Growing skin: A computational model for skin expansion in reconstructive surgery

Abstract

The goal of this manuscript is to establish a novel computational model for stretch-induced skin growth during tissue expansion. Tissue expansion is a common surgical procedure to grow extra skin for reconstructing birth defects, burn injuries, or cancerous breasts. To model skin growth within the framework of nonlinear continuum mechanics, we adopt the multiplicative decomposition of the deformation gradient into an elastic and a growth part. Within this concept, we characterize growth as an irreversible, stretch-driven, transversely isotropic process parameterized in terms of a single scalar-valued growth multiplier, the in-plane area growth. To discretize its evolution in time, we apply an unconditionally stable, implicit Euler backward scheme. To discretize it in space, we utilize the finite element method. For maximum algorithmic efficiency and optimal convergence, we suggest an inner Newton iteration to locally update the growth multiplier at each integration point. This iteration is embedded within an outer Newton iteration to globally update the deformation at each finite element node. To demonstrate the characteristic features of skin growth, we simulate the process of gradual tissue expander inflation. To visualize growth-induced residual stresses, we simulate a subsequent tissue expander deflation. In particular, we compare the spatio-temporal evolution of area growth, elastic strains, and residual stresses for four commonly available tissue expander geometries. We believe that predictive computational modeling can open new avenues in reconstructive surgery to rationalize and standardize clinical process parameters such as expander geometry, expander size, expander placement, and inflation timing.

Characterization of human skin through skin expansion

“…Skin growth was not considered although an overview on the mechanobiology underlying skin growth sustains that tensile stress applied to skin appears to stimulate skin growth [Silver et al 2003]. Researchers recently are looking for a model to describe the growth of the skin under tensile stress, establishing computational models for stretch-induced skin growth under expansion [Buganza Tepole et al 2011] and also patient-specific finite element simulation of skin growth in situ [Zöllner et al 2012]. …”

Virtual testing of advanced composites, cellular materials and biomaterials: A review

“…The application of virtual testing in understanding the mechanics of skin is progressing rapidly. Tepole and co-workers [151,152] published their recent implementation of such an approach for skin growth, expansion and stretching. A typical implementation of skin growth in a child is shown in Figure 28 for increasing skin area.…”

“…A typical implementation of skin growth in a child is shown in Figure 28 for increasing skin area. The authors developed a computational model, based on a nonlinear continuum mechanics, for stretch-induced skin growth during tissue expansion [151,152]. Skin growth was multiplicatively decomposed into elastic and growth deformation gradient parts.…”

A framework for studying dynamics and stability of diffusive–reactive interfaces with application to Cu 6 Sn 5 intermetallic compound growth

“…Examples of such phenomena include dendritic growth in Li-ion batteries [1,2], growth of brittle intermetallic compounds in solder joints [3], tissue growth [4][5][6] and growth of compounds under chemicalvapour deposition [7]. The interplay between the aforementioned driving forces can not only affect the growth rate of the materials involved, but can also change the interface morphology from being flat, to scalloped to even dendritic.…”