RESUMO
BACKGROUND: Acupuncture has been widely used for chronic musculoskeletal pain syndrome (MPS). Due to the strong influence of sham acupuncture (SA) in clinical trials, the treatment of MPS by acupuncture remains controversial. Different types of SA procedures might produce different responses. The purpose of this systematic review was to assess the effect of SA on MPS. METHODS: We searched 8 literature databases for randomized controlled trials (RCTs) on acupuncture for chronic MPS with SA as a control from database inception to November 29, 2022. SA included superficial acupuncture on non-acupoints (SANAs), non-penetration on acupoints (NPAs), and non-penetration on non-acupoints (NPNAs). Two independent reviewers assessed the risk of bias and conducted the research selection, data extraction, and quality assessment of the included RCTs. We conducted data analysis using the RevMan 5.3 and STATA 14 software packages, and traditional meta-analysis was adopted for direct comparison. A network meta-analysis (NMA) was executed using frequency models in which we combined all available direct and indirect evidence from RCTs. The pain-related indicators were set as primary outcomes, and GRADEpro online was implemented for the assessment of evidence quality. RESULTS: Forty-two RCTs were included in this study, encompassing a total of 6876 patients and incorporating 3 types of SA procedures. In our traditional meta-analysis, true acupuncture (TA) was more effective than SANAs, NPAs, and NPANAs concerning MPS. In the NMA, TA was the most effective modality, followed by SANAs, NPAs and NPANAs, and then the blank control (BC). In this NMA and according to the therapeutic effects in the pain indicators, the rankings of SA were as follows: SANA (surface under the cumulative ranking curve [SUCRA], 65.3%), NPA (SUCRA, 46.2%), and NPANA (SUCRA, 34.2%). The quality of the evidence for outcomes ranged from "low" to "moderate." CONCLUSIONS: Compared with SA, TA was effective in treating MPS. The effects produced by different SA procedures were different, and the order of effects from greatest to least was as follows: SANA, NPA, and NPANA.
