Background: Chronic low back pain (CLBP) is the most common chronic pain condition and is often resistant to\nconventional treatments. Acupuncture is a popular alternative for treating CLBP but its mechanisms of action\nremain poorly understood. Evidence suggests that pain regulatory mechanisms (particularly the ascending and\nsecondarily the descending pain modulatory pathways) and psychological mechanisms (e.g., expectations, pain\ncatastrophizing and self-efficacy) may be involved in the pathogenesis of CLBP and its response to treatments.\nWe will examine these mechanisms in the treatment of CLBP by electroacupuncture (EA).\nMethods: We present the aims and methods of a placebo-controlled, participant-blinded and assessor-blinded\nmechanistic study. Adult patients with CLBP will be randomized to receiving 16 sessions of real (active) or sham\n(placebo) EA over the course of 8 weeks. The primary pain regulatory measure for which the study was powered is\ntemporal summation (TS), which approximates ascending pain facilitation. Conditioned pain modulation (CPM),\nrepresenting a descending pain modulatory pathway, will be our secondary pain regulatory measure. The primary\npsychological measure is expectations of benefit, and the secondary psychological measures are pain catastrophizing\nand self-efficacy in managing pain. Main clinical outcomes are back pain bothersomeness on a 0â??100 visual analog\nscale (primary), Roland Morris Disability Questionnaire (secondary), and relevant items from the National Institutes of\nHealth (NIH) Patient-Reported Outcome Measures Information System (secondary). We hypothesize that compared\nto sham, real EA will lead to greater reduction in TS after 8 treatment sessions (4 weeks); and that reduction in TS\n(and secondarily, increase in CPM) after 8 treatment sessions will mediate reduction in back pain bothersomeness from\nbaseline to week 10 (clinical response) to EA. We also hypothesize that the three psychological factors are moderators\nof clinical response. With 100 treatment completers, the study is designed to have 80% power to detect a mediumsized\nbetween-group effect (d = 0.5) on temporal summation.\nDiscussion: To the best of our knowledge, this is the first appropriately powered, placebo-controlled clinical trial\nevaluating mechanisms of EA in the treatment of CLBP. Trial registration: ClinicalTrials.gov, NCT02503475. Registered on 15 July 15 2015. Retrospectively registered.
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