Mechanical response of uterine tissue under the influence of hemostatic clips: A non-linear finite-element approach

Abstract

A modeling strategy to predict the ability of surgical clips to achieve mechanical hemostasis when applied to the cut edge of a thick and muscular tissue is presented in this work. Although such a model may have broad utility in the design of hemostatic clips and other surgical and wound closure applications, our particular focus was on uterine closure following a Cesarean delivery. Mechanical closure of a blood vessel, which is the first step in the hemostatic process, is established when the compressive forces on the outer surface of a blood vessel are sufficient to overcome the local blood pressure and collapse the vessel. For thick tissue, forces applied to the tissue surface set up a stress distribution within the tissue that, if sufficient to mechanically close all vessels, will lead to cessation of local blood flow. The focus of the current work was on utilization of a planar and nonlinear finite element model to predict the pressure distribution within uterine tissue under the influence of hemostatic clips. After experimental model validation with a polymer tissue phantom, design curves were numerically developed, which consisted of the clip force necessary to achieve hemostasis for a given thickness tissue as well as the resulting deformed tissue thickness. Such curves could form the basis for a preliminary clip design, which would provide initial design guidance before more expensive experimental studies were required.