Abstract
BackgroundAdditively manufactured porous metallic structures have recently received great attention for bone implant applications. The morphological characteristics and mechanical behavior of 3D printed titanium alloy trabecular structure will affect the effects of artificial prosthesis replacement. However, the mechanical behavior of titanium alloy trabecular structure at present clinical usage still is lack of in-depth study from design to manufacture as well as from structure to mechanical function.MethodsA unit cell of titanium alloy was designed to mimick trabecular structure. The controlled microarchitecture refers to a repeating array of unit-cells, composed of titanium alloy, which make up the scaffold structure. Five kinds of unit cell mimicking trabecular structure with different pore sizes and porosity were obtained by modifying the strut sizes of the cell and scaling the cell as a whole. The titanium alloy trabecular structure was fabricated by 3D printing based on Electron Beam Melting (EBM). The paper characterized the difference between the designs and fabrication of trabecular structures, as well as mechanical properties and the progressive collapse behavior and failure mechanism of the scaffold.ResultsThe actual porosities of the EBM-produced bone trabeculae are lower than the designed, and the load capacity of a bearing is related to the porosity of the structure. The larger the porosity of the structure, the smaller the stiffness and the worse the load capacity is. The fracture interface of the trabecular structure under compression is at an angle of 45o with respect to the compressive axis direction, which conforms to Tresca yield criterion. The trabeculae-mimicked unit cell is anisotropy. Under quasi-static loading, loading speed has no effect on mechanical performance of bone trabecular specimens. There is no difference of the mechanical performance at various orientations and sites in metallic workspace. The elastic modulus of the scaffold decreases by 96%–93% and strength reduction 96%–91%, compared with titanium alloy dense metals structure. The apparent elastic modulus of the unit-cell-repeated scaffold is 0.39–0.618 GPa, which is close to that of natural bone and stress shielding can be reduced.ConclusionWe have systematically studied the structural design, fabrication and mechanical behavior of a 3D printed titanium alloy scaffold mimicking trabecula bone. This study will be benefit of the application of prostheses with proper structures and functions.
Highlights
At present, 3D printing technology has developed vigorously in the medical field [1, 2] and has been successfully used in orthopedic treatment [3, 4]
The 3D printing technology cannot only realize the individualized manufacture of medical devices, and is superior to the traditional technology in the construction of the microstructures of implants [5, 6]. It can make titanium alloy [7, 8] and other metal powders into fabricate three-dimensional porous metal implants with different porous structures, whose microstructure is similar to human bone trabecula, and whose porosity, pore size, pore volume, spatial arrangement and other surface properties as well as elastic modulus can be completely determined by design [9, 10]
It can be seen that the porosity produced by 3D printing is always lower than that designed
Summary
3D printing technology has developed vigorously in the medical field [1, 2] and has been successfully used in orthopedic treatment [3, 4]. The 3D printing technology cannot only realize the individualized manufacture of medical devices, and is superior to the traditional technology in the construction of the microstructures of implants [5, 6] It can make titanium alloy [7, 8] and other metal powders into fabricate three-dimensional porous metal implants (metal trabeculae) with different porous structures, whose microstructure is similar to human bone trabecula, and whose porosity, pore size, pore volume, spatial arrangement and other surface properties as well as elastic modulus can be completely determined by design [9, 10]. With the development of 3D printing technology and new biological materials, the application of trabecular structure in artificial joint replacement [18] is increasing, and the design, fabrication and mechanical properties of trabecular structures are the focus of current research [19]. The mechanical behavior of titanium alloy trabecular structure at present clinical usage still is lack of in-depth study from design to manufacture as well as from structure to mechanical function
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