Pullout tests of bone screws have been performed on cadaver bones, animal bones or synthetic bones. These materials have been proven to be poor models from experimental observation, giving results with too much variability or difference. The finite element method was used in this study to evaluate the holding power for bone screws subject to the changes of outer diameter, inner diameter, pitch and radiuses of tip and bottom round corner. The displacement control mode was used in a way that 1 mm displacement was applied on the flatness region of bone screw head and the reaction force was then recorded to simulate the ability of pullout force. Numerical results showed that the patterns of tip corner on the bone screw were a deciding factor on the pullout force of bone screw. This study was significant for establishing a good bone-screw FEM model and suggesting important threaded parameters in selecting or manufacturing a bone screw to increase its holding power.

Bidomain models are commonly used for studying and simulatingelectrophysiological waves in the cardiac tissue. Most of thetime, the associated PDEs are solved using explicit finitedifference methods on structured grids. We propose an implicitfinite element method using unstructured grids for an anisotropicbidomain model. The impact and numerical requirements ofunstructured grid methods is investigated using a test casewith re-entrant waves.