STRESS OPTIMIZATION OF RHOMBIC TRANSPOSITION FLAPS USING THE FINITE ELEMENT METHOD

Abstract

Use of local skin flaps is a common practice in plastic and reconstructive surgery for complex wound closure. As a consequence of transposing these flaps, however, a stress field is created throughout the tissue. Previous work suggests a relationship between the stress field and a reduction in blood flow which can delay the process of wound healing, and may also cause many undesirable effects on tissue functionality. The objective of this research was to design an optimized version of rhombic transposition flaps by minimization of maximum von Mises stress with constraints on maximum compressive stress and undeformed/deformed configurations. To accomplish this objective, a finite element (FE) model was developed within a commercially available FE analysis package (ANSYS®). It used an Ogden hyperelastic material model with reliable geometry/meshing to ensure convergent results. It also incorporated a novel approach to model sutures. To study material uncertainties of skin, four different sets of constants were used. By defining flap geometry using adjustable parameters, the process of wound closure was simulated for a large number of configurations to identify optimized configurations. The results suggest a design that is comparable in design to Z-plasty and can be easily implemented. The proposed flap, which can be employed for 60° to 90° rhombic defects, reduced the maximum von Mises stress by 43% and 53% (on average) with respect to the flaps of Limberg (60° defect) and Dufourmentel (60° to 90° defects), respectively.