A review of spinal cord stimulation systems for chronic pain

Figures & data

Table 1 Selection of SCS literature with focus on back ± lower limb pain studies

Study	Year	Design, cohort, sample size, follow-up	Reported findings	Comments
Barolat et al^Citation28	2001	Prospective, multicenter observational case series n=41 Follow-up: 1 year Cohort: back and leg pain (with predominant pain in back)	Tests SCS systems with paddle electrodes and RF stimulator n=15 at 1 year At 12 months, 88% of patients reported fair-excellent pain relief for leg pain following SCS At 12 months, 68% of the patients reported fair-excellent pain relief for back pain following SCS	Groups pain relief of fair to excellent into one group Three patients dropped from study at 6 months: two due to inadequate pain relief and one classified as technical failure because power required to induce satisfactory paresthesia to control pain was inadequate. This methodology skews the outcome data
Kemler et al^Citation58	2004	RCT n=54 (36 randomized to SCS + PT; 18 randomized to PT only) Follow-up: 2 years Cohort: CRPS	Tests either SCS + PT or PT only Significant improvement for those receiving SCS + PT: VAS mean improvement of 2.1 versus 0 cm for PT only Global perceived effect scale of 43% for SCS + PT group versus 6% for PT only	Complications for 38% of patients, occurring mostly in first 12 months
North et al^Citation59	2005	Prospective RCT (with optional cross over). n=50 Follow-up average of 3 years Cohort: FBSS	Tests either reoperation or SCS: 52% of patients receiving (through cross over or by randomization) SCS reported long-term success, compared with 19% receiving (through cross over or by randomization) reoperation. SCS is more successful than reoperation for treating radicular pain	Excluded patients with primary or significant back pain Reoperation success rates tie with record low reported in literature Cross overs were counted as an outcome measure (ITT analysis questions this approach). Furthermore, despite some reoperation patients meeting successful outcome benchmark, they chose to cross over in an attempt to try and gain even further pain relief
Kumar et al^Citation56	2008	Prospective RCT n=100 (52 randomized to SCS, 48 randomized to CMM) Follow-up: 2 years Multicenter (across 12 centers internationally) Cohort: FBSS patients	Tests either SCS + CMM or CMM only: n=42 receiving stimulation at 2 years experienced significantly lower levels of leg pain but reported no difference in back pain SCS treatment led to better outcomes when measured using ODI, QOL, and patient satisfaction measures Analgesic intake and nondrug therapies did not change with either treatment	45% experienced complications, 31% required surgical revision Authors comment that if data are managed in statistically conservative manner, then 33% of patients receiving SCS will have significantly less leg pain Comparative group receiving CMM but not placebo-controlled group
Turner et al^Citation60,Citation61	2010	Prospective, controlled cohort study SCS trial, n= 51; multidisciplinary PC n=39; UC, n=68 Follow-up at 6, 12, and 24 months Cohort: workers compensation recipients with FBSS	Tests SCS against UC and a multidisciplinary PC At 6 months, SCS patients had greater improvement in leg pain and function but with concomitant higher rates of opioid use At 12 and 24 months, the groups did not differ in rates of clinically meaningful leg pain of function or in work status Within 18 months, 19% had SCS removed	Study among very specific cohort/patient subpopulation Workcover patients could only receive SCS if they joined study SCS > PC and UC  Baseline pain  Baseline Roland-Morris Disability  Duration of pain  Time in WC claim system <25% of SCS patients received psych assessment/screening SCS conversion rate was 58%, significantly lower than that reported in literature Implanter experience unclear No comparative or alternative population treated alongside WC group to act as control group
De Vos et al^Citation62	2012	Prospective, observational case series n=41 Follow-up: 12 months Cohort: FBSS	Tests paddle-shaped SCS lead efficacy in capturing both back and leg pain Baseline leg pain mean of 8, dropped to 3.2, and baseline low back pain mean of 7.5, dropped to 4.2 at 12 months 71% experienced >50% pain relief for legs and 51% of patients experienced >50% pain relief for back	By 12 months, n=6 reported no or minimal pain relief, postulated that the FBSS and treatment thereof masked pain of different etiologies such as OA No control group
Moriyama et al^Citation63	2012	Prospective, observational, multicenter, open-label case series n=55 Follow-up: 6 months Cohort: CRPS, FBSS, and PVD	Tests that patients likely to benefit from SCS n=29 at 6-month follow-up where the overall VAS mean baseline of 74 mm dropped to 29.7 mm CRPS and PVD cases responding better than FBSS patients
Geurts et al^Citation26	2013	Prospective, observational, consecutive case series n=84 Follow-up at min 0.2 to max 11.9 years Cohort: CRPS-1	Tests long-term treatment efficacy of SCS for CRPS-1 n=79 41% of patients experience ≥30% pain relief at endpoint Pain relief stabilizes and holds over time Having <50% pain relief at SCS trial was a highly significant indicator of long-term treatment failure	Treatment success defined as ≥30% pain relief on baseline rather than ≥50% Minor common complications: lead migration in 23 patients, seven experience hardware malfunction requiring surgical intervention, seven infections, 44 battery replacements (mean battery life of 4.4 years). Data may reflect outmoded hardware/technologies used at start of trial No major complications
Van Buyten et al^Citation18	2013	Prospective, multicenter, open-label, observational study n=83 Follow-up: 6 months Cohort: majority FBSS (81%), predominantly low back pain	Tests safety and efficacy of HF SCS n=72 proceed to implant Back pain: mean VAS from 8.4 to 2.7 at 6 months Leg pain: mean VAS from 5.4 to 1.4 at 6 months 74% had ≥50% back pain relief at 6 months Subset of 14 had previously failed conventional SCS. HF10 able to capture or rescue eleven of these with good results	Note the use of both statistical mean and median. Mean baseline VAS scores reported but then median % change in pain was reported. No comparative group/control group – use of baseline for control
Al-Kaisy et al^Citation64	2014	Prospective, multicenter, observational case series n=72 Follow-up: 24 months Cohort: chronic unresponsive LBP (17% previously failed conventional SCS)	Tests safety and long-term efficacy of HF SCS on back and leg pain n=65 at 24-month follow-up Significant pain relief sustained Back pain: mean VAS from 8.4 to 3.3 at 2 years (P≤0.001) Leg pain: mean VAS from 5.4 to 2.3 (P≤0.001) HF SCS is safe treatment 60% had ≥50% back pain relief at 24 months	Observational study only
De Ridder et al^Citation65	2015	Retrospective, multicenter, comparative trial n=102 Follow-up: 2 weeks Cohort: majority FBSS and diabetic neuropathic pain. All patients had been using conventional SCS for at least 6 months	Tests efficacy of novel burst stimulation SCS against tonic/conventional SCS Overall burst stimulation had significantly better pain suppression over tonic stimulation: back pain was suppressed 29% better and limb pain 31% better when compared with tonic stimulation burst SCS able to “rescue” 62% of patients who no longer responded to tonic stimulation	No control group All participants were acclimated to conventional SCS prior to trial Very short 2-week study period
Kapural et al^Citation22	2015	Prospective, multicenter RCT n=198 Follow-up: 12 months Cohort: chronic back ± leg pain	Tests safety and efficacy of conventional versus HF SCS n=171 successful trial and implanted. Randomized 1:1. N=90, HF; and n=81, conventional SCS. Equally safe HF SCS therapy subjects did not experience paresthesia The mean pre HF SCS VAS was 7.4, 12 months post HF SCS the mean VAS was 2.5 (67% decrease): conventional SCS 7.8 to 4.3 (44% decrease) Mean leg pain HF SCS pre 7.1 to 2.1 (70% decrease), conventional SCS 7.6 to 3.8 (49% decrease) Remitter N pain scores ≤2.5 VAS at 12 months Mean back pain: HF SCS: 68.5% versus conventional SCS 36.3%. Mean leg pain: HF SCS 67.4% versus conventional SCS 42.5% Both the forms of SCS are safe and effective but HF is significantly more effective	Subjects and investigators could not be masked due to the nature of conventional SCS treatment Note the application of ≥40% rather than ≥50% reduction in back pain as eligibility measure for proceeding to implant Used ≥50% pain reduction for assessing outcome measures HF SCS recharged daily, whereas conventional typically had longer recharge intervals Patients naive to SCS of any form
Russo et al^Citation29	2015	Retrospective, multicenter, observational case series n=256 Follow-up: 6 months Cohort: range of chronic pain diagnoses, including back only, back + limb, head ± neck, complex pain patterns. 30% of cohort had previously failed conventional SCS	Tests efficacy of HF SCS in real world/routine clinical practice n=186 permanent implant Overall, ~50% reduction in pain from baseline was sustained for 6 months. Back ± leg pain responded best Able to “rescue” majority of patients who had previously failed conventional SCS	Authors acknowledge that uncontrolled real-world application of SCS is different in controlled studies and therefore carries weaknesses such as no control group but alternatively offers insights into clinical experience Wide variation in indications
Liem et al^Citation15	2015	Prospective, multicenter, open-labeled observational study n=51 Follow-up: 12 months Cohort: several diagnoses, including FBSS, CRPS, radiculopathy, and lumbar stenosis	Tests DRG SCS as a treatment for neuropathic pain n=32 permanent implant Overall pain reduced by 56% at 12 months and 60% of patients reported ≥50% improvement in pain Pain localized to back was reduced by 42% (n=10), leg pain reduced by 62% (n=20), and foot pain reduced by 80% (n=10)	No comparative/control group: observational study only. Authors used patient baseline measure as control Relatively high incidence of adverse events

Notes: Only studies with larger sample sizes and those published after 2000 were included. Adapted from Taylor RS, Desai MJ, Rigoard P, Taylor RJ. Predictors of pain relief following spinal cord stimulation in chronic back and leg pain and failed back surgery syndrome: a systematic review and meta-regression analysis. Pain Pract. 2014;14(6):489–505. With permission from John Wiley and Sons, copyright ©2013.²⁵

Abbreviations: CMM, conventional medical management; CRPS, complex regional pain syndrome; DRG, dorsal root ganglion; FBSS, failed back surgery syndrome; HF, high frequency; ITT, intention-to-treat; min, minimum; max, maimum; OA, osteoarthritis; ODI, Oswestry disability index; PC, pain clinic; PT, physical therapy; PVD, peripheral vascular disease; QOL, quality of life; RCT, randomized controlled trial; RF, radio frequency; SCS, spinal cord stimulation; UC, usual care; VAS, visual analog scale; WC, workers compensation; LBP, low back pain.

Figure 1 (A) Posterior anterior fluoroscopy image and (B) lateral fluoroscopy image of T8-T10 placement of linear leads (Nevro Corp.) for the treatment of chronic back and leg pain.

Note: Images courtesy of Metro Pain Group.
Abbreviations: L, left; R, right.

Figure 2 (A) Posterior anterior fluoroscopy image and (B) lateral fluoroscopy image of leads placed bilaterally at T12 and L1 dorsal root ganglions for the treatment of chronic idiopathic orchialgia pain.

Note: Images courtesy of Metro Pain Group.
Abbreviations: L, left; R, right.

Figure 3 Intraoperative image of NX3000 anchor system by Nevro Corp.

Note: Images courtesy of Gillian Nowesenitz.

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