Biomechanical analysis for the epidural needle insertion

In order to test the hypothesis about reduction in the deformation of the ligamentum flavum due to tension inside the ligamentum flavum, nonlinear finite element (FE) analysis was employed. As a preliminary analysis of natural tissue, nonlinear FE analysis was applied to a rubber plate. Assuming that the rubber is third-order Mooney-Rivlin model, the analysis and the experimental curves overlap with each other until pierced point. The maximum major strain calculated by FE analysis was feasible to predict pierced point. To apply nonlinear FE analysis for the porcine ligamentum flavum, the Mooney-Rivlin coefficient of the porcine ligamentum flavum was identified from the tensile test data. Assuming that the sharp bar pierced the ligamentum flavum when the maximum major strain reached a constant value, the required displacement became shorter by 1.0mm by applying the initial tension.