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Long-Term Durability of Restorative Neurostimulation for Chronic Mechanical Low Back Pain – Two-Year Pivotal Trial Results

      Introduction: Chronic mechanical low back pain (CMLBP) can be caused by impaired neuromuscular control and degeneration of the multifidus muscles resulting in functional instability of the lumbar spine. Available treatment options often lack long-term effectiveness and prognosis is unfavourable. An implantable Restorative Neurostimulation system (ReActiv8® by Mainstay Medical), that stimulates the L2 medial branches of the dorsal rami to reactivate neuromuscular control, received FDA Premarket Approval based on evidence from the ReActiv8-B pivotal trial (clinicaltrials.gov/show/NCT02577354). Here we report the two-year results of the open-label phase of this trial.
      Methods: Participants had refractory, activity limiting CMLBP with average low back pain VAS≥6cm, Oswestry Disability Index ODI≥21 points, evidence of multifidus inhibition (prone-instability-test) and no indication for spine surgery. Participants self-administered up to 60-minutes of stimulation per day and were followed-up through two years.
      Results: At baseline (N=204), participants were 47±9 years of age, had backpain for 14±11 years, average LBP-VAS of 7.3±0.7cm, ODI of 39.1±10.3 points, EQ-5D (quality-of-life) of 0.585±0.174 and had LBP on 97±8% of days during the year before enrolment.
      At two-years (N=159), all prespecified outcome measures showed statistically significant (P<0.0001) and clinically substantial improvements compared to baseline. Average LBP-VAS improved by -4.8±2.4cm (-65.9±32.6%), ODI by -21.7±16.8points
      (-54.7±39.2%) and EQ-5D by 0.215±0.215; 71% of participants had ≥50% LBP-VAS improvement; 66% had VAS≤2.5cm (LBP-resolution); 62% had ≥20points ODI improvement; 77% had ≥50% improvement in LBP-VAS and/or ODI; 80% were “Definitely satisfied” with the treatment and 59% voluntarily eliminated or reduced opioid consumption. The overall safety profile is favourable, and no lead migrations were observed.
      Discussion: Long-term restorative neurostimulation is an effective and durable treatment option with an encouraging safety profile for patients with refractory, activity limiting CMLBP, impaired multifidus motor control and no indications for spine surgery. Clinically substantial improvements, which progressively accrue through two years, are consistent with the restorative mechanism of action.
      Conflicts of Interest Statement: The ReActiv8-B study was sponsored by Mainstay Medical, who paid the study sites to perform study-related activities, including Assoc Prof Bruce Mitchell’s site.