Clinical study of a micro-implantable pulse generator for the treatment of peripheral neuropathic pain: 3-month and 6-month results from the COMFORT-randomised controlled trial.

BACKGROUND: We report the results from the first large, postmarket, multicentre, randomised controlled trial (RCT) evaluating peripheral nerve stimulation (PNS) for the treatment of chronic peripheral pain with a micro-implantable pulse generator (micro-IPG). METHODS: Subjects meeting eligibility were randomised (2:1) to either the active arm receiving PNS and conventional medical management (CMM) or the control arm receiving CMM alone. Treatments were limited to the following areas: lower back, shoulder, knee and foot/ankle. RESULTS: At 6 months, the active arm achieved an 88% responder rate with a 70% average reduction in pain. At the 3-month primary endpoint, the active arm achieved an 84% responder rate with an average pain reduction of 67% compared with the control arm, which achieved a 3% responder rate with an average pain reduction of 6%. Both responder rate and pain reduction in the active arm were significantly better than in the control arm (p<0.001). A majority of patient-reported outcomes also reached statistical significance. There have been no reports of pocket pain and no serious adverse device effects. 81% of subjects found the external wearable component of the PNS system to be comfortable. CONCLUSIONS: This study successfully reached its primary endpoint-the active arm achieved a statistically significant superior responder rate as compared with the control arm at 3 months. These RCT results demonstrated that PNS, with this micro-IPG, is efficacious and safe. This ongoing study will follow subjects for 3 years, the results of which will be reported as they become available.

Defining the Boundaries of Patient Perception in Spinal Cord Stimulation Programming.

OBJECTIVES: Recent developments in spinal cord stimulation (SCS) programming have initiated new modalities of imperceptible stimulation. However, the boundaries of sensory perception are not well defined. The BEnchtop NEuromodulation Following endIng of Trial study aimed to create a map of perceptual threshold responses across a broad range of SCS parameters and programming to inform subperception therapy design. MATERIALS AND METHODS: This multicenter study was conducted at seven US sites. A total of 43 patients with low back and/or leg pain who completed a percutaneous commercial SCS trial were enrolled. Test stimulation was delivered through trial leads for approximately 90 minutes before removal. SCS parameters, including amplitude, frequency, pulse width (PW), electrode configuration, cycling, and multifrequency stimulation were varied during testing. Paresthesia threshold (PT), comfort level (CL), perceptual coverage area, and paresthesia quality (through patient selection of keywords) were collected. Differences were evaluated with analysis of variance followed by post hoc multiple comparisons using t-tests with Bonferroni correction. RESULTS: PT was primarily determined by PW and was insensitive to frequency for constant frequency stimulation (range: 20 Hz-10 kHz; F(1284) = 69.58, p < 0.0001). For all tests, CL was approximately 25% higher than PT. The dominant variable that influenced paresthesia quality was frequency. Sensations described as comfortable and tingling were most common for frequencies between 60 Hz and 2.4 kHz; unpleasant sensations were generally more common outside this range. Increasing distance between active electrodes from 7 mm to 14 mm, or cycling the SCS waveform at 1 Hz, decreased PT (p < 0.0001). Finally, PT for a low-frequency stimulus (ie, 60 Hz) was unaffected by mixing with a sub-PT high-frequency stimulus. CONCLUSIONS: In contrast to previous work investigating narrower ranges, PW primarily influenced PT, independently of frequency. Paresthesia quality was primarily influenced by pulse frequency. These findings advance our understanding of SCS therapy and may be used to improve future novel neuromodulation paradigms.

Multiphase Spinal Cord Stimulation in Participants With Chronic Back or Leg Pain: Results of the BENEFIT-02 Randomized Clinical Trial.

OBJECTIVE: This study aimed to assess the safety and effectiveness of a new charge-distributed multiphase stimulation paradigm during an extended spinal cord stimulation (SCS) trial. MATERIALS AND METHODS: This prospective, multicenter, randomized, single-blind, feasibility study included participants with chronic low back and/or leg pain and baseline numerical rating scale (NRS) for overall pain intensity ≥6. After a successful commercial SCS trial, participants were randomized to multiphase SCS therapy A (approximately 600-1500 Hz) or B (approximately 300-600 Hz), delivered via an investigational external pulse generator and existing leads during an 11-to-12-day testing period. Primary end points were mean NRS change from baseline to final in-office visit for each multiphase therapy and between therapies. Secondary end points included mean NRS change from end of commercial trial to final study visit and incidence of device-related adverse events (AEs). Additional measures included patient-reported outcomes collected at home through electronic watches and written diaries. Power usage was compared between multiphase and commercial therapies. RESULTS: A total of 122 participants initiated a commercial trial; 77 were randomized to a multiphase arm, and 65 completed the study. Reductions in mean NRS scores from baseline to final study visit were significant for multiphase therapy A and B (-4.3 and -4.7, respectively; both p < 0.0001). There was no statistically significant difference in mean NRS reduction or percent pain relief between multiphase therapies. In an additional analysis, 63.9% of participants reported greater pain relief with multiphase than with commercial SCS therapy in the at-home setting. On average, multiphase required less power than did commercial devices. One non-serious device-related AE was reported, and no infections occurred during the extended trial. CONCLUSIONS: Multiphase SCS effectively reduced pain in participants with chronic low back and/or leg pain during a trial, with no unanticipated device-related AEs reported. Future studies should evaluate long-term effectiveness of multiphase stimulation. CLINICAL TRIAL REGISTRATION: The Clinicaltrials.gov registration number for the study is NCT03594266.

Systemic Opioid Prescribing Patterns and Total Cost of Care in Patients Initiating Spinal Cord Stimulation Therapy: A Retrospective Analysis.

BACKGROUND: Few studies have evaluated patterns of systemic opioid use among patients initiating spinal cord stimulation therapy for chronic pain. This study evaluated systemic opioid discontinuation and/or dose reduction and total health care cost after the start of spinal cord stimulation therapy. METHODS: Using a commercial insurance claims database (2008-2017), we analyzed opioid utilization patterns in patients initiating spinal cord stimulation therapy over a 1-year baseline and 2-year follow-up. The primary end point was defined as either discontinuation (≥365-day gap between prescription fills or total days' supply in follow-up ≤30 days) or ≥50% reduction in average daily morphine milligram equivalent dose. "Costs" were defined as total payer plus patient out-of-pocket payments. RESULTS: A total of 5,878 patients met the selection criteria. Of these, 152 (2.6%) showed no opioid prescription data at any point in the study period. Among patients with one or more prescriptions, 42.0% met the primary end point (22.0% discontinued, and 20.0% reduced their dose by 50% or more). Mean total adjusted costs were significantly reduced in years 1 and 2 of follow-up relative to baseline (excluding device insertion costs). The average time to breakeven when accounting for device trial and permanent insertion cost was 3.1 years among those who met the composite end point and 4.2 years among those who did not. CONCLUSIONS: This analysis shows that among patients who continued spinal cord stimulation therapy for at least 2 years, a significant proportion were able to reduce and/or discontinue systemic opioid use, with costs after the start of therapy significantly reduced relative to baseline.

Long-Term Efficacy of a Novel Spinal Cord Stimulation Clinical Workflow Using Kilohertz Stimulation: Twelve-Month Results From the Vectors Study.

BACKGROUND AND OBJECTIVES: Multiple variables play a role in spinal cord stimulation (SCS) treatment outcomes, including patient anatomy, pain pattern, lead location, stimulation parameters, and so on. A wide range of stimulation parameters are considered safe and on-label, and as a result a growing number of new frequencies and frequency-combinations are being incorporated into standard practice. A standardized approach to therapy delivery may provide more consistent outcomes for more patients. The Vectors study evaluated whether there is significant sustained improvement in pain and functional outcomes when therapy is delivered using a standardized approach. MATERIALS AND METHODS: Vectors, a post-market, single-arm study evaluated the safety and efficacy of SCS with an implantable neurostimulator starting with 1 kHz stimulation, targeting the T9-T10 disc space following paresthesia mapping. Subjects with chronic intractable low back and leg pain (visual analogue scale [VAS] ≥ 50 mm) were enrolled. The primary endpoint was change in overall pain (VAS) at the three-month visit compared to baseline. Subjects were followed through 12 months. Secondary endpoints included changes in low back and leg pain, quality of life (European Quality of Life - Five Dimensions, EQ-5D-5L), disability (Oswestry Disability Index, ODI), individual subject goals, and subject satisfaction. RESULTS: There was a significant reduction in overall pain (VAS; 45.4 mm) through the three-month visit, which was sustained through 12 months. At 12 months, 79% of subjects had ≥50% improvement in at least one pain domain (overall, lowback or leg) with 85% of subjects reporting therapy satisfaction. There was a decrease in disability and an improvement in quality of life with 70% of subjects achieving a personal activity goal by the three-month visit. CONCLUSIONS: Long-term pain relief and improvement in quality of life and function were achieved when following a standardized workflow. CLINICAL TRIAL REGISTRATION: The Clinicaltrials.gov registration number for the study is NCT03345472.

Using Lower Amplitudes to Maintain Effective High Dose Spinal Cord Stimulation Therapy (SCS Dosing Pilot Study).

BACKGROUND: Spinal cord stimulation is an effective therapy for chronic back and/or leg pain. Amplitude dose-response studies are lacking; therefore, little guidance exists regarding the minimum amplitude requirements with specific high dose parameters. This study characterized the minimum amplitude level that maintained SCS therapy satisfaction and pain relief when stimulating at 1000 Hz and 90 µsec. MATERIALS AND METHODS: Qualified patients had back and leg pain, an implanted neurostimulator programmed to 1000 Hz and 90 µsec, and were very or somewhat satisfied with the therapy, and an average overall VAS pain score ≤ 4 from a daily diary. Patients received four blinded amplitudes (titrated from 80%, 60%, 40%, and 20% of baseline perception threshold), approximately two weeks each, with 1000 Hz and 90 µsec and position-adaptive stimulation enabled. Patients' satisfaction and overall VAS pain scores were collected for each period. All patients continued through the study, even after reporting lack of therapy satisfaction or pain relief. RESULTS: The minimum amplitude, which maintained therapy satisfaction, was 80% of perception threshold for two patients, 60% for one patient, and 20% for 21 patients. Additionally, six patients lost satisfaction changing from their baseline amplitude to 80% perception threshold. The minimum amplitude level, which maintained overall pain relief, was 80% perception threshold for three patients, 60% perception threshold for one patient, 40% perception threshold for two patients, and 20% perception threshold for 19 patients. Five patients required the setting they were programmed to during the baseline period. CONCLUSION: The qualified study patients defined an implanted population reporting good pain relief and satisfaction using HD SCS therapy at baseline. The majority of these patients were able to maintain therapy satisfaction and pain relief (70% and 63.3%, respectively) with 20% perception threshold amplitude. Amplitudes below perception threshold could potentially maintain effective SCS therapy with HD stimulation in a subset of patients.

Options: A Prospective, Open-Label Study of High-Dose Spinal Cord Stimulation in Patients with Chronic Back and Leg Pain.

BACKGROUND: Therapeutic approaches to spinal cord stimulation (SCS) continue to evolve and improve patient outcomes in patients receiving SCS therapy secondary to failed back surgery syndrome. OBJECTIVES: The aim of this study was to evaluate pain relief and other patient outcomes of SCS using selected high-dose programming parameters. STUDY DESIGN: This was a prospective cohort study. SETTING: This study took place at 11 centers in North America. METHODS: Forty-four SCS-naive patients underwent trialing, starting with 1,000 Hz frequency, 90 µs pulse width followed by 300 Hz frequency, 800 µs pulse width, if pain relief was inadequate. Patients with 50% or greater pain relief were eligible for permanent implantation. Patient's pain rating, global impression of change, health-related quality of life, functional disability, satisfaction/recommendation, stimulation perception, device programming, and adverse events were assessed at 3 months postimplant. RESULTS: There were significant improvements from baseline in mean Numeric Rating Scale (NRS-11) pain scores for overall pain (7.5 to 3.8; P < 0.01), back pain (7.2 to 3.4; P < 0.01), leg pain (7.2 to 3.1; P < 0.01), Oswestry Disability Index (ODI) score (51.5 to 32.1; P < 0.01), and European Quality of Life-Five Dimensions, version 5L score (EQ-5D-5L) (0.58 to 0.74; P < 0.01). Twenty-eight of 32 patients (88%) had significant, favorable improvement in Patient Global Impression of Change (PGIC). Eighty-four percent of patients were "satisfied," and 78.1% would "definitely" recommend SCS. Eighteen patients (56%) used 1,000 Hz frequency and 90 µs pulse width exclusively; these patients experienced mean NRS-11 overall pain score improvement of 4.7 points. Device-, therapy-, or procedure-related adverse events were experienced in 19 patients (40%, 19 of 48), and all events resolved without reoperation and were similar to those observed with traditional SCS systems. LIMITATIONS: There was no active or sham comparator group, and therefore the reported effects may not be solely attributable to therapy effects and may be related to other, nonspecific effects of SCS. CONCLUSIONS: Improvements in pain relief, PGIC, EQ-5D-5L, ODI, and patient satisfaction were all clinically relevant and statistically significant. Future studies are needed to understand how these high-dose parameters perform versus a standard comparator. KEY WORDS: Spinal cord stimulation, high-frequency electrical stimulation, failed back surgery syndrome, neurostimulation, prospective, nonrandomized study.

Systemic Opioid Reduction and Discontinuation Following Implantation of Intrathecal Drug-Delivery Systems for Chronic Pain: A Retrospective Cohort Analysis.

OBJECTIVE: The study evaluated systemic opioid utilization before and after initiation of intrathecal drug therapy in patients with chronic, noncancer pain, as well as the effect of opioid elimination on payer costs. METHODS: This was a retrospective cohort analysis of administrative claims data (2011-2016), evaluating patients using systemic opioids for chronic, noncancer pain, newly implanted with an intrathecal drug-delivery system. Patients were excluded for spasticity, cancer, and device explant. The primary outcome was reduction or discontinuation of systemic morphine milligram equivalents during a 395-day follow-up period. The secondary outcome was total commercial insurer payments. RESULTS: Of 9223 total patients, 631 met selection criteria. From baseline to 395-day follow-up, average daily morphine milligram equivalents decreased in 81.5% of patients, and 43.3% discontinued systemic opioid therapy entirely. Among patients who continued systemic opioids, average daily morphine milligram equivalents decreased in 74.9% of patients. Logistic regression found that morphine milligram equivalents of <50 mg/day prior to initiation of intrathecal drug delivery was associated with two times the odds of discontinuation vs. ≥90 mg/day (odds ratio = 2.08, 95% confidence interval 1.42-3.02, p = 0.001). Mean annual payer costs were reduced 29% for patients who discontinued vs. continued systemic opioids (-$11,115 per patient). CONCLUSIONS: A meaningful proportion of patients discontinue or decrease systemic opioid use following initiation of intrathecal drug delivery. Standard of care should include opioid dose tapering prior to intrathecal drug delivery to maximize the probability of systemic opioid discontinuation.

Systemic opioid elimination after implantation of an intrathecal drug delivery system significantly reduced health-care expenditures.

OBJECTIVE: To compare health-care expenditures over a 12-month horizon for chronic pain patients with implanted intrathecal drug delivery systems (IDDS) who eliminated or continued systemic opioids postimplant. METHODS: Claims data from commercial and Medicare databases were searched for patients who had an IDDS, used systemic opioids before implant, and had 12 months pre- and 13 months postimplant continuous medical and pharmacy coverage. The number and characteristics of patients who eliminated or continued systemic opioids were determined at four times postimplant: 30 days (allowing a systemic opioid washout period), 120 days, 150 days, and 210 days. Multivariable models evaluated the effect of eliminating opioids on health-care expenditures at each of those times. RESULTS: Three hundred eighty-nine patients met inclusion criteria, and 51% completely eliminated systemic opioids (12% within the 30-day washout and an additional 39% by the end of the one-year horizon). Systemic opioid elimination within 120 to 210 days postimplant was associated with a reduction of $3,388 to $4,465 in inpatient and outpatient expenditures, and $4,689 to $5,571 in inpatient, outpatient, and drug expenditures. CONCLUSIONS: Fifty-one percent of patients completely eliminated systemic opioids in the year after IDDS implant. This elimination resulted in a 10% to 17% reduction in yearly inpatient, outpatient, and drug expenditures.