Design And Construction Study Of A Bionic 3D Mechanical Equilibrium Auricle Framework

Background:Due to the complicated anatomical structure of auricular,difficult framework carving with limited material from costal cartilage,and susceptibility to skin necrosis after prosthesis transplanted,auricular reconstruction is one of the most challenging techniques among plastic surgery.Therefore,it is an urgent issue to create an ideal auricular framework with minimal material usage,personalized rapid manufacturing,and lower incidences of skin necrosis.Finite element analysis is an effective computerized method that could offer a possibility to evaluate the stability of the auricular framework with favorable function to simulate,analyze and predict the mechanical feedback from the transplanted prosthesis to the surrounding tissues.Meanwhile,there is an available way to achieve the ideal framework with satisfactory biomechanics properties by utilizing the personalized 3D printed bio-medical polymers framework to replace the costal cartilage.Objective:Finite element analysis technique,which simulates the reconstructive process,was used to analyze the mechanical effect generated between the skin and the implanted ear scaffold.Guided by the FEA results,a novel auricular scaffold structurewas proposed to reduce the mechanical damage of the overlying skin.This FEA method could explore the feasibility of the 3D-printed PUA auricular framework with polyurethane material and also give the bio-mechanical and bio-safe evidence for auricular structure innovation.Methods:1.The finite element method was utilized to simulate the auricular reconstruction process.The scapha and fossa triangularis was modified by using shape optimization software to achieve optimized models.The optimized designing models were chosen for clinical application to verify the validity of the finite element analysis.2.The bionic auricular implant was explored to achieve the most stable structure with the reference criteria which was according to the China standard auricular cartilage anatomy,compared to the most available commercial auricular implant.3.A photocuring polyurethane(PUA)material was synthesized by the raw materials of DL-1000 and DL-2000 polyether diols,isophorone diisocyanate(IPDI),and hydroxyethyl methacrylate(HEMA).The feasibility of stereolithography for the polyurethane-based personalized auricular framework was investigated through the preliminary evaluation of the structural characterization,mechanical properties,molding effect,printing parameters,and material biocompatibility.Results:1.The displacement and stress of the post-optimized auricular framework model were declined 64.91%and 40.06%,respectively.The clinical follow-up of the post-optimized auricular framework proposal was revealed that the incidence of overlying skin ulceration was decreased from 16.3%to 5.08%.All these data confirmed that the improved design framework could effectively reduce the rates of skin necrosis.2.Compared to Medpor,the stress and displacement of the post-optimized auricular framework model were declined 21.60%and 20.00%,respectively.And the FEA results also showed the stress-strain concentration was transferred from the susceptible area to skin necrosis to the steading area.This novel auricular framework decreases the risk of cartilage disclosure.3.The elastic modulus of PUA material is significantly lower than that of commercial HDPA.This material showed no obvious toxicity with the Vitro cytotoxicity test,and favorable biocompatibility was revealed according to the subcutaneous implantation test.After irradiating scan with 405 nm laser,it can be quickly cured to mold with well flexibility and lesser deformation and warping.Conclusions:1.Compared to the conventional framework,the optimized auricular framework could effectively reduce the incidence of skin necrosis under the same stressful environment.Our study could increase the biomechanical cognition on the auricular framework and cover skin during the negative suction process,which has important clinical significance for protecting against skin necrosis.2.Based on the mechanical balance concepts,sub-unit structures of this novel auricular framework could support reciprocally to resist the deformation under stress.This also could enhance the anti-pressure tolerance with a better aesthetic appearance.3.Polyurethane matrix composites can be prepared by adjusting the types and proportions of diluents to obtain different mechanical strengths,which could enhance the mechanical properties of the implanted prosthesis and improve the compress resistance with complex structures.