Restorative neurostimulation outcomes for mechanical chronic low back pain: delayed-start crossover from optimal medical management and 2-year treatment longitudinal analyses from the RESTORE randomized controlled trial.

BACKGROUND CONTEXT: Mechanical chronic low back pain (CLBP) associated with lumbar multifidus muscle dysfunction is a major cause of long-term disability. Available nonoperative and interventional treatments often provide limited and transient benefit. Restorative neurostimulation is intended to activate the lumbar multifidus to restore neuromuscular control and address the underlying pathophysiology of mechanical CLBP.

PURPOSE: The purpose of this extension of the original randomized controlled trial was to track outcomes in a crossover group for the subsequent treatment year. Participants in the original treatment group were also followed for an additional year, allowing long-term clinical follow-up.

STUDY DESIGN/

SETTING

RESTORE is a postmarket, multicenter, open-label randomized controlled trial performed at 25 clinical sites in the United States.

PATIENT SAMPLE: A total of 203 participants were randomized 1:1 to restorative neurostimulation or optimal medical management. At the completion of the randomized phase, 80/96 (83%) eligible control participants elected to cross over to restorative neurostimulation treatment. These participants and the original treatment group were followed for an additional year.

OUTCOME MEASURES: Oswestry Disability Index (ODI), back pain (Numerical Rating Scale [NRS]), and health-related quality of life (EuroQol 5-Dimension 5-Level [EQ-5D-5L]) were assessed at 18 and 24 months postrandomization. Outcomes included responder rates based on minimal clinically important change thresholds, pain remission, composite responder definitions, work ability, subject global impression of change, opioid use, and number needed to treat.

METHODS

This prespecified delayed-start crossover analysis included a nonrandomized comparison of outcomes between early and delayed-start treatment groups, with within-group analyses serving as the primary basis for inference regarding crossover efficacy. Longitudinal outcomes for the treatment group were analyzed using mixed models for repeated measures. Crossover group outcomes were analyzed using completer analyses.

RESULTS

The treatment group improvements were sustained through 24 months, with mean changes from baseline of -24.6±17.1 in ODI, -4.2±2.4 in NRS, and +0.189±0.163 in EQ-5D-5L (all p<.001). After crossover, participants demonstrated significant improvements after 1 year of active therapy, with mean changes from baseline of -21.1±14.8 in ODI, -3.8±2.2 in NRS, and +0.191±0.144 in EQ-5D-5L (all p<.001), comparable in magnitude to those observed in the treatment group at the same timepoint. At 12 months, responder rates in the treatment group were 70% for ODI ≥15 point improvement, 53% for ≥50% NRS reduction, 52% for NRS remission, and 72% for the composite endpoint, compared with 17%, 6%, 6%, and 12% in the control group, respectively; after crossover, corresponding responder rates at 12 months of active therapy were 64%, 61%, 60%, and 73%, consistent in magnitude with those observed in the treatment group at the equivalent timepoint of therapy. Corresponding numbers needed to treat ranged from 1.7 to 2.2 and remained similarly low when the crossover outcomes were compared with control.

CONCLUSIONS

These findings reinforce the role of restorative neurostimulation as an effective therapeutic option for patients with multifidus dysfunction-related CLBP who have exhausted conservative care and suggest that earlier intervention may reduce prolonged disability and loss of quality of life.