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. 2024 Sep 20;10(18):e38209.
doi: 10.1016/j.heliyon.2024.e38209. eCollection 2024 Sep 30.

Design and study of additively manufactured Three periodic minimal surface (TPMS) structured porous titanium interbody cage

Kun Li  1 , ChunYan Tian  1 , QiuJiang Wei  1 , XinRui Gou  1 , FuHuan Chu  1 , MengJie Xu  1 , LinHui Qiang  1   2   3 , ShiQi Xu  1   2   3
Affiliations

Design and study of additively manufactured Three periodic minimal surface (TPMS) structured porous titanium interbody cage

Kun Li et al. Heliyon. .

Abstract

Objective: TPMS porous structures have adjustable stiffness, a smooth surface, and highly connected pores, which help avoid stress concentration within the dot-matrix structure and promote cell adhesion and proliferation. A cervical interbody cage based on this type of porous structure was designed and fabricated, and its mechanical properties and biocompatibility were evaluated.

Methods: TPMS porous structures have adjustable stiffness, a smooth surface, and highly connected pores, which help avoid stress concentration within the dot-matrix structure and promote cell adhesion and proliferation. A cervical interbody cage based on this type of porous structure was designed and fabricated, and its mechanical properties and biocompatibility were evaluated.

Results: The volume fraction of the 3D-printed TC4-based Tubular-G structure was linearly related to compressive strength. Adjusting the volume fraction resulted in a Tubular-G structure with a modulus and yield strength similar to human bone, without stress concentration within the structure. The designed and fabricated TC4-based Tubular-G porous cervical interbody cage demonstrated excellent anti-sagging properties and biocompatibility.

Conclusions: The volume fraction of the 3D-printed TC4-based Tubular-G structure was linearly related to compressive strength. Adjusting the volume fraction resulted in a Tubular-G structure with a modulus and yield strength similar to human bone, without stress concentration within the structure. The designed and fabricated TC4-based Tubular-G porous cervical interbody cage demonstrated excellent anti-sagging properties and biocompatibility.

Keywords: 3D printing; Cervical interbody cage; Three periodic minimal surfaces; Tubular-G.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Image 1
Graphical abstract
Fig. 1
Fig. 1
Offset parameter versus volumetric fraction.
Fig. 2
Fig. 2
Measurement of the pore size.
Fig. 3
Fig. 3
20 %, 30 %, 50 %, and 70 % volume fractions after 4∗4∗4 array Tubular-G.
Fig. 4
Fig. 4
3D printed Tubular-G structures in four volume rates, from left to right, 20 % volume fraction, 30 % volume fraction, 50 % volume fraction, and 70 % volume fraction.
Fig. 5
Fig. 5
The body-centered cubic structure.
Fig. 6
Fig. 6
Four cage models: (a): Type A cage; (b): Type B cage; (c): Type C cage; (d): Type D cage.
Fig. 7
Fig. 7
Mechanical testing of cervical interbody cage; (a): Static compression of cervical interbody cage; (b): Sinking experiment of cervical interbody cage.
Fig. 8
Fig. 8
Compressed image of Tubular-G structure at 50 % volume fraction.
Fig. 9
Fig. 9
Image of equivalent modulus of elasticity and yield stress with respect to relative density; (a): Ashby's formula for relative density versus Young's modulus; (b): Ashby's formula for relative density versus yield strength.
Fig. 10
Fig. 10
Stress contour plots of the five models under peak load. (a) Tubular-G structure with 20 % volume fraction; (b) Tubular-G structure with 30 % volume fraction; (c) Tubular-G structure with 50 % volume fraction; (d) Tubular-G structure with 70 % volume fraction; (e) Body-centered cubic structure; (f) Connecting points of the Body-centered cubic structure.
Fig. 11
Fig. 11
Titanium interbody cage made by 3D printing; (a): Cervical interbody cage with 20 % volume fraction Tubular-G structure, from left to right, Types A, B, C, D of the design in 2.5, respectively; (b): Cervical interbody cage with 30 % volume fraction Tubular-G structure, from left to right, Types A, B, C, D of the design in 2.5, respectively.
Fig. 12
Fig. 12
Stiffness and yield load of the cervical interbody cage; (a): Stiffness; (b): Yield Load.
Fig. 13
Fig. 13
Compression curves of the cervical interbody cage; (a): 20-A; (b):30-A.
Fig. 14
Fig. 14
Load-displacement curves of the two types of cervical interbody cages and the polyurethane block.
Fig. 15
Fig. 15
Cell attachment to the cage; (a) 20-A cage; (b) 30-A cage.
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