Intramuscular stimulation for chronic myofascial pain

Background: Myofascial pain is a common musculoskeletal disorder characterized by muscles in a contracted state with increased tone and stiffness. It is one of the most common chronic pain syndromes that lead to disability and lower quality of life, creating a significant public health and economic burden. Intramuscular stimulation (IMS) is a dry needling technique that targets specifically chronic myofascial pain and is utilized in multidisciplinary pain centers around the world. Despite its wide use, the effect of IMS has been poorly studied. Methods: We conducted two chart reviews to generate information regarding IMS effectiveness and the feasibility of conducting a randomized clinical trial (RCT). Success rate of pain improvement (at least 1 unit reduction on pain score) was documented in percentage. In addition, an inter-rater reliability test was conducted to assess the consistency among IMS practitioners in examining patients. Intra-class correlation coefficient (ICC) and multiple-raters kappa were used to assess the agreement between practitioners in identifying number of taut bands and identifying taut bands in each muscle respectively. Results: From the two chart reviews, we found that a majority of patients (nearly 30%) had their pain for 10 or more years. Most of them had chronic low back pain. The percentage of success was at least 34% (95% CI: 25%, 43%) and 30% (95% CI: 22%, 38%) for worst and average pain (last week) respectively. For inter-rater reliability test, ICC values ranged from 0.64 to 0.77 (substantial agreement) but kappa values of identifying tender taut band in each muscle were ranged from -0.05 (poor agreement) to 0.46 (moderate agreement). Conclusion: Chart review showed positive results regarding short-term effect of IMS in relieving chronic pain and improving pain consequences. Given the difficulty in treating chronic pain, it is worth conducting a sham controlled RCT to further evaluate the effect of IMS. Population characteristics and success rate of pain improvement will be used in justifying the type and size of sample in the design of a RCT. Good consistency among practitioners in treating patients has to be achieved before conducting the RCT.Medicine, Faculty ofMedicine, Department ofExperimental Medicine, Division ofGraduat