Spinal cord stimulation for failed back surgery syndrome: Outcomes in a workers’ compensation setting

Pocket pain following spinal cord stimulator generator implantation: A narrative review of this under-reported risk

INTRODUCTION

Spinal cord stimulation (SCS) is a well-established treatment option for chronic pain. Pain over the implantable pulse generator, or pocket pain, is an incompletely understood risk of SCS implantation which may limit the efficacy of treatment and patient quality of life. The goal of this narrative review is to analyze the literature to gain a more thorough understanding of the incidence and risk factors for the development of pocket pain to help guide treatment options and minimize its occurrence in the future.

METHODS

A literature review was conducted investigating the development of pocket pain in patients with SCS for the management of a variety of pain conditions.

RESULTS

In total, 305 articles were included in the original database search and 50 met the criteria for inclusion. The highest level of evidence for papers that specifically investigated pocket pain was level III. Four retrospective, observational analyses included pocket pain as a primary outcome. The remainder of the included studies listed pocket pain as an adverse event of SCS implantation.

CONCLUSIONS

There is a relative dearth of primary literature that examines the incidence, characteristics, and health economic implications of pocket pain in patients with SCS. This highlights the need for large-scale, high-quality prospective or randomized controlled trials examining pocket pain. This may ultimately help prevent and reduce pocket pain leading to improved efficacy of treatment and greater patient quality of life.

Long-term efficacy of spinal cord stimulation for chronic primary neuropathic pain in the contemporary era: a systematic review and meta-analysis

INTRODUCTION

Spinal cord stimulation (SCS) is a modern neuromodulation technique extensively proven to be an effective modality for treatment of chronic neuropathic pain. It has been mainly studied for complex regional pain syndrome (CRPS) and failed back surgery syndrome (FBSS) and recent data almost uniformly establishes its statistically significant positive therapeutic results. It has also been compared with other available treatment modalities across various studies. However, long term data on maintenance of its efficacious potential remains less explored. Few studies have reported data on long follow-up times (>= 12 months) and have compared its efficacy with other treatment options for chronic pain, respectively. Our study pools and analyzes the available data and compares SCS with other treatment options. It also analyzes the efficacy of SCS in long term management of patients with chronic pain.

EVIDENCE ACQUISITION

We reviewed all the data available on MEDLINE, Embase and Cochrane CENTRAL using a search strategy designed to fit our pre-set inclusion and exclusion criteria. Both single-arm and double-arm studies were included. The primary outcome was defined as decrease of visual analogue scale (VAS) by >50% at 6, 12 and/or 24 months after SCS.

EVIDENCE SYNTHESIS

According to the pooled data of double-arm studies, SCS has unanimously proven its superiority over other treatment options at 6 months follow-up; however it fails to prove statistically significant difference in results at longer treatment intervals. Dorsal root ganglion stimulation, a relatively recent technique with the same underlying physiologic mechanisms as SCS, showed far more promising results than SCS. Single-arm studies show around 70% patients experiencing greater than 50% reduction in their VAS scores at 6 and 12 months.

CONCLUSIONS

SCS is a viable option for management of chronic neuropathic pain secondary to FBSS and CRPS. However, data available for its long term efficacy remains scarce and show no further statistically significant results.

Factors Predicting Clinically Relevant Pain Relief After Spinal Cord Stimulation for Patients With Chronic Low Back and/or Leg Pain: A Systematic Review With Meta-Analysis and Meta-Regression

RATIONALE

To optimize results with spinal cord stimulation (SCS) for chronic low back pain (CLBP) and/or leg pain, including persistent spinal pain syndrome (PSPS), careful patient selection based on proved predictive factors is essential. Unfortunately, the necessary selection process required to optimize outcomes of SCS remains challenging.

OBJECTIVE

This review aimed to evaluate predictive factors of clinically relevant pain relief after SCS for patients with CLBP and/or radicular leg pain, including PSPS.

MATERIALS AND METHODS

In August 2023, PubMed, Cinahl, Cochrane, and EMBASE were searched to identify studies published between January 2010 and August 2023. Studies reporting the percentage of patients with ≥50% pain relief after SCS in patients with CLBP and leg pain, including PSPS at 12 or 24 months, were included. Meta-analysis was conducted to pool results for back, leg, and general pain relief. Predictive factors for pain relief after 12 months were examined using univariable and multivariable meta-regression.

RESULTS

A total of 27 studies (2220 patients) were included for further analysis. The mean percentages of patients with substantial pain relief were 68% for leg pain, 63% for back pain, and 73% for general pain at 12 months follow-up, and 63% for leg pain, 59% for back pain, and 71% for general pain at 24 months follow-up assessment. The implantation method and baseline Oswestry Disability Index made the multivariable meta-regression model for ≥50% back pain relief. Sex and pain duration made the final model for ≥50% leg pain relief. Variable stimulation and implantation method made the final model for general pain relief.

CONCLUSIONS

This review supports SCS as an effective pain-relieving treatment for CLBP and/or leg pain, and models were developed to predict substantial back and leg pain relief. To provide high-grade evidence for predictive factors, SCS studies of high quality are needed in which standardized factors predictive of SCS success, based on in-patient improvements, are monitored and reported.

Long-term Outcomes in Use of Opioids, Nonpharmacologic Pain Interventions, and Total Costs of Spinal Cord Stimulators Compared With Conventional Medical Therapy for Chronic Pain

Importance

Spinal cord stimulators (SCSs) are increasingly used for the treatment of chronic pain. There is a need for studies with long-term follow-up.

Objective

To determine the comparative effectiveness and costs of SCSs compared with conventional medical management (CMM) in a large cohort of patients with chronic pain.

Design, Setting, and Participants

This was a 1:5 propensity-matched retrospective comparative effectiveness research analysis of insured individuals from April 1, 2016, to August 31, 2018. This study used administrative claims data, including longitudinal medical and pharmacy claims, from US commercial and Medicare Advantage enrollees 18 years or older in Optum Labs Data Warehouse. Patients with incident diagnosis codes for failed back surgery syndrome, complex regional pain syndrome, chronic pain syndrome, and other chronic postsurgical back and extremity pain were included in this study. Data were analyzed from February 1, 2021, to August 31, 2022.

Exposures

SCSs or CMM.

Main Outcomes and Measures

Surrogate measures for primary chronic pain treatment modalities, including pharmacologic and nonpharmacologic pain interventions (epidural and facet corticosteroid injections, radiofrequency ablation, and spine surgery), as well as total costs.

Results

In the propensity-matched population of 7560 patients, mean (SD) age was 63.5 (12.5) years, 3080 (40.7%) were male, and 4480 (59.3%) were female. Among matched patients, during the first 12 months, patients treated with SCSs had higher odds of chronic opioid use (adjusted odds ratio [aOR], 1.14; 95% CI, 1.01-1.29) compared with patients treated with CMM but lower odds of epidural and facet corticosteroid injections (aOR, 0.44; 95% CI, 0.39-0.51), radiofrequency ablation (aOR, 0.57; 95% CI, 0.44-0.72), and spine surgery (aOR, 0.72; 95% CI, 0.61-0.85). During months 13 to 24, there was no significant difference in chronic opioid use (aOR, 1.06; 95% CI, 0.94-1.20), epidural and facet corticosteroid injections (aOR, 1.00; 95% CI, 0.87-1.14), radiofrequency ablation (aOR, 0.84; 95% CI, 0.66-1.09), or spine surgery (aOR, 0.91; 95% CI, 0.75-1.09) with SCS use compared with CMM. Overall, 226 of 1260 patients (17.9%) treated with SCS experienced SCS-related complications within 2 years, and 279 of 1260 patients (22.1%) had device revisions and/or removals, which were not always for complications. Total costs of care in the first year were $39 000 higher with SCS than CMM and similar between SCS and CMM in the second year.

Conclusions and Relevance

In this large, real-world, comparative effectiveness research study comparing SCS and CMM for chronic pain, SCS placement was not associated with a reduction in opioid use or nonpharmacologic pain interventions at 2 years. SCS was associated with higher costs, and SCS-related complications were common.

Effect of Spinal Cord Burst Stimulation vs Placebo Stimulation on Disability in Patients With Chronic Radicular Pain After Lumbar Spine Surgery: A Randomized Clinical Trial

IMPORTANCE

The use of spinal cord stimulation for chronic pain after lumbar spine surgery is increasing, yet rigorous evidence of its efficacy is lacking.

OBJECTIVE

To investigate the efficacy of spinal cord burst stimulation, which involves the placement of an implantable pulse generator connected to electrodes with leads that travel into the epidural space posterior to the spinal cord dorsal columns, in patients with chronic radiculopathy after surgery for degenerative lumbar spine disorders.

DESIGN, SETTING, AND PARTICIPANTS

This placebo-controlled, crossover, randomized clinical trial in 50 patients was conducted at St Olavs University Hospital in Norway, with study enrollment from September 5, 2018, through April 28, 2021. The date of final follow-up was May 20, 2022.

INTERVENTIONS

Patients underwent two 3-month periods with spinal cord burst stimulation and two 3-month periods with placebo stimulation in a randomized order. Burst stimulation consisted of closely spaced, high-frequency electrical stimuli delivered to the spinal cord. The stimulus consisted of a 40-Hz burst mode of constant-current stimuli with 4 spikes per burst and an amplitude corresponding to 50% to 70% of the paresthesia perception threshold.

MAIN OUTCOMES AND MEASURES

The primary outcome was difference in change from baseline in the self-reported Oswestry Disability Index (ODI; range, 0 points [no disability] to 100 points [maximum disability]; the minimal clinically important difference was 10 points) score between periods with burst stimulation and placebo stimulation. The secondary outcomes were leg and back pain, quality of life, physical activity levels, and adverse events.

RESULTS

Among 50 patients who were randomized (mean age, 52.2 [SD, 9.9] years; 27 [54%] were women), 47 (94%) had at least 1 follow-up ODI score and 42 (84%) completed all stimulation randomization periods and ODI measurements. The mean ODI score at baseline was 44.7 points and the mean changes in ODI score were -10.6 points for the burst stimulation periods and -9.3 points for the placebo stimulation periods, resulting in a mean between-group difference of -1.3 points (95% CI, -3.9 to 1.3 points; P = .32). None of the prespecified secondary outcomes showed a significant difference. Nine patients (18%) experienced adverse events, including 4 (8%) who required surgical revision of the implanted system.

CONCLUSIONS AND RELEVANCE

Among patients with chronic radicular pain after lumbar spine surgery, spinal cord burst stimulation, compared with placebo stimulation, after placement of a spinal cord stimulator resulted in no significant difference in the change from baseline in self-reported back pain-related disability.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03546738.

Development of Machine Learning-Based Models to Predict Treatment Response to Spinal Cord Stimulation

BACKGROUND

Despite spinal cord stimulation's (SCS) proven efficacy, failure rates are high with no clear understanding of which patients benefit long term. Currently, patient selection for SCS is based on the subjective experience of the implanting physician.

OBJECTIVE

To develop machine learning (ML)-based predictive models of long-term SCS response.

METHODS

A combined unsupervised (clustering) and supervised (classification) ML technique was applied on a prospectively collected cohort of 151 patients, which included 31 features. Clusters identified using unsupervised K-means clustering were fitted with individualized predictive models of logistic regression, random forest, and XGBoost.

RESULTS

Two distinct clusters were found, and patients in the cohorts significantly differed in age, duration of chronic pain, preoperative numeric rating scale, and preoperative pain catastrophizing scale scores. Using the 10 most influential features, logistic regression predictive models with a nested cross-validation demonstrated the highest overall performance with the area under the curve of 0.757 and 0.708 for each respective cluster.

CONCLUSION

This combined unsupervised-supervised learning approach yielded high predictive performance, suggesting that advanced ML-derived approaches have potential to be used as a functional clinical tool to improve long-term SCS outcomes. Further studies are needed for optimization and external validation of these models.

Concept of the Number Needed to Treat for the Analysis of Pain Relief Outcomes in Patients Treated with Spinal Cord Stimulation

In the rapidly evolving field of spinal cord stimulation (SCS), measures of treatment effects are needed to help understand the benefits of new therapies. The present article elaborates the number needed to treat (NNT) concept and applies it to the SCS field. We reviewed the basic theory of the NNT, its calculation method, and its application to historical controlled trials of SCS. We searched the literature for controlled studies with ≥20 implanted SCS patients with chronic axial back and/or leg pain followed for ≥3 months and a reported responder rate defined as ≥50% pain relief. Relevant data necessary to estimate the NNT were extracted from the included articles. In total, 12 of 1616 records were eligible for inclusion. The records reported 10 clinical studies, including 7 randomized controlled trials, 2 randomized crossover trials, and 1 controlled cohort study. The studies investigated traditional SCS and more recently developed SCS modalities, including 10 kHz SCS. In conclusion, the NNT estimate may help SCS stakeholders better understand the effect size difference between compared treatments; however, interpretation of any NNT should take into account its full context. In addition, comparisons across trials of different therapies should be avoided since they are prone to interpretation biases.

Prevalence and predictors of return to work following a spinal cord injury using a work disability prevention approach: A systematic review and meta-analysis

Purpose

Worldwide, spinal cord injuries are associated with diminished participation in the labor market. Inconclusive reporting and differences between workplace settings for individuals with spinal cord injury (SCI) make conceptualizing return to work rates among this population inherently challenging. The objectives of this study are to explore factors associated with return to work (RTW) following an SCI. Moreover, the factors were classified according to the work disability prevention framework. Finally, we conducted a meta-analysis of the prevalence of RTW following an SCI.

Methods

Original articles were identified through a literature search in four health databases. The study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines for the mapping and identification of records. Included studies contained primary studies that included the nature of the injury, antecedent factors associated with the injury, and study characteristics and RTW outcomes. Exclusion criteria for the studies included if there was no discussion of RTW outcomes, systematic reviews, and meta-analyses.

Results

A total of 461 full-text articles were assessed for eligibility, and eight studies were included and assessed using the Critical Appraisal Skills Programme checklist, Risk of Bias, and Newcastle–Ottawa Scale. Four studies identified personal system factors, four identified healthcare system factors, two identified compensation system factors, and one identified workplace system factors.

Conclusions

Attempts to optimize RTW among persons with SCI are inherently difficult due to the diversity of this client population. Findings from the studies included in this systematic review support the utility of interventions for facilitating RTW, such as vocational rehabilitation and workplace accommodations, while simultaneously acknowledging the limitations in identifying specific interventions as facilitatory or inhibitory throughout the process.

Treatment of chronic axial back pain with 60-day percutaneous medial branch PNS: Primary end point results from a prospective, multicenter study

Background

The objective of this prospective, multicenter study is to characterize responses to percutaneous medial branch peripheral nerve stimulation (PNS) to determine if results from earlier, smaller single‐center studies and reports were generalizable when performed at a larger number and wider variety of centers in patients recalcitrant to nonsurgical treatments.

Materials & Methods

Participants with chronic axial low back pain (LBP) were implanted with percutaneous PNS leads targeting the lumbar medial branch nerves for up to 60 days, after which the leads were removed. Participants were followed long‐term for 12 months after the 2‐month PNS treatment. Data collection is complete for visits through end of treatment with PNS (primary end point) and 6 months after lead removal (8 months after start of treatment), with some participant follow‐up visits thereafter in progress.

Results

Clinically and statistically significant reductions in pain intensity, disability, and pain interference were reported by a majority of participants. Seventy‐three percent of participants were successes for the primary end point, reporting clinically significant (≥30%) reductions in back pain intensity after the 2‐month percutaneous PNS treatment (n = 54/74). Whereas prospective follow‐up is ongoing, among those who had already completed the long‐term follow‐up visits (n = 51), reductions in pain intensity, disability, and pain interference were sustained in a majority of participants through 14 months after the start of treatment.

Conclusion

Given the minimally invasive, nondestructive nature of percutaneous PNS and the significant benefits experienced by participants who were recalcitrant to nonsurgical treatments, percutaneous PNS may provide a promising first‐line neurostimulation treatment option for patients with chronic axial back pain.

Neuromodulation for chronic pain

Neuromodulation is an expanding area of pain medicine that incorporates an array of non-invasive, minimally invasive, and surgical electrical therapies. In this Series paper, we focus on spinal cord stimulation (SCS) therapies discussed within the framework of other invasive, minimally invasive, and non-invasive neuromodulation therapies. These therapies include deep brain and motor cortex stimulation, peripheral nerve stimulation, and the non-invasive treatments of repetitive transcranial magnetic stimulation, transcranial direct current stimulation, and transcutaneous electrical nerve stimulation. SCS methods with electrical variables that differ from traditional SCS have been approved. Although methods devoid of paraesthesias (eg, high frequency) should theoretically allow for placebo-controlled trials, few have been done. There is low-to-moderate quality evidence that SCS is superior to reoperation or conventional medical management for failed back surgery syndrome, and conflicting evidence as to the superiority of traditional SCS over sham stimulation or between different SCS modalities. Peripheral nerve stimulation technologies have also undergone rapid development and become less invasive, including many that are placed percutaneously. There is low-to-moderate quality evidence that peripheral nerve stimulation is effective for neuropathic pain in an extremity, low quality evidence that it is effective for back pain with or without leg pain, and conflicting evidence that it can prevent migraines. In the USA and many areas in Europe, deep brain and motor cortex stimulation are not approved for chronic pain, but are used off-label for refractory cases. Overall, there is mixed evidence supporting brain stimulation, with most sham-controlled trials yielding negative findings. Regarding non-invasive modalities, there is moderate quality evidence that repetitive transcranial magnetic stimulation does not provide meaningful benefit for chronic pain in general, but conflicting evidence regarding pain relief for neuropathic pain and headaches. For transcranial direct current stimulation, there is low-quality evidence supporting its benefit for chronic pain, but conflicting evidence regarding a small treatment effect for neuropathic pain and headaches. For transcutaneous electrical nerve stimulation, there is low-quality evidence that it is superior to sham or no treatment for neuropathic pain, but conflicting evidence for non-neuropathic pain. Future research should focus on better evaluating the short-term and long-term effectiveness of all neuromodulation modalities and whether they decrease health-care use, and on refining selection criteria and treatment variables.

Invasive Treatments for Low Back Disorders

OBJECTIVE

This abbreviated version of the American College of Occupational and Environmental Medicine's Low Back Disorders guideline reviews the evidence and recommendations developed for invasive treatments used to manage low back disorders.

METHODS

Comprehensive systematic literature reviews were accomplished with article abstraction, critiquing, grading, evidence table compilation, and guideline finalization by a multidisciplinary expert panel and extensive peer-review to develop evidence-based guidance. Consensus recommendations were formulated when evidence was lacking and often relied on analogy to other disorders for which evidence exists. A total of 47 high-quality and 321 moderate-quality trials were identified for invasive management of low back disorders.

RESULTS

Guidance has been developed for the invasive management of acute, subacute, and chronic low back disorders and rehabilitation. This includes 49 specific recommendations.

CONCLUSION

Quality evidence should guide invasive treatment for all phases of managing low back disorders.

Percutaneous Peripheral Nerve Stimulation of the Medial Branch Nerves for the Treatment of Chronic Axial Back Pain in Patients After Radiofrequency Ablation

OBJECTIVE

Lumbar radiofrequency ablation is a commonly used intervention for chronic back pain. However, the pain typically returns, and though retreatment may be successful, the procedure involves destruction of the medial branch nerves, which denervates the multifidus. Repeated procedures typically have diminishing returns, which can lead to opioid use, surgery, or implantation of permanent neuromodulation systems. The objective of this report is to demonstrate the potential use of percutaneous peripheral nerve stimulation (PNS) as a minimally invasive, nondestructive, motor-sparing alternative to repeat radiofrequency ablation and more invasive surgical procedures.

DESIGN

Prospective, multicenter trial.

METHODS

Individuals with a return of chronic axial pain after radiofrequency ablation underwent implantation of percutaneous PNS leads targeting the medial branch nerves. Stimulation was delivered for up to 60 days, after which the leads were removed. Participants were followed up to 5 months after the start of PNS. Outcomes included pain intensity, disability, and pain interference.

RESULTS

Highly clinically significant (≥50%) reductions in average pain intensity were reported by a majority of participants (67%, n = 10/15) after 2 months with PNS, and a majority experienced clinically significant improvements in functional outcomes, as measured by disability (87%, n = 13/15) and pain interference (80%, n = 12/15). Five months after PNS, 93% (n = 14/15) reported clinically meaningful improvement in one or more outcome measures, and a majority experienced clinically meaningful improvements in all three outcomes (i.e., pain intensity, disability, and pain interference).

CONCLUSIONS

Percutaneous PNS has the potential to shift the pain management paradigm by providing an effective, nondestructive, motor-sparing neuromodulation treatment.

The dimensions of "failed back surgery syndrome": what is behind a label?

BACKGROUND

The term failed back surgery syndrome (FBSS) has been criticized for being too unspecific and several studies have shown that a variety of conditions may underlie this label. The aims of the present study were to describe the specific symptoms and to investigate the primary and secondary underlying causes of FBSS in a contemporary series of patients who had lumbar spinal surgery before.

METHODS

We used a multilevel approach along three different axes defining symptomatic, morphological, and functional pathology dimensions.

RESULTS

Within the study period of 3 years, a total of 145 patients (74 f, 71 m, mean age 51a, range 32-82a) with the external diagnosis of FBSS were included. Disk surgery up to 4 times and surgery for spinal stenosis up to 3 times were the commonest index operations. Most often, the patients complained of low back pain (n = 126), pseudoradicular pain (n = 54), and neuropathic pain (n = 44). Imaging revealed osteochondrosis (n = 61), spondylarthrosis (n = 48), and spinal misalignment (n = 32) as the most frequent morphological changes. The majority of patients were assigned at least to two different symptomatic subcategories and morphological subcategories, respectively. According to these findings, one or more functional pathologies were assigned in 131/145 patients that subsequently enabled a specific treatment strategy.

CONCLUSIONS

FBSS has become rather a vague and imprecisely used generic term. We suggest that it should be avoided in the future both with regard to its partially stigmatizing connotation and its inherent hindering to provide individualized medicine.

The Long-term Effectiveness of the Automatic Position-Adaptive System in Spinal Cord Stimulation: A Retrospective Comparative Study with a Two-Year Follow-up

OBJECTIVE

To compare the nonadaptive manual system with the position-adaptive system in subjects with permanent spinal cord stimulator (SCS) implantation over a two-year follow-up period.

DESIGN

Retrospective study.

SETTING

Tertiary university-based national hospital.

SUBJECTS

Patients who underwent permanent SCS implantation procedures.

METHODS

Patients were divided into an adaptive group and a nonadaptive group according to the type of implanted SCS device. The primary outcome was the change (%) in pain intensity from baseline between the adaptive and nonadaptive groups at 24 months after SCS implantation. The secondary outcomes were comparisons of detailed clinical variables such as the scores of patient pain and satisfaction during the two-year follow-up after SCS therapy. Further, the number of subjects with SCS removal or revision within two years after SCS implantation was investigated.

RESULTS

Of 187 patients with permanent SCS implantation, 85 in the nonadaptive group and 64 in the position-adaptive group were finally analyzed. The reduction in pain intensity at 24 months was higher in the adaptive group (-38.6%) than in the nonadaptive group (-30.8%, P = 0.05). Similarly, patient satisfaction with the SCS treatment at 24 months was superior in the adaptive group than in the nonadaptive group (85.7% vs 67.5% were satisfied in each group, respectively, P = 0.024). During the two years, 5.3% of patients (N = 10) underwent SCS removal and 7.0% (N = 13) underwent revision procedures.

CONCLUSIONS

There was a trend of a sustained reduction in pain intensity as well as improvement in patient satisfaction at two-year follow-up in the position-adaptive system, suggesting long-term benefit over the nonadaptive manual system during SCS treatment.

Effect of Spinal Cord Stimulation on Early Disability Pension in 198 Failed Back Surgery Syndrome Patients: Case-Control Study

BACKGROUND

Spinal cord stimulation (SCS) has proven to be a cost-effective treatment for failed back surgery syndrome (FBSS). However, the effect on patients’ working capability remains unclear.

OBJECTIVE

To evaluate the impact of SCS on working capability and to identify the factors behind permanent disability in FBSS patients.

METHODS

The study group consisted of 198 working-age patients with SCS trialed or implanted for FBSS in a single center between 1996 and 2014. For each patient, 3 living controls, matched by age, gender, and birthplace, were otherwise randomly selected by the Population Register Center. The data on working ability were obtained from the Social Insurance Institution. Patients were divided into 3 groups: SCS trial only, SCS implanted permanently, and SCS implanted but later explanted.

RESULTS

A rehabilitation subsidy was given to 68 patients and 8 controls for a mean of 5.2 (95% confidence interval [CI] 2.4-8.2) and 0.2 (95% CI 0.05-0.6) days per month (P < .05). At the end of follow-up, 16 (37%), 13 (33%), 25 (22%), and 27 (5%) subjects were on disability pension (DP) in the SCS trial, SCS explanted, SCS permanent, and control groups. Patients in the SCS trial-only group were significantly more often on DP than were patients with permanent SCS (odds ratio 2.6; 95% CI 1.2-5.9; P = .02)

CONCLUSION

Permanent SCS usage was associated with reduced sick leave and DP. Prospective study will be required to assess possible predictive value.

Percutaneous Peripheral Nerve Stimulation for Chronic Low Back Pain: Prospective Case Series With 1 Year of Sustained Relief Following Short-Term Implant

INTRODUCTION

Percutaneous peripheral nerve stimulation (PNS) provides an opportunity to relieve chronic low back pain and reduce opioid analgesic consumption as an alternative to radiofrequency ablation and permanently implanted neurostimulation systems. Traditionally, the use of neurostimulation earlier in the treatment continuum has been limited by its associated risk, invasiveness, and cost.

METHODS

Percutaneous PNS leads (SPRINT MicroLead) were placed bilaterally to target the medial branches of the dorsal rami nerves under image guidance. The percutaneous leads were connected to miniature wearable stimulators (SPRINT PNS System) for the 1-month therapy period, after which the leads were removed. Pain and disability were assessed long-term up to 12 months after lead removal.

RESULTS

Substantial, clinically significant reductions in average pain intensity (≥50% reduction as measured by the Brief Pain Inventory Short Form) were experienced by a majority of subjects (67%) at end of treatment compared to baseline (average 80% reduction among responders; P < 0.05, analysis of variance; n = 9). Twelve months after the end of PNS treatment, a majority of subjects who completed the long-term follow-up visits experienced sustained, clinically significant reductions in pain and/or disability (67%, n = 6; average 63% reduction in pain intensity and 32-point reduction in disability among responders). No serious or unanticipated adverse events were reported.

CONCLUSIONS

This study challenges the long-held notion that a positive trial of PNS should be followed by a permanent implant in responders. Percutaneous PNS may serve as an effective neurostimulation therapy for patients with chronic low back pain and should be considered earlier in the treatment continuum as a motor-sparing means of avoiding opioids, denervation, and permanently implanted neurostimulation systems.

Effectiveness and Safety of Dorsal Root Ganglion Stimulation for the Treatment of Chronic Pain: A Pooled Analysis

INTRODUCTION

Since it became available in the mid-2010s, dorsal root ganglion (DRG) stimulation has become part of the armamentarium to treat chronic pain. To date, one randomized controlled trial, and several studies of moderate sample size and various etiologies have been published on this topic. We conducted a pooled analysis to investigate the generalizability of individual studies and to identify differences in outcome between chronic pain etiologic subgroups and/or pain location.

MATERIALS AND METHODS

One prospective, randomized comparative trial and six prospective, single-arm, observational studies were identified that met pre-defined acceptance criteria. Pain scores and patient-reported outcome (PRO) measures were weighted by study sample sizes and pooled. Safety data are reported in aggregate form.

RESULTS

Our analysis included 217 patients with a permanent implant at 12-month follow-up. Analysis of pooled data showed an overall weighted mean pain score of 3.4, with 63% of patients reporting ≥50% pain relief. Effectiveness sub-analyses in CRPS-I, causalgia, and back pain resulted in a mean reduction in pain intensity of 4.9, 4.6, and 3.9 points, respectively. Our pooled analysis showed a pain score for primary affected region ranging from 1.7 (groin) to 3.0 (buttocks) and responder rates of 80% for foot and groin, 75% for leg, and 70% for back. A substantial improvement in all PROs was observed at 12 months. The most commonly reported procedural or device complications were pain at the IPG pocket site, lead fracture, lead migration, and infection.

CONCLUSIONS

DRG stimulation is an effective and safe therapy for various etiologies of chronic pain.

Spinal Cord Stimulation vs Conventional Therapies for the Treatment of Chronic Low Back and Leg Pain: A Systematic Review of Health Care Resource Utilization and Outcomes in the Last Decade

Objective

The purpose of this review is to critically appraise the literature for evidence supporting the health care resource utilization and cost-effectiveness of spinal cord stimulation (SCS) compared with conventional therapies (CTs) for chronic low back and leg pain.

Methods

The PubMed, MEDLINE, Embase, CINAHL, and Rehabilitation & Sports Medicine databases were searched for studies published from January 2008 through October 2018, using the following MeSH terms: “spinal cord stimulation,” “chronic pain,” “back pain,” “patient readmission,” “economics,” and “costs and cost analysis.” Additional sources were added based on bibliographies and consultation with experts. The following data were extracted and analyzed: demographic information, study design, objectives, sample sizes, outcome measures, SCS indications, complications, costs, readmissions, and resource utilization data.

Results

Of 204 studies screened, 11 studies met inclusion criteria, representing 31,439 SCS patients and 299,182 CT patients. The mean age was 53.5 years for SCS and 55.6 years for CT. In eight of 11 studies, SCS was associated with favorable outcomes and found to be more cost-effective than CT for chronic low back pain. Compared with CT, SCS resulted in shorter hospital stays and lower complication rates and health care costs at 90 days. SCS was associated with significant improvement in health-related quality of life, health status, and quality-adjusted life-years.

Conclusions

For the treatment of chronic low back and leg pain, the majority of studies are of fair quality, with level 3 or 4 evidence in support of SCS as potentially more cost-effective than CT, with less resource expenditure but higher complication rates. SCS therapy may yet play a role in mitigating the financial burden associated with chronic low back and leg pain.

Electrode movement prevention – an animal model

Electrode migration is the most common complication of spinal cord stimulation (SCS). The problem of longitudinal migration has already been solved, but lateral migration remains the most common current complication. The present article describes new electrodes fixation opportunities for the reduction of lateral migration in SCS. The pig was chosen as an animal model to illustrate a new protocol of electrode fixation for the control of lateral and longitudinal migration. The displacement of the electrode was measured using two different optical methods: the digital image stereo-correlation and the digital image processing methods. Fixation with two anchors has always considerably reduced electrode displacement and when fixation is done with two anchors and a loop then lateral migration is reduced by 62.5 % and longitudinal migration is reduced by 94.1 %. It was shown that the results are significantly different at the α=0.001 significance level. Based on a statistical evaluation it is possible to state that the differences between experimental results obtained for three different protocols of lead fixation are statistically significant and we can recommend the new fixation method for common practice.

Does Spinal Cord Stimulation Due to Failed Back Surgery Syndrome Lead to Permanent Occupational Disability?

OBJECTIVE

Spinal cord stimulation (SCS) is a recommended treatment method for patients afflicted by failed back surgery syndrome (FBSS). Although SCS is shown to be clinically effective, not many patients return to work (RTW). The aim of this study is to assess the RTW rate of these patients.

MATERIALS AND METHODS

We prospectively evaluated 102 patients with FBSS, managed by low frequency SCS at a single institution in Poland. RTW rate was the main endpoint in the study. Additionally, we browsed the first 300 records in Google and extracted the suggested RTW time post-SCS implantation.

RESULTS

Mean follow-up was 8.5 years. 79.4% of patients were actively working at the baseline. Fifteen patients were sick leave benefit claimants (15/81; 18.5%) and six were permanently disabled (6/81; 7.4%). In the follow-up, 40 did not change their work status. Only 2 of 21 patients resumed work and the total RTW rate was 9.5%. On the other hand, 38 of 81 patients (46.9%), who actively worked before SCS, gained disability status. Out of entire group, 20.6% (21 of 102) were not working at the baseline and 55.9% (57 of 102) were not working in the follow-up. Neither factor influenced RTW rate. In the second stage of the study, internet data search yielded a mean RTW time of 6.1 weeks.

CONCLUSIONS

Unlike the well-analyzed effectiveness of SCS, RTW remains an underutilized outcome measure. The RTW rate in our series was the second lowest in the reviewed literature. We demonstrated that half of the patients with an implanted SCS either did not resume their work or left their job.

Spinal Cord Stimulation

Spinal cord stimulation (SCS) has been well established as a safe and effective treatment of pain derived from a wide variety of etiologies. Careful patient selection including a rigorous trial period and psychological evaluation are essential. When patients proceed to permanent implantation, various considerations should be made, such as the type of lead, type of anesthesia, and waveform patterns for SCS. This article discusses the common indications for SCS, patient selection criteria, and pertinent outcomes from randomized clinical trials related to common indications treated with SCS. Technical considerations, such as type of implant, anesthesia, and programming, are also discussed.

Spinal Cord Stimulation: Clinical Efficacy and Potential Mechanisms

Spinal cord stimulation (SCS) is a minimally invasive therapy used for the treatment of chronic neuropathic pain. SCS is a safe and effective alternative to medications such as opioids, and multiple randomized controlled studies have demonstrated efficacy for difficult-to-treat neuropathic conditions such as failed back surgery syndrome. Conventional SCS is believed mediate pain relief via activation of dorsal column Aβ fibers, resulting in variable effects on sensory and pain thresholds, and measurable alterations in higher order cortical processing. Although potentiation of inhibition, as suggested by Wall and Melzack's gate control theory, continues to be the leading explanatory model, other segmental and supraspinal mechanisms have been described. Novel, non-standard, stimulation waveforms such as high-frequency and burst have been shown in some studies to be clinically superior to conventional SCS, however their mechanisms of action remain to be determined. Additional studies are needed, both mechanistic and clinical, to better understand optimal stimulation strategies for different neuropathic conditions, improve patient selection and optimize efficacy.

Neuropathic Pain Medication Use Does Not Alter Outcomes of Spinal Cord Stimulation for Lower Extremity Pain

INTRODUCTION

Spinal cord stimulation (SCS) for the treatment of lower extremity pain is believed to the result of increased activity in the descending inhibitory and decreased activity in the ascending excitatory tracts. Evidence suggests that the analgesia afforded by SCS may be altered using certain neuropathic pain medications that also modulate neurotransmitters in these sensory tracts. We hypothesize that neuropathic pain medications may alter the response to SCS therapy.

METHODS

One hundred and fifteen subjects undergoing SCS therapy for lower extremity pain were retrospectively examined. The pharmacologic profile, including stable use of neuropathic and opioid medications, were recorded. Three separate logistic regression models examined the odds ratio of primary outcomes; a successful SCS trial, a 50% decrease in pain or a 50% reduction in opioid use one year after implant.

RESULTS

Neither the use of opioids or neuropathic pain medications were associated with changes in the odds of a successful SCS trial or a 50% pain reduction. A higher dose of chronic opioids use prior to a trial was associated with greater odds of having a 50% reduction in opioid use following implant. OR 1.02, 95% CI 1.01-1.02, p-value < 0.01).

CONCLUSIONS

The use of neuropathic pain medications did not change the odds of either a successful SCS trial, or of experiencing a 50% reduction in pain at one year. The association between higher opioid doses and greater odds of a 50% reduction in opioid use may be the reflective of SCS's ability to reduce opioid reliance in chronic pain patients.

The Results of Treating Failed Back Surgery Syndrome by Adhesiolysis: Comparing the One- and Three-Day Protocols

Background

The optimal treatment of failed back surgery syndrome (FBSS) is controversial. Limited studies have demonstrated the satisfactory outcomes of percutaneous adhesiolysis in FBSS, which can be performed as a 1 day or 3 days procedure. In the current randomized clinical trial, we compared the clinical and functional outcomes of these 2 techniques.

Methods

In this study, 60 patients with FBSS were randomly assigned into 2 equal groups: 1 day group and 3 days group. Before and at 4 and 12 weeks after the procedure, pain intensity was measured using visual analogue scale (VAS). The Oswestry disability index (ODI) was also completed. Pain reduction of 50% or more was defined as treatment success.

Results

Significant pain relief and ODI improvement were obtained in the 2 groups with adhesiolysis (P < 0.001). However, pain intensity remained the same before and at 4 and 12 weeks after adhesiolysis. ODI score was significantly lower in 1 day group in the 1 month visit (P < 0.001). Treatment was successful in 76.7% and 83.3% of the patients in 1 day and 3 days groups, respectively (P = 0.519).

Conclusions

Adhesiolysis is an effective treatment for pain relief and functional improvement in FBSS. The results of 1 day and 3 days procedures are comparable. Based on these findings, the authors recommend using 1 day technique, which can potentially decrease the patients' discomfort, hospital stay, and cost of treatment.

Cost-Effectiveness Data Regarding Spinal Cord Stimulation for Low Back Pain

STUDY DESIGN

Review of published literature pertaining to spinal cord stimulation (SCS) cost data analysis.

OBJECTIVE

To acquire, organize, and succinctly summarize the available literature regarding the costs associated with, and the cost-effectiveness of, SCS.

SUMMARY OF BACKGROUND DATA

Chronic back and limb pain is a pervasive complaint in modern society, with estimated annual costs of medical care greater than $100 billion. The traditional standard medical management with or without intermittent surgical decompression/fusion has been plagued by high costs and inconsistent results, leading to poor patient satisfaction and functional outcome, and questions from policy makers regarding use of limited healthcare resources. Neuromodulation techniques, including SCS have recently become more common in the treatment of chronic back/leg pain, with clinical studies showing a high degree of efficacy in alleviating otherwise intractable pain. Given the relatively high upfront costs associated with the hardware and implantation, policy makers have, however, questioned their use in the framework of cost-containment and resource utilization. We reviewed the available literature summarizing cost data of SCS in chronic back and limb pain, as an understanding of these data will be vital to justify continued payment for this expensive, but often very effective, treatment modality.

METHODS

We performed a PubMed literature search utilizing the following terms: "spinal cord stimulation," "SCS," "financial," "cost," "cost-effectiveness," and "cost-utility." All studies published in English and containing complete or partial cost evaluations of SCS for chronic back and limb pain were included.

RESULTS

The search revealed 21 studies that evaluated cost data, with or without outcomes analysis and cost-utility analysis, for patients with chronic back and limb pain. The overwhelming majority of data presented shows that SCS is not only an effective treatment option for these patients, but also represents cost savings and efficient use of healthcare resources relative to current standards of care. Although not all studies performed cost-utility analyses, those that did tended to show SCS falling well within accepted thresholds of "willingness-to-pay" on the part of third-party payers. That being said, the articles included in this review were almost all small, retrospective, single-institution studies. In addition, many of them relied on modeling for their analyses, and published literature values for cost and/or outcomes data rather than prospectively collected patient data. Although the data presented in this review are encouraging, it should serve as a foundation for a thorough, prospective, cost-utility analysis of SCS in chronic back and limb pain so that the role of this important treatment modality may be cemented in the treatment paradigm for these patients without questions from third-party payers.

CONCLUSION

The large majority of data covering costs of SCS argue in favor of the cost-effectiveness of this treatment modality for chronic neuropathic pain, especially in comparison to reoperation and medical management. Although most of the higher-quality evidence is relatively short-term, clinical experience with the durability of treatment benefit of SCS in these patients is promising. Given the pushback regarding high upfront costs of implantation, longer-term, prospective, randomized studies evaluating this topic will be important to help maintain third-party payer reimbursements for SCS.

LEVEL OF EVIDENCE

5.

Treatment Options for Failed Back Surgery Syndrome Patients With Refractory Chronic Pain: An Evidence Based Approach

STUDY DESIGN

A significant number of lumbar postsurgical patients continue to suffer persistent pain and limited function and are termed to have "Failed back surgery syndrome" (FBSS). This review evaluates clinical trial data for the treatment of FBSS patients.

OBJECTIVE

Using an evidence-based approach to evaluate FBSS treatments will assist clinicians in choosing the most effective options for FBSS patients. Furthermore, reducing the utilization of less effective therapies may result in substantial financial savings for this patient population.

SUMMARY OF BACKGROUND DATA

Treatments for FBSS may be generally categorized as physical therapy and exercise, medications, interventional procedures, neuromodulation, and reoperation. Careful review and classification of the level of evidence available for each category of treatment for FBSS patients will help guide clinical decision-making.

METHODS

A literature review was performed for FBSS treatments. The publications were arranged hierarchically according to the North American Spine Society's guidelines as randomized controlled trials (RCTs), prospective studies, retrospective chart, and systematic reviews. Book chapters, nonsystematic reviews, and expert opinions were excluded. The review focused on studies with at least 20 FBSS patients and 6-month follow-up.

RESULTS

Evidence is weak for medications and reoperation, but strong for active exercise and interventional procedures such as adhesiolysis. The strongest evidence for long-term treatment is for spinal cord stimulation (SCS), showing favorable Level I RCT results compared with conventional medical management and reoperation. In addition, high-frequency SCS at 10 kHz has demonstrated superiority over traditional, low-frequency SCS for treating low back and leg pain in a recent Level I RCT.

CONCLUSION

Clinicians may increasingly utilize levels of evidence during their evaluation of each FBSS patient to render the best therapeutic plan, likely resulting in improved long-term pain control and reducing costs by avoiding less effective modalities. New directions in SCS show promising results for the treatment of FBSS.

LEVEL OF EVIDENCE

1.

Pocket Pain and Neuromodulation: Negligible or Neglected?

OBJECTIVES

Pain encountered at the site of the implantable pulse generator (IPG) after invasive neuromodulation is a well-known and important complication. The reported incidence of implant site pain is variable, ranging between 0.4 and 35%. Implant site pain has never been systematically studied and no treatment guidelines are available.

MATERIAL AND METHODS

We performed an observational study (study registration number mp05728) on the incidence and the determining factors of implant site pain, the subjective rating of intensity by sending questionnaires (n = 554) to our cohort of neuromodulation patients with IPGs. The number of revision surgeries and explants due to implant site pain were also analyzed.

RESULTS

Total response rate was 50% (n = 278). Pain patients suffered significantly (p < 0.05) more often from IPG site pain than other patients undergoing neuromodulation therapies. Up to 64% of patients undergoing spinal cord stimulation reported IPG site discomfort or pain. Severe pocket pain was found in up to 8% of patients. No association was found between other variables (age, BMI, duration of follow-up, gender, smoking, number of pocket surgeries) and implant site pain.

CONCLUSION

Pocket pain represents an important problem after invasive neuromodulation and is more prevalent in pain patients. We believe further technological improvements with miniaturized IPGs will impact the incidence of pocket pain and could even obviate the need for an IPG pocket.

Percutaneous Peripheral Nerve Stimulation for the Treatment of Chronic Low Back Pain: Two Clinical Case Reports of Sustained Pain Relief

As the leading cause of disability among U.S. adults, chronic low back pain (LBP) is one of the most prevalent and challenging musculoskeletal conditions. Neuromodulation provides an opportunity to reduce or eliminate the use of opioids to treat chronic LBP, but the cost and invasiveness of existing methods have limited its broad adoption, especially earlier in the treatment continuum. The present case report details the results of a novel method of short-term percutaneous peripheral nerve stimulation (PNS) in 2 subjects with chronic LBP. At the end of the 1-month therapy, stimulation was discontinued and the leads were withdrawn. PNS produced clinically significant improvements in pain (62% average reduction in Brief Pain Inventory Question #5, average pain), and functional outcomes (73% reduction in disability, Oswestry Disability Index; 83% reduction in pain interference, Brief Pain Inventory). Both subjects reduced nonopioid analgesic use by 83%, on average, and the one subject taking opioids ceased using all opioids. The only adverse event was minor skin irritation caused by a topical dressing. The clinically significant improvements were sustained at least 4 months after start of therapy (79% average reduction in pain; both reported minimal disability; 100% reduction in opioids; 74% reduction nonopioids). The results reveal the utility of this novel, short-term approach and its potential as a minimally invasive neuromodulation therapy for use earlier in the treatment continuum to produce sustained pain relief and reduce or eliminate the need for analgesic medications, including opioids, as well as more expensive and invasive surgical or therapeutic alternatives.

Complications of Spinal Cord Stimulation and Peripheral Nerve Stimulation Techniques: A Review of the Literature

OBJECTIVE

Spinal cord and peripheral neurostimulation techniques have been practiced since 1967 for the relief of pain, and some techniques are also used for improvement in organ function. Neuromodulation has recognized complications, although very rarely do these cause long-term morbidity. The aim of this article is to present a review of complications observed in patients treated with neurostimulation techniques.

METHODS

A review of the major recent publications in the literature on the subjects of spinal cord, occipital, sacral, and peripheral nerve field stimulation was conducted.

RESULTS

The incidence of complications reported varies from 30% to 40% of patients affected by one or more complications. Adverse events can be subdivided into hardware-related complications and biological complications. The commonest hardware-related complication is lead migration. Other lead related complications such as failure or fracture have also been reported. Common biological complications include infection and pain over the implant. Serious biological complications such as dural puncture headache and neurological damage are rarely observed.

CONCLUSIONS

Spinal cord and peripheral neurostimulation techniques are safe and reversible therapies. Hardware-related complications are more commonly observed than biological complications. Serious adverse events such as neurological damage are rare.

Electrical neurostimulation for chronic pain: On selective relay of sensory neural activities in myelinated nerve fibers

Chronic pain affects about 100 million adults in the US. Despite their great need, neuropharmacology and neurostimulation therapies for chronic pain have been associated with suboptimal efficacy and limited long-term success, as their mechanisms of action are unclear. Yet current computational models of pain transmission suffer from several limitations. In particular, dorsal column models do not include the fundamental underlying sensory activity traveling in these nerve fibers. We developed a (simple) simulation test bed of electrical neurostimulation of myelinated nerve fibers with underlying sensory activity. This paper reports our findings so far. Interactions between stimulation-evoked and underlying activities are mainly due to collisions of action potentials and losses of excitability due to the refractory period following an action potential. In addition, intuitively, the reliability of sensory activity decreases as the stimulation frequency increases. This first step opens the door to a better understanding of pain transmission and its modulation by neurostimulation therapies.

A review of spinal cord stimulation systems for chronic pain

Spinal cord stimulation (SCS) applications and technologies are fast advancing. New SCS technologies are being used increasingly in the clinical environment, but often there is a lag period between the clinical application and the publishing of high-quality evidence on safety and efficacy. Recent developments will undoubtedly expand the applicability of SCS, allowing more effective and individualized treatment for patients, and may have the potential to salvage patients who have previously failed neuromodulation. Already, high-level evidence exists for the safety, efficacy, and cost-effectiveness (Level I–II) of traditional SCS therapies in the treatment of chronic refractory low back with predominant limb pain (regardless of surgical history). More than half of all patients with chronic painful conditions experience sustained and significant levels of pain reduction following SCS treatment. Although only limited evidence exists for burst stimulation, there is now Level I evidence for both dorsal root ganglion SCS and high-frequency SCS that demonstrates compelling results compared with traditional therapies. The body of evidence built on traditional SCS research may be redundant, with newer iterations of SCS therapies such as dorsal root ganglion SCS, high-frequency SCS, and burst SCS. A number of variables have been identified that can affect SCS efficacy: implanter experience, appropriate patient selection, etiologies of patient pain, existence of comorbidities, including psychiatric illness, smoking status, and delay to SCS implant following pain onset. Overall, scientific literature demonstrates SCS to be a safe, effective, and drug-free treatment option for many chronic pain etiologies.

Younger age predicts greater effectiveness of spinal cord stimulation for chronic pain

BACKGROUND

Spinal cord stimulation (SCS) is an accepted surgical treatment for neuropathic pain in failed back syndrome or complex regional pain syndrome. However, even in the best selected surgical cases the predictors of adequate pain control are not well defined. The aim of this study was to identify predictors of outcome in patients who underwent SCS in our center.

METHODS

We performed a retrospective analysis of our neurosurgical database for patients who underwent SCS over the last 8 years in an attempt to identify factors predictive of outcome.

RESULTS

Forty-one patients underwent implantation of epidural electrodes, 34 patients had a successful stimulation trial and received permanent devices. Nine patients experienced a late failure at a median time of 7.8 months (range, 4.5-19 months) after implantation. Age was significantly associated with outcome. Younger patients had a significantly lower rate of treatment failure, and none of the patients above 65 years had a successful long-term outcome.

CONCLUSIONS

Our results suggest that younger age is associated with greater long-term effectiveness of spinal cord stimulation and therefore age may influence the success of SCS therapy with older patients having a greater tendency to failure. Earlier intervention may be beneficial in these chronic pain patients.

A Comparison of the Effects of Burst and Tonic Spinal Cord Stimulation on Hyperalgesia and Physical Activity in an Animal Model of Neuropathic Pain

BACKGROUND

Parameters of spinal cord stimulation (SCS) play a role in its effectiveness and may impact SCS mechanisms and outcomes. For example, SCS applied in a bursting pattern may result in better pain relief than that for tonic SCS for neuropathic pain. We tested the effectiveness of different SCS pulse frequencies given at 2 different burst frequencies in an animal model of neuropathic pain.

METHODS

After Sprague-Dawley rats were anesthetized, neuropathic pain was induced using the spared nerve injury model, and an epidural SCS lead was implanted in the upper lumber spinal cord. One of the 8 different SCS parameters was delivered daily for 4 days at 90% motor threshold 2 weeks after nerve injury. Four burst patterns were administered at 4- or 40-Hz frequency with a train of 4 pulses at frequencies of 60, 500, and 1000 Hz. Sham and tonic patterns at 16, 60, and 160 Hz were chosen as controls. Paw withdrawal threshold was assessed before the surgery and 15 minutes before, during, and after SCS daily for 4 days. Physical activity (distance, crossing, rearing, and grooming) was assessed before surgery, before SCS on day 1, and after SCS on day 4.

RESULTS

Animals showed a decrease in paw withdrawal threshold and physical activity levels 2 weeks after nerve injury. During stimulation, burst SCS with pulse frequencies of 60, 500, or 1000 Hz were more effective for improving paw withdrawal threshold than sham and tonic SCS at 16 Hz. Burst SCS with higher pulse frequencies (500 and 1000 Hz) than 60-Hz SCS and burst SCS with higher pulse frequencies (1000 Hz) than 160-Hz SCS were more effective. In addition, tonic SCS at 160 Hz and burst SCS with higher pulse frequencies (500 and 1000 Hz) significantly increased the distance traveled. Burst SCS at 4 Hz with pulse frequency of 1000 Hz also increased the number of crossings when compared with sham control and tonic SCS at 16 Hz.

CONCLUSIONS

The current study shows that a variety of SCS pulse frequencies applied with a burst frequency result in greater improvement in hyperalgesia and activity levels than tonic SCS in a neuropathic pain model during stimulation.

Failed back surgery syndrome: whose failure? Time to discard a redundant term

Failed back surgery syndrome or "failed back syndrome" refers to persistent pain after spinal surgery. This opinion piece will discuss the back ground and scale of failed back surgery syndrome. There will be a description of the medical and psychological factors that have been reported as predictors of poor outcome from spinal surgery. The management of failed back surgery syndrome will be discussed with a personal viewpoint based on working with this patient group for fifteen years. It will be argued that failed back surgery syndrome and failed back syndrome are now redundant terms and are not useful for either patient or healthcare provider, and so should be discarded.Key words Failed back surgery syndrome, failed back syndrome.

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.

A review of economic factors related to the delivery of health care for chronic low back pain

INTRODUCTION AND METHODS

We describe tools used to evaluate the economic impact of health care interventions, discuss the economic burden of chronic low back pain, and review evidence on the cost-effectiveness of treating failed back surgery syndrome with spinal cord stimulation, intrathecal drug delivery, acupuncture, epidural injections, disc prosthesis, lumbar fusion, and noninvasive therapies. We also mention the lack of cost studies for emerging therapies, such as vibrotherapy and peripheral nerve field stimulation. Topics include types of cost studies; the economic perspectives taken by such studies; direct and indirect costs; measures of success; definitions of cost-effectiveness, incremental cost-effectiveness, incremental cost-utility ratios, and quality-adjusted life years; the concept of maximum willingness to pay; and the use of cost-effectiveness models.

CONCLUSION

The fact that chronic low back pain arises from a variety of causes makes choosing appropriate treatment difficult. Determining the cost-effectiveness of various treatments for chronic low back pain depends on well-designed and well-executed randomized controlled trials with parallel economic evaluations. Researchers can use economic models to extrapolate costs and outcomes over the long term.

The appropriate use of neurostimulation of the spinal cord and peripheral nervous system for the treatment of chronic pain and ischemic diseases: the Neuromodulation Appropriateness Consensus Committee

INTRODUCTION

The Neuromodulation Appropriateness Consensus Committee (NACC) of the International Neuromodulation Society (INS) evaluated evidence regarding the safety and efficacy of neurostimulation to treat chronic pain, chronic critical limb ischemia, and refractory angina and recommended appropriate clinical applications.

METHODS

The NACC used literature reviews, expert opinion, clinical experience, and individual research. Authors consulted the Practice Parameters for the Use of Spinal Cord Stimulation in the Treatment of Neuropathic Pain (2006), systematic reviews (1984 to 2013), and prospective and randomized controlled trials (2005 to 2013) identified through PubMed, EMBASE, and Google Scholar.

RESULTS

Neurostimulation is relatively safe because of its minimally invasive and reversible characteristics. Comparison with medical management is difficult, as patients considered for neurostimulation have failed conservative management. Unlike alternative therapies, neurostimulation is not associated with medication-related side effects and has enduring effect. Device-related complications are not uncommon; however, the incidence is becoming less frequent as technology progresses and surgical skills improve. Randomized controlled studies support the efficacy of spinal cord stimulation in treating failed back surgery syndrome and complex regional pain syndrome. Similar studies of neurostimulation for peripheral neuropathic pain, postamputation pain, postherpetic neuralgia, and other causes of nerve injury are needed. International guidelines recommend spinal cord stimulation to treat refractory angina; other indications, such as congestive heart failure, are being investigated.

CONCLUSIONS

Appropriate neurostimulation is safe and effective in some chronic pain conditions. Technological refinements and clinical evidence will continue to expand its use. The NACC seeks to facilitate the efficacy and safety of neurostimulation.

The appropriate use of neurostimulation: avoidance and treatment of complications of neurostimulation therapies for the treatment of chronic pain. Neuromodulation Appropriateness Consensus Committee

INTRODUCTION

The International Neuromodulation Society (INS) has determined that there is a need for guidance regarding safety and risk reduction for implantable neurostimulation devices. The INS convened an international committee of experts in the field to explore the evidence and clinical experience regarding safety, risks, and steps to risk reduction to improve outcomes.

METHODS

The Neuromodulation Appropriateness Consensus Committee (NACC) reviewed the world literature in English by searching MEDLINE, PubMed, and Google Scholar to evaluate the evidence for ways to reduce risks of neurostimulation therapies. This evidence, obtained from the relevant literature, and clinical experience obtained from the convened consensus panel were used to make final recommendations on improving safety and reducing risks.

RESULTS

The NACC determined that the ability to reduce risk associated with the use of neurostimulation devices is a valuable goal and possible with best practice. The NACC has recommended several practice modifications that will lead to improved care. The NACC also sets out the minimum training standards necessary to become an implanting physician.

CONCLUSIONS

The NACC has identified the possibility of improving patient care and safety through practice modification. We recommend that all implanting physicians review this guidance and consider adapting their practice accordingly.

Epidural spinal cord stimulation for neuropathic pain: a neurosurgical multicentric Italian data collection and analysis

BACKGROUND

Spinal cord stimulation (SCS) is a technique used worldwide to treat several types of chronic neuropathic pain refractory to any conservative treatment. The aim of this data collection is to enforce evidence of SCS effectiveness on neuropathic chronic pain reported in the literature and to speculate on the usefulness of the trial period in determining the long-term efficacy. Moreover, the very low percentage of undesired side effects and complications reported in our case series suggests that all implants should be performed by similarly well-trained and experienced professionals.

METHOD

A multicentric data collection on a common database from 11 Italian neurosurgical departments started 3 years ago. Two different types of electrodes (paddle or percutaneous leads) were used. Of 122 patients, 73 % (N = 89) were submitted to a trial period, while the remaining patients underwent the immediate permanent implant (N = 33). Statistical comparisons of continuous variables between groups were performed.

RESULTS

Most of the patients (80 %) had predominant pain to their lower limbs, while only 17 % of patients had prevalent axial pain. Significant reduction in pain, as measured by variation in visual analogue scale (VAS) score, was observed at least 1 year after implantation in 63.8 % of the cases, 59.5 % of patients who underwent a test trial and 71.4 % of patients who underwent permanent implant at once. No statistical differences were found between the lower-limb pain group and the axial pain group.

CONCLUSIONS

No relevant differences in long-term outcomes were observed in previously tested patients compared with patients implanted at once. Through this analysis we hope to recruit new centres, to give more scientific value to our results.

The failed back surgery syndrome: pitfalls surrounding evaluation and treatment

This article describes the costs and risk factors for failed back surgery syndrome and reviews the diagnosis and treatment strategies commonly used to address this syndrome. The purpose of this review is to describe some of the treatment pitfalls associated with these approaches from a physiatric perspective.