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. 2025 Apr 22;14(3):1103–1115. doi: 10.1007/s40122-025-00737-3

Four-Year Follow-Up from a Prospective, Multicenter Study of Percutaneous 60-Day Peripheral Nerve Stimulation for Chronic Low Back Pain

Christopher A Gilmore 1,✉, Timothy R Deer 2, Mehul J Desai 3, Sean Li 4, Michael J DePalma 5, Steven P Cohen 6,7, Brandon D Swan 8, Meredith J McGee 8, Joseph W Boggs 8
PMCID: PMC12085521  PMID: 40261580

Abstract

Introduction

Chronic low back pain (LBP) is a leading cause of healthcare expenditure and long-term disability associated with complex treatment challenges and the need for progressively invasive interventions. Percutaneous 60-day Peripheral Nerve Stimulation (PNS) is a minimally invasive neurostimulation treatment that has shown efficacy for chronic LBP, providing sustained improvements through 1 year of follow-up after treatment. The present work explores the long-term clinical outcomes of Percutaneous 60-day PNS for chronic LBP approximately 4 years after initial treatment.

Methods

Follow-up surveys were sent to participants from a prior prospective study who reported clinically meaningful reductions in pain, disability, or pain interference 12 months after Percutaneous 60-day PNS for LBP. The present long-term follow-up survey assessed current levels of LBP, disability, pain interference, and Patient Global Impression of Change (PGIC). Use of medications and other interventions for LBP treatment since completing Percutaneous 60-day PNS was also surveyed.

Results

In total, 23 participants returned completed long-term follow-up surveys. A majority of survey respondents (65%, n = 15/23) reported sustained, clinically meaningful (≥ 30%) relief of back pain compared with baseline an average of 4.7 years after PNS treatment was initiated. On average, these long-term responders reported clinically substantial (≥ 50%) reductions in pain (average 63% reduction), as well as clinically meaningful improvements in disability and quality of life. Furthermore, 70% (n = 16/23) of survey respondents avoided progression to more costly, invasive, and/or destructive LBP pain interventions (i.e., radiofrequency ablation, neurostimulation implant, or lumbar surgery).

Conclusions

Treatment with Percutaneous 60-day PNS provided clinically meaningful pain relief among a majority of surveyed participants an average of more than 4 years after the short-term treatment. These results demonstrate that Percutaneous 60-day PNS can provide durable outcomes that are often sustained for multiple (4+) years by patients with chronic axial LBP who subsequently avoid the need for more invasive treatment interventions.

Clinical Trial Registration

The Clinicaltrials.gov registration number for the initial study is NCT03179202.

Keywords: Chronic low back pain, Chronic pain, Neuromodulation, Percutaneous peripheral nerve stimulation, Peripheral nerve stimulation

Key Summary Points

Why carry out this study?
Chronic low back pain (LBP) is a leading cause of healthcare expenditure and long-term disability that is difficult to treat and often requires progressively invasive interventions.
Percutaneous 60-day Peripheral Nerve Stimulation (PNS) is a minimally invasive treatment that has been found to provide clinically meaningful pain relief, reductions in disability, and improvements in quality of life that extend beyond the short-term treatment period, but the durability of these effects has only been documented for approximately 1 year after treatment in prior studies.
This study is the first to explore the long-term durability of relief in patient-reported outcomes at least 4 years following Percutaneous 60-day PNS of the lumbar medial branch nerves through a follow-up survey of participants from a prior prospective trial for chronic LBP.
What was learned from the study?
During the 4+ year follow-up after Percutaneous 60-day PNS treatment was initiated, a majority of survey respondents (65%, n = 15/23) reported sustained, clinically meaningful relief of back pain compared with baseline, and 70% of survey respondents (n = 16/23) avoided progression to more costly, invasive, and/or destructive LBP interventions, reporting no radiofrequency ablation (RFA), neurostimulation implant, or lumbar surgery.
These results demonstrate that Percutaneous 60-day PNS can provide durable outcomes that are sustained for multiple (4+) years in some patients with chronic axial LBP, which may mitigate the need for more invasive treatment interventions.
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Introduction

As a leading cause of disability among adults worldwide, chronic low back pain (LBP) represents a major public health burden [1–4]. Treatment of chronic LBP is challenging owing to its complex nature, which includes involvement of both peripheral and central pain generators [5, 6]. Conventional approaches to LBP treatment, such as physical therapy, medication management, anesthetic or steroid injections, and surgical interventions are often associated with variable efficacy and significant drawbacks, including undesirable side effects [7–11]. These challenges underscore the need to identify new treatments to address the underlying causes of chronic LBP to provide durable pain relief. Central sensitization is believed to play a key role in the persistence of chronic LBP, including when the pain is nonspecific in origin or endures long after an acute tissue injury heals or stabilizes. Factors such as prolonged exposure to pain signals, chronic inflammation, and psychological stressors may heighten nociceptor sensitivity and diminish the body’s ability to inhibit nociceptive signaling, resulting in maladaptive central nervous system (CNS) processing and persistent pain [12–19]. Successful long-term improvement of chronic LBP symptoms and conditions may, therefore, require interventions capable of reversing maladaptive changes in CNS pain processing [18, 20, 21].

Percutaneous 60-day Peripheral Nerve Stimulation (PNS) is a minimally invasive, nondestructive treatment that has demonstrated clinically meaningful pain relief, reductions in disability, and improvements in quality of life that extend beyond the short-term treatment period [22–33]. Through selectively targeted stimulation of the medial branch nerves for LBP, Percutaneous 60-day PNS is designed to generate proprioceptive neural inputs both directly, through activation of sensory afferent fibers with stimulation, and indirectly, following efferent fiber activation of the lumbar multifidi muscles. These stimulation-evoked inputs to the CNS are hypothesized to convey focal, robust physiological signals that may modulate central plasticity to reduce chronic pain long-term [34]. Prior studies have reported sustained, long-term reductions in pain, pain-related disability, and/or pain interference through 12 months after short-term delivery of Percutaneous 60-day PNS, which supports this centrally-mediated mechanism of action, but the durability of these effects multiple years after Percutaneous 60-day PNS has not yet been reported. The objective of this study was to explore for the first time the long-term patient-reported outcomes several years following Percutaneous 60-day PNS of the lumbar medial branch nerves through a follow-up survey of participants from a prior prospective trial for chronic LBP approximately 4 years prior [23].

Methods

This follow-up survey was completed as a protocol addendum to a prior prospective multicenter case series study protocol, which was approved by an institutional review board (IRB; Quorum Review IRB, now Advarra, Seattle, WA, USA) and was registered on ClinicalTrials.gov (NCT03179202). The initial prospective study followed good clinical practice and was conducted within the ethical guidelines outlined in the Declaration of Helsinki. Prior to participation in the initial prospective study, participants provided written informed consent. Individuals with chronic axial LBP who were screened for participation in the initial study met inclusion criteria if they reported pain confined to the lumbar region lasting at least 12 weeks with an average score ≥ 4 on a 0–10 scale and had previously experienced failure with at least two types of LBP treatments (e.g., medications, physical therapy, injections, or interventional procedures). Key exclusion criteria included radicular leg pain, recent lumbar interventions (lumbar anesthetic injections within 3 months or lumbar radiofrequency ablation (RFA) within 6 months), and any contraindications for the Percutaneous 60-day PNS system. There were no stipulations regarding the specific etiology of back pain for enrollment apart from the listed exclusion criteria; participants with various sources of axial pain were enrolled, with lumbar spondylosis and degenerative disc disease being the most reported diagnoses.

Following a baseline physical assessment to confirm eligibility and LBP-related medical history, individuals with an average LBP intensity score ≥ 4 (Brief Pain Inventory question no. 5 (BPI-5)) from a 7-day diary were eligible to undergo Percutaneous 60-day PNS lead implantation. Leads were implanted using fluoroscopic and/or ultrasound guidance to bilaterally target the medial branch nerves as they course over the lamina medial and inferior to the facet joint. Successful implantation was confirmed through ultrasound visualization of stimulation-evoked activation of the lumbar multifidi and concomitant participant reports of comfortable sensations in the affected region. Postimplantation, the leads were connected to wearable stimulators (SPRINT® PNS System and MicroLead™, SPR® Therapeutics, Cleveland, OH, USA; Fig. 1), and participants used PNS for 6–12 h/day for up to 60 days. At the end of the 60-day period, the percutaneous PNS leads were gently withdrawn during a clinic visit, without surgery. Participants returned to the clinic for regular follow-up visits for up to 12 months after lead removal (i.e., 14 months after starting treatment).

Fig. 1.

Fig. 1

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Percutaneous 60-day Peripheral Nerve Stimulation (PNS) system and anatomic targeting of lead placement at a lumbar medial branch of the dorsal ramus. A flexible, fine-wire, open-coil lead (A) delivers PNS from a rechargeable body-worn stimulator controlled by a wireless handheld remote (B). Leads were placed bilaterally targeting the medial branches of the dorsal ramus, inferior and medial to the facet joint, as they travel over the lamina at the spinal level in the center of the participant’s region of pain (C). An example anteroposterior (AP) fluoroscopic image of the introducer needle location during lead placement is shown (D)

Participants who completed the 12-month visit and reported clinically meaningful improvement in at least one of the three outcome measures (≥ 30% reduction in Brief Pain Inventory question no. 5 (BPI-5); ≥ 10-point reduction in the Oswestry Disability Index (ODI); or  ≥ 30% reduction in Brief Pain Inventory question no. 9 (BPI-9)) were potential candidates for participation in the presently reported long-term follow-up survey. The follow-up survey and protocol addendum were reviewed by the IRB and determined to meet exemption criteria. Of the eight original clinical sites that enrolled participants in the initial study, six were approached for participation in the follow-up survey (sites with ≤ one participant meeting the survey eligibility criteria were not invited to participate), and five sites agreed to participate (one site was unable to participate owing to administrative challenges; Fig. 2). Among the 47 participants who were potential candidates for long-term follow-up at the six invited sites, 10 were determined to be unavailable for participation (7 from the site that was unable to participate, 1 who died of unrelated causes after previous study completion, and 2 who declined participation). Therefore, a total of 37 eligible participants were mailed follow-up surveys by their respective sites. Each respective site distributed follow-up surveys to eligible participants concurrently, irrespective of the amount of time elapsed since each participant completed the prior 12-month visit. The follow-up survey included validated measures to assess current levels of LBP, back-pain related disability (ODI), pain interference (BPI-9), and Patient Global Impression of Change (PGIC). In addition, participants were asked to rate their PNS treatment satisfaction and report medications and other treatments used for LBP since their last study visit. Prior publications reported the results of the initial study through the primary endpoint (at the end of 60 days of treatment) [25] and following 12 months of follow-up (at 14 months from start of treatment) [23]. The present report describes the results from the long-term follow-up survey completed by study participants approximately 4 years after Percutaneous 60-day PNS treatment. Safety outcomes were assessed previously during the original 14-month study and followed to resolution [23, 25], and while they were not specifically reassessed in the long-term follow-up survey, no serious or unanticipated adverse events were previously reported during the prospective 14-month follow-up. In the present long-term follow up survey evaluation, participants were asked about any changes in their medical status since completing the initial study, and no device-related adverse effects were identified.

Fig. 2.

Fig. 2

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Long-term follow-up survey participant flow diagram. Participants completing the prior multicenter study [23, 25] were eligible to participate in the long-term follow-up survey if they had clinically meaningful improvement(s) at the final study visit 14 months after the start of Percutaneous 60-day medial branch PNS with at least one of three outcomes (≥ 30% reduction in pain intensity (Brief Pain Inventory question no. 5, BPI-5); ≥ 10-point reduction in disability (Oswestry Disability Index, ODI); or ≥ 30% reduction in pain interference (Brief Pain Inventory question no. 9, BPI-9)). Six sites from the prior study were invited to participate (sites with ≤ 1 participant meeting the survey eligibility criteria were not invited), and five sites participated (1 declined owing to administrative bandwidth). Of the 37 eligible participants who received follow-up surveys, 23 participants completed and returned the survey that reported their pain relief, disability, pain interference, change in quality of life, low back pain (LBP) medications, and other treatments used since last study visit, as well as satisfaction with PNS treatment at the time of long-term follow-up; PI principal investigator

Statistical Methods

Statistical analyses were reported on data collected from eligible participants who completed the long-term follow-up survey. Data were analyzed using one-way repeated measures analysis of variance (ANOVA) with post hoc Tukey–Kramer adjustment for multiple comparisons (JMP®, version 18.0. SAS Institute Inc., Cary, NC, USA, 1989–2025). Data are reported as mean (standard deviation, SD), unless otherwise noted.

Results

In total, 23 out of 37 (62%) participants who were potential candidates for long-term follow-up completed and returned the survey. Respondents were on average 53.8 years of age (SD 13.4 years), 65% female, and had experienced LBP for an average of 13.1 years (SD 13.9 years) at baseline. Surveyed participants reported an average pain intensity of 6.6 (BPI-5, SD 1.5) at the time of their first visit during the initial study. Additional participant demographics are provided in Table 1.

Table 1.

Participant demographics and baseline information

Participants responding to survey, n 23
Body mass index (BMI) 29.0 (4.9)
Age, years 53.8 (13.4)
Low back pain (LBP) duration, years 13.1 (13.9)
Sex, % female 65%
Average LBP intensity at baseline 6.6 (1.5)
LBP etiology*
 Lumbar spondylosis, n (%) 13 (57%)
 Degenerative disc disease, n (%) 6 (26%)
 Unknown/nonspecific, n (%) 5 (22%)
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Results shown as mean (standard deviation, SD) unless otherwise stated

*Multiple etiologies may apply to a given participant

Among all survey respondents, mean reported pain relief was 41% (SD 35%, n = 23) at long-term follow-up. A majority of participants completing the long-term follow-up survey (65%, n = 15/23) reported clinically meaningful (≥ 30%) relief of LBP compared with baseline (i.e., prior to receiving Percutaneous 60-day PNS several years earlier, Fig. 3A). Among these long-term responders who experienced clinically meaningful pain relief, the mean duration of follow-up time elapsed from start of Percutaneous 60-day PNS treatment was 4.7 years (range 4.0–5.9 years). Further, among long-term responders, there was a statistically significant effect of PNS treatment on average pain intensity (n = 15, p < 0.001), and average pain scores at long-term follow-up were significantly lower when compared with baseline (Fig. 3B, n = 15, p < 0.001). Participants who were long-term responders reported on average clinically substantial (≥ 50%) reductions in pain (average reduction of 63%, SD 21%; Fig. 4A) and clinically meaningful improvements in disability (average of 11.5-point reduction in ODI, SD 14.6; Fig. 4B) and quality of life (average of 5.5 PGIC, equivalent to “minimally”-to-“much improved”; Fig. 4C).

Fig. 3.

Fig. 3

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Pain scores among responders completing the long-term follow-up survey. A A majority of survey respondents (65%, n = 15/23) reported experiencing clinically meaningful reductions in pain (≥ 30% relief) from stimulation therapy compared with before they enrolled in the clinical trial of Percutaneous 60-day PNS for chronic LBP. B Statistically significant reductions from baseline in average pain intensity (BPI-5) were achieved in the n = 15/23 responders (from panel A) at the end of the Percutaneous 60-day PNS treatment, at follow-up at 14 months after starting PNS treatment, and at long-term follow-up occurring 4.0–5.9 years after starting PNS treatment. There was a statistically significant effect of PNS treatment on average pain intensity (repeated measures analysis of variance (ANOVA), n = 15, p < 0.001) and average pain scores at long-term follow-up were statistically significantly lower when compared with baseline (post hoc Tukey–Kramer, p < 0.001). Data shown as mean ± standard error of the mean (SEM)

Fig. 4.

Fig. 4

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Pain relief and improvements in secondary outcomes in long-term responders. Participants who were long-term responders 4+ years after receiving Percutaneous 60-day medial branch PNS reported on average clinically substantial (≥ 50%) pain relief (A; 63%) and improvements in disability (B; ≥ 10-point ODI reduction) and quality of life (C; Patient Global Impression of Change (PGIC))

Further, 70% of survey participants reported either clinically substantial pain relief or clinically meaningful (≥ 10-point (pt)) improvement in disability at long-term follow-up (n = 16/23). Overall participant satisfaction with PNS treatment in long-term follow-up survey was high, with a majority of survey respondents (61%, n = 14/23) reporting that they preferred use of stimulation therapy to taking pain medications.

A majority of survey respondents (70%, n = 16/23) avoided progression to more costly, invasive, and/or destructive LBP interventions, reporting no RFA, neurostimulation implant, or lumbar surgery during the 4+ year follow-up (Fig. 5). While some respondents did go on to receive additional treatments, the overall rate of progression to these interventions was 0.1 interventions per participant per year of follow-up (Table 2), with RFA being the most common post-PNS procedure (n = 4). Medication usage by survey respondents at long-term follow-up was most commonly nonopioid analgesics (e.g., nonsteroidal antiinflammatory drugs (NSAIDs)); six total participants reported opioid use (average morphine milligram equivalent (MME) 27.1 mg (SD 17.8 mg) among n = 5 participants who reported opioid dosage).

Fig. 5.

Fig. 5

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Intervention avoidance in long-term follow-up. An average of 4+ years after Percutaneous 60-day PNS, a majority (70%, n = 16/23) of survey respondents avoided progression to more costly, invasive, and/or destructive LBP interventions (i.e., reported no use of radiofrequency ablation (RFA), neurostimulation implant, or lumbar surgery) in long-term follow-up

Table 2.

Long-term healthcare resource utilization in follow-up

Total number of radiofrequency ablation (RFA), neurostimulation, or surgery procedures reported in long-term follow-up (among n = 23) 9 procedures (n = 7)
Calculated participant × years of follow-up (since completion of prior multicenter trial) 78.2 participant × years
Rate of use of other interventions (i.e., RFA, neurostimulation, surgery) in long-term follow-up 0.1 procedures per participant per year
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To further evaluate the potential influence of concurrent treatments on patient outcomes, subgroup analyses were performed on the basis of the use of additional interventional pain procedures, physical therapy, and/or opioids during the long-term follow-up period. In total, 75% percent of participants who did not receive additional interventional treatments (i.e., RFA, neuromodulation, or surgery) after Percutaneous 60-day PNS (n = 12/16) reported clinically meaningful pain relief, whereas 43% of participants who did receive additional interventional treatments (n = 3/7) reported clinically meaningful pain relief. Similarly, 75% of participants who did not engage in physical therapy during follow-up (n = 9/12) reported clinically meaningful pain relief, whereas 55% of those participants who did engage in physical therapy (n = 6/11) reported clinically meaningful pain relief. In addition, 71% of participants who were not taking opioid medications at the time of follow-up (n = 12/17) reported clinically meaningful pain relief, whereas 50% of those participants who were taking opioids (n = 3/6) reported clinically meaningful pain relief. These findings suggest that the observed improvements are related to the study device and not driven by additional interventions received in the time after PNS, since participants who did not pursue additional interventional treatments or other concurrent therapies after Percutaneous 60-day PNS more frequently reported clinically meaningful pain relief.

Discussion

This report is the first to describe the durable, long-term effectiveness of Percutaneous 60-day PNS of the lumbar medial branch nerves for chronic LBP at least 4 years after treatment. Prior findings from this prospective multicenter clinical trial demonstrated that Percutaneous 60-day PNS of the medial branches resulted in clinically meaningful reductions in pain intensity, disability, and/or pain interference for a majority of participants [25] that continued through 14 months after start of treatment [23]. In the present work, which surveyed individuals who sustained therapeutic benefit at least 1 year after receiving the Percutaneous 60-day PNS treatment, a majority of survey respondents (65%) continued to report clinically meaningful relief of chronic LBP from PNS treatment at long-term follow-up. These results demonstrate that clinically meaningful reductions in disabling chronic LBP can be maintained for more than 4 years after short-term, Percutaneous 60-day PNS.

Participants reported sustained improvements in other patient-centric outcomes at long-term follow-up, including disability and quality of life, with a majority of survey respondents (70%) exhibiting clinically meaningful reductions in disability scores and/or clinically substantial relief of chronic LBP from PNS treatment. These results are concordant with the outcomes described in prior clinical studies evaluating Percutaneous 60-day PNS of lumbar medial branches [23, 25, 28, 30, 35, 36], as well as a published meta-analysis of PNS targeting the lumbar medial branches for chronic LBP [37]. Given that a majority of surveyed participants (70%) avoided use of RFA, neurostimulation implant, or lumbar surgery during long-term follow-up, incorporating Percutaneous 60-day PNS earlier into the treatment continuum for chronic axial LBP may preclude or reduce the need for more destructive or invasive procedures, potentially leading to reduced healthcare costs and improved patient outcomes. In addition, by addressing pain and disability earlier in the course of treatment for LBP, Percutaneous 60-day PNS may prevent the progression of chronic pain conditions, improve long-term prognosis, and reduce overall treatment costs [38].

Evidence of durable, long-term improvements following Percutaneous 60-day PNS, as demonstrated in the present and prior studies, supports the theory that short-term treatment may provide long-term sustained benefits through the modulation of central pain processing [22–25, 33, 39–43]. The mechanism of action by which Percutaneous 60-day PNS produces sustained improvements in chronic axial LBP that outlast the treatment period has been postulated to involve peripherally-induced reconditioning of the CNS [34]. The prolonged pain relief may also enable patients to engage in more physical activity, sleep better, and experience improved mood—factors that may help reinforce the pain-relieving effects of PNS and contribute to the observed long-term benefits that extend well beyond the initial treatment period. The proposed theory that peripherally targeted treatments may reverse centrally mediated pain is supported by the results of the present work, given that a majority of survey respondents (65%) experienced long-term, sustained improvements in axial LBP ranging from 4 to nearly 6 years after Percutaneous 60-day PNS treatment.

Limitations of the initial prospective multicenter study have been previously reported [23, 25] and include the absence of a control group and randomization of enrolled participants. While this subsequent survey does not have a large sample size and there is a potential for nonresponse bias or self-selection bias among participants who responded to the long-term follow-up survey, the survey response rate (62%) is concordant with the ≥ 40–60% rates that are commonly reported for survey studies [44–47]. In addition, a comparison of 12-month outcomes between participants who did not respond to the survey (n = 14) and the broader group of all participants who received surveys (n = 37) (12-month BPI-5: 43% versus 47%; 12-month ODI: 14.5-pt versus 12.9-pt; 12-month BPI-9: 44% versus 45%, reductions, respectively) suggests that there were no meaningful differences in mean outcomes based on survey response. Furthermore, baseline average pain scores did not differ meaningfully between survey respondents and nonrespondents (baseline BPI-5: 6.0 versus 6.1, respectively). Taken together, these findings reduce the likelihood that outcomes of the present study were significantly impacted by nonresponse or selection bias. In addition, while this study was sponsored by the device manufacturer, which may introduce the potential for perceived or actual bias, all conflicts of interest relevant to the study have been disclosed; efforts were made to ensure objectivity in study design, analysis, and reporting and to limit the risk of bias in survey assessment, including multiple attempts by study sites to follow-up with participants, completion of surveys without influence by the device manufacturer or clinical study staff, and use of validated outcome measures in the long-term follow-up survey. Since surveys were completed by participants remotely (i.e., not in clinic), objective functional outcomes were not able to be included to assess functional improvements following Percutaneous 60-day PNS in this study, although objective functional improvements corresponding with patient-reported improvements in quality of life and pain relief have been documented in a double-blinded randomized controlled trial (RCT) of Percutaneous 60-day PNS [33] and may be considered in future studies.

While the absence of a control group limits direct comparisons, subgroup analyses suggest that the long-term pain relief observed in this cohort was not meaningfully influenced by concurrent treatments. Notably, participants who avoided additional interventional pain procedures, physical therapy, or opioid medications more frequently reported clinically meaningful pain relief than those who did not. These patterns suggest that the therapeutic benefit observed is attributable to the device intervention rather than to external or adjunctive treatments alone. The promising results of this survey demonstrating durable relief of chronic axial LBP that is sustained for multiple (4+) years corroborate and extend the findings of previously published prospective studies of this treatment, substantiate the evidence showing that Percutaneous 60-day PNS can mitigate the need for more invasive treatment interventions in some patients, and support the clinical utility of Percutaneous 60-day PNS.

Conclusions

Percutaneous 60-day PNS provided clinically substantial pain relief and/or improvements in disability and quality of life for the majority of surveyed respondents more than 4 years after short-term, Percutaneous 60-day PNS treatment. These results demonstrate that Percutaneous 60-day PNS can provide durable outcomes that are sustained for multiple (4+) years in some patients with chronic axial LBP, which may mitigate the need for more invasive treatment interventions. Therefore, as a minimally invasive therapy, short-term, Percutaneous 60-day PNS may provide a promising neurostimulation treatment for patients with chronic axial LBP.

Acknowledgements

The authors thank the study participants and staff members at each clinical site for their substantial contributions during the conduct of this clinical study and completion of the long-term follow-up survey. The authors also thank SPR team members, Lauren Easley, Rosemary Zang, and Sara Anderson for their significant contributions.

Author Contributions

Christopher A. Gilmore, Timothy R. Deer, Mehul J. Desai, Sean Li, Michael J. DePalma, and Steven P. Cohen contributed to the design of the clinical study, supervised participant recruitment and enrollment, conducted study procedures, and/or contributed to drafting of the manuscript. Brandon D. Swan contributed significantly to data analysis and drafting of the manuscript. Meredith J. McGee and Joseph W. Boggs contributed significantly to the conception and design of the study, oversaw conduct of the clinical trial, managed data analysis, and contributed to the drafting of the manuscript. All authors approved the final manuscript.

Funding

Sponsorship for this study and Rapid Service Fee were funded by SPR Therapeutics, Inc.

Data Availability

The datasets generated during and/or analyzed during the current study may be made available on reasonable request by the corresponding author or the study sponsor.

Declarations

Conflicts of Interest

The authors declare the following conflicts of interest in connection with the submitted material: Christopher A. Gilmore, Timothy R. Deer, Mehul J. Desai, Sean Li, and Michael J. DePalma have research sponsored by SPR Therapeutics; Christopher A. Gilmore, Timothy R. Deer, Mehul J. Desai, and Sean Li are consultants for SPR; Brandon D. Swan, Meredith J. McGee, and Joseph W. Boggs are employees of and named on patents assigned to SPR Therapeutics; and Timothy R. Deer, Mehul J. Desai, Meredith J. McGee, and Joseph W. Boggs have stock options in SPR Therapeutics.

Ethical Approval

This follow-up survey was completed as a protocol addendum to a prior prospective multicenter case series study protocol, which was approved by an institutional review board (IRB; Quorum Review IRB, now Advarra, Seattle, WA, USA) and was registered on ClinicalTrials.gov (NCT03179202). The initial prospective study followed good clinical practice and was conducted within the ethical guidelines outlined in the Declaration of Helsinki. Prior to participation in the initial prospective study, participants provided written informed consent. The follow-up survey and protocol addendum were reviewed by the IRB and determined to meet exemption criteria.

Footnotes

Prior Presentation: These results were previously presented in abstracts and presentations at the Sixth Annual American Society of Pain & Neuroscience (ASPN) Conference (11–14 July 2024, Miami Beach, FL, USA), the American Society of Regional Anesthesia and Pain Medicine (ASRA Pain Medicine) 23rd Annual Pain Medicine Meeting (21–23 November 2024, Las Vegas, Nevada, USA), and the 2025 North American Neuromodulation Society (NANS) Annual Meeting (30 January–1 February 2025, Orlando, FL, USA).

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Data Availability Statement

The datasets generated during and/or analyzed during the current study may be made available on reasonable request by the corresponding author or the study sponsor.

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