Assessment of Myofascial Trigger Points with ultrasound: a methodology combining external vibration with Power Doppler Imaging and B-mode

Introduction: This case series explores a novel methodology for identifying myofascial trigger points (MTrPs) by integrating Doppler and B-mode ultrasound with externally applied vibratory stimulation. The study aims to address the current lack of accessible and objective tools for MTrP assessment in clinical settings. Case presentation: Five participants were included: four healthy individuals and one post-stroke patient. A custom-designed vibration device was developed to apply mechanical stimulation to the gastrocnemius medialis muscle, while ultrasound imaging was collected using a standardized setup. To optimize vibration signal detection within muscle tissue, different configurations of the electrodes transmitting the vibration and the Doppler modes (Color Doppler and Power Doppler Imaging (PDI)) were tested. Results: PDI demonstrated superior sensitivity to vibration-induced muscle responses compared to conventional Color Doppler. A consistent pattern was identified among healthy participants. This pattern consisted of well-defined, non-vibratory zones surrounded by vibratory regions, corresponding to hypoechoic areas on B-mode ultrasound. These findings are suggestive of MTrPs and distinct from other stiff anatomical structures, such as fascia, tendons, or fibrotic tissue, which appear hyperechoic. In the stroke patient, pathological muscle adaptations reduced the consistency and visibility of vibratory stimulus propagation; however, MTrP-compatible areas were still identified. Notably, dry needling altered the Doppler signal in this case, attenuating the previously observed pattern. Conclusions: This proof-of-concept study demonstrates the feasibility and reproducibility of a cost-effective assessment protocol that uses conventional ultrasound modes. Combining PDI, B-mode, and vibration may improve the objective identification of MTrPs and expand capabilities in musculoskeletal practice.