Long-term safety of spinal cord stimulation systems in a prospective, global registry of patients with chronic pain

Spinal Cord Stimulation Explantation and Chronic Pain: A Systematic Review and Technology Recommendations

Background

Chronic pain affects 20.5% of the US population, costing $296 billion annually in lost productivity. Spinal cord stimulation (SCS) has become a key treatment for refractory neuropathic and nociceptive pain, with increasing usage due to technological advancements. However, the durability of SCS therapy, including explantation rates, remains a concern. Understanding explantation causes is essential for improving patient selection and device effectiveness. This study aims to analyze SCS explantation rates and reasons, as well as evaluate the financial burden of these procedures on the healthcare system.

Methods

Three primary screening methods were used: manual search with keywords, MeSH term query, and reference list screening. The search covered PubMed, Cochrane, and Web of Science databases from inception to November 2024, yielding 719 articles. After applying eligibility criteria, 72 articles were identified, and 25 were selected for analysis. Data extraction was done by independent reviewers, with a second reviewer ensuring accuracy. Discrepancies were resolved by the corresponding editor.

Results

We reviewed data from 13,026 patients who underwent permanent SCS implantation between 1984 and 2024, across 25 studies. A total of 1882 patients (9.82%) underwent explantation. The most common reason was lack of efficacy and inadequate pain relief (38%), followed by lead failure (15%) and infection (14%). While SCS is generally effective, issues related to device longevity and patient satisfaction persist, with explantation rates due to technical failures and lack of efficacy being concerns.

Conclusion

SCS efficacy varies, with explantation rates reaching up to 38%, often due to inadequate pain relief. Most explantations occur within the first year, despite SCS being a safe and effective treatment. High implantation costs ($35,000 to $70,000) and revision costs ($15,000 to $25,000) raise concerns among payors. The hardware-driven model limits waveform flexibility, highlighting the need for innovation.

Twelve-Month Clinical Trial Results of a Novel, Dorsal Horn Dendrite Stimulation Waveform for Chronic Neuropathic Low Back Pain

OBJECTIVES

The aim of this study was to evaluate the effectiveness and safety of a novel subperception spinal cord stimulation (SCS) waveform paradigm designed to target the dorsal horn dendrites for treating chronic neuropathic low back pain (LBP). The final 12-month results are reported here.

MATERIALS AND METHODS

Twenty-seven participants were implanted with a commercial SCS system. Devices were programmed to deliver the waveform (frequency 100 Hz, pulse width 1000 μsec, T9-T10 disk bipole) at decreasing stimulation perception threshold amplitudes (80%, 60%, then 40%) over a 14-week period. Participants were blinded to the program settings. Participants then received their preferred program for further evaluation at 26 and 52 weeks after activation. Outcome measures included back pain score (visual analogue scale [VAS]), Brief Pain Inventory (BPI), EuroQol 5-Dimension 5-Level (EQ-5D-5L), 36-Item Short Form Health Survey (SF-36), treatment satisfaction, and clinician global impression of change (CGIC).

RESULTS

At 52 weeks (n = 24), the responder rate (≥50% pain relief) was 65.6%, and the high-responder rate (≥80% pain relief) was 56.5%. The mean change from baseline in pain VAS was -43.94 mm (95% CI -57.89, -30.00; p < 0.001) and mean pain relief was 64.69% ± 39.43%. BPI and SF-36 scores remained significantly improved (p ≤ 0.001). EQ-5D-5L index and EuroQoL-VAS further improved, and 87.0% of participants met the minimum clinically important difference for the EQ-5D-5L index. Treatment satisfaction was 83%, and 91% of participants had a CGIC rating of "much improved" or above. No serious study-related adverse events were reported.

CONCLUSIONS

The 12-month trial results show sustained improvements in pain, quality of life, and health-related outcomes. This novel subperception dorsal horn dendrite SCS approach seems a safe and promising treatment option for patients with chronic neuropathic LBP. The open-source availability of this waveform on commercial SCS platforms allows widespread patient access. Further evaluation seems warranted.

CLINICAL TRIAL REGISTRATION

The Clinicaltrials.gov registration number for the study is ACTRN12618000647235 (anzctr.org.au).

The Opinion of Healthcare Professionals About a Proposed European Registry of Neuromodulation for Chronic Pain: An Online Survey

INTRODUCTION

During the last decade, the complementary value of real-world data (through registries or medical records) and data from randomized clinical trials has been recognized as increasingly important. In the field of neuromodulation, only a few industry-independent nationwide neuromodulation registries are available. The interest in creating a European registry has increased but without a successful result. The goal of this online survey is to gain further insights into the need for and burden of a European registry for neuromodulation.

MATERIALS AND METHODS

An online survey was developed and distributed during the 3rd Joint Congress of the International Neuromodulation Society European Chapters in September 2023 (Hamburg, Germany). Healthcare professionals were asked to indicate the need for a European registry, the items that should be collected, and the restrictions to access of a European registry.

RESULTS

In total, 125 respondents opened the link to the survey, of whom 104 completed (at least partly) the survey. Of the 104 responses, 91% indicated that there is a need for a European registry, whereas 6% indicated there is no need. The main reasons for establishing a registry on a European level were the possibility of collecting real-world evidence (84%), the potential to collect big data from European patients (82%), to evaluate safety in neuromodulation (70%), and the possibility of reporting yearly on European activity in neuromodulation (51%). Indications for neuromodulation, patient characteristics, and follow-up assessments were most often stated as items that should be collected. Access should not only be granted to implanters but also to nurses, the assessment team, and other physicians, as agreed on by 64%, 52%, and 51%, respectively.

DISCUSSION

More than 90% of the respondents believed that a European registry for neuromodulation is needed, mainly to obtain real-world (big) data about the effectiveness and safety of this therapy. This survey clearly pointed to the need for a European registry for which it seems key to ensure financial and logistical support, in addition to in-depth legal guidance in developing this registry.

Two-year outcomes using fast-acting sub-perception therapy for spinal cord stimulation: results of a real-world multicenter study in the United States

BACKGROUND

Fast-acting Sub-perception Therapy (FAST) is a novel spinal cord stimulation (SCS) modality delivering paresthesia-free pain relief. Our study evaluated the longer-term, real-world impact of FAST on chronic pain.

RESEARCH DESIGN AND METHODS

As part of a multicenter, real-world, consecutive case series, we retrospectively identified patients who used FAST-SCS and analyzed their data. The numerical rating scale (NRS) was used to evaluate the overall pain.

RESULTS

Data from 315 patients were analyzed at baseline and their last available follow-up (median 6.8 months after SCS implantation). At the time of the analysis, 12-, 18-, and 24-month data were available for 112, 86, and 50 patients, respectively. At the last follow-up, NRS pain score was reduced by 5.5 ± 2.5 compared to baseline (from 7.8 ± 1.7 to 2.3 ± 2.0; p < 0.0001). Interim long-term analysis showed that results were sustained for up to 2 years, with 64% of patients reporting a minimal overall pain score (NRS ≤2/10).

CONCLUSION

This ongoing, real-world, multicenter study showed that FAST-SCS achieved significant paresthesia-free pain relief, while long-term interim analysis suggests that outcomes could be sustained for up to 2 years. Our data provide preliminary insights into the potential utility of this low-frequency sub-perception SCS paradigm using a biphasic active recharge pulse shape.

TRIAL REGISTRATION

ClinicalTrials.gov (CT.gov identifier: NCT01550575).

Sensory-substitution based sound perception using a spinal computer-brain interface

Sensory substitution offers a promising approach to restore lost sensory functions. Here we show that spinal cord stimulation (SCS), typically used for chronic pain management, can potentially serve as a novel auditory sensory substitution device. We recruited 13 patients undergoing SCS implantation and translated everyday sound samples into personalized SCS patterns during their trial phase. In a sound identification task-where chance-level performance was 33.3%-participants ( n = 8 ) achieved a mean accuracy of 72.8% using only SCS input. We observed a weak positive correlation between stimulation bitrate and identification accuracy. A follow-up discrimination task ( n = 5 ) confirmed that reduced bitrates significantly impaired participants' ability to distinguish between consecutive SCS patterns, indicating effective processing of additional information at higher bitrates. These findings demonstrate the feasibility of using existing SCS technology to create a novel neural interface for a sound prosthesis. Our results pave the way for future research to enhance stimulation fidelity, assess long-term training effects, and explore integration with other auditory aids for comprehensive hearing rehabilitation.

Spinal Neuromodulation for Peripheral Arterial Disease of Lower Extremities: A Ten-Year Retrospective Analysis

OBJECTIVE

This long-term retrospective study evaluated the survival and amputation outcome of subjects who received neuromodulation therapy for the management of peripheral arterial disease (PAD).

MATERIALS AND METHODS

The study reviews the health data of a single cohort of 51 patients who received spinal neuromodulation (spinal cord stimulation [SCS] or dorsal root ganglion stimulation [DRG-S]) for PAD from 2007 to 2022 in a single German center. Survival rate and major amputation rate were determined. Pain, quality of life, walking distance, and opioid usage were assessed before implantation (baseline), one, six, and 12 months (M) after implantation, and then annually (during a follow-up visit). Implant-related complications also were documented.

RESULTS

In total, 51 patients (37 men [mean age 68.9 ± 10.2 years], 14 women [mean age (68.7 ± 14.6 years]) underwent SCS (n = 49) or DRG-S (n = 2) implantation owing to persistent ischemic pain. The follow-up mean years ± SD is 4.04 ± 2.73. At baseline, patients were classified as Rutherford's category 3 (n = 23), category 4 (n = 15) or category 5 (n = 9). At 24 M, 42 of 47 patients did not require a major amputation after the implant. All the patients reported nearly complete pain relief from pain at rest. A total of 75% of patients were able to walk >200 m, and 87% of patients who used opioids at baseline were off this medication at 24 M. Overall, 93% of patients reported an improvement in their overall health assessment. These improved outcomes were sustained through years three to 10 for patients who have reported outcomes.

CONCLUSIONS

Our single-center data support the efficacy of spinal neuromodulation for improvements in limb salvage, pain relief, mobility, and quality of life. The data also show that neuromodulative therapy has a long-term therapeutic effect in patients with chronic limb pain with Rutherford category 3, 4, and 5 PAD.

Long-term explantation risk in patients with chronic pain treated with spinal cord or dorsal root ganglion stimulation

OBJECTIVE

To investigate long-term explantation risks and causes for the explantation of neuromodulation devices for the treatment of chronic pain from different manufacturers.

METHODS

This retrospective analysis included patients implanted with a system for spinal cord stimulation (SCS) or dorsal root ganglion (DRG) stimulation at Sahlgrenska University Hospital between January 2012 and December 2022. Patient characteristics, explantation rates and causes for explantation were obtained by reviewing medical records.

RESULTS

In total, 400 patients were included in the study. Including all manufacturers, the cumulative explantation risk for any reason was 17%, 23% and 38% at 3, 5 and 10 years, respectively. Explantation risk due to diminished pain relief at the same intervals was 10%, 14% and 23%. A subgroup comparison of 5-year explantation risk using Kaplan-Meier analysis did not show a statistically significant difference between the manufacturers. In multivariable Cox regression analyses, there was no difference in explantation risk for any reason, but for explantation due to diminished pain relief, a higher risk was noted for Medtronic (preferably older types of SCS devices) and DRG stimulation. No other predictive factor for explantation was found.

CONCLUSIONS

Although SCS and DRG stimulation are well-established and safe treatments for chronic pain, the long-term explantation risk remains high. The difference between manufacturers highlights the importance of technological evolution for improving therapy outcomes. Increased stringency in patient selection and follow-up strategies, as well as further development of device hardware and software technology for increased longevity, could possibly reduce long-term explantation risks.

Smaller thoracic canal diameters are associated with thoracic radiculopathy and abdominal pain after spinal cord stimulator paddle lead placement

INTRODUCTION

It is not uncommon for patients to experience postoperative neurologic deficit, thoracic radiculopathy, abdominal pain, or lower extremity paresthesia after the implantation of thoracic spinal cord stimulator (SCS) paddle leads. Smaller thoracic canal diameters have previously been associated with postoperative neurologic deficits.

OBJECTIVE

This imaging study examined whether postoperative SCS neurologic complaints other than neurologic deficit may be correlated with thoracic spinal canal diameter.

METHODS

Patients who underwent thoracic laminotomy for SCS paddle lead placement between January 2018 and March 2023 were identified. Preoperative thoracic canal diameter was measured on MRI or CT imaging in the sagittal plane from T5/6 to T11/12. The canal diameters of patients with and without new postoperative neurologic complaints were compared.

RESULTS

Two hundred forty-six patients underwent thoracic laminotomy for SCS paddle lead placement. Thoracic radiculopathy, abdominal pain, and lower extremity paresthesia occurred in 3.7% (9/246), 2.8% (7/246), and 2.0% (5/246) patients, respectively. The mean canal diameter for patients without neurologic complaint, thoracic radiculopathy, abdominal pain, and lower extremity paresthesia was 13.1 mm, 12.0 mm (p < 0.0001), 12.1 mm (p < 0.01), and 12.8 mm (p = 0.365), respectively.

CONCLUSION

A smaller thoracic canal diameter is associated with postoperative thoracic radiculopathy and abdominal pain. We believe that surgical planning to create adequate space for SCS leads is critical in preventing postoperative neurologic complaints of deficit, thoracic radiculopathy, and abdominal pain.

Incidence of Infections, Explantations, and Displacements/Mechanical Complications of Spinal Cord Stimulation During the Past Eight Years

OBJECTIVES

The overall awareness and potential of real-world data have drastically increased in the medical field, with potential implications for postmarket medical device surveillance. The goal of this study was to evaluate real-world data on incidence of infections, explantations, and displacements/mechanical complications of spinal cord stimulation (SCS) during the past eight years and to forecast point estimates for the upcoming three years on the basis of the identified patterns.

MATERIALS AND METHODS

Based on electronic health records from 80 healthcare organizations within the TriNetX data base in the USA, data of 11,934 patients who received SCS as treatment for persistent spinal pain syndrome type 2 (PSPS T2) were extracted. Events of interest were explantations and displacements/mechanical complications of both the lead and implanted pulse generator (IPG), in addition to infection rates from 2015 to 2022. Mann-Kendall tests were performed to detect monotonic trends in the time series. Forecasts were conducted for the upcoming three years for every event of interest.

RESULTS

Statistically significant increasing time trends were revealed for the annual incidence of IPG and lead displacements/mechanical complications in patients with PSPS T2 over the past eight years. These time trends were visible in both male and female patients and in smokers and nonsmokers. For annual incidence of explantations and infections, no significant time effect was observed. In 2025, the incidence of displacements/mechanical complications of the lead (3.07%) is predicted to be the highest, followed by explantations of the IPG (2.67%) and lead (2.02%).

CONCLUSIONS

Based on real world data, device explantation was the most frequent event of interest, with negative peaks in the time series in 2016 and 2020, presumably due to the introduction of rechargeable pulse generators and to the COVID-19 pandemic, respectively.

Neuromodulation and Habituation: A Literature Review and Conceptional Analysis of Sustaining Therapeutic Efficacy and Mitigating Habituation

Spinal cord stimulation (SCS) is a therapeutic modality for the treatment of various chronic pain conditions that has rapidly evolved over the past 50 years. Unfortunately, over time, patients implanted with SCS undergo a habituation phenomenon leading to decreased pain relief. Consequently, the discovery of new stimulation waveforms and SCS applications has been shown to prolong efficacy and reduce explantation rates. This article explores various SCS waveforms, their applications, and proposes a graded approach to habituation mitigation. We suspect the neural habituation phenomenon parallels that seen in pharmacology. Consequently, we urge further exploration of the early introduction of these stimulation strategies to abate spinal cord stimulation habituation.

Conversion of a medical implant into a versatile computer-brain interface

BACKGROUND

Information transmission into the human nervous system is the basis for a variety of prosthetic applications. Spinal cord stimulation (SCS) systems are widely available, have a well documented safety record, can be implanted minimally invasively, and are known to stimulate afferent pathways. Nonetheless, SCS devices are not yet used for computer-brain-interfacing applications.

OBJECTIVE

Here we aimed to establish computer-to-brain communication via medical SCS implants in a group of 20 individuals who had been operated for the treatment of chronic neuropathic pain.

METHODS

In the initial phase, we conducted interface calibration with the aim of determining personalized stimulation settings that yielded distinct and reproducible sensations. These settings were subsequently utilized to generate inputs for a range of behavioral tasks. We evaluated the required calibration time, task training duration, and the subsequent performance in each task.

RESULTS

We could establish a stable spinal computer-brain interface in 18 of the 20 participants. Each of the 18 then performed one or more of the following tasks: A rhythm-discrimination task (n = 13), a Morse-decoding task (n = 3), and/or two different balance/body-posture tasks (n = 18; n = 5). The median calibration time was 79 min. The median training time for learning to use the interface in a subsequent task was 1:40 min. In each task, every participant demonstrated successful performance, surpassing chance levels.

CONCLUSION

The results constitute the first proof-of-concept of a general purpose computer-brain interface paradigm that could be deployed on present-day medical SCS platforms.

Exploring new horizons in pain relief: introducing Volume 14 of Pain Management

To our readers, welcome to the first issue of Volume 14 of Pain Management. 2023 marked a significant year for the journal, as we received an impact factor of 1.7 and increased the number of issues from 8 to 12. This foreword presents some of our content highlights from 2023, covering our top articles from the year and providing you with an insight into what to expect in the forthcoming year.