Lomber omurga sonlu eleman model çalışması ve lomber dinamik stabilizasyon sistemi analizi

Finite element (FE) method is a reliable analysis tool in mechanical engineering as well as in other fields such as electronics and thermodynamics. The use of FE models in biomechanics increased in last couple of decades, particularly in spine biomechanics, largely due to better computational resources available. However, development of spine FE model is a cumbersome and non-trivial task, owing to the complex geometry of the spinal segments. FE models have been used to produce general behaviors of the musculoskeletal systems with almost all physiological and anatomical features. The main objective of the present thesis is to develop accurate FE models of the human lumbar and thoracic spine. Lumbar FE models are particularly important for the clinicians as well as academicians. It is because low back pain constitute as the most prevalent disease of spine. A novel method was suggested in this thesis to construct an integrated interface between the discs and the vertebrae. The exact geometry was obtained from CT scan data. Multi-block method was used to place nodes over the vertebrae and intervertebral disc surfaces, and hexahedral element was used to mesh the discs and vertebrae. Truss elements were used to simulate the ligaments. Facet joints were simulated by unidirectional gap elements. Material properties were assigned to spinal components using the values from the literature. Pure moments were applied to a flying node which was coupled with top surface of first vertebrae. Lower part of last vertebrae in each model was constrained in all directions. The predicted motion response of FE model was compared with the published in vitro studies in all motion planes and found to be in good agreement. The validated FE model was used to study the biomechanical parameters of the lumbar spine in intact and instrumented cases. Various designs of instruments were applied to both the thoracic and the lumbar models. The effect of the instruments on the kinematic, i.e. range of motion (ROM), and kinetic, i.e. intradiscal pressure (IDP), facet load (FL), and ligament stress (LS), parameters of the lumbar spine and the thoracic spine were investigated. The lumbar instruments included posterior dynamic stabilization (PDS), fusion, interspinous fusion, and pedicle screws with spring rods. Design modifications were suggested after comparing the biomechanical behavior of the instrumented models with intact models.