Session: Research Posters

Paper Number: 112314

112314 - Finite Element Analysis of 3D Printed Stand-Alone Transforaminal Lumbar Interbody Fusion Cages Under Various Loadings 

With the development of material science and engineering, spinal biomechanics and the wide application of interbody fusion, lumbar interbody fusion cages have developed rapidly to treat severe spine diseases. The traditional metal lumbar interbody fusion cage would cause stress shielding and bone remodeling because of their relatively high Young’s modulus compared to natural bone. Therefore, titanium alloy lumbar fusion has been gradually replaced by Polyether-ether-ketone (PEEK) fusion cage in recent years. PEEK exhibits excellent biocompatibility and is X-ray penetrable compared to Titanium alloy. At the point of mechanical properties, the elastic modulus of PEEK fusion device is 3.5GPa, which is close to the cortical bone to avoid stress shielding. Furthermore, carbon fiber reinforced PEEK (CFR-PEEK) interbody fusion cages have been developed, exhibiting the stable mechanical properties under physiological environment. Moreover, the strength and elastic modulus of CFR-PEEK cages can be optimized based on the weight percentage of carbon fiber in the polymer matrix. 

Various manufacturing techniques can be adapted to produce lumbar cages. The traditional lumbar fusion cage is made of titanium alloy and is usually cast or forged. Because titanium has high chemical activity at high temperature and may be polluted by oxygen, nitrogen, carbon, and other elements, the processing and manufacturing process of titanium alloy is highly demanding, not to mention mold development is costly. For CFR-PEEK and PEEK cages, conventional manufacturing methods such as injection molding are not allowed to produce the challenging cage designs due to the high melting point of PEEK. PEEK and CFR-PEEK cages are usually machined from bulk material, which causes large number of material loss. Compared to the above manufacturing techniques, additive manufacturing, also called 3D printing technology, is an effective technology for rapid prototyping and medical device production. Moreover, 3D printing technology can overcome the issues of conventional fabrication approaches and allow for the fabrication of controllable structures with desired porosity, pore size, architecture, and etc.

This study investigated the mechanical properties of TLIF cages produced by traditional method and 3D printing technology using finite element analysis (FEA) under five different body motions, including standing, lifting objects, lifting objects & forward bending, lateral bending, and forward bending. Stress analysis of traditional titanium alloy Ti-6Al-4V cage, 3D printed Polyetheretherketone (PEEK) TLIF cage, and 3D printed porous carbon fiber reinforced Polyetheretherketone (CFR-PEEK) with various infill densities by FEA showed the mechanical properties of 3D printed CFR-PEEK solid cage is comparable to Ti-6Al-4V cage with maximum Von-Mises stress of 12.391 MPa, total deformation of 0.0029257 mm under the ‘standing’ condition with a 1000N axial compressive force. The minimum factor of safety (SF) for Ti-6Al-4V cages are above 15 under all postures, while 3D printed PEEK solid cages under some postures are not reliable with a SF smaller than the recommended value of 2.0. On the other hand, SF for 3D printed CFR-PEEK porous cages was above 2.0 with an infill density 50% and above, demonstrating that 3D printed CFR-PEEK would be an excellent candidate for the lumbar cages.

Presenting Author: Minjae Kang California State University Fullerton

Presenting Author Biography: Minjae Kang is an undergraduate student at California State University, Fullerton. His research interests include advanced manufacturing of artificial tissues and organs and biomechanics.

Authors:

Yufei Zhang California State University Fullerton
Minjae Kang California State University Fullerton
Siheng Su California State University Fullerton