Introduction: Mechanical chronic low back pain (CLBP) can be caused by impaired neuromuscular control and degeneration of the multifidus muscles, the most important stabilizers of the lumbar spine. An implantable Restorative Neurostimulation system (ReActiv8® by Mainstay Medical) bilaterally stimulates the medial branches of the L2 dorsal rami to override underlying multifidus inhibition to facilitate motor control restoration. The ReActiv8-B randomized sham-controlled pivotal trial provided published evidence of safety, effectiveness, and durability of this therapy (clinicaltrials.gov/show/NCT02577354). Here we will report the three-year durability results.
Methods: Eligible patients had activity limiting mechanical CLBP with Visual Analog Scale (VAS) ≥6cm; Oswestry Disability Index (ODI) ≥21 points despite medical management, including at least medication and physical therapy. They had evidence of impaired multifidus motor control (positive prone instability test) and no indication for spine surgery. Participants delivered stimulation for up to 30 minutes twice daily causing repetitive tonic multifidus contractions and remain in long-term follow-up.
Results: At baseline (N=204), participants were 47±9 years of age, had a history of 14±11 years of backpain, average LBP-VAS of 7.3±0.7 cm, ODI of 39±10, EQ-5D of 0.585±0.174 points and had pain on 97±8% of days in the prior year prior. Despite limited effectiveness, 37% of participants were using opioids at baseline.
At 3 years (N=129), average LBP-VAS had improved by 4.9±2.4 cm (68.1%), ODI by 22.9±15.2 points (58.9%) and EQ-5D by 0.220±0.196 (All p<0.0001); 77% of participants had a ≥50% LBP-VAS improvement; 68% reported LBP-Resolution (LBP-VAS≤2.5 cm); 64% had a ≥20-point ODI improvement and 86% of participants were “definitely satisfied” with the treatment. As pain and disability are interdependent symptoms, treatment success is determined by both: 83% had an improvement of ≥50% in LBP-VAS and/or ≥20points in ODI, and 57% had these improvements in both. Of participants using opioids at baseline, 72% had voluntarily discontinued (51%) or decreased (21%) consumption. The overall safety profile is favorable compared to other neurostimulation systems and no lead migrations were observed. During the third follow-up year, 6 participants requested device removal citing resolution of pain.
Discussion: Overall trial results demonstrate effectiveness, durability, and safety. Progressive long-term improvements are consistent with the restorative mechanism of action.
Impact and application to the field: Restorative neurostimulation should be considered in patients with intractable mechanical CLBP associated with multifidus control impairment refractory to specialist physical therapy.
The Author declares no conflict of interest
