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Leonardo Kapural,1 Jim Melton,2 Billy Kim,3 Priyesh Mehta,4 Abindra Sigdel,5 Alexander Bautista,6 Erika A Petersen,7 Konstantin V Slavin,8,9 John Eidt,10 Jiang Wu,11 Said Elshihabi,12 Jason Matthew Schwalb,13 H Edward Garrett Jr,14 Elias Veizi,15 Giancarlo Barolat,16 Ravi R Rajani,17 Peter C Rhee,18 Maged Guirguis,19 Nagy Mekhail20 1Carolinas Pain Institute and Center for Clinical Research, Winston-Salem, NC, USA; 2Department of Vascular Surgery, Cardiovascular Health Clinic, Oklahoma City, OK, USA; 3Department of Vascular Surgery, The Surgical Clinic, Nashville, TN, USA; 4Department of Pain Medicine, Meta Medical Research Institute, Dayton, OH, USA; 5Department of Surgery, University of Louisville, Louisville, KY, USA; 6Department of Anesthesiology and Perioperative Medicine, University of Louisville, Louisville, KY, USA; 7Department of Neurosurgery, University of Arkansas, Little Rock, AR, USA; 8Department of Neurosurgery, University of Illinois at Chicago, Chicago, IL, USA; 9Department of Neurology, Jesse Brown VA Medical Center, Chicago, IL, USA; 10Department of Vascular Surgery, Baylor Scott and White Heart and Vascular Hospital Dallas, Dallas, TX, USA; 11Department of Anesthesiology & Pain Medicine, University of Washington Medical Center, Seattle, WA, USA; 12Department of Neurosurgery, Legacy Brain & Spine Surgical Center, Atlanta, GA, USA; 13Department of Neurosurgery, Henry Ford Medical Group, Detroit, MI, USA; 14Department of Vascular Surgery, University of Tennessee-Memphis, Memphis, TN, USA; 15Department of Pain Medicine, VA Northeast OH Healthcare System, Cleveland, OH, USA; 16Department of Neurosurgery, Barolat Neuroscience, Presbyterian/St Luke’s Medical Center, Denver, CO, USA; 17Department of Vascular Surgery, Emory University and Grady Memorial Hospital, Atlanta, GA, USA; 18Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN, USA; 19Department of Interventional Pain Management, Ochsner Health System, New Orleans, LA, USA; 20Department of Pain Management, Cleveland Clinic, Cleveland, OH, USACorrespondence: Leonardo Kapural, Carolinas Pain Institute and Center for Clinical Research, 145 Kimel Park Dr #330, Winston-Salem, NC, 27103, USA, Email lkapuralmd@gmail.comPurpose: This multicenter, randomized, double-blinded, active sham-controlled pivotal study was designed to assess the efficacy and safety of high-frequency nerve block treatment for chronic post-amputation and phantom limb pain.Patients and Methods: QUEST enrolled 180 unilateral lower-limb amputees with severe post-amputation pain, 170 of whom were implanted with the Altius device, were randomized 1:1 to active-sham or treatment groups and reached the primary endpoint. Responders were those subjects who received ≥ 50% pain relief 30 min after treatment in ≥ 50% of their self-initiated treatment sessions within the 3-month randomized period. Differences between the active treatment and sham control groups as well as numerous secondary outcomes were determined.Results: At 30-min, (primary outcome), 24.7% of the treatment group were responders compared to 7.1% of the control group (p=0.002). At 120-minutes following treatment, responder rates were 46.8% in the Treatment group and 22.2% in the Control group (p=0.001). Improvement in Brief Pain Inventory interference score of 2.3 ± 0.29 was significantly greater in treatment group than the 1.3 ± 0.26-point change in the Control group (p = 0.01). Opioid usage, although not significantly different, trended towards a greater reduction in the treatment group than in the control group. The incidence of adverse events did not differ significantly between the treatment and control groups.Conclusion: The primary outcomes of the study were met, and the majority of Treatment patients experienced a substantial improvement in PAP (regardless of meeting the study definition of a responder). The significant in PAP was associated with significantly improved QOL metrics, and a trend towards reduced opioid utilization compared to Control. These data indicate that Altius treatment represents a significant therapeutic advancement for lower-limb amputees suffering from chronic PAP.Keywords: post-amputation pain, phantom limb pain, neuromodulation, peripheral nerve stimulation, high-frequency nerve block