Comparison of the Pullout Strength of Auxetic Orthopedic Screws

Auxetic metamaterials have attracted increasing attention due to their interesting mechanical properties the most important of which is negative Poisson’s ratio. Since one of the main problems with orthopedic screws is their lack of stability when stretching, auxetic structures may be able to play a key role in making these screws. This structure, when used in the construction of these screws, by applying tensile load, expands radially and resists failure. In this study, in order to compare the effect of auxetic structure on the stability of orthopedic screw, 5 tubular auxetic structures were designed and their Poisson s ratio were calculated using Finite Element Analysis. Then, their tensile strengths were calculated by applying a tensile force using FEM. After that, by creating a thread on these tubular structures, it was screwed and their pullout force was calculated by FEM. In addition to the auxetic structures, a non-auxetic structure was used for comparison. The compared results showed that the use of auxetic structure can increase the pullout fixation strength of orthopedic screws.