Experimental Study Of 3D Printed Porous Ti6Al4V Scaffolds In Repairing Of Femoral Condyle Bone Defects In Rats

BackgroundBone defect is still one of the most common orthopedic problems,which seriously affects human health.Clinically,bone defects caused by trauma,tumor resection and congenital malformation need to be repaired by bone grafting.Autografts and allografts are the most commonly used bone grafts,but they have shortcomings such as limited supply,disease transmission and high complication rates.Porous Ti6Al4V scaffolds can overcome the shortcomings of traditional bone grafts,provide mechanical support while guiding bone tissue regeneration,which is a feasible method for repairing bone defects.The porosity and pore size of the scaffolds can affect cell adhesion,cell migration,capillary formation and new bone formation.However,the optimum porosity and pore size of the scaffolds for cell growth and bone ingrowth are still inconclusive.In this study,porous Ti6Al4V scaffolds with different porosity and pore size were fabricated by 3D printing(selective laser melting)to verify the safety and effectiveness of the scaffolds in bone defects repairing,and to explore the most suitable porosity and pore size for bone defects repair.The results provide experimental basis for the clinical application of porous Ti6A14V scaffolds in the future.MethodsPorous Ti6A14V scaffolds with porosity of 60%and 70%,and pore sizes of 500?m,600 ?m and 700 ?m were designed by computer-aided design(CAD)software.The scaffolds were fabricated by 3D printing(selective laser melting)technology using Ti6A14V ELI powder as raw material.The mechanical properties and physical properties of porous Ti6A14V scaffolds were investigated by compression experiments,contact angle measurements and protein adsorption experiments.The cytotoxicity of the porous Ti6A14V scaffolds were evaluated by Cell Counting Kit-8 assay,live/dead cell staining and scanning electron microscopy observation.The proliferation of cells on the surface of porous Ti6A14V scaffolds were studied by cell fluorescence photographing and DNA content measurement.Alkaline phosphatase activity and relative expression of osteogenic genes(bone morphogenetic protein-2,collagen type 1,osteocalcin,osteopontin and Runt-related transcription factor-2)were assessed to study the influence of porosity and pore size on osteogenic differentiation of bone marrow mesenchymal stem cells.The distal femoral condyles defect of Sprague-Dawley rats was repaired with porous Ti6A14V scaffolds.Micro-CT analysis and histological staining were used to analyze the bone ingrowth and explore the optimum porosity and pore size combination for bone ingrowth.ResultsPorous Ti6A14V scaffolds fabricated by 3D printing(selective laser melting)are consistent with the design.The porous Ti6A14V scaffolds have a compressive strength of 73 MPa-207 MPa,and an elastic modulus of 2.1 GPa-4.7 GPa.The contact angles of the scaffold surfaces are smaller than 90°.The porous Ti6A14V scaffolds did not induce a cytotoxic effect.Porous Ti6A14V scaffold with a porosity of 60%and a pore size of 500 ?m is more suitable for cell proliferation and osteogenic differentiation in vitro and bone ingrowth in vivo compared with other scaffolds.ConclusionThe porous Ti6A14V scaffolds fabricated by 3D printing had high compressive strength and elastic modulus similar to human bone tissue.The scaffolds did not induce a cytotoxic effect and had a good biocompatibility.Bone defects can be effectively repaired by the porous Ti6A14V scaffolds,and the optimum porosity and pore size was 60%and 500 ?m.