, the implanted sacroiliac joint displayed increased initial stability that subsequently normalized to intact sacroiliac joint values.

A Prospective Multicenter Case Series Utilizing Intraoperative Neuromonitoring With Evoked Compound Action Potentials to Confirm Spinal Cord Stimulation Lead Placement.

OBJECTIVES: The use of intraoperative neuromonitoring (IONM) has been adapted to address issues of safety and proper lead positioning in spinal cord stimulation. This multicenter case series seeks to incorporate the use of evoked compound action potential (ECAP) and late response (LR) recording and compare it with the results obtained with IONM, specifically electromyography (EMG), for the confirmation of lead placement. This study aimed to establish a correlation between ECAPs, LR, and EMG and publish human recordings of ECAPs and LR during their use with IONM. MATERIALS AND METHODS: Standard neuromonitoring protocols were followed at two institutions, with two separate physicians and with seven patients, as part of a larger ongoing study registered with ClinicalTrials.gov (NCT02924129). Stimulation and recording were performed, top and bottom, on each percutaneous lead. Stimulation amplitude was increased considering ECAP, LR, and EMG thresholds. RESULTS: ECAPs, LRs, and EMG signals were observed in all patients. The onset of LR signals on implanted electrodes and EMG signal on subdermal electrodes was well correlated (rs = 0.94, p < 0.001), with a median LR:EMG value of 1.06 (N = 21). LR:EMG for the top (mean = 0.97, N = 8) vs bottom (mean = 1.15, N = 13) of the lead was compared using a paired Wilcoxon signed rank test and an independent samples Mann-Whitney test, revealing a marginally significant and a statistically significant difference (p = 0.078 and p = 0.015, respectively). Mean LR:ECAP was >2 in all locations and approximately 3.5 overall. LR:ECAP between the top and bottom of the lead was significantly different (Wilcoxon test, p < 0.01, N = 12). CONCLUSIONS: LR correlated with EMG; leads with bilateral (not necessarily symmetric) EMG activity showed LR:ECAP > 1.5. An LR:ECAP of <1, with LR/EMG generated before the ECAP, indicated that the lead is too lateral. The use of ECAP and LR has the potential of maintaining objective lead placement, without the need for needle placement with IONM.

Durability of Clinical and Quality-of-Life Outcomes of Closed-Loop Spinal Cord Stimulation for Chronic Back and Leg Pain: A Secondary Analysis of the Evoke Randomized Clinical Trial.

Importance: Chronic pain is debilitating and profoundly affects health-related quality of life. Spinal cord stimulation (SCS) is a well-established therapy for chronic pain; however, SCS has been limited by the inability to directly measure the elicited neural response, precluding confirmation of neural activation and continuous therapy. A novel SCS system measures the evoked compound action potentials (ECAPs) to produce a real-time physiological closed-loop control system. Objective: To determine whether ECAP-controlled, closed-loop SCS is associated with better outcomes compared with fixed-output, open-loop SCS at 24 months following implant. Design, Setting, and Participants: The Evoke study was a double-blind, randomized, controlled, parallel arm clinical trial with 36 months of follow-up. Participants were enrolled from February 2017 to 2018, and the study was conducted at 13 US investigation sites. SCS candidates with chronic, intractable back and leg pain refractory to conservative therapy, who consented, were screened. Key eligibility criteria included overall, back, and leg pain visual analog scale score of 60 mm or more; Oswestry Disability Index score of 41 to 80; stable pain medications; and no previous SCS. Analysis took place from October 2020 to April 2021. Interventions: ECAP-controlled, closed-loop SCS was compared with fixed-output, open-loop SCS. Main Outcomes and Measures: Reported here are the 24-month outcomes of the trial, which include all randomized patients in the primary and safety analyses. The primary outcome was a reduction of 50% or more in overall back and leg pain assessed at 3 and 12 months (previously published). Results: Of 134 randomized patients, 65 (48.5%) were female and the mean (SD) age was 55.2 (10.6) years. At 24 months, significantly more closed-loop than open-loop patients were responders (≥50% reduction) in overall pain (53 of 67 [79.1%] in the closed-loop group; 36 of 67 [53.7%] in the open-loop group; difference, 25.4% [95% CI, 10.0%-40.8%]; P = .001). There was no difference in safety profiles between groups (difference in rate of study-related adverse events: 6.0 [95% CI, -7.8 to 19.7]). Improvements were also observed in health-related quality of life, physical and emotional functioning, and sleep, in parallel with opioid reduction or elimination. Objective neurophysiological measurements substantiated the clinical outcomes and provided evidence of activation of inhibitory pain mechanisms. Conclusions and Relevance: ECAP-controlled, closed-loop SCS, which elicited a more consistent neural response, was associated with sustained superior pain relief at 24 months, consistent with the 3- and 12-month outcomes.

Passive Recharge Burst Spinal Cord Stimulation Provides Sustainable Improvements in Pain and Psychosocial Function: 2-year Results From the TRIUMPH Study.

STUDY DESIGN: Prospective, international, multicenter, single-arm, post-market study. OBJECTIVE: The aim of this study was to assess long-term safety and effectiveness of spinal cord stimulation using a passive recharge burst stimulation design for chronic intractable pain in the trunk and/or limbs. Herein we present 24-month outcomes from the TRIUMPH study (NCT03082261). SUMMARY OF BACKGROUND DATA: Passive recharge burst spinal cord stimulation (B-SCS) uniquely mimics neuronal burst firing patterns in the nervous system and has been shown to modulate the affective and attentional components of pain processing. METHODS: After a successful trial period, subjects received a permanent SCS implant and returned for follow-up at 6, 12, 18, and 24 months. RESULTS: Significant improvements in physical, mental, and emotional functioning observed after 6 months of treatment were maintained at 2 years. Pain catastrophizing scale (PCS) scores dropped below the population norm. Health-related quality of life on EQ-5D improved across all domains and the mean index score was within one standard deviation of norm. Pain reduction (on NRS) was statistically significant (P < 0.001) at all timepoints. Patient reported pain relief, a stated percentage of improvement in pain, was consistent at all timepoints at 60%. Patients reported significant improvements across all measures including activity levels and impact of pain on daily life. At 24 months, 84% of subjects were satisfied and 90% would recommend the procedure. Subjects decreased their chronic pain medication intake for all categories; 38% reduced psychotropic and muscle relaxants, 46% reduced analgesic, anti-convulsant and NSAIDs, and 48% reduced opioid medication. Adverse events occurred at low rates without unanticipated events. CONCLUSION: Early positive results with B-SCS were maintained long term. Evidence across multiple assessment tools show that B-SCS can alleviate pain intensity, psychological distress, and improve physical function and health-related quality of life.Level of Evidence: 3.

Burst spinal cord stimulation can attenuate pain and its affective components in chronic pain patients with high psychological distress: results from the prospective, international TRIUMPH study.

BACKGROUND CONTEXT: Psychological characteristics such as catastrophizing and depression have been shown to negatively impact outcome prognosis after spinal interventions. PURPOSE: To evaluate whether high psychological distress, defined as clinically elevated levels of catastrophizing and depression, is associated with poorer outcomes after spinal cord stimulation utilizing a passive recharge burst stimulation design. This proprietary waveform may uniquely attenuate the emotional aspects of chronic pain given its affects on the medial pain pathway projecting to the dorsal anterior cingulate cortex and anterior insula. STUDY DESIGN/SETTINGS: Data were extracted from the prospective, multi-center, single-arm, international TRIUMPH study. The purpose of TRIUMPH was to assess long-term (2 years) safety and effectiveness of spinal cord stimulation for chronic pain in the trunk and/or limbs using a passive recharge enabled burst spinal cord stimulation (B-SCS) system. PATIENT SAMPLE: Two subsets of study patients were identified; those with (n=31) and those without (n=54) high psychological distress. OUTCOME MEASURES: Psychological and functional outcomes as well as pain intensity and impact of pain on life were administered at baseline and all follow intervals. Additionally, patient satisfaction and patient global impression of change were assessed at all follow-up intervals. METHODS: Psychological distress (PD) was defined as a baseline score of ≥ 30 on the Pain Catastrophizing Scale (PCS) and ≥ 10 on the Patient Health Questionnaire Depression scale (PHQ-9). Nondistressed (ND) patients had scores below these thresholds on both scales. All patients were implanted with a B-SCS system and completed data collection for the 24-month follow-up visit. This study was funded by Abbott. JMH is a consultant for Abbott and has received <$20,000 in lifetime consulting fees from Abbott. SMF is a consultant for Abbott and has received >$50,000 in lifetime consulting fees from Abbott. BB is an Abbott employee. RAC is a former Abbott employee. JJY is a consultant for Abbott and has received <$2,500 in lifetime consulting fees from Abbott. RESULTS: Of the 128 participants with 24-month data, 31 (24%) and 54 (35%) met the criteria for PD and ND, respectively. Baseline measures indicated a more severe chronic pain profile and worse quality of life in the PD group. Two years after implant, 71% were no longer clinically catastrophizing and 58% were no longer clinically depressed. Notably, more than half of the PD patients on antidepressants discontinued or decreased their medication. Health-related quality of life was 82% higher in the PD group at 24 months, reaching levels similar to the ND group. Psychological distress did not impact outcomes after SCS therapy; composite multi-responder rates were similar in the 2 groups throughout the follow-up period. Patient reported pain relief (58% PD vs. 61% ND) was equivalent in each group. In both groups, 81% were satisfied or very satisfied with the pain relief provided. CONCLUSIONS: Our results showed that B-SCS appears to be as effective in a chronic pain population with high psychological distress as in those without distress. This may be due to the unique mechanism of action with the stimulation design involving the emotional-affective medial pain pathway in the brain.

Improving the Management of Patients with Osteoporosis Undergoing Spinal Fusion: The Need for a Bone Mineral Density-Matched Interbody Cage.

With an increasingly aging population globally, a confluence has emerged between the rising prevalence of degenerative spinal disease and osteoporosis. Fusion of the anterior spinal column remains the mainstay surgical intervention for many spinal degenerative disorders. However, decreased vertebral bone mineral density (BMD), quantitatively measured by dual x-ray absorptiometry (DXA), complicates treatment with surgical interbody fusion as weak underlying bone stock increases the risk of post-operative implant-related adverse events, including cage subsidence. There is a necessity for developing cages with advanced structural designs that incorporate bioengineering and architectural principles to tailor the interbody fusion device directly to the patient's BMD status. Specifically, lattice-designed cages that mimic the web-like structure of native cancellous bone have demonstrated excellent resistance to post-operative subsidence. This article provides an introductory profile of a spinal interbody implant designed intentionally to simulate the lattice structure of human cancellous bone, with a similar modulus of elasticity, and specialized to match a patient's bone status across the BMD continuum. The implant incorporates an open pore design where the degree of pore compactness directly corresponds to the patient's DXA-defined BMD status, including patients with osteoporosis.