Design And Application Of Personalized Porous Tantalum Implant Prostheses For Clinical Use

Porous tantalum has the advantages of excellent abrasion and corrosion resistance and good biocompatibility,which lead to the wide applications of porous tantalum as an orthopedic implant material.The conventional clinical implants can not meet the requirements for shape and size and mechanical properties by some bone defects resulting from trauma,bone tumors or congenital malformations,since they are uniformly designed and produced modularly.Combination of 3D printing technology and numerical simulation is a promising strategy to design and prepare patient-specific prostheses.In this work,a simple database for the mechanical properties of 3D printed porous tantalum standard samples with different pore diameters and wire diameters were first constructed.Then,by taking two patients as examples,we established the procedure and principles to design and screen personalized porous tantalum prostheses: 1)to construct the finite element models of the patient-specific prostheses and the boneed from themputed tomography(CT)data of patients;2)to numerically simulate the stress and displacement of the prostheses and bone using the finite element analysis software ABAQUS;3)to determine the patient-specific porous tantalum prostheses with appropriate pore diameter and wire diameter by combining the simulated data and the doctor’s suggestion and the price of the printed prostheses.The clinical implantation verifies the effectiveness of the established procedure and principles.The main work and conclusions are summarized as follows:(1)The compressive mechanical properties of 3D printed porous tantalum samples with various pore diameters(600-1200 μm)and wire diameters(300-600 μm)were detected.The results show that the Young’s modulus and yield strength of the 3D printed porous tantalum samples are 1.3-6.0 GPa and 20-180 MPa,respectively.the Young’s modulus and yield strength increase with the increase of the wire diameter and decrease with the increase of the pore diameter.(2)With the help of medical image processing software and industrial three-dimensional design software,the bone models and the prostheses models of two patients(Patient 1: age = 84,weight = 71 kg,tibia bone defect after total knee replacement;Patient 2: age = 33;weight = 50 kg,large segmented fibula defect after tumor ectomy)were reconstructed and designed.The finite element analysis was used to investigate the effects of the mechanical properties of porous tantalum on the mechanical responses of the prostheses and surroung bones.Based on these two examples,four principles to design and screen prostheses were proposed: Matchable shape and size of the prostheses with the bone defect;No destruction of the prostheses after implanted;Effective stress transmission from the prostheses to bone;No destruction of the bone after prostheses implantation.(3)On the premise of the proposed four principles,by combining the suggestions from the doctor and the consideration for cost of 3D printed prostheses,we finally designed personalized 3D printed porous tantalum prostheses for the two patients.The clinal follow-up shows that the designed prostheses are safe and effective in treating the bone defects.In conclusion,we constructed a mechanical property library of 3D printed porous tantalum and proposed effective procedures and principles to design and screen patient-specific prostheses,which are beneficial to guid the design of porous tantalum prostheses and facilitate their clinical applications.