Sensor-Driven Position-Adaptive Spinal Cord Stimulation for Chronic Pain

Background: Variation in the intensity of neurostimulation due to body position is a practical problem formany patients implanted with spinal cord stimulation (SCS) systems because positional changes may result inoverstimulation or understimulation that leads to frequent need for compensatory manual programmingadjustments.Objectives: The purpose of this study was to assess the safety and effectiveness of a novel type of SCStherapy designed to automatically adapt stimulation amplitude in response to changes in a patient’s position oractivity. The primary objective of the study was to demonstrate that automatic position-adaptive SCS benefitedpatients in terms of pain relief and/or convenience compared with neurostimulation adjusted with conventionalmanual programming. Secondary objectives included assessment of worsened pain relief with automaticadjustment; change in pain score; and the number of manual programming adjustments with position-adaptiveneurostimulation compared with manual programming.Study Design: Prospective, multicenter, open-label, randomized crossover study.Setting: Ten interventional pain management centers in the US.Methods: Patients were enrolled a minimum of one week after a successful SCS screening trial. They werethen implanted with the RestoreSensorTM neurostimulation device (Medtronic, Inc., Minneapolis, MN) that couldbe programmed to either automatic position-adaptive stimulation (AdaptiveStimTM) or manual adjustment ofstimulation parameters. After implant, all devices were programmed to conventional manual adjustment for a4-week postoperative period. The patients were then randomized to either conventional manual programmingadjustment or position-adaptive stimulation with crossover to the opposite treatment arm occurring at 6 weeksafter randomization. The patients were followed for another 6 weeks after crossover. This study was conductedunder an FDA-approved Investigational Device Exemption (IDE) and approval of the responsible Institutional ReviewBoards (IRBs) of the study centers.Results: Seventy-nine patients were enrolled in the study. In an intent-to-treat analysis, 86.5% of patients achievedthe primary objective of improved pain relief with no loss of convenience or improved convenience with no loss ofpain relief using automatic position-adaptive stimulation compared with using conventional manual programmingadjustment alone. This was statistically significantly greater than the predefined minimum success rate of 25%,P < 0.001 (exact one-sided 97.5% lower confidence limit was 76.5%). Only 2.8% of patients reported worsened painrelief during position-adaptive stimulation compared with manual programming. There was a statistically significantreduction in the mean numeric pain rating scale score compared with baseline scores in both treatment arms.Additionally, position-adaptive stimulation demonstrated a statistically significant 41% reduction in the daily averagenumber of programming button presses for amplitude adjustment compared with manual programming (18.2 perday versus 30.7 per day, P = 0.002). Functional improvements reported with position-adaptive stimulation included:improved comfort during position changes (80.3%); improved activity (69%); and improved sleep (47.9%). Adverseevents associated with uncomfortable sensations from stimulation did not differ significantly between treatmentarms. The incidence of device-related serious adverse events was 3.9%.Limitations: Patients and physicians were not blinded to whether devices were programmed to automaticposition-adaptive stimulation or manual adjustment. Responses to assessment questionnaires were based onpatient recall.Conclusions: The study demonstrated that automatic position-adaptive stimulation is safe and effective inproviding benefits in terms of patient-reported improved pain relief and convenience compared with using manualprogramming adjustment alone.Key words: spinal cord stimulation, neurostimulation, position sensing, physical activity accelerometer,neuromodulation, effectiveness, pain relief, position-adaptive stimulation, posture-adaptive stimulation, AdaptiveStimClinical Trial: NCT01106404