Page 132 - IJB-9-2

International Journal of Bioprinting Design and manufacture of high-performance bone plate

Figure 7. Results of bone plates filled with different porous structural units.

matches the bone plate frame, whether the plate with Under the condition that the mechanical properties
optimized topology is close, whether the processing and biocompatibility of the three structural units are
requirements are met, and whether the porous structure able to meet the requirements, H unit may be suitable
is beneficial to the improvement of the mechanical for surgeries that require removing the plate, and B
properties and biocompatibility of the plate. We chose unit may be suitable for surgeries that do not require
a porous structure that is suitable for the plate with removing the plate. The mass test showed that the mass
optimized topology using the methods of simulation and of the H-shaped plate was 12.05 g, which is 20.93%
filling of the porous structure. After the selection of H lower than that of the original plate, while the mass of
unit, R unit, and B unit with good mechanical properties, the B-shaped plate was 11.05 g, which is 27.49% lower
we simulated and filled the optimized topology plate than that of the original plate. With its strength ensured,
according to the generation rules of porous structure there was a sharp decline in the mass of the new plate
(Figure 7). By observing the plates filled with three and an improvement in its biocompatibility. After the
kinds of porous structures, we found that all the plates plates filled with the porous structure were meshed, it
were characterized by a close fit between the porous was difficult to make a comparative analysis on stress
structure and the solid part after the plates with optimized due to the substantial data size; nevertheless, it was
topology were filled with different units. The porosity, undeniable that the mechanical properties improved
mean pore size, and surface-area-to-volume ratio met the compared with those before filling.
design requirements of the porous structure. The porous 3.5 Assembly of the plates and opening of the
structures generated by different units on the plate met screw holes
the processing requirements. However, by examining We imported the designed biological fixation plates into
the processing risks of plates filled with different porous Materialise Magics and the femur model for simulated
structural units, we found that the maximum diagonal assembly and then conducted a collision test. There was
spacing of the H unit (honeycomb unit) was 1 mm, and its no interference between models, and the fit was good,
shape was approximate to a round hole, which can partly thus satisfying the use requirements. Previously, we did
ascertain the success of processing.
not set threads at the fixed hole position to facilitate the
Furthermore, due to its simple structure, we can simulation analysis; however, it is essential to set threads
guarantee the success of processing by adjusting the in practical application. The screws were designed based
placement mode (perpendicular to the substrate). After on ASTM F543-07 Standard Specification and Test
the plates with optimized topology were filled with R Methods for Metallic Medical Bone Screws, test method
unit, the protrusion of the unit node was 0.8 mm, and the standard, and the actual situation, and screws with a
overhang angle was close to 40°, which suggests a dangerous diameter of 3.5 mm were selected. In Figure 8, the arrows
processing state. Furthermore, the lap joint between pillars indicate the design results. Before the screw hole was set,
was at risk of breakage. After the plates with optimized we closed the holes of the original femur and the femoral
topology were filled with B unit, there was protrusion; plate, imported six screw models, and adjusted the screw
however, the protrusion was small (0.2 mm). The lap joints position to the original hole position of the plate. Boolean
between all units of the porous structure of B unit were subtraction was performed to finish the setting of the
continuous and met the processing requirements. screw hole (Figure 8).

Volume 9 Issue 2 (2023) 124 https://doi.org/10.18063/ijb.v9i2.658