ECAP-controlled Closed-loop Spinal Cord Stimulation for Chronic Non-surgical Refractory Back Pain

Study Design. Subgroup analysis of patients with chronic non-surgical refractory back pain (NSRBP) from two prospective multicenter clinical trials to 12-month follow-up. Objective. To evaluate pain-related and holistic response, safety events as well as neurophysiologic metrics associated with the use of evoked compound action potential (ECAP)-controlled closed-loop spinal cord stimulation (SCS) for patients with chronic back pain without prior surgery. Summary of Background Data. Innovations in SCS such as the development of physiologic ECAP-controlled closed-loop SCS overcome limitations of traditional, fixed-output SCS for the treatment of NSRBP. The outcomes of closed-loop SCS to 12-month follow-up for patients with NSRBP have not been previously reported. Methods. Patient-reported outcome measures for pain intensity, physical function, health-related quality of life, sleep quality and emotional function were collected from 68 patients with NSRBP in two prospective multicenter clinical trials. Change in opioid use, its reduction or elimination were assessed at 12-month follow-up. A validated composite outcome measure comprising the different health domains was used to evaluate holistic treatment response through minimal clinically important differences (MCIDs). Objective device metrics provide information on system utilization, loop performance (dose accuracy), and neurophysiologic dose metrics. Results. At 12-months, 79% of patients reported ≥50% reduction in pain intensity and 48% obtained ≥80% pain relief. Significant improvements in all patient-reported outcome measures assessed were observed at 3- and 12-months. Voluntary reduction or elimination of opioid use was observed in approximately half of the patients that were taking opioids at baseline. System utilization was >80%, dose ratio was >1.3 (i.e., 30% above ECAP threshold) with a high dose accuracy keeping the elicited ECAP within 3.5 μV of the target ECAP set on the system. Conclusion. ECAP-controlled closed-loop SCS represents a safe and effective treatment option for patients with NSRBP.