Design and fabrication of elastic two-component polymer-metal disks using a 3D printer under different loads for the lumbar spine

Abstract

One of the significant issues in the biomechanics of the intervertebral discs is the origin of the forces on the spine in the lumbar region. This issue can be gravity and the effects of inertia, muscles, intra-abdominal pressure, fascia, and ligaments. Recently, the 3D printing technique with biocompatible metals is used to strengthen the intervertebral discs. In this study, the three-dimensional printing (3DP) technique was used to fabricate the body of the disc. The prepared disc was multi-component and coated with Hydroxyapatite (HA) bioceramic nanoparticles using the plasma spray technique. To investigate the mechanical properties, the compressive strength test, hardness test, the stress-strain diagram, and the toughness were obtained from mechanical testing. The biological behavior of the disc was investigated in the Simulated Body Fluid (SBF) after 21 days. To characterize HA and coated disc the morphology and phase structure of the surface were evaluated using Scanning Electron Microscope (SEM) and X-ray diffraction (XRD) techniques. The obtained mechanical results of three samples with a metal layer, without metal layer, and metal layer coated with HA nanoparticles were used in the mechanical simulation of the component. The artificial disk is an implant with the ability to maintain movement on the surgical surface, which reduces the side effects of vertebral connection in the destruction of adjacent components. Since the success of using an artificial disk depends on maintaining the mechanical functions of the intervertebral disc, it is useful to study the behavior of the artificial disk under different loads using Finite Element Method (FEM). In this research, the models are evaluated by comparing their behavior with experimental data and FEM data. Then, the elastic modulus and the optimal Poisson ratio were used for the two parts of the nucleus (the central part of the disk) and the annulus (the layers around the nucleus).