A national survey of spinal cord stimulation trial-to-permanent conversion rates

Long-Term Outcome in Patients With Spinal Cord Stimulation for Failed Back Surgery Syndrome: A 20-Year Audit of a Single Center

STUDY DESIGN

This is a retrospective, observational study.

INTRODUCTION

Spinal cord stimulation (SCS) has found its application in chronic pain treatment, with failed back surgery syndrome (FBSS) as one of the most important indications. However, to date, little is known about the long-term effectiveness of the treatment. The aim of this study is to analyze retrospectively the long-term outcomes of SCS treatment in a single multidisciplinary pain center on predominant radicular pain, using devices of a single manufacturer.

MATERIALS AND METHODS

Patient data on overall patient satisfaction, pain intensity, and adverse events were retrospectively collected in our clinical practice between January 1998 and January 2018, for 191 patients who received a permanent SCS implant. Secondary health measures included the influence of opioid and nicotine use on pain reduction after therapy.

RESULTS

The trial-to-implant ratio was 93.6%. At a mean follow-up of 10.6 years, 78.5% of the patients were satisfied with the treatment outcome, with a significant pain reduction of an average three points on a Numeric Rating Scale. Opioid and nicotine usage did not have a significant link with the pain reduction one year after the treatment. Furthermore, devices had an average battery lifespan of 8.4 years. A total of 248 revisions were recorded. A total of 24 patients (11.7%) acquired an infection; 7 of 204 patients had an infection during the trial period, 2 of 191 patients had an infection in the first postoperative year, and 15 of 191 patients had an infection after the first year. The average time to infection, if not in the first year, was 10.1 years.

CONCLUSIONS

A successful long-term outcome regarding pain relief in patients with predominant radicular pain due to FBSS is established with SCS therapy.

Transcutaneous Afferent Patterned Stimulation for Essential Tremor: Real-World Evidence with Long Term Follow-Up

Background

Transcutaneous afferent patterned stimulation (TAPS) is a non-invasive neuromodulation therapy for the treatment of hand tremor in patients with essential tremor (ET). This retrospective post-market analysis evaluated the usage, effectiveness, and safety of TAPS in patients using TAPS beyond a 90-day trial period in a real-world setting.

Methods

Study personnel screened a manufacturer's database for TAPS devices that had been prescribed for the treatment of ET and used beyond a 90-day trial period between August 2019 and January 2023. The device logs were collected to extract the therapy usage, accelerometry measurements, and on-board ratings of tremor improvement. Study personnel also evaluated results of a voluntary survey requested by the manufacturer after the 90-day trial period. Adverse events were assessed from patients' complaints reported to the manufacturer.

Results

A total of 1,223 patients in the manufacturer's database met the study criteria. The patients had used therapy between 90 and 1,233 days, with average usage of 5.6 sessions per week. Accelerometry data indicated 89% of patients experienced tremor improvement, with an average 64% improvement. 63% of patients rated at least half of their sessions as improved. No significant habituation was observed in patients who used therapy for more than one year. Approximately 62% of survey respondents either had reduced medication or planned to consult physicians about their medication usage. No serious safety events were reported, and 10% of patients reported minor safety complaints.

Discussion

The analysis demonstrates the real-world effectiveness and safety of TAPS beyond a 90-day trial period over a longer timeframe and in a larger population size than previously published evidence.

Spinal Cord Stimulation for Failed Back Surgery Syndrome: to Trial or Not to Trial?

Spinal cord stimulation (SCS) is a recommended therapy to treat failed back surgery syndrome (FBSS). A trial period is practiced to enhance patient selection. However, its fundamental evidence is limited, especially concerning long-term benefit and therapy safety. We compared the long-term (5.3 ± 4.0 years) clinical outcome and therapy safety of a trialed and nontrialed implantation strategy, including multidimensional variables and pain intensity fluctuations over time. A multicenter cohort analysis was performed in 2 comparable groups of FBSS patients. Regarding eligibility, patients had to be treated with SCS for at least 3 months. While the Trial group comprised patients who underwent an SCS implantation after a successful trial, the No-Trial group encompassed patients who underwent complete implantation within 1 session. The primary outcome measures were pain intensity scores and complications. The Trial and No-Trial groups consisted of 194 and 376 patients (N = 570), respectively. A statistically but not clinically significant difference in pain intensity (P = .003; effect = 0.506 (.172-.839)) was found in favor of the Trial group. No interaction between a time dependency effect and pain intensity was noted. Whereas trialed SCS patients were more likely to cease opioid usage (P = .003; OR = .509 (.326-.792)), patients in the No-Trial group endured fewer infections (P = .006; proportion difference = .43 (.007-.083)). Although the clinical relevance of our findings should be proven in future studies, this long-term real-world data study indicates that patient-centered assessments on whether an SCS trial should be performed have to be investigated. According to the current ambiguous evidence, SCS trials should be considered on a case-by-case basis. PERSPECTIVE: The currently available comparative evidence, together with our results, remains ambiguous on which SCS implantation strategy might be deemed superior. An SCS trial should be considered on a case-by-case basis, for which further investigation of its clinical utility in certain patient populations or character traits is warranted.

Evidence-based consensus guidelines on patient selection and trial stimulation for spinal cord stimulation therapy for chronic non-cancer pain

Spinal cord stimulation (SCS) has demonstrated effectiveness for neuropathic pain. Unfortunately, some patients report inadequate long-term pain relief. Patient selection is emphasized for this therapy; however, the prognostic capabilities and deployment strategies of existing selection techniques, including an SCS trial, have been questioned. After approval by the Board of Directors of the American Society of Regional Anesthesia and Pain Medicine, a steering committee was formed to develop evidence-based guidelines for patient selection and the role of an SCS trial. Representatives of professional organizations with clinical expertize were invited to participate as committee members. A comprehensive literature review was carried out by the steering committee, and the results organized into narrative reports, which were circulated to all the committee members. Individual statements and recommendations within each of seven sections were formulated by the steering committee and circulated to members for voting. We used a modified Delphi method wherein drafts were circulated to each member in a blinded fashion for voting. Comments were incorporated in the subsequent revisions, which were recirculated for voting to achieve consensus. Seven sections with a total of 39 recommendations were approved with 100% consensus from all the members. Sections included definitions and terminology of SCS trial; benefits of SCS trial; screening for psychosocial characteristics; patient perceptions on SCS therapy and the use of trial; other patient predictors of SCS therapy; conduct of SCS trials; and evaluation of SCS trials including minimum criteria for success. Recommendations included that SCS trial should be performed before a definitive SCS implant except in anginal pain (grade B). All patients must be screened with an objective validated instrument for psychosocial factors, and this must include depression (grade B). Despite some limitations, a trial helps patient selection and provides patients with an opportunity to experience the therapy. These recommendations are expected to guide practicing physicians and other stakeholders and should not be mistaken as practice standards. Physicians should continue to make their best judgment based on individual patient considerations and preferences.

Trends in spinal cord stimulation utilization: change, growth and implications for the future

Chronic pain impacts more than 100 million Americans and has a significant impact on the economy and quality of life. Spinal cord stimulation (SCS) has demonstrated efficacy in managing a growing number of chronic pain conditions. This in combination with an increasing number of physicians trained in SCS placement has produced significant changes in utilization, expense and sites of service related to SCS. In particular, there has been a large increase in SCS placement by non-surgeons, use of percutaneous leads and performance in ambulatory surgery centers instead of inpatient settings. There are also notable differences in SCS use related to age, race, insurance coverage and geography. There is a large potential market and use of these therapies is predicted to grow from $2.41 billion in 2020 to $4.12 billion US dollars globally by 2027. At the same time, there is increasing scrutiny around utilization of this therapy related to cost, complications, long-term efficacy and explant rates that has the potential to impact access to this therapy in the future. We must examine our indications, technique and management to optimize outcomes and utilization of SCS going forward.

Role of patient selection and trial stimulation for spinal cord stimulation therapy for chronic non-cancer pain: a comprehensive narrative review

Background/importance

Patient selection for spinal cord stimulation (SCS) therapy is crucial and is traditionally performed with clinical selection followed by a screening trial. The factors influencing patient selection and the importance of trialing have not been systematically evaluated.

Objective

We report a narrative review conducted to synthesize evidence regarding patient selection and the role of SCS trials.

Evidence review

Medline, EMBASE and Cochrane databases were searched for reports (any design) of SCS in adult patients, from their inception until March 30, 2022. Study selection and data extraction were carried out using DistillerSR. Data were organized into tables and narrative summaries, categorized by study design. Importance of patient variables and trialing was considered by looking at their influence on the long-term therapy success.

Findings

Among 7321 citations, 201 reports consisting of 60 systematic reviews, 36 randomized controlled trials (RCTs), 41 observational studies (OSs), 51 registry-based reports, and 13 case reports on complications during trialing were included. Based on RCTs and OSs, the median trial success rate was 72% and 82%, and therapy success was 65% and 61% at 12 months, respectively. Although several psychological and non-psychological determinants have been investigated, studies do not report a consistent approach to patient selection. Among psychological factors, untreated depression was associated with poor long-term outcomes, but the effect of others was inconsistent. Most RCTs except for chronic angina involved trialing and only one RCT compared patient selection with or without trial. The median (range) trial duration was 10 (0–30) and 7 (0–56) days among RCTs and OSs, respectively.

Conclusions

Due to lack of a consistent approach to identify responders for SCS therapy, trialing complements patient selection to exclude patients who do not find the therapy helpful and/or intolerant of the SCS system. However, more rigorous and large studies are necessary to better evaluate its role.

Screening trials of spinal cord stimulation for neuropathic pain in England—A budget impact analysis

Screening trials of spinal cord stimulation (SCS) prior to full implantation of a device are recommended by expert guidelines and international regulators. The current study sought to estimate the budget impact of a screening trial of SCS and the costs or savings of discontinuing the use of a screening trial. A budget impact analysis was performed considering a study population that reflects the size and characteristics of a patient population with neuropathic pain in England eligible for SCS. The perspective adopted was that of the NHS with a 5-year time horizon. The base case analysis indicate that a no screening trial strategy would result in cost-savings to the NHS England of £400,000–£500,000 per year. Sensitivity analyses were conducted to evaluate different scenarios. If ≥5% of the eligible neuropathic pain population received a SCS device, cost-savings would be >£2.5 million/year. In contrast, at the lowest assumed cost of a screening trial (£1,950/patient), a screening trial prior to SCS implantation would be cost-saving. The proportion of patients having an unsuccessful screening trial would have to be ≥14.4% for current practice of a screening trial to be cost-saving. The findings from this budget impact analysis support the results of a recent UK multicenter randomized controlled trial (TRIAL-STIM) of a policy for the discontinuation of compulsory SCS screening trials, namely that such a policy would result in considerable cost-savings to healthcare systems.

60-Day PNS Treatment May Improve Identification of Delayed Responders and Delayed Non-Responders to Neurostimulation for Pain Relief

Objective

Conventional neurostimulation typically involves a brief (eg, ≤10-day) trial to assess presumed effectiveness prior to permanent implantation. Low trial conversion rates and high explant rates due to inadequate pain relief highlight the need for improved patient identification strategies. The development of a 60-day percutaneous peripheral nerve stimulation (PNS) system enables evaluation of outcomes following an extended temporary treatment period of up to 60 days, that may obviate or validate the need for permanent implant. The present study provides the first real-world evidence regarding patient response throughout a 60-day PNS treatment period.

Methods

Anonymized data listings were compiled from patients who underwent implantation of temporary percutaneous leads and opted-in to provide real-world data to the device manufacturer during routine interactions with device representatives throughout the 60-day treatment.

Results

Overall, 30% (222/747) of patients were early responders (≥50% pain relief throughout treatment). Another 31% (231/747) of patients initially presented as non-responders but surpassed 50% pain relief by the end of treatment. Conversely, 32% (239/747) of patients were non-responders throughout treatment. An additional 7% (55/747) of patients initially presented as responders but fell below 50% relief by the end of the treatment period.

Conclusion

An extended, 60-day PNS treatment may help identify delayed responders, providing the opportunity for sustained relief and improving access to effective PNS treatment. Compared to a conventionally short trial of ≤10 days, a longer 60-day PNS treatment may also help reduce explant rates by identifying delayed non-responders unlikely to benefit long-term. These scenarios support the importance of an extended 60-day temporary PNS stimulation period to help inform stepwise treatment strategies that may optimize outcomes and cost-effectiveness.

Research design considerations for randomized controlled trials of spinal cord stimulation for pain: Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials/Institute of Neuromodulation/International Neuromodulation Society recommendations

ABSTRACT

Spinal cord stimulation (SCS) is an interventional nonpharmacologic treatment used for chronic pain and other indications. Methods for evaluating the safety and efficacy of SCS have evolved from uncontrolled and retrospective studies to prospective randomized controlled trials (RCTs). Although randomization overcomes certain types of bias, additional challenges to the validity of RCTs of SCS include blinding, choice of control groups, nonspecific effects of treatment variables (eg, paresthesia, device programming and recharging, psychological support, and rehabilitative techniques), and safety considerations. To address these challenges, 3 professional societies (Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials, Institute of Neuromodulation, and International Neuromodulation Society) convened a meeting to develop consensus recommendations on the design, conduct, analysis, and interpretation of RCTs of SCS for chronic pain. This article summarizes the results of this meeting. Highlights of our recommendations include disclosing all funding source and potential conflicts; incorporating mechanistic objectives when possible; avoiding noninferiority designs without internal demonstration of assay sensitivity; achieving and documenting double-blinding whenever possible; documenting investigator and site experience; keeping all information provided to patients balanced with respect to expectation of benefit; disclosing all information provided to patients, including verbal scripts; using placebo/sham controls when possible; capturing a complete set of outcome assessments; accounting for ancillary pharmacologic and nonpharmacologic treatments in a clear manner; providing a complete description of intended and actual programming interactions; making a prospective ascertainment of SCS-specific safety outcomes; training patients and researchers on appropriate expectations, outcome assessments, and other key aspects of study performance; and providing transparent and complete reporting of results according to applicable reporting guidelines.

Does a screening trial for spinal cord stimulation in patients with chronic pain of neuropathic origin have clinical utility and cost-effectiveness (TRIAL-STIM)? A randomised controlled trial

Supplemental Digital Content is Available in the Text.

The TRIAL-STIM randomised controlled trial found no evidence that a spinal cord stimulation screening trial strategy provides superior patient outcomes compared to a no trial screening approach.

Spinal cord stimulation (SCS) is an established treatment of chronic neuropathic pain. Although a temporary SCS screening trial is widely used to determine whether a patient should receive permanent SCS implant, its evidence base is limited. We aimed to establish the clinical utility, diagnostic accuracy, and cost-effectiveness of an SCS screening trial. A multicentre single-blind, parallel two-group randomised controlled superiority trial was undertaken at 3 centres in the United Kingdom. Patients were randomised 1:1 to either SCS screening trial strategy (TG) or no trial screening strategy (NTG). Treatment was open label, but outcome assessors were masked. The primary outcome measure was numerical rating scale (NRS) pain at 6-month follow-up. Between June 2017 and September 2018, 105 participants were enrolled and randomised (TG = 54, NTG = 51). Mean numerical rating scale pain decreased from 7.47 at baseline (before SCS implantation) to 4.28 at 6 months in TG and from 7.54 to 4.49 in NTG (mean group difference: 0.2, 95% confidence interval [CI]: −1.2 to 0.9, P = 0.89). We found no difference between TG and NTG in the proportion of pain responders or other secondary outcomes. Spinal cord stimulation screening trial had a sensitivity of 100% (95% CI: 78-100) and specificity of 8% (95% CI: 1-25). The mean incremental cost-effectiveness ratio of TG vs NTG was £78,895 per additional quality-adjusted life-year gained. In conclusion, although the SCS screening trial may have some diagnostic utility, there was no evidence that an SCS screening TG provides superior patient outcomes or is cost-effective compared to a no trial screening approach.

Sustained Long-Term Outcomes With Closed-Loop Spinal Cord Stimulation: 12-Month Results of the Prospective, Multicenter, Open-Label Avalon Study

BACKGROUND

Spinal cord stimulation (SCS) activates the dorsal column fibers using electrical stimuli. Current SCS systems function in fixed-output mode, delivering the same stimulus regardless of spinal cord (SC) activation.

OBJECTIVE

To present long-term outcomes of a novel closed-loop SCS system that aims to maintain the SC activation near a set target level and within a therapeutic window for each patient. SC activation is measured through the evoked compound action potential (ECAP) generated by each stimulus pulse.

METHODS

Fifty patients with lower back and/or leg pain who were successfully trialed received a permanent system (Evoke; Saluda Medical, Sydney, Australia). Ratings of pain (visual analog scale), quality of life, function, sleep, and medication use were collected at baseline and at each visit. SC activation levels were reported in summary statistics. The therapeutic window for each individual patient was defined as the range of ECAP amplitudes between sensation threshold and uncomfortably strong stimulation.

RESULTS

At 12 mo, the proportion of patients with ≥50% relief was 76.9% (back), 79.3% (leg), and 81.4% (overall), and the proportion with ≥80% pain relief was 56.4% (back), 58.6% (leg), and 53.5% (overall). Patients spent a median of 84.9% of their time with stimulation in their therapeutic window, and 68.8% (22/32) eliminated or reduced their opioid intake. Statistically significant improvements in secondary outcomes were observed.

CONCLUSION

The majority of patients experienced more than 80% pain relief with stable SC activation, as measured by ECAP amplitude at 12 mo, providing evidence for the long-term effectiveness of the Evoke closed-loop SCS system.

A Deep Brain Stimulation Trial Period for Treating Chronic Pain

Early studies of deep brain stimulation (DBS) for various neurological disorders involved a temporary trial period where implanted electrodes were externalized, in which the electrical contacts exiting the patient's brain are connected to external stimulation equipment, so that stimulation efficacy could be determined before permanent implant. As the optimal brain target sites for various diseases (i.e., Parkinson's disease, essential tremor) became better established, such trial periods have fallen out of favor. However, deep brain stimulation trial periods are experiencing a modern resurgence for at least two reasons: (1) studies of newer indications such as depression or chronic pain aim to identify new targets and (2) a growing interest in adaptive DBS tools necessitates neurophysiological recordings, which are often done in the peri-surgical period. In this review, we consider the possible approaches, benefits, and risks of such inpatient trial periods with a specific focus on developing new DBS therapies for chronic pain.

Explantation of Percutaneous Spinal Cord Stimulator Devices: A Retrospective Descriptive Analysis of a Single-Center 15-Year Experience

OBJECTIVES

The aims of this study were to identify the reasons for explanation of spinal cord stimulator (SCS) devices and to further quantify the proportions and time lines of these causes of explantation in order to determine improvement opportunities for the development of best practices.

DESIGN

Retrospective, single academic center.

MATERIALS AND METHODS

Patients who were implanted with percutaneous SCS devices from 2002 to 2015 and with follow-up available until the end of September 2017 were included in this retrospective chart analysis.

RESULTS

Of the 356 patients trialed, 252 underwent implantation of an SCS device with a permanent to trial ratio of 71%. Of the patients who had a permanent implant, 50% had failed back surgery syndrome, 25% had complex regional pain syndrome, and 25% had other diagnoses. At the end of the study period, the explantation rate was 30%. The causes for explantation included biological complications (26.6%), paresthesia limitations or side effects (26.6%), hardware complications (13.3%), ineffective pain control (28%), and no further need for stimulation therapy (5.3%).

CONCLUSIONS

Device removal is not uncommon, and opportunities to enhance the long-term success of SCS devices do exist. These include modification of trialing methods, achieving better paresthesia overlay, using magnetic resonance imaging (MRI) conditional equipment, development of robust technologies and hardware to reduce equipment malfunction, and improving efficacy with new innovative wave forms.

A Review of Clinical Data on Salvage Therapy in Spinal Cord Stimulation

BACKGROUND

Since its introduction in 1967, neuromodulation through spinal cord stimulation (SCS) or dorsal root ganglion stimulation (DRGs) has advanced significantly in both the technology and indications for use. There are now over 14,000 SCS implants performed worldwide every year. This review focuses on mechanisms behind the loss of efficacy in neuromodulation and current data on salvage therapy, defined as the conversion of a neuromodulation device to an alternative SCS or DRG stimulation, in the event of loss of efficacy or failure of a trial.

STUDY DESIGN

A narrative review of clinical studies regarding habituation, explant data, and salvage therapy with SCS.

METHODS

Available literature was reviewed on spinal cord stimulation technology and salvage therapy. Data sources included relevant literature identified through searches of PubMed, MEDLINE/OVID, SCOPUS, and manual searches of the bibliographies of known primary and review articles.

OUTCOME MEASURES

The primary outcome measures were to understand the mechanisms of loss of efficacy, provide a review of explants due to failure in treatment, and summarize the data on current salvage therapy in SCS.

RESULTS

A total of eight studies and four abstracts/poster presentations were identified and reviewed. Of the eight studies, only one was a randomized controlled trial.

CONCLUSIONS

There is limited evidence for the appropriate treatment alternatives, but from data currently available the conversion from conventional tonic stimulation to burst, high frequency (10 kHz), multiple wave forms, and/or DRGs may be appropriate in select patients and will require further research to determine the most appropriate first line salvage in the context of the underlying pain pathology.

Trial Versus No Trial of Spinal Cord Stimulation for Chronic Neuropathic Pain: Cost Analysis in United Kingdom National Health Service

OBJECTIVES

The aim of the current project was to evaluate the spinal cord stimulation (SCS) screening trial success rate threshold to obtain the same cost impact across two identical sets of patients following either a prolonged screening trial prior to implantation strategy or a full implant without a screening trial.

MATERIALS AND METHODS

A cost impact analysis was carried out from a health care perspective and considered trial to implant rates reported in the literature. Items of resource use were costed using national averages obtained from the National Health Service (NHS) reference cost data base. Cost components were added up to derive total patient level costs for the NHS. Only the costs associated with the screening trial procedures and devices were considered.

RESULTS

The most conservative of our estimates suggest that a failure rate of less than 15% is cost saving to the NHS. A failure rate as high as 45% can also be cost saving if the less expensive nonrechargeable SCS devices are used. All the thresholds observed represent a considerably higher screening failure rate than that reported in the latest randomized controlled trials (RCTs) of SCS. A trial to implant ratio of 91.6% could represent savings between £16,715 (upper bound 95% CI of rechargeable implantable pulse generator [IPG] cost) and £246,661 (lower bound 95% CI of nonrechargeable IPG cost) per each 100 patients by adopting an implantation only strategy.

CONCLUSIONS

Considerable savings could be obtained by adopting an implantation strategy without a screening trial. It is plausible that accounting for other factors, such as complications that can occur with a screening trial, additional savings could be achieved by choosing a straight to implant treatment strategy. Nevertheless, additional evidence is warranted to support this claim.

Permanent Paddle-lead Trial for Spinal Cord Stimulation

Objectives

A significant number of chronic pain patients rely on spinal cord stimulation (SCS) for treatment of their intractable pain. A screening trial using percutaneous electrodes is an integral step for predicting a successful treatment course with a permanent SCS system. Most of these trials are performed in an outpatient ambulatory surgical center and some in the office setting. However, there are select patients who are considered poor candidates for percutaneous trials. We present the initial report of patients who have received surgical implantation of permanent paddle-leads for SCS trials at our institution and show that this was a safe and effective alternative for our patients who could not undergo percutaneous trials. 

Methods

We retrospectively reviewed the hospital charts of 12 patients who underwent permanent surgically-implanted paddle-lead trials from 2014 to 2017. Success was considered positive with a 50% reduction in pain rating. If positive, patients were brought back to the operating room to have the implanted leads connected to an internalized pulse generator.   

Results

All 12 patients met the criteria for a successful trial. Only one patient had his SCS system surgically removed after nine months. None of our patients reported or returned with paddle-lead migrations or infections. 

Conclusions

We report that surgically-implanted paddle-lead trials were a safe and effective alternative to percutaneous trials in our patients who were deemed poor candidates for percutaneous trials. No complications occurred and all of our patients received a second surgery for internalization of the SCS system. Patients who have previously failed percutaneous trials may be false-negatives to SCS. 

Minimally Invasive Placement of Spinal Cord Stimulator Paddle Electrodes Is Associated With Improved Perioperative and Long-Term Experience Among Neuropathic Pain Patients

STUDY DESIGN

Prospective, observational cohort study.

OBJECTIVE

This study compared in-hospital and long-term outcomes among spinal cord stimulation (SCS) patients undergoing paddle insertion by open or minimally invasive surgery (MIS) approaches.

SUMMARY OF BACKGROUND DATA

Patients with treatment-refractory extremity neuropathic pain may benefit from SCS. Conventional placement of surgical paddles for an external neurostimulation trial is through open laminectomy, but MIS techniques may offer advantages.

METHODS

Twenty SCS patients were prospectively assessed. Open patients underwent caudal thoracic laminectomy for multicolumnar electrode paddle placement. MIS patients underwent paddle placement through interlaminar flavectomy using tubular retractors. Demographic data included age, sex, underlying diagnosis, and preoperative visual analog scale (VAS) extremity scores. Intraoperative data included operative duration, blood loss, and number of device passages to achieve final position. Perioperative data included VAS back pain scores; trial data included time-to-trial and time-to-decision. Postoperative data included 1 month VAS back pain scores and 1 year follow-up device complications.

RESULTS

No demographic differences were observed among surgical cohorts. MIS procedures had shorter operative duration (P = 0.03), less blood loss (P < 0.001), and similar median number of device passages (2 vs 1.5, P = 0.71). MIS patients reported less perioperative surgical back pain (P < 0.05). External neurostimulation trials began sooner among MIS patients who also made sooner decision whether to implant the SCS device (2.8 ± 1.4 vs 4.3 ± 1.0 days, P = 0.013). Similar 1 month back pain scores were reported between surgical cohorts (P = 0.08).

CONCLUSION

MIS techniques for SCS surgical paddle implantation is associated with less perioperative morbidity and surgical site back pain, shorter external neurostimulator trial duration, and long-term device stability benefits.

LEVEL OF EVIDENCE

2.

Specialty-Based Variations in Spinal Cord Stimulation Success Rates for Treatment of Chronic Pain

OBJECTIVES

Spinal cord stimulation (SCS) has emerged as an appropriate modality of treatment for intractable chronic pain. The present study examines variations in SCS trial-to-permanent conversion rates based on provider types performing the procedure.

MATERIALS AND METHODS

We designed a large, retrospective analysis using the Truven MarketScan data base analyzing adult SCS patients with provider information available, with or without IPG implantation from the years 2007-2012. Patients were categorized based on provider type performing the implantation including anesthesiologists, neurosurgeons, orthopedic surgeons, and physical medicine and rehabilitation (PM&R). Univariate and multivariate models identified factors associated with successful conversion.

RESULTS

A total of 7667 unique instances of SCS implants were identified across five providers. Overall, 4842 (63.2%) of those receiving trials underwent permanent SCS system implantation. Anesthesiology performed the majority of implants (62.8%), followed by neurosurgery (22.0%), orthopedic surgery (10.2%), and PM&R (5.3%). Compared to anesthesiologists, both neurosurgeons (OR 10.99, 95% CI [9.11, 13.25]; p < 0.001) and orthopedic surgeons (OR 4.64, 95% CI [3.81, 5.65]; p < 0.001) had significantly higher conversion rates, while PM&R (OR 0.71, 95% CI [0.58, 0.87]; p = 0.001) had significantly lower. Percutaneous implants comprised 5473 (71.4%) of all implants. Neurosurgeons and orthopedic surgeons performed a significantly greater number of paddle implants among the different providers (p < 0.0001). Explant rates were similar across all cohorts analyzed (average 11.6%; p = 0.546).

CONCLUSIONS

In this nationwide analysis, our results suggest that over a recent five-year period, conversion rates are highest when SCS trials are performed by neurosurgeons and orthopedic surgeons. The study has important implications for establishing uniform guidelines for training, patient selection, and education of physicians across multiple disciplines.

The Volume-Outcome Effect: Impact on Trial-to-Permanent Conversion Rates in Spinal Cord Stimulation

OBJECTIVES

Conversion rates from trial leads to permanent spinal cord stimulation (SCS) systems have important implications for healthcare resource utilization (HCRU) and pain management. We hypothesized that there is a volume-outcome effect, with chronic pain patients who visit high volume SCS implanters will have higher trial-to-permanent conversion rates.

MATERIALS AND METHODS

We designed a large, retrospective analysis using the Truven MarketScan database analyzing adult SCS patients with provider information available, with or without IPG implantation from the years 2007 to 2012 was designed. Patients were divided into three provider-based groups: high (>25), medium (9-24), and low (3-8) volume providers. Univariate and multivariate models identified factors associated with successful conversion.

RESULTS

A total of 17,850 unique trial implants were performed by 3028 providers. Of 13,879 patients with baseline data available, 8981 (64.7%) progressed to permanent SCS. Higher volume providers were associated with slightly higher conversion rates (65.9% vs. 63.3% low volume, p = 0.029), explant rates (9.2% vs. 7.7% medium volume, p = 0.026), younger age (52.0 ± 13.4 years vs. 53.0 ± 13.4 years, p = 0.0026), Medicare/Medicaid (47.8% vs. 35.0% low volume, p < 0.0001), Southern region (53.5% vs. 38.9% low volume, p < 0.0001), and higher Charlson comorbidity scores (1.0 [SD = 1.4], p = 0.0002). Multivariate regression results showed female gender (1.13 [95% CI: 1.05-1.22], p < 0.001) and high volume providers associated with higher odds of successful trial conversion (1.12 [95% CI: 1.02-1.22], p = 0.014).

CONCLUSIONS

In this nationwide analysis, high volume providers achieved higher trial-to-permanent SCS conversion rates than lower volume providers. The study has implications for both training requirements and referral patterns to delineate minimum implant experience necessary for provider proficiency. Future studies may be useful to understand HCRU differences.

Complications related to the use of spinal cord stimulation for managing persistent postoperative neuropathic pain after lumbar spinal surgery

OBJECT

Structural spinal surgery yields improvement in pain and disability for selected patients with spinal stenosis, spondylolisthesis, or a herniated intervertebral disc. A significant fraction of patients exhibit persistent postoperative neuropathic pain (PPNP) despite technically appropriate intervention, and such patients can benefit from spinal cord stimulation (SCS) to alleviate suffering. The complication profile of this therapy has not been systematically assessed and, thus, was the goal of this review.

METHODS

A comprehensive literature search was performed to identify prospective cohorts of patients who had PPNP following structurally corrective lumbar spinal surgery and who underwent SCS device implantation. Data about study design, technique of SCS lead introduction, and complications encountered were collected and analyzed. Comparisons of complication incidence were performed between percutaneously and surgically implanted systems, with the level of significance set at 0.05.

RESULTS

Review of 11 studies involving 542 patients formed the basis of this work: 2 randomized controlled trials and 9 prospective cohorts. Percutaneous implants were used in 4 studies and surgical implants were used in 4 studies; in the remainder, the types were undefined. Lead migration occurred in 12% of cases, pain at the site of the implantable pulse generator occurred in 9% of cases, and wound-related complications occurred in 5% of cases; the latter 2 occurred more frequently among surgically implanted devices.

CONCLUSIONS

Spinal cord stimulation can provide for improved pain and suffering and for decreased narcotic medication use among patients with PPNP after lumbar spinal surgery. This study reviewed the prospective studies forming the evidence base for this therapy, to summarize the complications encountered and, thus, best inform patients and clinicians considering its use. There is a significant rate of minor complications, many of which require further surgical intervention to manage, including lead migration or implant infection, although such complications do not directly threaten patient life or function.

Intrathecal Pharmacology Update: Novel Dosing Strategy for Intrathecal Monotherapy Ziconotide on Efficacy and Sustainability

INTRODUCTION

Intrathecal drug delivery is a well-defined strategy to treat malignant and nonmalignant pain. Ziconotide is a well-studied intrathecal medicine option that has many attractive qualities, as it is non-granulomagenic, overdose or underdose is not associated with cardiopulmonary compromise or death, and is a non-opoid analgesic. However, it has had slow adoption into pain care algorithms because it has been historically plagued with the connotation of having a narrow therapeutic window and a low sustainability rate. We introduce a novel dosing strategy to improve patient outcomes and sustainability.

METHODS

Patients were identified as being an intrathecal candidate and trialed with ziconotide based on the current standard of care. Patient demographics, diagnosis, previous treatment failures, and pre-implant visual analog scale (VAS) scores were recorded. Once the trial was deemed successful, based on the dual bolusing strategy, the patient underwent device implantation. Consecutive patients were prospectively followed. Ziconotide was then initiated with a flex dosing strategy, weighted during nocturnal dosing. Outcome endpoints included: reduction in VAS, side effects, durability of therapy, and systemic opioid use prior to implant and at last visit were noted (calculated to daily morphine equivalents). Primary endpoint was tolerability of ziconotide at three months following new dosing strategy. No industry support or funding was obtained for this project.

RESULTS

All enrolled patients met the endpoint of the study of tolerability of ziconotide at three months. Numbers declined to 75% of patients at four months, and 70% of patients at six months. The discontinuing side-effects were most commonly urinary retention and visual hallucinations. There were no serious adverse events and no unresolved complications reported. Numerical rating scale (NRS) decreased on average from 9.06 to 1.8. Opioid reduction in morphine equivalents averaged 91.5%

DISCUSSION

The efficacy and tolerability of monotherapy ziconotide may be improved by using a weighted bolus flex dosing strategy as compared with slow continuous infusions.

CONCLUSION

We present a novel strategy to deliver ziconotide using a unique continuous infusion flex dosing strategy. Further randomized, prospective, higher-powered studies are needed to critically evaluate the conclusions suggested by this limited prospective case series.