Localization of Muscle Edema and Changes on Muscle Contractility After Dry Needling of Latent Trigger Points in the Gastrocnemius Muscle

Background. Myofascial trigger points (TrPs) are hyperirritable spots within taut bands of skeletal muscles that elicit local and referred pain when stimulated. Among the variety of techniques used for treating TrPs, dry needling (DN) is the most commonly applied intervention. The physiological mechanisms underlying the effects of DN remain to be elucidated. Objective. To examine changes in skeletal muscle after DN in the area where the TrP is located. Methods. We measured in vivo changes that occur in human skeletal muscle one hour after DN over a TrP with magnetic resonance imaging (MRI) and tensiomyography. The study included 18 asymptomatic subjects with a latent TrP in one medial gastrocnemius muscle, and the contralateral leg was used as control. Results. The results showed that MRI signal intensity significantly increased one hour after the DN intervention, suggesting the presence of intramuscular edema. Tensiomyographic parameters showed higher muscle stiffness with an improvement in contraction time after DN. Conclusions. This is the first study showing intramuscular edema after TrP DN in human skeletal muscle. Future research should focus on using DN therapy in patients with active TrPs and on monitoring changes occurring at longer follow-up with imaging techniques.