| Interbody fusion is used in clinics to decompress patients with cervical degenerative disease.Restore the height of the patient’s interbody;reconstruction of spinal stability of the patient.The design concept of the interbody fusion device has been developed from a simple usable structure to conform to the anatomical characteristics of the spine,so that every patient can obtain a reliable postoperative fusion device.Personalized design can ensure the stability and anti-sinking performance of the fusion device in patients.In this dissertation,the three-dimensional structure of interbody fusion cages was investigated from the perspective of personalized design.In this paper,the Mimics and Geomagics softwares were used to establish the C4-5segment finite element model of the patient’s cervical spine,and the finite element model was verified by analyzing the rotation angle of the cervical vertebra and the stress distribution of the intervertebral disc under normal upright condition.The Opti Struct software was used for topology optimization of two initial design structures(box and ellipsoid).Since the volume fraction set by topology optimization was 50% and 30%respectively,four interbody fusion configurations were finally obtained,that is,the box fusion device of 50% volume fraction and 30% volume fraction,and the ellipsoid fusion of 50% volume fraction and 30% volume fraction.The stiffness matrices of 6 unit cells of the two types(cube cell and Schwarz cell)were obtained by using homogenization method,and 4×6,namely 24 fusion models,were finally obtained.Finally,the biomechanical evaluation of the fusion devices were completed by Abaqus software.Through biomechanical evaluation,it can be found that: 1)the larger the porosity of the cell,the lower the stiffness,and the smaller the stress shielding effect,which is helpful for the rehabilitation of the surgical site of patient;2)the configuration obtained by topology optimization design is reliable,but it should be noted that the secondary design will change the mechanical properties of the structure,and the combination with high porosity cell may lead to structural failure;3)the maximum Von Mises stress of the vertebrae implanted with an ellipsoid fusion device is lower than that of the vertebrae implanted with a box fusion device,suggesting that the implantation of an ellipsoid fusion device could reduce the risk of vertebral settlement;4)Both ellipsoidal and cubic configurations of the Schwarz cell filled fusion cages had higher maximum Von Mises stress,suggesting that the Schwarz cell could promote bone fusion.The maximum Von Mises stress of the bone graft bed was lower with the ellipsoidal fusion device filled with cubic cell,which indicated that the risk of vertebral settlement could be reduced to the greatest extent by using the ellipsoidal fusion device filled with cubic cell elements.Both cubic cell and Schwarz cell have their own advantages.Using finite element method,it is found that the yield strength of cubic cell is lower than that of Schwarz cell with the same porosity.After biomechanical evaluation,it is found that the implantation of an ellipsoid fusion device reduced the risk of vertebral settlement compared with the box fusion device.In this study,patients with cervical degenerative diseases were treated with personalized porous interbody fusion cages,which can restore the height of the patient’s interbody and ensure the stability after implantation.This study provided a new method for the design of customized interbody fusion cages. |
