Objective: The aim of this survey was to collect user (patient and health care professional) satisfaction, therapy outcomes and device settings from patients who utilize a single spinal cord stimulation model for treatment of chronic pain in day-to-day clinical practice.

Methods: The design was a clinical survey. The survey population were patients with chronic back and leg pain receiving spinal cord stimulation therapy, and the health care professionals who treat the patients and program the implantable neurostimulator.

Patient data were collected once and at a time when spinal cord stimulation provided stable pain relief. Data was presented in aggregate form. Near 50 data-items were captured per patient, including demographics (e.g., age, gender, prior surgeries), technical data (e.g., implant details, stimulation parameters), patient reported outcomes (e.g., pain change, goal achievement, work) and satisfaction and health care professional satisfaction (e.g., satisfaction with neurostimulator size). Descriptive statistics were used to summarize the data. Continuous variables are summarized by computing mean and standard deviation.

Results: Clinical staff from nine European sites independently collected data from 124 patients. Patients were on average 54.3 (±11.2) years old and had chronic pain for 9.9 (±6.0) years. The average time since spinal cord stimulation onset was 2.6 years. The indication for spinal cord stimulation was for overall pain (68.5%, 85/124), leg pain (22.6%, 28/124) and back pain (8.9%, 11/124). On average, patients reported an improvement in pain of 70.3% (± 17.1%) and pain medication was reduced for 82.3% (102/124) of patients. Thirty-two patients (25.8%) returned to work of whom 16 (12.9%) returned to full time work. Functional goals measured on a VAS scale (0-100), were predefined by 110 patients, mostly for pain/medication reduction, improved quality of life, and mobility. On average, there was an improvement in the predefined goal, of 73.3% (±17.0%).

Conclusions: The clinical survey provided an overview of the use of spinal cord stimulation for a specific device and indication in a day-to-day clinical setting.

Spinal cord stimulation (SCS) is a proven safe and effective therapy that can help to manage many types of chronic intractable pain. SCS uses low voltage (electrical) stimulation of the spinal nerves to help block the sensation of pain. To achieve SCS, a small battery-powered generator is implanted under the skin to transmit an electrical current to the spinal cord. The electrical current generated interrupts pain signals being sent to the brain and an individual being treated generally feels pain relief. SCS is mostly offered to patients with refractory chronic back and leg pain (CBLP), nowadays referred to as persistent spinal pain syndrome (PSPS). SCS therapy is first offered during a trial period in which an SCS lead with electrodes, which is placed over the dorsal column of the spinal cord, is connected to an external neurostimulator through a percutaneous cable. Stimulation parameters are then selected to optimize pain control. In patients who respond to the therapy (>50% pain reduction) an implantable neurostimulator (INS) provides continuous SCS-therapy. After INS implant, the patient returns to the pain clinic at regular intervals for SCS-therapy check-ups and/or optimization. It can take weeks to months until SCS-therapy is optimized, and pain suppression has reached a stable level.

Several clinical studies on SCS therapy for treatment of chronic pain have been performed over decades.^1–5 The effectiveness of SCS for treatment of PSPS has been shown in several observational and controlled studies.^5–9 In most controlled SCS studies the focus has been on clinical outcomes, such as pain, functionality and pain medication use and have been performed in selected patient populations. Registries, on the other hand, often include patients with different pain etiologies and SCS devices.^10,11 Most SCS devices offer different stimulation waveforms, such as low-dose (tonic or conventional) and higher energy waveforms (e.g., Burst, HF10, DTM). Several studies have demonstrated clinical effectiveness of SCS with these higher energy stimulation waveforms for treatment of PSPS in controlled study settings.^12–17 However, not much is known about SCS use and the programmed stimulation parameters in this patient population in day-to-day clinical use in specialized pain clinics. Some INS’s contains an accelerometer that records the orientation of the implanted device and provide some metrics on the body position of the user (e.g., upright, horizontal, recline). Until now, no studies or registries have been performed that provide information on the use of these technologies in pain clinics where SCS is offered per standard of care. The aim of this post-implant survey is intended to collect user experiences, and outcomes and device settings from patients who use spinal cord stimulation with a single neurostimulator model for treatment of chronic refractory back and leg pain.

Survey design

The project was designed as a cross-sectional, health research study in which clinical and product-related data from many different patients were collected by the treating medical staff at a single point in time once SCS treatment had stabilized, and during routine patient follow-up. Additionally, the project contained market research on experiences and satisfaction of the treating healthcare professional with the SCS device (See below Data Collection for details)

Neurostimulator

The INS investigated in the survey is the Intellis neurostimulator (model 97715, Medtronic). The device is small and rechargeable, has dedicated battery technology that guarantees fast recharging and allows programming of different stimulation modes, such as low-energy (tonic, conventional) and higher-energy modes. Furthermore, the INS contains an accelerometer that records the orientation of the device and with that provides metrics on orientation of the user and finally, is MRI-conditional which means it is specifically designed and tested to operate safely in the unique environment of a Magnetic Resonance Imaging (MRI) scanner.

Participants

1. Patients
1. At least 18 years old.
2. Being diagnosed with PSPS and refractory to best medical treatment.
   1. PSPS-T1, where no (relevant) surgery was performed.
   2. PSPS-T2, surgical end stage after one or several operative interventions on the lumbar neuroaxis, indicated to relieve lower back pain, radicular pain or the combination of both without positive effect.
3. Having chronic pain that exists for at least 6 months with a pain intensity of 5 or higher measured on numeric rating scale
4. Received the selected INS per standard of care and local requirements and
5. Treatment of chronic pain has been stabilized.

2. Health care professionals, who treated the patients that are included in this survey.

Sites that were candidate to participate in this survey were selected based on the following criteria

1. located in Europe
2. SCS volume (> 10 SCS implants for PSPS per year)
3. using already the selected INS
4. inclusion of at least 4 patients (due to aggregate data collection requirements)
5. data from existing database or easily retrievable from patient files

Data collection

The sponsor provided the participating sites with an aggregated data collection tool that is an Excel file able to automatically generate reports of aggregated data. The site’s clinical staff independently collected and manually entered patient data into the tool that automatically populated the summary reports with the data aggregated. The site provided only the aggregated reports to the sponsor.

Collected data consisted of (the complete list of data items is shown in Table 1):

1. Demographic parameters (e.g., age, gender, indication for SCS)
2. Technical details SCS (e.g., lead model, INS placement, stimulation waveform, battery)
3. Programming data (e.g., # cathodes and anodes, stimulation parameters)
4. Patient reported outcomes and satisfaction (e.g., pain change, goal achievement, work)
5. HCP survey (e.g., INS MRI conditionality, INS size)

Five aggregated reports (Demographics, Technical Details, Programming Group, Outcomes, HCP Survey) were signed by the site data collector and submitted electronically to the project sponsor. The data collected was aggregated, therefore no individual patient data were identifiable from the report provided.

Descriptive statistics were used to summarize the data collected in the site aggregated reports. Continuous variables are summarized by computing mean and standard deviation,¹ minimum, maximum. Categorical variables were summarized with counts and percentages. Summary statistics are reported with maximum 1 decimal, as appropriate. The R software, version 4.3.1, (R Foundation, Vienna, AT) was used.

Ethics/IRB

Submission to the Ethics committee was done, depending on the local requirement. Data were provided to the sponsor in an aggregated and fully anonymized format. In case requested by the local ethics board, the sites were provided with a data release form that should be signed by the patient prior to data collection.

¹The combined standard deviation for all reports is computed as the square root of the weighted mean of the sums of the variance and the squared difference between the site mean and the overall mean.

Survey data from 124 patients were collected at 9 hospitals/pain clinics. Table 2 summarizes the patients’ demographic and medical history data. On average the patients were 54.3 years old and had chronic pain for 9.9 years. Most patients were female (55.6%). The indication PSPS for SCS was mainly for overall back and leg pain (68.5%) but also leg pain (22.6%) and back pain (8.9%). Almost all subjects had prior back surgery (91.1%) or PSPS-T2, with 79.8% of patients having had between 1 and 3 surgeries. Eleven patients (8.9%) had had no prior back surgery (PSPS-T1). Table 3 shows the summary on technical details. The average time between SCS implantation and clinical survey data capture was 931.6 days, or approximately 2.6 years. Some patients may have had another INS model prior to receiving the INS being investigated. Of all patients, 101 had percutaneous leads and 23 had a surgical lead implanted. Most patients (70.2%) had 2 percutaneous leads implanted and for the majority placed in the median position (66.9%), followed by the paramedian (29.8%) position. The INS was placed for most patients in the gluteal region (51.6%) but also the abdominal (27.4%) and the flank (21%) region.

Spinal cord stimulation programming

The stimulation modes used were higher energy waveforms (65.3%) or conventional/tonic stimulation (34.7%), and paresthesia sensations were felt in 38.7% of cases. Figure 1 shows the programmed contact location for the back (Top) and leg (Bottom) pain. For the treatment of back pain, the target centered around T9 with a distribution between mid T8 and disc T9/T10. For the treatment of leg pain, however, the target centered near mid T8. From the eight possible different programming group options (A-H), group A was used by most patients (86.3%). This group had 4 programs in 50.8% of the cases and was used 74.4% of the time. Two other programmed groups (B and C) were used by 52.4% and 46.8% of patients, respectively. Table 4 summarizes for most used group (program group A), the active number of cathodes and anodes, stimulation intensity, pulse duration and stimulation frequency. On average, patients had their stimulation on during 95% of the time. Data based on the last 10 recharges showed an average neurostimulator charge duration of 41.4 minutes once per 2.7 days. 45.3% (39/86) of patients had the Accelerometer Orientation in the neurostimulator activated and data on position trends were available from 32 patients (Table 3). The mean percentage time patients were in the following positions: upright, mobile, reclining, and all lying, were, 37%, 3.4%, 8.5% and 51.2% respectively.

Figure 1 Contact Locations for treating Back pain (top) and Leg pain (bottom).

Patient reported outcomes

The summary on outcomes are shown in Table 5. Patients reported a mean improvement in pain of 70.4%. One hundred and ten patients (88.7%) had a predefined functional goal prior to starting SCS. At the time of the survey patients reported an improvement in their predefined goals of 75.4%. Furthermore, pain medication was reduced in 102 (82.3%) patients and 32 patients (25.8%) returned to work. Figure 2 shows the patient satisfaction outcomes. Patient satisfaction for treatment of pain rated as “Somewhat satisfied, Satisfied or Very satisfied” was reported by 116 (93.6%) patients. 116 (93.6%), 113 (91.1%) and 103 (83.1%) patients were “Somewhat satisfied, Satisfied or Very satisfied” for respectively recharge ease, recharging time and recharge frequency.

Figure 2 Patient satisfaction: % (n=124).

Health care professional satisfaction

Figure 3 represents HCP satisfaction. HCPs were “Satisfied or Very Satisfied”, in 98.0% for the MRI conditionality of the INS, in 96.8% for the size of the INS, in 94.9% for use of the objective orientation data and in 92.7% for SCS programming ease.

Figure 3 Health care professional satisfaction: % (n/Resp).

The patients included in the CS had a similar age and duration of chronic pain as reported in other studies.^1–8 Most patients (74%) in the CS received SCS after 0-2 spine surgeries. The patients described in this CS demonstrated effective suppression of back and/or leg pain, even over longer periods of time, as is indicated by the wide range of data capture since SCS onset (up to 8813 days after SCS implant). The pain suppression by SCS was accompanied by an overall reduction in pain medication in more than 80% of patients. Apart from these benefits, patients additionally showed an improvement of 74% in achieving their goals for living, and a quarter of participants returned to work. These benefits and improvements are in line with what has been reported in controlled studies and registries.^15–17 Finally, these outcomes are reflected in the high overall satisfaction with SCS by these patients. Optimization of SCS therapy has been shown in earlier studies (registries) to require a patient individual approach. This may be partly due to anatomical (physiological) differences between subjects, as is illustrated by the variation in the anatomical target for both treating the back pain component and the leg pain component (Figure 1). Additionally, treatment of the predominant pain indication, such as leg pain or back pain, may require specific waveforms. Examples are lower energy waveforms, such as tonic/conventional stimulation regularly used for leg pain or higher energy waveforms, such as DTM that are commonly used for back and back-and-leg pain.^{1–4,11–17} The patients’ individual approach is further illustrated by the variation in programming, such as the number of programs to accommodate specific needs during the day, and stimulation parameters (frequencies, pulse durations and amplitudes).

The INS used in this CS demonstrated flexibility to patients with PSPS, who are treated with SCS. The majority of patients were using high energy waveforms. Due to the higher energy requirements, patients need to recharge their INS more often compared to tonic, low energy stimulation. However, the ease of recharging the INS and the time to recharge the INS were widely accepted by patients, as illustrated by their user satisfaction. Use of the device for these patients was well recognized and appreciated by the health care professionals who implant and/or program the SCS devices. Both the size of the INS and the MRI conditionality, i.e. the limited number of conditions for a patient to receive and MRI were highly valued, similarly as the ease of programming and information provided by the Snapshot report. The latter can provide objective data on the patient’s functional activities.¹⁸ Overall, the CS has shown to be an effective tool to provide a cross-sectional overview of the use of SCS for a specific patient population and neurostimulator device.

This CS shows that SCS is offered in a standardized method across pain clinics in Europe and describes user experiences, therapy outcomes and device settings from patients who use this therapy for treatment of chronic refractory pain.

This is a descriptive analysis performed on a selected set of clinicians. According to the nature of retrospective/prospective observational research data and since the sponsor can’t monitor the single patient data included selection bias could be possible.

The research project was sponsored by Medtronic. The participating hospitals and clinics received financial compensation for the time spent on data collection and entry. HH, CS and RB are Medtronic employees.

The authors declare that there are no conflicts of interest.

1. North RB, Kidd DH, Farrokhi F, et al. Spinal cord stimulation versus repeated lumbosacral spine surgery for chronic pain: a randomized, controlled trial. Neurosurgery. 2005;56(1):98–106.
2. Kumar K, Taylor RS, Jacques L, et al. Spinal cord stimulation versus conventional medical management for neuropathic pain: a multicentre randomised controlled trial in patients with failed back surgery syndrome. 2007;132(1-2):179–188.
3. Kumar K, Taylor RS, Jacques L, et al. The effects of spinal cord stimulation in neuropathic pain are sustained: a 24-month follow-up of the prospective randomized controlled multicenter trial. 2008;63(4):762–770.
4. Gatzinsky K, Baardsen R, Buschman HP. Evaluation of the effectiveness of percutaneous octapolar leads in pain treatment with spinal cord stimulation of patients with failed back surgery syndrome during a 1-year follow-up: a prospective multicenter international study. Pain Pract. 2017;17(4):428–437.
5. Fishman M, Cordner H, Justiz R, et al. Twelve-month results from multicenter, open-label, randomized controlled clinical trial comparing differential target multiplexed spinal cord stimulation and traditional spinal cord stimulation in subjects with chronic intractable back and leg pain. Pain Pract. 2021;21(8):912–923.
6. Deer T, Slavin KV, Amirdelfan K, et al. Success using neuromodulation with BURST (SUNBURST) study: results from a prospective, randomized controlled trial using a novel burst waveform. 2018;21(1):56–66.
7. Kapural L, Yu C, Doust MW, et al. Novel 10-kHz high-frequency therapy (HF10 therapy) is superior to traditional low-frequency spinal cord stimulation for the treatment of chronic back and leg pain: the SENZA-RCT randomized controlled trial. 2015;123(4):851–860.
8. Rigoard P, Basu S, Desai M, et al. Multicolumn spinal cord stimulation for predominant back pain in failed back surgery syndrome patients: a multicenter randomized controlled trial. 2019;160(6):1410–1420.
9. De Ridder D, Vanneste S, Plazier M, van der Loo E, Menovsky T. Burst spinal cord stimulation: toward paresthesia-free pain suppression. 2010;66(5):986–990.
10. Brinzeu A, Cuny E, Fontaine D, et al. Spinal cord stimulation for chronic refractory pain: long-term effectiveness and safety data from a multicentre registry. Eur J Pain. 2019;23(5):1031–1044.
11. Schultz DM, Calodney AK, Mogilner AY, et al. Spinal cord stimulation (SCS)—the Implantable Systems Performance Registry (ISPR). 2016;19(8):857–863.
12. Al Kaisy A, Palmisani S, Pang D, et al. Prospective, randomized, sham-control, double-blind, crossover trial of subthreshold spinal cord stimulation at various kilohertz frequencies in subjects suffering from failed back surgery syndrome (SCS frequency study). 2018;21(5):457–465.
13. Wille F, Breel JS, Bakker EW, et al. Altering conventional to high-density spinal cord stimulation: an energy dose-response relationship in neuropathic pain therapy. 2017;20(1):71–80.
14. Thomson SJ, Tavakkolizadeh M, Love JS, et al. Effects of rate on analgesia in kilohertz frequency spinal cord stimulation: results of the PROCO randomized controlled trial. 2018;21(1):67–76.
15. Benyamin R, Galan V, Hatheway J, et al. Options: a prospective, open-label study of high-dose spinal cord stimulation in patients with chronic back and leg pain. Pain Physician. 2020;23(1):87–98.
16. De Jaeger M, Goudman L, Brouns R, et al. The long-term response to high-dose spinal cord stimulation in patients with failed back surgery syndrome after conversion from standard spinal cord stimulation: an effectiveness and prediction study. 2021;24(3):546–555.
17. Hatheway JA, Mangal V, Fishman MA, et al. Long-term efficacy of a novel spinal cord stimulation clinical workflow using kilohertz stimulation: twelve-month results from the Vectors study. 2021;24(3):556–565.
18. Schultz DM, Webster LR, Kosek P, et al. Sensor-driven position-adaptive spinal cord stimulation for chronic pain. Pain Physician. 2012;15(1):1–12.