Experimental simulation of non-ballistic wounding by sharp and blunt punches.

Despite a long history of gross and microscopic descriptions of blunt and sharp force injury to the dermal tissues, few have addressed the mechanisms underlying such trauma. The need to develop an understanding of how non-ballistic injury occurs calls for an ability to biomechanically model the process. We recently introduced a basic skin and subcutaneous model, which we used to investigate wounding from a spherical object. Here we employ the same model to examine wounding caused by a sharp wedge shaped object and a blunt rectangular object. Macroscopic examination and SEM views of the surface and cross sections of blunt and sharp force tears show that while in the former there is a clean cut through the skin into the underlying sponge, in the latter there is a tissue plug confined to the skin that is smaller than the impacting rectangle. Fracture initiation in the subdermal tissue occurs at the angles of the impacting object. In sharp force trauma, there is localized breaching of the skin layer coupled with the wedging action of the impacting object. Because the subdermal tissue, in this case the underlying hydrated foam, is attached to the base of the skin, it will contribute to further tearing of the foam beneath the line of contact.