Research On Finite Element Analysis And Repair Of Thigh Prosthetic Socket Based On 3D Reconstruction

According to statistics,the number of physically disabled people in China is tens of millions.In order for these disabled people to be able to restore some basic functions of daily life,medical personnel will usually customize the prosthesis for them.Prostheses include prosthetic sockets,supporting parts,joints,false feet,etc.The prosthetic socket is the direct connecting part of the handicapped and the prosthesis,which plays a role of fixation,bearing and stress.The customization of the cavity is the most important factor for the customization of the prosthesis,and the acceptance of the cavity is directly related to the wearability of the disabled.Therefore,how to design firm,durable,comfortable acceptance of the cavity is always the focus of research.In view of the backwardness of the thigh prosthetic receiving cavity plaster casting process,the repair type depends on the level of the prosthetic technician,the improvement of wearable experience is small,the CAD method is expensive,the requirement of computer skills of prosthetic technicians is high,the process is complicated,the patient's experience is poor,and the potential stress concentration may exist,this paper conducted the following research work:A depth camera was used to scan the limb and stored the point clouds in all angles.Based on the point cloud library and VS2012,the KD tree was constructed to realize fast nearest neighbor search,and the K neighborhood FPFH features of any point in the cloud were calculated.The initial registration of the adjacent frame clouds was carried out by the random sampling algorithm.The exact registration was realized by the ICP algorithm.The point cloud registration with affine transformation characteristics was studied.Registration algorithm was proposed to improve registration accuracy.Compared with CT reconstruction results,it was proved that the 3D reconstruction result based on depth camera has small error and high accuracy.From the reverse modeling of volunteers' CT image,bone and soft tissues were segmented through regional growth,section segmentation and other methods.After surface repair and fitting,NURBS surfaces were formed.Through modeling of solid bodies,skeleton,soft tissue,bushing and socket solid model were established,and the model was assembled in accordance with the geometric relationship to satisfy the input requirement of finite edement imitation.The finite element simulation method was used to analyze the force of the residual limb-prosthetic socket system.The general stress distribution under the rule of the geometric shape of the limb was given.The distribution of the stress and shear force in the key area under the typical gait period was obtained,and the effect of the prestress is explained.According to the simulation results,the cavity repair proposal was put forward,which can effectively connect the prosthetic technician experience platform.According to the results of the three-dimensional reconstruction of the limb surface and the repair conclusion of the finite element simulation,the model of the thigh prosthetic sockets was repaired and the STL file was derived from model.The parameters of 3D printing were set and the PLA was selected as the socket material,and the experiment of the prosthesis socket rapid prototyping was carried out by the 3D printer.The experimental results show that 3D printing has short molding time and high accuracy,and is conducive to quick modification according to the trial wear condition of the disabled.In conclusion,this paper makes a detailed study on the non-contact scanning,force analysis and molding methods in the process of the prosthetic sockets customization,and solves some shortcomings of the existing methods.It has important application value and practical significance.