İnsan omurga biyomekanik sonlu elemanlar metodu uygulaması

Since its development in the mid 20th Century, the finite element (FE) method has shown to be a reliable tool, not only in mechanical engineering, but also in other fields such as electronics, or thermodynamics. In biomechanics, the principles of continuum mechanics and constitutive equations so far successfully applied to plastics, metals, and rubbers, have demonstrated their potential to reproduce general behaviors of the musculoskeletal system, when coupled to finite element models. The main of goal of the present thesis is to develop accurate FE models of the human cervical and the lumbar spine. A novel method was suggested to construct an integrated interface between the discs and the vertebrae. Hexahedral element was used to mesh the discs and vertebrae. Truss elements were used to simulate the ligaments. The exact geometry was obtained from CT scan data. All the main features of the human spine were modeled; vertebrae, intervertebral discs, and ligaments. Pure moments were used in simulations and lower part of each models were constrained in all directions. The predicted motion responses of both models were compared with the published in vitro studies in the literature and they were in good agreement. The effect change in the geometry of the cervical spine on the biomechanical parameters was studied. An FE model with the symmetry assumption in the mid-sagittal plane was developed using the CT data similar to the accurate cervical model. The reason to use such assumption is the numerous FE models in the literature symmetry approximation. The comparison of the biomechanical parameters showed that the symmetric model produces reasonable results and using the symmetry assumption reduce the modeling time. Different types of instruments were applied to both the cervical and the lumbar models. The effect of the instruments on the kinematic, range of motion (ROM), and kinetic, intradiscal pressure (IDP), facet load (FL), and ligament stress (LS), parameters of the cervical and the lumbar spine were investigated. The instruments included total disc replacement (TDR), posterior dynamic stabilization (PDS), fusion, interspinous fusion, and sacroiliac wings. Design modifications were suggested after comparing the biomechanical behavior of the instrumented models with intact models.