Features of approximation of finite-element models of transpedicular spinal fixation and their computational efficiency

The work investigates the method of transpedicular fixation (TPF), which is widely used at present in the surgical treatment of various spinal pathologies. The technique allows for correction of deformations and stabilization of the spinal column, while the layout and extent of the metal structure are determined by the nosology and preferences of the surgeon. Biomechanics methods, including computer modeling and numerical calculations, were used to assess the stress-strain state of one of the TPF variants. The purpose of the study was to conduct a comparative assessment of the simplified PTK model with the results of standard modeling, and to substantiate the validity of the proposed approximation method for further scientific research. The main objective of the study was to create three-dimensional models of spinal-motor segments and the transpedicular system (TPS), followed by the calculation of their stress-strain state under compression load using the finite element method (FEM). The simulation was performed in SolidWorks Simulation using static analysis to determine stresses and deformations. The study examined a biomechanical model of the lumbar (L1–L5) spine of a patient at the Scientific Research Institute of Traumatology, Orthopedics and Neurosurgery of the Saratov State Medical Uni-versity named after V.I. Razumovsky. Special attention is paid to the balance between the accuracy of the geometric representation of the model and computational efficiency, as well as possible errors associated with sampling and approximation. The results of the study showed that the maximum equivalent stresses arising from a 400 KN load on the lumbar spine in a solid-state non-polygonal model exceed the stresses in the polygonal model by no more than 7–10 %, which is sufficient to assert the possibility of estimating the VAT of spinal segments using a simplified model.