A finite element model of acupuncture needling

Acupuncture is a centuries-old treatment that has been gaining popularity and acceptance with Western medicine in recent decades. Though it is a low-cost and low-risk treatment for various physical ailments, very little is known about the mechanisms by which acupuncture works. Ex vivo needle rotation in subcutaneous tissue causes the connective tissue fibrils near the needle to reorient in a spiral pattern as shown by Lange vin et al [1]. There is a mechanical coupling between the needle and tissue that is demonstrated by the increased force required to remove the needle from the tissue after rotation [2]. This coupling is believed to allow mechanical forces to be transmitted from the needle to the tissue, initiating a mechanotransduction mechanism that triggers the body's healing response. An in vitro system is being designed using a collagen-based tissue equivalent to investigate this hypothesis. To aid in designing this in vitro assay, a finite element model was created to study the tissue deformation caused by needling. The collagen gel was modeled as a viscoelastic material, with the acupuncture needle being represented as a rigid body. A contact model was created in which the acupuncture needle is inserted into the collagen gel and then rotated, mimicking the therapeutic procedure. The finite element model shows deformation gradients in the same pattern as the observed fibril alignment. The model will serve as an aid in designing the in vitro model with appropriate dimensions so that the inherent boundary conditions experienced by the collagen gel do not affect the results obtained.