In patients with disabling mechanical (musculoskeletal) chronic low back pain, a new implantable neurostimulator showed clinically meaningful benefit at 120 days, as per the findings of an international randomized, prospective sham-controlled, double-blind trial.

This study (ReActiv8-B) was carried out at twenty-six multidisciplinary centers for determining the efficacy and safety of an implantable, restorative neurostimulator designed for restoring multifidus neuromuscular control and expediting the relief of symptoms.

Overall, 204 subjects having refractory chronic low back pain and a positive prone instability test underwent implantation and were subsequently randomly segregated to therapeutic (102 participants) or low-level sham (102 participants) stimulation of medial branch of dorsal ramus nerve (multifidus nerve supply) for thirty minutes twice daily.

Comparison of responder proportions (an improvement of ≥30% on low back pain visual analogue scale (VAS) without a rise in the use of analgesic agents) at 120 days was the major outcome ascertained. Following the evaluation of the major outcome, subjects in the control group switched to therapy stimulation. The combined cohort was evaluated through one year for the long-term outcomes and noxious effects.

The major outcome was inconclusive with regard to therapy superiority. No major inter-group differences were noted regarding the percentage of people who attained ≥30% low back pain-VAS improvement without elevation in analgesics usage (57.1% vs 46.6%). The prespecified secondary endpoints and analyses showed consistency with a modest but substantial therapeutic benefit at 120 days.

The improvements from the baseline, which continued to accumulate in all the endpoints following conclusion of double-blind phase, were clinically significant at one year. The occurrence of severe side effects (procedure/device-associated) (3.9%) compared favorably with the rates published for other neuromodulation treatments for chronic pain. Although the primary endpoint of the trial was inconclusive, yet this trial yielded essential understanding and significant design considerations for the future neuromodulation clinical trials.