Research On Parametric Design Method Of Bone Tissue Gradient Porous Scaffold

The problem of bone defects,especially large bone defects,caused by trauma,tumors,infections and congenital diseases in China every year that makes the market more and more demanding for personalized implants.With the combination of additive manufacturing technology and computer-aided design in medical applications,more and more design methods of porous scaffold have been proposed.The first proposed method is based on periodic porous unit cell arrangement.The process of this method is usually complicated,difficult,and time consuming.Even though some scholars have proposed algorithms for parametric modeling and automated assembly to improve design efficiency.The established porous model only has surface morphological features,and the internal pore structure is single and has a certain gap with the internal structure of the real bone tissue.In response to this problem,based on the previous research,through the modeling characteristics of Triply Periodic Minimal Surface(TPMS),some innovative parametric design method for bone tissue gradient porous scaffold has been proposed.This continuous gradient change makes the biological and mechanical properties of porous scaffold more regular.At the same time,for the shortage of the method of periodic porous unit cell arrangement,a parametric design method of conventional gradient porous scaffold has been proposed,which makes the calculation efficiency higher and can generate more complex porous scaffold.This research mainly focuses on the following aspects:Firstly,the Marching Cube(MC)algorithm is used to reconstruct the TPMS surface.Each implicit surface can generate two kinds of unit cell,and creating unit cell library,defining the porosity,exploring the relationship between the cell threshold and its porosity.Based on this,a parameterized design algorithm for TPMS homogeneous porous scaffold has been proposed.Secondly,a parametric design method for TPMS gradient porous scaffold which is based on distance field and use the reference geometries as the gradient reference has been proposed.The method targets the linear gradient distribution of porosity or pore size and the linear gradient can also be optimized by Gaussian function.More complex gradient porous scaffold can be obtained by this method.Thirdly,a parametric design method of TPMS fusion porous scaffold which is achieved by manual partitioning or Voronoi3 D splitting has been proposed.This method uses the Gaussian function to calculate the weight value of the sub-region to achieve complex fusion under arbitrary spatial partitions,and finally the complex functional gradient porous scaffold under fusion can be obtained.Then,for the problems existing in the design method of periodic porous unit cell arrangement,a parametric design method of conventional gradient porous scaffolds has been proposed.This method is based on distance field and Gaussian function optimization,and also uses voxelization,isoparametric element mapping and materialized wireframe algorithms can ultimately be used to generate more complex gradient porous scaffold.Finally,combined with the needs of clinical,using the modular design concept on the Rhino GH platform and the RhinoCommonSDK toolkit for secondary development,build the bone tissue parametric design application system.