Acupuncture for Myofascial Pain Syndrome: A Network Meta-Analysis of 33 Randomized Controlled Trials

Myofascial pain syndrome (MPS) is a common muscle disorder characterized by acute or chronic trigger point pain, muscle stiffness, and fatigue. It represents the leading cause of chronic and persistent regional pain, including shoulder pain, chronic back pain, tension-type headaches, and facial pain. In pain clinics, the prevalence of MPS may reach up to 70% and appears to be more common in women. Management of MPS is based on a multidimensional approach, and failing to treat pain symptoms associated with MPS on time may result in dysfunction, disability, and financial loss for patients.

Acupuncture therapy is commonly considered a popular and effective form of initial treatment for MPS when performed by a skilled practitioner. Various acupuncture techniques exist, including manual acupuncture (MA), electro-acupuncture (EA), dry-needling (DN), acupuncture points injection, and fire-needle (FN). However, no comprehensive comparison between these different techniques was available, and few systematic reviews had compared their safety. This created confusion about which technique represents the best choice for treating MPS.

Network meta-analysis allows an integrated analysis of all randomized controlled trials that have compared different acupuncture therapies head to head or with placebo or sham acupuncture, while fully respecting randomization.

The researchers conducted a network meta-analysis to assess and compare the efficacy and safety of different acupuncture therapies for treating MPS. They searched the Cochrane Central Register of Controlled Trials, PubMed, Web of Science, EMBASE, and Chinese Biomedical Literature Database from their inceptions to February 2016. They included only full texts of randomized controlled trials comparing acupuncture therapies with any other therapies or placebo-sham acupuncture. Two reviewers independently assessed eligibility and extracted data.

The primary outcomes included pain intensity (measured by visual analog scale or numerical rating scale), pressure pain threshold (PPT), and adverse events. The secondary outcome was physical function, assessed by range of motion (ROM). The researchers used Stata 13.0 software to conduct pair-wise meta-analyses using the DerSimonian and Laird method, followed by network meta-analysis using the mvmeta package based on a multiple regression model. They checked evidence of inconsistency using the node-splitting method and used a random effects model.

Results were reported with 95% confidence intervals, and a P value less than 0.05 was considered statistically significant.

Thirty-three trials with 1,692 patients were included. Patients were allocated to 22 kinds of interventions, of which dry needling and manual acupuncture were the most frequently investigated interventions. Compared with placebo-sham acupuncture, scraping combined with warming acupuncture and moxibustion (SWAM) was found to be more effective for decreasing pain intensity, with a standardized mean difference (SMD) of -3.6 (95% confidence interval ranging from -5.2 to -2.1). Miniscalpel-needle (MSN) was more effective for increasing the pressure pain threshold (SMD = 2.2, 95% CI ranging from 1.2 to 3.1).

Trigger point injection with bupivacaine (BTrP-I) was associated with the highest risk of adverse events, with an odds ratio of 557.2 (95% CI ranging from 3.6 to 86867.3). Only electro-acupuncture showed a significant difference in range of motion (SMD = -4.4, 95% CI ranging from -7.5 to -1.3). The network meta-analysis results for pain intensity showed reductions compared to placebo-sham for multiple treatments: -1.7 for BTrP-I, -3.0 for DN&MET, -2.5 for EA&ESNC, -3.6 for SWAM, -1.9 for FN, -1.3 for MSN, -1.8 for MDIMST, -1.5 for LTrP-I, -0.6 for DN, -1.7 for EA, and -1.2 for MA. For adverse events compared to placebo-sham, significant increased risks were found for MSN (OR = 76.2), DN (OR = 117.0), BTX-A-TrP-I (OR = 407.1), and BTrP-I (OR = 557.2).

The SUCRA ranking probabilities showed SWAM, DN&MET, and EA&ESNC had greater effects than other treatments for pain score, while MSN, laser, and MDIMST showed greater effects for PPT. Manual acupuncture showed greater safety than other acupuncture treatments for adverse events.

The existing evidence suggests that most acupuncture therapies, including acupuncture combined with other therapies, are effective in decreasing pain and improving physical function in patients with myofascial pain syndrome. However, additional investigation on the safety of these therapies is required. For clinicians, the choice of treatment should consider the specific clinical condition and patient preferences. Scraping combined with warming acupuncture and moxibustion appears most effective for pain relief, though its safety profile remains unclear.

Miniscalpel-needle may be most effective for improving pressure pain threshold and physical function, but with lower safety. Manual acupuncture appears to be the safest method, though with weaker analgesic effects. The analysis was limited by lack of clarity concerning treatment periods, repetitive randomized controlled trials with small sample sizes, wide credibility intervals, and insufficient blinding in most studies. More head-to-head trials comparing acupuncture therapies in MPS patients with larger sample sizes and sufficient blinding are warranted.

Given the ambiguity on safety, ongoing and further randomized controlled trials should pay more attention to adverse events potentially occurring during acupuncture therapies.