Experimental Research On A Novel 3d Printing Porous Titanium Alloy Interbody Fusion Cage

Objectives:1)To test the physical properties of a porous titanium alloy cervical intervertebral fusion cage made by 3D printing technology;2)To evaluate the fusion efficacy by placing it in an animal model of sheep cervical fusion.Methods:1)Physical property test:Scanning electron microscope was used to observe the surface characteristics of the porous metal structure inside the cage and measure the diameter of the aperture and the diameter of the metal trabecula.The elastic modulus and compressive strength of the porous material inside the cage,and overall stiffness were measured by a mechanical tester..2)Animal experiment:16 Small Tail Han sheep were selected and divided into 2 groups.After the 3/4 cervical discectomy,porous titanium alloy(experimental group)and PEEK(control group)cages were implanted to perform fusion surgery.At the two time points of 3 months and 6 months after operation,four animals were sacrificed in each group and were taken for X-ray,Micro-CT,and histological examination.Result:1)Scanning electron microscopy showed that an octahedral crystal lattice structure inside the cage,with adjacent pores communicating with each other,with an aperture of 597±46 ?m and a metal trabeculum diameter of 413±78 ?m;the porous material had a Young's modulus of 19.6± At 0.8 GPa,the compressive strength was 37.6±2.3 GPa and stiffness of the cage was 17633±882 N·mm,which was lower than the solid titanium alloy cage(P<0.05)and higher than the PEEK cage(P<0.05).2)The animals in both groups had good postoperative activities and eating,and no serious complications occurred during the experimental period.X-ray examination showed no displacement of intervertebral cages and disrupt of internal fixation instrument.Micro-CT showed that in the control group,bony fusion was initially achieved at 3 months,but bone fusion was achieved in both groups at 6 months.Histological examination showed that within 3 months,the experimental group had a certain number of new bone growth inside pores.After bone ingrowth,the number of new bones increased further at 6 months and formed excellent osseointegration.In the control group,the fusion cage was connected with the upper and lower vertebral through the bone bridge,but there was a large gap between the surface of the cage and the bone tissue.At 6 months,there was no difference in bone mineral volume ratio(BV/TV ratio)between the two groups(P>0.05),and the bone-contacting implant surface ratio(BCSR)of the experimental group was significantly higher than control group(P<0.05).Conclusion:The new type of porous titanium alloy interbody fusion cage is conducive to bone ingrowth because of the size of pores and the rough surface,also have the similar Young's modulus of the bone tissue.In the animal experiment,the fusion efficacy similar to the PEEK cage is obtained.