Abstract
INTRODUCTION
Spinal cord stimulation (SCS) is a well-established treatment for chronic pain. Advancements in SCS systems have focused on eliminating paresthesias, but long-term success rates remain suboptimal. Variability in spinal cord (SC) activation with open-loop systems results in unpredictable inhibition of pain processing pathways, and may limit the efficacy of SCS. We report the first randomized, double-blind, pivotal study of SCS and the first therapy to measure real-time in Vivo SC neurophysiology using evoked compound action potentials (ECAPs). This study provides comparative efficacy and safety of ECAP-controlled closed-loop (CL) feedback stimulation compared to open-loop (OL) stimulation, and objective evidence of the mechanism of action of SCS.
METHODS
A total of 134 subjects were randomized into OL or CL. Subjects and the clinical staff were blinded to the treatment assignment. Both groups received the same device. Programming was equivalent with the only difference being that the closed-loop feedback feature was enabled in the Investigational group. A pain assessment and other patient reported outcome measures per IMMPACT were collected. ECAPs were also collected in both groups to compare the magnitude of SC activation and the percentage of time within the therapeutic window.
RESULTS
The primary composite endpoint demonstrated superior results in overall pain responders (P = .005) for CL-SCS (82.3%) compared to OL-SCS (60.3%). In addition, all prespecified hierarchical endpoints demonstrated better outcomes in the CL group, with both back pain reduction (P = .015) and back pain responders (P = .003) demonstrating superiority. The magnitude of SC activation was 7 times greater for CL-SCS and CL subjects spend 50% more time within the therapeutic window. In both groups, subjects showed improvements across disability, psychological, sleep, quality of life, and satisfaction.
CONCLUSION
ECAP-controlled closed-loop SCS has demonstrated superior overall pain relief compared to open-loop SCS. The study has just completed the primary outcome data analysis.
ECAP‐Controlled Closed‐Loop Spinal Cord Stimulation Efficacy and Opioid Reduction over 24‐Months: Final Results of the Prospective, Multicenter, Open‐Label Avalon Study