Computational mechanical modeling of human skin for the simulation of reconstructive surgery procedures

Skin is the most extended organ in human body representing 16% of the total body weight with a surface extension up to 2 m². From a mechanical viewpoint, skin can be described by an hyperelastic membrane, particularly when computational modeling for in-silico testing of reconstructive surgery procedures is needed. These procedures often involves complex topological manipulations of the skin tissue in order to minimize post-operative scarring. In this paper, the simulation of reconstructive surgery procedures is described by FE membrane models developed within the framework of finite strain elasticity (an hyperelastic incompressible model for skin is adopted). An algorihm is presented to generally describe complex topologies of cutting and removing of material, while suturing is enforced by suitable multi-point constraints along wound boundaries. The archetypal reconstructive surgery of the Z-plasty is here considered, where a rotational transposition of resulting triangular flaps is involved, leading to severe stress/strain localization and displacement discontinuities. The results are discussed in terms of key deformation parameters commonly used to guide surgical decisions during reconstructive procedures. Apart from the direct applications to surgery of human skin, the computational tool proposed can be used with reference to artifical materials (like for instance polymeric hydrogels produced with advanced 3D printing technologies), whose mechanical behaviour resambles that of the natural skin tissue.