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Chronic low back pain can be caused by impaired control and degeneration of the multifidus muscles and consequent functional instability of the lumbar spine. Available treatment options have limited effectiveness and prognosis is unfavorable. We conducted an international randomized, double-blind, sham-controlled trial at 26 multidisciplinary centers to determine safety and efficacy of an implantable, restorative neurostimulator designed to restore multifidus neuromuscular control and facilitate relief of symptoms (clinicaltrials.gov identifier: NCT02577354). Two hundred four eligible participants with refractory mechanical (musculoskeletal) chronic LBP and a positive prone instability test indicating impaired multifidus control were implanted and randomized to therapeutic (N = 102) or low-level sham (N = 102) stimulation of the medial branch of the dorsal ramus nerve (multifidus nerve supply) for 30 minutes twice daily. The primary endpoint was the comparison of responder proportions (≥30% relief on the LBP visual analogue scale without analgesics increase) at 120 days. After the primary endpoint assessment, participants in the sham-control group switched to therapeutic stimulation and the combined cohort was assessed through 1 year for long-term outcomes and adverse events. The primary endpoint was inconclusive in terms of treatment superiority (57.1% vs 46.6%; difference: 10.4%; 95% confidence interval, −3.3% to 24.1%, P = 0.138). Prespecified secondary outcomes and analyses were consistent with a modest but clinically meaningful treatment benefit at 120 days. Improvements from baseline, which continued to accrue in all outcome measures after conclusion of the double-blind phase, were clinically important at 1 year. The incidence of serious procedure- or device-related adverse events (3.9%) compared favorably with other neuromodulation therapies for chronic pain.

Neuromodulation, specifically spinal cord stimulation (SCS), has become a staple of chronic pain management for various conditions including failed back syndrome, chronic regional pain syndrome, refractory radiculopathy, and chronic post operative pain. Since its conceptualization, it has undergone several advances to increase safety and convenience for patients and implanting physicians. Current research and efforts are aimed towards novel programming modalities and modifications of existing hardware. Here we review the recent advances and future directions in spinal cord stimulation including a brief review of the history of SCS, SCS waveforms, new materials for SCS electrodes (including artificial skins, new materials, and injectable electrodes), closed loop systems, and neurorestorative devices.

Impaired neuromuscular control and degeneration of the multifidus muscle have been linked to the development of refractory chronic low back pain (CLBP). An implantable restorative-neurostimulator system can override the underlying multifidus inhibition by eliciting episodic, isolated contractions. The ReActiv8-B randomized, active-sham-controlled trial provided effectiveness and safety evidence for this system, and all participants received therapeutic stimulation from four months onward. This study aimed to evaluate the two-year effectiveness of this restorative neurostimulator in patients with disabling CLBP secondary to multifidus muscle dysfunction and no indications for spine surgery. Open-label follow-up of 204 participants implanted with a restorative neurostimulation system (ReActiv8, Mainstay Medical, Dublin, Ireland) was performed. Pain intensity (visual analog scale [VAS]), disability (Oswestry disability index [ODI]), quality-of-life (EQ-5D-5L), and opioid intake were assessed at baseline, six months, one year, and two years after activation. At two years (n = 156), the proportion of participants with ≥50% CLBP relief was 71%, and 65% reported CLBP resolution (VAS ≤ 2.5 cm); 61% had a reduction in ODI of ≥20 points, 76% had improvements of ≥50% in VAS and/or ≥20 points in ODI, and 56% had these substantial improvements in both VAS and ODI. A total of 87% of participants had continued device use during the second year for a median of 43% of the maximum duration, and 60% (34 of 57) had voluntarily discontinued (39%) or reduced (21%) opioid intake. At two years, 76% of participants experienced substantial, clinically meaningful improvements in pain, disability, or both. These results provide evidence of long-term effectiveness and durability of restorative neurostimulation in patients with disabling CLBP, secondary to multifidus muscle dysfunction. The study is registered on clinicaltrials.gov with identifier NCT02577354.

Conventionally, peripheral nerve stimulation (PNS) for treatment of chronic pain has involved a two-stage process: a short-term (e.g., 7 days) trial and, if significant pain relief is achieved, a permanent PNS system is implanted. A percutaneous PNS treatment is now available where a coiled lead may be implanted for up to 60 days with the goal of producing sustained relief. In the present review, published prospective trials using percutaneous PNS treatment were identified and synthesized. The collected evidence indicates that percutaneous PNS treatment for up to 60 days provides durable clinically significant improvements in pain and pain interference. Similar efficacy across diverse targets and etiologies supports the broad applicability for use within the chronic pain population using this nonopioid technology.

Peripheral nerve stimulation (PNS) has evolved with various applications and durations of therapy. In recent years, extensive data has been developed on a 60-day treatment using a novel approach. Confusion exists on the use of a trial therapy, a permanent implant, and a 60-day duration treatment. The American Society of Pain and Neuroscience (ASPN) seeks to clarify the literature associated with this neuromodulation approach. A diverse group of experts was nominated to provide opinions and guidance based on evidence-graded assessment and clinical knowledge. This guidance is the first to specifically assess the clinical use of 60-day PNS and best medical practice.