Effect Of Pore Structure On Bone Ingrowth Into Porous Titanium Alloy Scaffolds Fabricated By 3D Printing: An In Vivo Animal Experiment

Background: 3D printed porous titanium alloy has a good effect on bone ingrowth has been widely recognized.However,the effects of different pore structures of this material on bone ingrowth are still under study.Selective laser melting(SLM)is one of the mainstream 3D printing technologies,which can produce metal scaffolds with accurately controlled pore size,porosity and interconnectivity.It is more and more widely used in the field of orthopaedics.Objective: To evaluate the effect of different pore structures of porous titanium alloy scaffolds with rhombic dodecahedron lattice on the formation of new bone tissue after implantation in rabbits and analyze the effect of pore structure design parameters on the bone ingrowth.Methods: Three kinds of porous titanium alloy scaffolds with rhombohedral dodecahedron as the basic structural unit(the theoreticalpore sizes were 900?m,1200?m,and 1500?m,which were named as P900,P1200 and P1500,respectively)were designed and prepared in advance.Scanning electron microscopy(SEM)was used to observe and characterize the structures of three kinds of scaffolds.Thirty healthy male rabbits were randomly divided into 6 groups according to different pore sizes and animal feeding periods,with 5 rabbits in each group.An animal(rabbit)model of femoral condyle defect was established and repaired using the above scaffolds,and the rabbits were sacrificed at 4 and 8weeks after operation.After the implanted scaffolds were collected,the ingrowth of bone and soft tissue in each group was evaluated by histomorphometry.Results:(1)SEM showed that the actual pore structure of the scaffolds fabricated by SLM was basically consistent with the theoretical design.(2)The histomorphological analysis showed that the bone tissue penetration length of P1500 group was greater than that of P900 and P1200 group at 4 weeks(P <0.05);the bone marrow-like tissue penetration length of the P1500 group was larger than that of the P900group(P <0.05);the new bone formation area of P900 group at 8 weeks was larger than that of P1200 and P1500 group(P <0.05).Conclusion:(1)SLM could accurately control the pore structure of the porous titanium alloy material,and could meet the design and manufacture of specific shape and special pore structure.(2)Three kindsof porous titanium alloy scaffolds with different pore structure prepared by SLM could achieve bone ingrowth during 8 weeks after implantation into rabbit bone.In particular,the P900 group was beneficial to the formation of new bone tissue.