Despite the significant advancements in intervertebral disc prostheses in recent years ^[1], they remain, to this day, the least favored medical solution among surgeons and the least appreciated by patients for treating damaged discs ^[2]. The current prostheses are still unable to accurately replicate several fundamental mechanical properties of the natural disc, such as auxeticity, energy absorption, and nonlinear stiffness ^[3]. This inability prevents them from mimicking correctly the natural mechanical behavior of the disc, adversely affecting the post-operative health and well-being of patients. To address these challenges, the current study explores novel bioinspired lattice-based polymeric architected structures, designed to mimic the complex mechanical behavior of the human annulus fibrosus. New cellular structures are developed to introduce complex mechanical functionalities into the lattices, whose performance is investigated using different polymers (hydrogels such as poly(ethylene glycol) diacrylate, alginate and gelatin methacrylate, and soft thermoplastics such as thermoplastic polyurethane and polylactide) to assess the coupled influence of cellular architecture and material microstructure. By tailoring cellular geometry, thickness, and material, these structures can reproduce nonlinear stiffness and axial-circumferential behaviors, including regional variations observed in natural discs. This precise control leads to sophisticated behaviors that conventional prostheses cannot achieve. The first derived replacement systems succeeded in replicating key mechanical characteristics of the natural annulus fibrosus, including auxeticity, nonlinear stiffness and region-dependent responses. These biomimetic lattices provide a promising pathway for the development of personalized, high-performance disc prostheses.

References:
1. Song, Guangsheng, et al. "Total disc replacement devices: Structure, material, fabrication, and properties." Prog. Mater. Sci. (2023): 101189.
2. Zechmeister, Ingrid, et al. "Artificial total disc replacement versus fusion for the cervical spine: a systematic review." Eur. Spine J. 20 (2011): 177-184.
3. Kandil, Karim, et al. "A novel bio-inspired hydrogel-based lattice structure to mechanically mimic human annulus fibrosus: A finite element study." Int. J. Mech. Sci. 211 (2021): 106775.