Simulating plastic surgery: from human skin tensile tests, through hyperelastic finite element models to real-time haptics.

In this paper, we provide a summary of a number of experiments we conducted to arrive at a prototype real-time simulator for plastic surgical interventions such as skin flap repair and inguinal herniotomy. We started our research with a series of in-vitro tensile stress tests on human skin, harvested from female patients undergoing plastic reconstructive surgery. We then used the acquired stress-strain data to fit hyperelastic models. Three models were considered: General Polynomial, Reduced Polynomial and Ogden. Only Reduced Polynomial models were found to be stable, hence they progressed to the next stage to be used in an explicit finite element model aimed at real-time performance in conjunction with a haptic feedback device. A total Lagrangian formulation with the half-step central difference method was employed to integrate the dynamic equation of motion of the mesh. The mesh was integrated into two versions of a real-time skin simulator: a single-threaded version running on a computer's main central processing unit and a multi-threaded version running on the computer's graphics card. The latter was achieved by exploiting recent advances in programmable graphics technology.