Fabrication of a lattice structure with periodic open pores through three-dimensional printing for bone ingrowth

Abstract

Lattice structures for implants can be printed by metal three-dimensional (3D)-printing and used as a porous microstructure to enhance bone ingrowth in 3D-printed orthopedic implants. However, the design and 3D-printed product can have differences. Thus, this study aimed to investigate whether targeted pores can be stably obtained despite printing errors. The specimen was printed in a cube shape with one side in 15 mm and a full lattice with a dode-thin structure in 1.15, 1.5, and 2.0 mm by selective laser melting method. Beam compensation was applied while serially increasing it until the vector was lost. For each specimen, the actual unit size and thickness of struts were measured 50 times. Pore size was calculated from the unit size and strut, and porosity was converted from the specimen’s weight. The actual average output for pore sizes 1.15, 1.5, and 2.0 mm were 257.9, 406.2, and 633.6 µm, respectively, and volume porosity was 62%, 70%, and 80%, respectively. No strut breakage or gross deformation in all 3D-printed specimens were observed, and the pores were uniformly fabricated with < 10% standard deviation. An actual printed structure in the micrometer-scaled structure indicated a significant difference from the design, although this error was not random. Although the accuracy was low, precision was high for pore cells, so reproducibility was secured stably. The target pore size and porosity were obtained by 3D-printing of a dode-thin structure with a unit size of 1.5 mm.