Three-dimensional Finite Element Analysis Of A 3D Printing Cervical Porous Metal Mesh Cage

ObjectiveBy using three-dimensional finite element method,two models of anterior cervical corpectomy and fusion(ACCF)with a traditional titanium mesh and a 3D printing cervical porous metal mesh cage were simulated.And we compared the Von-Mises stress distributions of the two models on the endplate,the titanium plates and the titanium meshes and the peak values of vertebral body movement,to evaluate the biomechanical properties of the 3D printing cervical porous metal mesh cage and provide theoretical basis for clinical application and next improvement.MethodThree dimensional CT data of cervical vertebrae of a 32 year-old healthy male volunteer was obtained and imported into 3D reconstruction software Mimics in Dicom format.After Mask treatment,the data was exported by STL format file.Then the obtained STL files were read into Geomagic,for reverse engineering reconstruction.A series of image processing,such as smoothing,grinding and de-noising,were carried out X on the 3D model to generate IGES file format of 3D graphics.Then,the file was imported into Ansys Workbench to establish a 3D finite element model of cervical spine(C3~C7).Then the Boolean operation was carried out,the material parameters were assigned,the contact was set,and the mesh was divided.The model used 40 N preload and 1.5Nm additional torque to perform forward and back flexion,left and right flexion,and left and right rotation.The validity of the model was evaluated by comparison with previous literatures.After the model was proved effective,a traditional titanium mesh and a 3D printing cervical porous metal mesh cage were used to simulate the anterior cervical corpectomy and fusion,and the stress distributions of the two models on the endplate,titanium plates and titanium meshes were compared.Results1.The 3D finite element model of cervical 3-7 vertebrae of normal people was successfully established.In addition,the range of motion of each segment of the cervical spine under the conditions of anterior flexion and posterior flexion,left and right lateral flexion and left and right rotation was similar to the results of previous literatures,and the model was effective.2.The results of finite element analysis of two models of ACCF with a traditional titanium mesh and a 3D printing cervical porous metal mesh cage:(1)Compared with the traditional titanium mesh,the maximum stress of the 3D printing cervical porous metal mesh cage decreased by 91% in the anterior flexion state under six working conditions.In the extensor state,it went down by 90%.In the left flexion state,it decreased by 98%.In the right flexion state,it was down 97%.When it was left-handed,it went down 86%.In the right-handed state,it was down 84%.(2)In six working conditions,in terms of the peak value of vertebral body movement,compared with the traditional titanium mesh cage,the maximum vertebral displacement peaks were the same in the flexion and right flexion states.In the posterior extension and left flexion,the maximum vertebral body displacement of the 3D printing cervical porous metal mesh cage increased by 0.02 mm and 0.16 mm,respectively.In the left and right rotation state,the maximum displacement was reduced by 0.04 mm and 0.21 mm,respectively.Each titanium mesh had its advantages and disadvantages.(3)Compared with the traditional titanium mesh,the greatest titanium plate stress of the 3D printing cervical porous metal mesh cage was increased by 7% in the flexion state,but it was reduced by 37% in the posterior extension,5% in the left and right flexion states,9% and 26% in the left and right rotation states,respectively.(4)Under the six working conditions,compared with the traditional XII titanium mesh,the maximum stress of the endplate of the 3D printing cervical porous metal mesh cage decreased by 51% in the forward flexion state under the C4 vertebral body.In the post extension condition,it dropped by 15%.In the left flexion state,it decreased by 55%.In the right flexion state,it decreased by 43%.In the left-handed case,it went down by 8%.In the right-handed case,it went down 12%.In the C6 vertebral body,compared with the traditional titanium mesh,the maximum stress of the 3D printing cervical porous metal mesh cage decreased by 43% in the forward flexion state.In the post extension condition,it decreased by 83%.In the left flexion state,it decreased by 70%.In the right flexion state,it decreased by 52%.In the left-handed case,it went down by 55%.In the right-handed state,it went down by 29%.Under the condition of forward flexion and extension,left and right rotation,the maximum stress of the end plate of the two kinds of titanium mesh was located at the rear edge of the end plate,but the stress of the end plate of the 3D printing cervical porous metal mesh cage was smaller than that of the traditional titanium mesh,and there was significant difference between the two kinds of titanium mesh.Conclusions1.The 3D finite element model of the cervical 3-7 vertebral bodies established is effective and can be used for 3D finite element analysis.2.Compared with traditional titanium mesh,the 3D printing cervical porous metal mesh cage has good immediate stability and stress distribution in theory.