From the rhombic transposition flap toward Z-plasty: An optimized design using the finite element method.

In this paper, an optimized design for rhombic transposition flaps is created using a reliable finite element model that assures convergence for stress and deformation results. Defining a general configuration for rhombic flaps, the surgical process of wound closure is simulated for a wide variety of patterns. To address the intrinsic uncertainties associated with modelling skin's mechanical properties, four different sets of material parameters are considered, to investigate statistical measures. The results suggest that implementing the rhombic flap technique in a way similar to Z-plasty leads to an optimized surgical technique. The proposed flap, which can be employed for 60° to 90° rhombic defects, can reduce the maximum von Mises stress by 53% (on average) with respect to the Dufourmentel flap, and, in the case of a 60° defect, 43% with respect to the Limberg flap. To avoid any depressed area such as dog-ear formation, the maximum compressive principal stress is examined to assure that it remains within the limits of the stresses in the existing surgical techniques. The deformed configuration is also taken into consideration. Ease of implementation, in terms of both construction and orientation with respect to the relaxed skin tension lines, is another design feature offered by the proposed flap.