Objective: To investigate the remote effect of acupuncture on the pain intensity and the endplate noise (EPN) recorded from a myofascial trigger point (MTrP) of the upper trapezius muscle.
Design: Randomized controlled trial.
Setting: University hospital.
Participants: Patients (N=20) with active MTrPs in upper trapezius muscles and no experience in acupuncture therapy.
Interventions: Patients were divided into 2 groups. Those in the control group received sham acupuncture, and those in the acupuncture group received modified acupuncture therapy with needle insertion into multiple loci to elicit local twitch responses. The acupuncture points of Wai-guan and Qu-chi were treated.
Main outcome measures: Subjective pain intensity (numerical pain rating scale) and mean EPN amplitude in the MTrP of the upper trapezius muscle.
Results: The pain intensity in the MTrP was significantly reduced after remote acupuncture (from 7.4+/-0.8 to 3.3+/-1.1; P<.001), but not after sham acupuncture (from 7.4+/-0.8 to 7.1+/-0.9; P>.05). The mean EPN amplitude was significantly lower than the pretreatment level after acupuncture treatment (from 21.3+/-9.5 microV to 9.5+/-3.5 microV; P<.01), but not after sham acupuncture treatment (from 19.6+/-7.6 microV to 19.3+/-7.8 microV; P>.05). The change in the pain intensity was significantly correlated with the change of EPN amplitude (r=0.685).
Conclusions: Both subjective changes in the pain intensity and objective changes of the EPN amplitude in the MTrP region of the upper trapezius muscle were found during and after acupuncture treatment at the remote ipsilateral acupuncture points. This study may further clarify the physiological basis of the remote effectiveness of acupuncture therapy for pain control.