电子束熔融制备多孔钛合金融合器的性能和椎间融合效果

Performance and intervertebral fusion effect of porous titanium alloy cage prepared by electron beam melting

目的探讨电子束熔融(EBM)制备多孔钛合金融合器的力学性能、生物相容性及椎间融合效果。方法通过计算机设计和EBM技术制备多孔钛合金(Ti-6Al-4V)融合器,通过电子显微镜观察其表征和微观结构,通过体外力学试验评估其弹性模型和抗压强度,通过四甲基偶氮唑盐微量酶反应比色法(MTT)法评估生物相容性。选取12只雄性成年小尾寒羊,建立小尾寒羊颈椎椎间融合模型,按照随机数字表法分为两组,每组6只。实验组置入3D打印椎间融合器,对照组置入聚醚醚酮(PEEK)融合器(中空处含有碎骨粒)。术后6个月行X线片检查,观察融合器是否有移位、松动或下沉;Micro-CT观察椎间隙骨小梁生长情况;组织学观察微观结构下椎间融合情况,分析两组融合器内的矿化骨百分比(MBF)和材料-骨结合百分比(BA)。结果多孔钛合金融合器是一个中间为八面体金属小梁、外围为金属框的结构,金属小梁的直径为(413±78)μm,孔径为(597±46)μm,孔隙率为(54.8±5.8)%;弹性模量为(19.6±0.8)GPa,压缩强度为(37.6±2.3)GPa,刚度为(17633±882)N/mm;多孔钛合金融合器具有良好的生物相容性。两组X线片均未见融合器出现移位和松动。两组Micro-CT检查可见贯通整个椎间隙的骨小梁分布,实现了骨性融合;实验组新生骨组织对金属小梁形成了结合紧密,对照组新生骨质和PEEK融合器之间仍可见到空隙。组织学显示实验组椎间隙MBF为(43.7±10.6)%,与对照组[(46.5±11.4)%]差异无统计学意义(P>0.05),而对照组骨小梁和PEEK融合器交界处可见较多的纤维组织包裹,骨组织与PEEK融合器未形成紧密融合;实验组BA为(53.7±12.8)%,对照组为(7.5±2.8)%(P<0.05)。结论EBM制备多孔钛合金融合器具有合适的力学性能和孔隙率、良好的生物相容性和椎间融合效果,具有临床应用前景。

Objective To investigate the mechanical properties and biocompiitibilitv of porous titanium iilloy fusion cages prepared by electron beam fusion(EBM)and to analyze the intervertebral fusion effect.Methods The porous titanium alloy(Ti-6Al-4V)cage was prepared by computer design and EBM technology.The characterization and microstructure were observed through electron microscope.The elasticity model and compressive strength were evaluated through in vitro mechanic al experiments,and the biocompatibility by methyl thiazolyl tetrazoliuni(MIT)method.Twelve Small-tail Han sheep were used to establish cervical fusion models and were divided into two groups according to the random number table,with six sheep per group.The experimental group was placed with a 3D printed cage,and the control group was placed with a poly-ether-ether-ketone(PEEK)cage(with bone particles in the hollow).X-ray examination was performetl at 6 months after operation to observe whether the fusion cage was displaced,loosened or sinking.The growth of trabecular bone in the intenertebral space was observed by Micro-CT.The microstructure of the intervertebral fusion was assessed through histopathology and the mineralized bone fraction(MBF)and bone apposition(BA)in the intervertebral space were measured.Results The porous titanium alloy cage was a structure with an octahedral metal trabecular in the middle and a metal frame on the periphery.The diameter of the metal trabecula was(413±78)μm,the pore diameter was(597±46)μm,the porosity was(54.8±5.8)%,the elastic inodiilus was(19.6±0.8)GPa,the compressive strength was(37.6±2.3)GPa,and the stiffness was(17633±882)N/nun.The porous titanium alloy cage had good bioconipatibility.X-rays showed no displacement and loosening of the cages in both gioups.Micro-CT examinations showed that the distribution of trabecular bone penetrated the entire intervertebral space and achieved bone fusion.The new bone tissue in experimental group formed a tight bond with the metal trabecula.However,there were gaps between the new bone and the PEEK cage in control group.Histopathology study showed that the MBF in the intervertebral space in experimental group was(43.7±10.6)%,which was not statistically different from that in control group[(46.5±11.4)%](P>0.05).While there were fibrous tissues at the junction of trabecular bone and PEEK cage in control group and the bone tissues and PEEK cage did not form a tight fusion.The BA in experimental group was(53.7±12.8)%,and in control group was(7.5±2.8)%(P<0.05).Conclusions The porous titanium alloy cage prepared by EBM has suitable mechanical properties and porosity,good hiocompatibility and intervertebral fusion effect.The porous titanium alloy cage has clinical application prospects.