Cormac Flynn1. 1. Bioengineering Institute, University of Auckland, Level 6, 70 Symonds Street, 1010 Auckland, New Zealand. c.flynn@auckland.ac.nz
Abstract
AIM: The achievement of a well-healed wound depends on many factors including its size and location on the body and the properties of the skin. The aim of this study is to develop computational wound closure models and compare the results of using different excision shapes. METHODS: Finite element models were developed that simulated the incision, excision and closure of skin. Skin was represented by an orthotropic constitutive law. The size of extrusions, maximum stresses and the force to close wounds with differently shaped excisions were analysed. RESULTS: Circular excisions resulted in closed wounds with extrusion heights 76% larger than fusiform or lazy S-plasty excisions. The extrusion length for circular excisions was 50% longer than the lazy S-plasty extrusion length. The maximum stresses around closed wounds with elliptical excisions were between 30 and 40% lower than the maximum stresses around fusiform and lazy S-plasty closed wounds. The force required to close an elliptical wound was between 27 and 66% lower than the closure force of fusiform and lazy S-plasty excisions. The orthotropic nature of skin and the orientation of the excision significantly influence the behaviour of the skin around the closed wound. The in vivo pre-stress, often ignored in wound closure models, influences the size of extrusions. Increasing the pre-stress by a factor of twenty decreased extrusion heights by 40%. A similar change in pre-stress decreased extrusion lengths by 50%. CONCLUSION: These models have potential as valuable clinical tools to determine the optimum excision shape that will minimise adverse stress fields and reduce scarring. Models that are patient-specific would be useful to design strategies to ensure favourable healing and improve the quality of life of the person.
AIM: The achievement of a well-healed wound depends on many factors including its size and location on the body and the properties of the skin. The aim of this study is to develop computational wound closure models and compare the results of using different excision shapes. METHODS: Finite element models were developed that simulated the incision, excision and closure of skin. Skin was represented by an orthotropic constitutive law. The size of extrusions, maximum stresses and the force to close wounds with differently shaped excisions were analysed. RESULTS: Circular excisions resulted in closed wounds with extrusion heights 76% larger than fusiform or lazy S-plasty excisions. The extrusion length for circular excisions was 50% longer than the lazy S-plasty extrusion length. The maximum stresses around closed wounds with elliptical excisions were between 30 and 40% lower than the maximum stresses around fusiform and lazy S-plasty closed wounds. The force required to close an elliptical wound was between 27 and 66% lower than the closure force of fusiform and lazy S-plasty excisions. The orthotropic nature of skin and the orientation of the excision significantly influence the behaviour of the skin around the closed wound. The in vivo pre-stress, often ignored in wound closure models, influences the size of extrusions. Increasing the pre-stress by a factor of twenty decreased extrusion heights by 40%. A similar change in pre-stress decreased extrusion lengths by 50%. CONCLUSION: These models have potential as valuable clinical tools to determine the optimum excision shape that will minimise adverse stress fields and reduce scarring. Models that are patient-specific would be useful to design strategies to ensure favourable healing and improve the quality of life of the person.