Effectiveness of ultrasound therapy for myofascial pain syndrome: a systematic review and meta-analysis

OBJECTIVE The objective of this review was to assess the therapeutic effect of ultrasound (US) on myofascial pain syndrome (MPS). DATE SOURCES PubMed, Embase, and Cochrane Library were searched to find relevant studies from January 1966 to May 2016 using keywords. Four investigators performed the data extraction. STUDY SELECTION Randomized controlled trials (RCTs) investigating the outcomes of pain and physical function between MPS patients receiving and not receiving US were selected by two researchers independently. DATA EXTRACTION Data were extracted from the RCTs. Risk of bias and study quality were evaluated following the recommendations of Cochrane Collaboration. Standardized mean difference (SMD) and 95% confidence interval (CI) were calculated. DATA SYNTHESIS A total of 10 studies involving 428 MPS patients were included. US therapy significantly reduced pain intensity (SMD [CI]=-1.41 [-2.15, -0.67], P=0.0002) and increased pain threshold (SMD [CI]=1.08 [0.55, 1.60], P<0.0001), but had no significant effect on cervical range of motion (ROM) of lateral flexion (SMD [CI]=0.40 [-0.19, 0.99], P=0.19), rotation (SMD [CI]=0.10 [-0.33, 0.52], P=0.66), or extension or flexion (SMD [CI]=0.16 [-0.35, 0.68], P=0.53). Heterogeneity between studies was mainly attributed to differences in the follow-up time, parameter of US, course of treatment, and the control group. The overall risk of bias from the included studies was high, and the evidence proving these effect calculations were assessed as low quality. CONCLUSION Owing to the high risk of bias and the across-trial heterogeneity of the studies, the current evidence is not clear enough to support US as an effective method to treat MPS. Clinical trials with methodological rigorousness and adequate power are needed to confirm it in the future.