Quantification of Strain in a Porcine Model of Skin Expansion Using Multi-View Stereo and Isogeometric Kinematics

Abstract

Tissue expansion is a popular technique in plastic and reconstructive surgery that grows skin in vivo for correction of large defects such as burns and giant congenital nevi. Despite its widespread use, planning and executing an expansion protocol is challenging due to the difficulty in measuring the deformation imposed at each inflation step and over the length of the procedure. Quantifying the deformation fields is crucial, as the distribution of stretch over time determines the rate and amount of skin grown at the end of the treatment. In this manuscript, we present a method to study tissue expansion in order to gain quantitative knowledge of the deformations induced during an expansion process. This experimental protocol incorporates multi-view stereo and isogeometric kinematic analysis in a porcine model of tissue expansion. Multi-view stereo allows three-dimensional geometric reconstruction from uncalibrated sequences of images. The isogeometric kinematic analysis uses splines to describe the regional deformations between smooth surfaces with few mesh points. Our protocol has the potential to bridge the gap between basic scientific inquiry regarding the mechanics of skin expansion and the clinical setting. Eventually, we expect that the knowledge gained with our methodology will enable treatment planning using computational simulations of skin deformation in a personalized manner.

Improving tissue expansion protocols through computational modeling

“…The experimental methodology used in this study closely follows our prior work with the exception of using three-dimensional photography instead of multi-view stereo, and the additional collection of punch biopsies for histology at the end of the process [6, 8, 9]. Briefly, animals are provided with food and water ad libitum per veterinary recommendations throughout the study.…”

“…The advantage of such system is that noninvasive measurements can easily be performed in clinical settings such as the operating room, either for an animal model as we show here, or for translation of this protocol to human patients, which we intend to do in the near future. The work presented here closely follows our previous work on skin expansion biomechanics [6, 8, 9]. In our previous studies, we used multi-view stereo to capture three-dimensional geometries.…”

Acellular dermal matrix cover improves skin growth during tissue expansion by affecting distribution of mechanical forces

“…IGA was performed using custom software (source code: https://bitbucket.org/abuganzatepole/isogeometric_kinematic_analysis/src/ master/) on three-dimensional photographs according to the protocol published previously. 11 Briefly, three-dimensional photographs of the grids were taken in vivo before the tissue expanders were inflated, immediately after each inflation, and at the end of the protocol. A second set of three-dimensional images was taken ex vivo after skin grids were excised.…”

“…The ratio between variables F and Fe (F/Fe) is proportional to (∝) growth Fg (F/Fe ∝growth Fg). 5,11 The heat maps show relative area change and histograms represent distribution of mechanical forces applied by the tissue expander.…”