Clinical Application Of 3D Printed Individual Titanium Alloy Implants In Bone Defect After Bone Tumor Resection In Lower Limb

Study background: The reconstruction of structure and function after bone tumor resection is a major clinical problem in orthopedics for a long time.Unlike general orthopedic surgery,the extent of bone resection of bone tumors depends on the surgical boundary of the tumor,and the traditional prosthesis often matches the extent of bone resection,resulting in a series of problems such as difficulty in prosthesis reconstruction after tumor resection,poor stability,and unsatisfactory postoperative functional recovery.At the same time,there are large differences in the skeletal structure of different individuals,which again greatly reduce the reliability of standardized prosthetic reconstruction.If the individual prosthesis with anatomical matching,good integration and long-term stability can be designed and prepared quickly according to the parameters of bone defect.It would be an effective way to solve the problem of bone defect repair after the resection of bone tumor.The technological characteristics of 3D printing rapid prototyping technology are exactly suitable for the fabrication of individually customized orthopedic implants,i.e.Many successful cases have been reported at home and abroad,However,the whole process still needs to be further studied and optimized to realize the rapid and routine production of personalized implants.In this study,we integrated the preparation of 3D printed individualized prostheses,simplified the design process and improved the preparation efficiency by introducing three basic procedures: engineering design,stress analysis,and prosthesis preparation,and finally displayed the intuitive surgical plan and postoperative efficacy in the form of clinical cases.Aim: 1.To explore a design process and preparation method of 3D printing individualized prosthesis;2.To calculate the stress distribution of 3D printing individualized prosthesis by finite element analysis,and to evaluate the rationality of prosthesis design;3.To test the effectiveness and practicability of 3D printing individualized prosthesis in the reconstruction of bone defect after resection of bone tumor by clinical trial.Method:(1)The image data of the diseased part of the patient were collected by CT scanning,and the required 3D model was reconstructed by four basic functions of Mimics19.0 software: threshold segmentation,region growth,vacancy filling and pixel erasing.The STL format file is further imported into the Geomagic studio 12 software and Magics 21.0 software,and the prosthesis data model is designed through streamline processing,shell extraction,segmentation,drilling,porous calculation and other processes.(2)ABAQUS 6.14 software was used for finite element analysis of the data model,and the model was modified and optimized according to the stress distribution of prosthesis.Then,the 3D data model of prosthesis was imported back to mimics19.0 software,which was installed in vitro to verify the accuracy of prosthesis matching.After the verification of the prosthesis model,the electron beam melting(EBM)equipment was used for 3D printing to prepare the individualized bone tumor prosthesis.After removal of support,high-pressure powder blowing,machining and other post-processing procedures,the prosthesis was sent to the supply room for ultrasonic cleaning,and the supply room for ultrasonic cleaning,high-temperature and high-pressure sterilization for standby.(3)During the operation,the individualized guide plate was used to assist in determining the osteotomy plane of the lesion.After precise osteotomy,the prosthesis was implanted into the defect site and fixed.X-ray examination was performed to evaluate the position and stability of the prosthesis.Results:(1)CT data were collected clearly and stored in DICOM format,with a fault interval of 0.625 mm.As the leading software of prosthesis design,Mimics 19.0 software ran through the whole design process to complete the personalized prosthesis model design.The Geomagic studio 12 software and Magics 21.0 software are seamlessly connected to complete the surface fairing and internal porous structure design of the model respectively.(2)The stress distribution on the surface of the prosthesis is is uniform,and the maximum stress is 77 MPa,which appears in the solid part of the prosthesis.The maximum contact stress of epiphyseal fracture was 9 MPa,and that of distal tibia was 32 MPa.(3)From January 2014 to December 2017,13 patients were treated with individualized 3D printing prosthesis.With the help of guide plate or navigation,the prosthesis can be installed accurately according to the design before operation,and the position of prosthesis and the immediate stability after operation are satisfactory.Conclusion: Through the design process of this project,we can design a customized prosthesis for bone defect after resection of bone tumor quickly and effectively.Through the finite element analysis,the design of prosthesis can be verified and optimized.The prosthesis designed and prepared in this study can achieve accurate design and installation,and has a broad application prospect.