Feasibility Study Of Individualized Porous Titanium Intervertebral Fusion Cage

Objective:Nowadays,the rapid development of percutaneous minimally invasive spine surgery techniques put forward high requirement for the dimensions of intervertebral cages.Biomedical titanium alloys have been widely used and the additive manufacturing technology has made significant progress.The purpose of this project:1.In order to measure the anatomical parameters of the lumbar degenerative diseases and evaluate the necessity of individualized lumbar intervertebral fusion.2.Preparation of porous titanium alloy interbody fusion cages using additive manufacturing techniques.3.The mechanical experiment of intervertebral fusion of porous titanium alloys was conducted to explore its feasibility.Methods:1.A total of 60 cases randomly selected in our department which patients of ct image data with lumbar degenerative diseases.Using the software of surgimap to measure the anatomical parameters of degenerative lumbar spine and analyze the anatomical features of degenerative lumbar spine.2.We had been selected the appropriate titanium alloy raw materials for constructing the best porous structure,then designed the 3D model of the lumbar interbody fusion device,finally used the EBM technology to prepare the interbody fusion cage.3.We had tested the mechanical properties of the porous titanium interbody fusion cages prepared by EBM in comparing with the PEEK material.Results:1.The height of intervertebral space in L1-S1 are higher than the anterior and posterior edge of the intervertebral space at the same level,which has statistical significance.The posterior edge of the lumbar vertebra,the height of the middle intervertebral space and the height of the posterior edge of the lumbar vertebrae which aren t increase significantly.The heights of posterior edge of male s L2 and L3 vertebral bodies were 33.89±2.08mm and 33.51±2.15mm,respectively,which were higher than female's 33.37±1.48mm and 33.01±2.35mm,there were significant statistical differences.The height of the lumbar intervertebral space doesn't show an increasing trend from beginning to end,and the height of the lumbar intervertebral space was generally 8-12 mm.The transverse and sagittal diameters of the male s vertebrae were bigger than female s at all levels which were significant statistical differences.The cross-sectional diameter of each vertebral body of L1-S1 was larger than that of the sagittal plane,and the difference between the cross-sectional diameter and the sagittal plane diameter were statistically significant.The sagittal diameter of the L5 vertebral body was the largest in all sagittal diameters,the cross-sectional diameter of L1-L5 gradually increases,which of S1 decreases slightly.From L1 to S1,the diameters of the upper and lower edges of each vertebral body are larger than the central diameter of the vertebral body.The transverse diameter of the upper edge of the vertebral body increases from L1 to L5 while the transverse diameter of the lower edge of the vertebral body increases from L1 to L4 in turn.The sagittal diameters of the upper,lower and middle vertebral bodies increased from L1 to L5 in turn.2.45-105umTi-6Al-4V ELI powder was selected.The shape of the cage was a double-convex curved cube design with a length of 22-26mm,a width of 9-11mm and a height of 8-12mm.The porosity was 63.6%,and the cell size was 620um.3.The average yield load is 15.8±0.8kN and the average compression stiffness is 9.01±0.37kN/mm,which are higher than that of PEEK group 13.04±0.41kN,8.49 ±0.11kN/mm,the differences were statistically significant.The average compressive elastic modulus of the porous titanium alloy group was 1.41±0.07GPa which of the control group was 3.52±0.13GPa,and the difference was statistically significant.Conclusion:1.Patients with lumbar spine degeneration have variations in anatomical parameters of the lumbar spine compared with healthy people which especially changes in the height of the intervertebral space.Interbody fusion cages of industrial mass production don t fully meet clinical needs,and it is necessary to customize the individual interbody fusion cage.2.The EBM technology successfully prepared a regular porous titanium intervertebral cage,which of the porosity was 63.6%and the unit size was 620um.The EBM technology can control the structural parameters of the porous titanium includes change the porosity,pore size,etc.,Therefore,the strength and elastic modulus of porous titanium alloy stents are variable.3.Porous titanium alloy interbody fusion device includes yield load and compressive stiffness which better than PEEK material respectively.The porous titanium alloy cage's average compressive elastic modulus was 1.41 ± 0.07GPa,between cortical bone and cancellous bone,which can promote bone fusion.