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.
This is an example of a paper in which statistical significance in used as a substitute for clinical significance. See figure 3: most studies on TENS are compatible with no effect. Moreover, all the studies considered are quite small (20 subjects maximum). As such, the conclusion of the review may sound misleading: it would probably be better to state that the quality and size of the reviewed studies was not sufficient to reach a meaningful conclusion on the subject (unless a very loose requirement for the effectiveness of a therapy is considered acceptable).
As an internist, I find it interesting to learn that adding electrical stimulation to trigger points may benefit patients. The heterogeneity of conditions and protocols used is a limitation. No one in my clinic does trigger point injections and it is difficult to compel others to do it with stimulation.