Research On Three-dimensional Wound Flattening Method For Mapping Skin Mechanical Behavior

In today’s society,human skin tissues are often damaged by physical,mechanical and chemical aggressions,which may cause extensive skin trauma and soft tissue defects in severe cases.At present,flap grafting is often used clinically for wound repair,but the process of preoperative design of flap shape is relatively rough,resulting in the flap shape often not fitting well with the wound,which is easy to cause infection and flap necrosis in the affected area,causing secondary pain to patients.Therefore,the precise and individualized design of the preoperative flap shape is an urgent problem to be solved.Determining the flap plane shape based on the 3D trauma morphology can be considered as the process of surface flattening,which provides a new idea for the quantitative design and analysis of preoperative flap shape.To address the disadvantages of the current preoperative flap shape design with low accuracy and more cumbersome preparation,this paper investigates the three-dimensional trauma flattening method for mapping its biomechanical properties based on the investigation of the mechanical behavioral properties of the skin.The study are listed as follows:This paper enriches the geometric and topological information of the trauma model and investigates the morphological initial flattening method of the 3D trauma surface.The storage characteristics of the trabecular model files are analyzed,and the information storage framework of the model is designed based on the class structure of point-edge-face,and the reconstruction of the original model topological information and the filtering of redundant data are realized by using the hash storage structure to improve the efficiency of the algorithm.The hierarchical structure of the trauma surface model is established to further deepen the morphological description of the trauma surface as a whole.On this basis,the morphological initial flattening method of the trabecular surface is proposed by integrating the existing surface flattening theories,and the concept of morphological distortion points is introduced to address the morphological peculiarities of the trabecular surface,and corresponding corrections are given to the original flattening process.The tensile properties,stress relaxation and creep properties of skin under large deformation are investigated,and its biomechanical behavioral characteristics are investigated.In the paper,three sets of mechanical tests are designed for pig skin samples taken from different directions,and pre-conditioning treatments are developed separately for different mechanical environments,taking into account the adaptability and structural specificity of the skin.The variation law of pig skin stress with strain is obtained by quasi-static tensile tests,and the corresponding characterization model is given.Meanwhile,two external manifestations of pig skin viscoelasticity: stress relaxation and creep phenomenon are verified,and their relationships with strain conditions and sample characteristics are explored.Mapping the skin biomechanical behavior properties,and a finite unit optimization method based on material deformation energy is proposed.Based on the initial flattening of the trabecular model,the deformation of the mesh cells on the model after flattening is analyzed.The finite cell model based on the deformation energy of the material is established by combining the mechanical parameters of the pig skin.The cell deformation is attributed to the equivalent load acting on the nodes,and the optimization model for the flattening of the trabecular surface is proposed.With the overall deformation energy as the optimization target,the nodal displacement is calculated and the nodal coordinates are updated by using equal bandwidth storage and Gaussian elimination method.The five-point interpolation method is introduced to visualize the deformation energy in the optimization process.A mesh model and a clinical example are selected for different situations for validation and case study.The operating interface for trabecular flattening and optimization analysis is created based on the MFC framework,and the algorithm program is written in C/C++,and the user can import the trabecular model for visualization,flattening optimization and file output.The material deformation energy-based trauma flattening method studied in this paper can effectively deal with the optimization of 3D trauma flattening,and can provide a reasonable and reliable preliminary guidance scheme for preoperative flap shape design in clinical trauma repair.The written user interface can simplify the design process and reduce the preoperative preparation time,which can promote the application of digital design to the field of clinical trauma repair in the future.