Beneficial Effects of Dry Needling for Treatment of Chronic Myofascial Pain Persist for 6 Weeks After Treatment Completion

This follow-up study investigated the durability of the effects of dry needling in the treatment of chronic myofascial pain syndrome. Myofascial pain syndrome is a painful condition affecting between 15% and 85% of the population over a lifetime, characterized by the presence of myofascial trigger points—palpable, tender nodules located in taut bands of skeletal muscle. When these points cause spontaneous pain, they are classified as active and are considered central to the development and maintenance of chronic pain. Dry needling, a technique that uses solid needles without injection of substances, has been shown to be effective in the immediate treatment of this condition, but few studies have evaluated the duration of its benefits.

The study followed 45 participants (13 men) with a mean age of 37 years, all presenting with neck pain for more than 3 months and active trigger points in the upper trapezius muscle. All had previously completed a protocol of 3 weekly sessions of dry needling and returned for evaluation 6 weeks after the end of treatment, with no additional intervention during the period. The methodology included standardized pain assessments using the visual analog scale (VAS) and the Brief Pain Inventory (BPI), as well as classification of trigger point status by two experienced clinicians. Participants were categorized as 'responders' when trigger point status changed from active to latent or non-palpable, and as 'non-responders' when active trigger points were maintained.

Secondary measures included pressure pain threshold, cervical range of motion, physical function, mood, and disability. The results demonstrated significant sustained benefits. Pain measures remained improved 6 weeks after treatment, with mean reductions of 2.29 points on the VAS for responders versus only 0.46 for non-responders. The Brief Pain Inventory showed a similar pattern, with improvement of 1.43 points for responders and worsening of 0.08 for non-responders.

Importantly, the number of participants who maintained the trigger point response was statistically significant. In addition to pain, there was sustained improvement in physical functioning measured by the SF-36 and reduction in disability assessed by the Oswestry Disability Index. For patients with unilateral trigger points, sustained improvement was observed in cervical lateral flexion and pressure pain threshold. The analysis identified important predictive factors: patients with higher pain scores at baseline were less likely to respond to dry needling, while those with greater pain reduction during treatment were more likely to have a sustained response.

Specifically, each unit decrease on the VAS resulted in a 6.3-fold increase in the odds of being a responder. The clinical implications are relevant for the practice of acupuncture and physical therapy. The study provides evidence that dry needling can provide lasting benefits, not just temporary relief. This supports its use as an effective intervention for chronic myofascial pain, especially when applied early and when significant pain reduction is achieved.

The identification of predictive factors may help clinicians select patients who are more likely to benefit from treatment. The study also contributes to understanding the relationship between trigger points and myofascial pain, suggesting that changes in trigger point status are associated with sustained pain reduction. Although the causal relationship has not been established, the correlation is clinically relevant. Limitations include the moderate sample size, the predominantly university population studied, which may not represent the general population with myofascial pain, and reliance on self-report to confirm the absence of additional treatments.

Despite these limitations, the study provides valuable evidence on the durability of the effects of dry needling, crucial information for clinical decision-making and the development of treatment protocols.