The effect of dry needling in the treatment of myofascial pain syndrome: a randomized double-blinded placebo-controlled trial

Myofascial pain syndrome is a common condition characterized by hypersensitive trigger points in taut bands of skeletal muscle, affecting 21-85% of individuals with regional pain complaints. This randomized, double-blinded, placebo-controlled study investigated the efficacy of dry needling compared with sham needling in the treatment of this condition. Thirty-nine patients with established myofascial pain syndrome were randomized into two groups: 22 received true dry needling with acupuncture needles inserted directly into the trigger points, and 17 received sham needling with a blunt needle that produced a pricking sensation without penetrating the skin. The treatment protocol consisted of six sessions distributed over four weeks, with the first four sessions performed twice a week and the last two sessions once a week.

Pain was assessed using the visual analog scale (VAS) and quality of life using the SF-36 questionnaire, with assessments performed before treatment, after the first session, and after the sixth session. The results demonstrated clear superiority of dry needling over sham treatment. In the dry needling group, pain scores decreased progressively and significantly at all assessments, dropping from 6.6 to 4.0 after the first session and reaching 2.2 after the complete course of treatment. In contrast, the control group showed a less pronounced reduction, from 6.4 to 5.3.

When the groups were directly compared, although baseline scores were similar, assessments after the first and sixth sessions showed significantly lower scores in the dry needling group. Regarding quality of life, the group that received dry needling showed significant improvement in all domains of the SF-36, including physical and mental components, while the control group showed significant improvement only in the vitality domain. In addition, there was a significant reduction in acetaminophen use only in the dry needling group, suggesting a reduced need for analgesic medication. The study also investigated the local twitch response during needling, finding better pain relief outcomes in patients who exhibited this response, supporting the hypothesis that obtaining this response is associated with greater treatment efficacy.

The clinical implications are substantial, as the study provides robust evidence that dry needling is an effective intervention for myofascial pain syndrome, providing significant pain relief and improvement in quality of life. The technique proved to be safe, with no procedure-related complications throughout the study. The findings support the theory that the therapeutic effect of needling is primarily related to mechanical stimulation of the trigger point by the needle, regardless of the injection of substances. However, the study has some important limitations that should be considered when interpreting the results.

The sample size was relatively small, limiting the generalizability of the findings, and there was no long-term follow-up to assess the durability of the observed benefits. In addition, to optimize access to trigger points across different muscle morphologies, different types of needles could have been used.