Precision and biomechanical properties of 3D printed artificial bone trabeculae based on Voronoi Tessellation algorithm / 中华创伤杂志

ABSTRACT

Objective:To investigate the processing accuracy and biomechanical properties of 3D printed artificial bone trabeculae with different porosity generated by the Voronoi Tessellation algorithm, and to provide a reference for improving the biomechanical properties of titanium alloy implants in orthopedics.Methods:A healthy adult male volunteer (aged 30 years, tall 175 cm and weight 70 kg) was selected to collect CT scan data of the lumbar spine. Five kinds of biomimetic artificial bone trabeculae with different porosity were generated using the Voronoi Tessellation algorithm, and divided into Tra_A (73.7%), Tra_B (74.1%), Tra_C (80.0%), Tra_D (80.2%) and Tra_E (85.7%) groups according to the porosity. Selective laser melting (SLM) 3D printing technology was used to process trabecular bone structures with different porosity into titanium alloy prosthesis with a diameter of 18 mm and a height of 20 mm. Each group had 3 samples. The internal structure of each sample was observed by industrial microscope, and the actual porosity of artificial bone trabecular of each group was calculated and compared with the theoretical porosity to evaluate the machining accuracy of artificial bone trabecular with different porosity. Finally, the ultimate load, yield strength and elastic modulus of each sample were evaluated by in vitro mechanical test, and the biomechanical properties of artificial bone trabeculae with different porosity were evaluated.Results:There were no cracks, fracture of connecting rod or accumulation of titanium alloy powder in all specimens. The average actual porosity of the five groups of artificial bone trabecular specimens was 66.0%, 65.5%, 71.8%, 72.5% and 78.1%, respectively. Compared with the theoretical porosity, it was smaller by 10.5%, 11.6%, 10.2%, 9.7% and 8.8%, respectively. In the in vitro mechanical tests for the five groups of artificial bone trabecular specimens, the mean value of ultimate load was 23.6 kN, 18.9 kN, 17.0 kN, 16.3 kN, 10.7 kN, respectively; the mean value of yield strength was 72.2 MPa, 58.7 MPa, 54.9 MPa, 52.2 MPa, and 36.1 MPa, respectively; the mean value of the actual elastic modulus was 7.5 GPa, 6.3 GPa, 4.5 GPa, 4.3 GPa and 2.4 GPa, respectively. With the increase of the porosity of artificial bone trabeculae, all three indicators above showed a decreasing trend. Conclusions:The artificial bone trabeculae generated by the Voronoi Tessellation algorithm and printed by SLM 3D have better machining quality. With the increase of porosity, the processing precision of the titanium alloy artificial bone tray specimens is better. Limit load, yield light and elastic modulus of artificial bone trabecula decrease with the increase of porosity.