3D-printed auxetic-structured intervertebral disc implant for potential treatment of lumbar herniated disc

In this study, a novel artificial intervertebral disc implant with modified “Bucklicrystal” structure was designed and 3D printed using thermoplastic polyurethane. The new implant has a unique auxetic structure with building blocks joined “face-to-face”. The accompanied negative Poisson’s ratio enables its excellent energy absorption and stability under compression. The deformation and load distribution behavior of the implant under various loading conditions (bending, torsion, extension and flexion) has been thoroughly evaluated through finite element method. Results show that, compared to natural intervertebral disc and conventional 3D implant, our new implant exhibits more effective stress transfer and attenuation under practical loading conditions. The implant's ability to contract laterally under compression can be potentially used to alleviate the symptoms of lumbar disc herniation. Finally, the biocompatibility of the implant was assessed in vitro and its ability to restore the physiological function of the disc segment was validated in vivo using an animal model. An auxetic scaffold with uniquely modified “Bucklicrystal” structure prepared by 3D printing, which can effectively alleviate lumbar disc herniation (LDH) due to auxetic effect. The superior mechanical properties (stress distribution, stiffness, strength, energy absorption and dissipation), biocompatibility and potential to restore the disc physiological functions been proved by FEA, in vitro and in vivo studies. [Display omitted] •Auxetic-structured IVD implant features negative Poisson's ratio (NPR) behavior.•Modified “Bucklicrystal”structure exhibits better energy absorption and stability.•The stress effectively and evenly transfers/attenuates in the auxetic implant.•Auxetic implant potentially alleviates the symptoms of lumbar disc herniation.