A Study on Self-tapping Design of Cortical Screw for Orthopaedic Application by Using Finite Element Analysis on Pull-out Strength and Bending Strength

One of the key parameters that determine the performance of the orthopaedic screw is the primary stability such as pull-out strength. The self-tapping flute designs have been adapted to the cortical screw to decrease insertion torque and increase pull-out strength, but the fluted tip resulted in decreasing of the screw strength. Therefore, this research was to study the different designs of the self-tapping screw. This study will use finite element analysis to determine the most appropriate screw design including the number and size of the flute, by the method of pull-out strength and bending strength analysis, before running the mechanical testing to validate the design and finite element analysis results. The analysis was based on the mechanical testing standard for metallic bone screw ASTM F543-17. The flute shape consists of non-fluted, edge fluted, bowl fluted and spiral fluted. The finite element analysis results show that the most appropriate screw designs are with 4 flutes with the size of 3 pitches from the tip, which overall, the bowl fluted is the optimal design for this self-tapping cortical screw which has the most appropriate pull-out strength and bending strength performance.