Potential Application of Entangled Porous Titanium Alloy Metal Rubber in Artificial Lumbar Disc Prostheses

Entangled Porous Titanium Alloy Metal Rubber(EPTA-MR)was used as a nucleus pulposus material in the design of non-fusion intervertebral disc prosthesis for the first time.A novel artificial lumbar intervertebral disc prosthesis was designed by reconstructing the lumbar model with reverse engineering technology,and the biomechanical behavior of the prosthesis was simulated under varied working conditions.The nucleus pulposus size was determined by the actual size of human prosthesis.EPTA-MR samples with different densities were prepared by medical titanium alloy wire experimental studies were conducted on static stiffness,damping energy consumption,and fatigue life.The results indicated that the static stiffness of EPTA-MR could reach approximately 1500 N mm and its loss factor remained higher than 0.2,and the variation range was relatively small,with excellent vibration damping capacity and bearing capacity.Among them,the overall performance of EPTA-MR with a density of 2.5 g em 3 was closer to that of the physiologic intervertebral disc.A macro experiment of five million fatigue vibration tests combined with microstructure observation exhibited a wear rate of only 0.9396 g-MC with no noticeable change in the internal micro-morphology.Therefore,the EPTA-MR has a broad application prospect as the nucleus pulposus material of artificial intervertebral disc prosthesis.

Review on Corrosion Characteristics of Porous Titanium Alloys Fabricated by Additive Manufacturing

Porous titanium and its alloys have been considered as promising implants owing to their low elastic modulus and capability to provide channels for bone growth.Currently,additive manufacturing(3D printing)techniques have been successfully applied to produce porous titanium alloys owing to the advantages of controllable and precise fabrication.Considering the safety aspect,an understanding of corrosion in porous titanium alloys and the corresponding mechanisms is important for their long-term application in the human body.In this paper,the recent progress in improving the corrosion properties of porous titanium alloys fabricated via 3D printing techniques is reviewed.The effects of pore type,porosity,electrolyte,and modification of the material on the corrosion properties of porous titanium alloys are introduced and discussed.In addition,the limitations of traditional methods for measuring the corrosion performance of porous titanium alloys were analysed.Perspectives for evaluating and improving the corrosion performance of porous titanium alloys using new methods are provided.

Anisotropic Porous Ti6Al4V Alloys Fabricated by Diffusion Bonding:Adaption of Compressive Behavior to Cortical Bone Implant Applications

In this work, porous Ti6Al4V alloys with 30%-70% porosity for biomedical applications were fabricated by diffusion bonding of alloy meshes. Pore structure was characterized by Micro-CT and SEM. Compressive behavior in the out-of-plane direction and biocompatibility with cortical bone were studied. The results reveal that the fabricated porous Ti6Al4V alloys possess anisotropic structure with square pores in the in-plane direction and elongated pores in the out-of-plane direction. The average pore size of porous Ti6Al4V alloys with 30%-70% porosity is in the range of 240-360 Bin. By tailoring diffusion bonding temperature, aspect ratio of alloy meshes and porosity, porous Ti6Al4V alloys with different compressive properties can be obtained, for instance, Young＇s modulus and yield stress in the ranges of 4-40 GPa and 70-500 MPa, respectively. Yield stress of porous Ti6Al4V alloys fabricated by diffusion bonding is close to that of alloys fabricated by rapid prototyping, hut higher than that of fabricated by powder sintering and space-holder method. Diffusion bonding temperature has some effects on the yield stress of porous Ti6Al4V alloys, but has a minor effect on the Young＇s modulus. The relationship between compressive properties and relative density conforms well to the Gibson-Ashby model. The Young＇s modulus is linear with the aspect ratio, while the yield stress is linear with the square of aspect ratio of alloy meshes. Porous Ti6Al4V alloys with 60%-70% porosity have potential for cortical bone implant applications.

Biomimetic Ti-6Al-4V alloy/gelatin methacrylate hybrid scaffold with enhanced osteogenic and angiogenic capabilities for large bone defect restoration

Titanium-based scaffolds are widely used implant materials for bone defect treatment.However,the unmatched biomechanics and poor bioactivities of conventional titanium-based implants usually lead to insufficient bone integration.To tackle these challenges,it is critical to develop novel titanium-based scaffolds that meet the bioadaptive requirements for load-bearing critical bone defects.Herein,inspired by the microstructure and mechanical properties of natural bone tissue,we developed a Ti-6Al-4V alloy(TC4)/gelatin methacrylate(GelMA)hybrid scaffold with dual bionic features(GMPT)for bone defect repair.GMPT is composed of a hard 3D-printed porous TC4 metal scaffold(PT)backbone,which mimics the microstructure and mechanical properties of natural cancellous bone,and a soft GelMA hydrogel matrix infiltrated into the pores of PT that mimics the microenvironment of the extracellular matrix.Ascribed to the unique dual bionic design,the resultant GMPT demonstrates better osteogenic and angiogenic capabilities than PT,as confirmed by the in vitro and rabbit radius bone defect experimental results.Moreover,controlling the concentration of GelMA(10%)in GMPT can further improve the osteogenesis and angiogenesis of GMPT.The fundamental mechanisms were revealed by RNA-Seq analysis,which showed that the concentration of GelMA significantly influenced the expression of osteogenesis-and angiogenesis-related genes via the Pi3K/Akt/mTOR pathway.The results of this work indicate that our dual bionic implant design represents a promising strategy for the restoration of large bone defects.

Electron Beam Melted Beta-type Ti–24Nb–4Zr–8Sn Porous Structures With High Strength-to-Modulus Ratio

Electron beam melting （EBM） has been used to manufacture β-type Ti-24Nb-4Zr-8Sn porous compo- nents with 70% porosity, EBM-produced components have favorable structural features （i.e. smooth strut surfaces, fewer defects） and an （α ＋ β）-type microstructure, similar to that subjected to aging treat- ment. EBM-produced components exhibit more than twice the strength-to-modulus ratio of porous Ti- 6A1-4V components having the same porosity. The processing-microstructure-property relationship and deformation behavior of EBM-produced components are discussed in detail. Such porous titanium com- ponents composed of non-toxic elements and having high strength-to-modulus ratio are highly attractive for biomedical applications.