Objective: Myofascial pain is a chronic pain disorder characterized by the presence of painful localized regions of stiff muscle and/or myofascial trigger points. Intramuscular myofascial trigger point injections are considered first-line treatments for myofascial pain. Common injectates include local anesthetics and botulinum toxin-A (BTX-A). The objective of this systematic review was to compare the effectiveness of local anesthetics and BTX-A on pain intensity in patients with myofascial pain. Methods: A comprehensive systematic search of 3 databases, EMBASE, CENTRAL, and Medline was conducted. The search was comprised of words to describe “myofascial pain” and “injections.” We performed a meta-analysis comparing local anesthetic and BTX-A injections across these follow-up week periods: 0 (immediately following the injection), 1 to 2, 3 to 4, 5 to 6, 7 to 8, 9 to 10, 11 to 12, 16, 18, 24 weeks with local anesthetics and BTX-A as subgroups. We also performed subgroup analyses comparing the effectiveness of local anesthetic injections and BTX-A injections at various muscle locations and comparing the effectives of single versus multiple injection sessions. Results: In total, 33 studies were included. A qualitative analysis suggested that local anesthetics and BTX-A were inconsistently effective at mitigating pain across all follow-up periods. The meta-analyses revealed that local anesthetic injections were more effective than BTX-A at mitigating pain intensity. Multiple injection sessions of local anesthetics were more beneficial than a single session. Conclusions: Additional studies are needed to determine sources of heterogeneity mediating the observed differences in effectiveness of local anesthetic and BTX-A injections among the studies. Additional replicative studies are also needed to delineate the relative efficacy and effectiveness of local anesthetic and BTX-A injection. The quantitative results of this study suggest that patients overall experience more pain relief with local anesthetic injections.

Background Myofascial pain is a prevalent chronic pain disorder, affecting a large proportion of the general population. Electric stimulation techniques such as transcutaneous electric stimulation (TENS) and electroacupuncture have been shown to be effective for managing chronic pain conditions including myofascial pain. The goal of this study was to review the literature on the effectiveness of electric stimulation techniques on myofascial pain. Methods A comprehensive systematic search of three databases—Medline, EMBASE, and Cochrane CENTRAL—was conducted using key words related to myofascial pain and trigger points, as well as various electric stimulation techniques. A total of 15 articles passed the inclusion and exclusion criteria for the study. Data were extracted from these studies and assessed qualitatively and quantitatively. Standardized mean differences (SMDs) were computed from pain intensity measures extracted from these studies. Subgroup analyses were performed to assess the effectiveness of treatment modality, number of treatment sessions, frequency of stimulation, location of treatment, and duration of treatment. Results The SMD for electric stimulation techniques on reported pain intensity was significant (P = 0.03), as was the SMD for the electroacupuncture subgroup (P = 0.02); the TENS subgroups’ effect was not significant (P = 0.17). The subgroup analyses tentatively suggest that frequency and number of treatments do not influence pain intensity, whereas the duration of treatment may have an effect. The qualitative results of this study revealed variability in the results among studies delivering TENS treatments. Conclusions Electric stimulation is effective at mitigating reported pain intensity at the location of the trigger point. Electroacupuncture presented with significant and larger effect sizes of improvement relative to TENS for reported pain intensity. Given that this review included a small number of studies, there is a need for additional research to confirm its findings. Additionally, studies assessing the parameters and physiological location of treatment are needed to inform the clinical use and recommendations of electric stimulation treatments.