Page 464 - IJB-9-5

International Journal of Bioprinting 3D-printed oblique lumbar interbody cage

studies report that 3D printing techniques have great 5. Conclusion
potential to solve the problems of creating a porous A new OLIF cage with embedded fixation screws was
(lattice) surface coating on dense titanium and a porous designed by integrating the FE and WTO analysis
titanium body [10-12,27,28] . Therefore, this study utilized based on statistical results of endplate morphology. The
metal 3D printing to manufacture our OLIF cage to simulated results showed that the embedded screw fixation
perform functional tests. Our 3D printer laboratory was can improve the stability of the OLIF cage and decrease
approved by the ISO13485 quality management system endplate damage. The OLIF cage with lattice manufactured
(Certificate Number: 1760.190828) to ensure that the via metal 3D printing was subject to mechanical testing,
implants meet the necessary regulations and to ensure and we found that the dynamic axial compression and
safety and quality.
compressive-shear tests exceeded FDA-recommended
The stiffness measured under axial load was 16,658 N/ values by about two times. However, the edge design of the
mm, and the endurance limit after 5 million dynamic tests OLIF cage must undergo further improvements to increase
was 6000 N [26,29,30] . These values were more than double the resistance against dynamic strength.
minimum battery of performance testing necessary for
stiffness at 7690 N/mm and endurance limit at 3000 N as Acknowledgments
recommended by the FDA. However, it was prone to cracks
at edge of the cage under 6000 N of cyclic force, suggesting Authors would like to thank Microware Precision Co., Ltd,
that the cage had insufficient support strength at the edge. Taiwan for their assistance in cage and screw manufacture.
It may be necessary to increase the edge wall thickness Funding
of the cage to enhance strength and maintain tissue
permeability and bone growth range. Post-processing can This study is supported in part by MOST project 109-2622-
also be considered to improve the lack of toughness in B-010-005 and 110-2221-E-075-004, Taiwan.
metal 3D printing.
Conflict of interest
The OLIF cage was not deformed, damaged, or
cracked when the testing force reached the upper limit The authors declare no conflicts of interest.
of the machine capability of 24,000 N during the static
compressive-shear test. Therefore, this value (24,000 N) Author contributions
was denoted as the ultimate compressive-shear strength. Conceptualization: Po-Liang Lai, Chun-Li Lin
This was higher than 95% of the vertebral cage strength Investigation: Shao-Fu Huang, Hsuan-Wen Wang, Pei-
values reported in the literature [26,29,30] . The corresponding Hsin Liu
stiffness can also be obtained as 19,643 N/mm, which is Methodology: Shao-Fu Huang, Hsuan-Wen Wang, Pei-
more than 8.85 times the FDA-recommended value of Hsin Liu
2219 N/mm. For the shear fatigue test, the OLIF cage Resources: Po-Liang Lai, Chun-Li Lin
was prone to damage on the anterior edge during the Writing – original draft: Po-Liang Lai
dynamic high-strength fatigue compression-shear test Writing – review & editing: Chun-Li Lin
above 3500 N. This phenomenon was consistent with the
results of the aforementioned dynamic axial compressive Ethics approval and consent to participate
test, implying that the cage edge thickness may need to
be improved. The endurance limit was at 2600 N for the Not applicable.
compressive-shear dynamic test, which is double the FDA-
recommended limit of 1225 N . Consent for publication
[26]
The embedded screws were not considered during Not applicable.
the compression/compressive-shear tests, which were
conducted in accordance with the ASTM 2077 regulations Availability of data
recommended by the FDA . The results of this test are Not applicable.
[26]
comparable to the recommended minimum battery
performance of the benchmark under the same testing References
conditions. Nevertheless, it may be necessary to perform
in vivo animal experiments in the future to evaluate the 1. Orita S, Inage K, Furuya T, et al., 2017, Oblique lateral
fixation ability of embedded bone screws and the bone interbody fusion (OLIF): Indications and techniques. Oper
growth ability within cage lattices. Tech Orthop, 27(4): 223–230.

Volume 9 Issue 5 (2023) 456 https://doi.org/10.18063/ijb.772