Anisotropic Tissue Motion Induced by Acupuncture Needling Along Intermuscular Connective Tissue Planes

Objectives: Acupuncture needle manipulation causes mechanical deformation of connective tissue, which in turn results in mechanical stimulation of fibroblasts, with active changes in cell shape and autocrine purinergic signaling. We have previously shown using ultrasound elastography in humans that acupuncture needle manipulation causes measurable movement of tissue up to several centimeters away from the needle. The goal of this study was to quantify the spatial pattern of tissue displacement and deformation (shear strain) in response to acupuncture needling along an intermuscular connective tissue plane compared with needling over the belly of a muscle. Design: Eleven (11) healthy human subjects underwent a single testing session during which robotic acupuncture needling was performed while recording tissue displacement using ultrasound. Outcome measures were axial and lateral tissue displacement as well as lateral shear strain calculated using ultrasound elastography postprocessing. Results: Tissue displacement and strain extended further in the longitudinal direction when needling between muscles, and in the transverse direction when needling over the belly of a muscle. Conclusions: The anisotropic tissue motion observed in this study may influence the spatial distribution of local connective tissue cellular responses following acupuncture needle manipulation.