Cerebral mechanism of opposing needling for managing acute pain after unilateral total knee arthroplasty: study protocol for a randomized, sham-controlled clinical trial

BACKGROUND: Opposing needling is a unique method used in acupuncture therapy to relieve pain, acting on the side contralateral to the pain. Although opposing needling has been used to treat pain in various diseases, it is not clear how opposing needling affects the activity of the central nervous system to relieve acute pain. We herein present the protocol for a randomized sham-controlled clinical trial aiming to explore the cerebral mechanism of opposing needling for managing acute pain after unilateral total knee arthroplasty (TKA). METHODS: This is a randomized sham-controlled single-blind clinical trial. Patients will be allocated randomly to two parallel groups (A: opposing electroacupuncture group; B: sham opposing electroacupuncture group). The Yinlingquan (SP9), Yanglingquan (GB34), Futu (ST32), and Zusanli (ST36) acupoints will be used as the opposing needling sites in both groups. In group A, the healthy lower limbs will receive electroacupuncture, while in group B, the healthy lower limbs will receive sham electroacupuncture. At 72 h after unilateral TKA, patients in both groups will begin treatment once per day for 3 days. Functional magnetic resonance imaging will be performed on all patients before the intervention, after unilateral TKA, and at the end of the intervention to detect changes in brain activity. Changes in pressure pain thresholds will be used as the main outcome for the improvement of knee joint pain. Secondary outcome indicators will include the visual analogue scale (including pain during rest and activity) and a 4-m walking test. Surface electromyography, additional analgesia use, the self-rating anxiety scale, and the self-rating depression scale will be used as additional outcome indices. DISCUSSION: The results will reveal the influence of opposing needling on cerebral activity in patients with acute pain after unilateral TKA and the possible relationship between cerebral activity changes and improvement of clinical variables, which may indicate the central mechanism of opposing needling in managing acute pain after unilateral TKA. TRIAL REGISTRATION: Study on the brain central mechanism of opposing needling analgesia after total kneearthroplasty based on multimodal MRI ChiCTR2100042429. Registered on January 21, 2021 SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13063-022-06066-6.