Evaluation of a cloverleaf screw head to minimize the slippage of medical screws

Abstract

Slippage occurs when a screw cannot be driven because the user’s power or torque is not transmitted due to plastic deformation of the screw head socket or driver tip. In this study, we evaluated a new cloverleaf-shaped screw head to minimize the slippage of medical screws. L-clover and S-clover heads were selected as new candidates and compared with triangular, Torx®, and hexagonal screw heads. For each head, the polar moment of inertia was calculated, the stress distribution was analyzed using a finite element method, and torsion tests of physical specimens were performed to analyze their slippage characteristics. The hexagonal head, which is used most commonly in medical screws, had the lowest resistance to slippage. However, the L-clover head had the best features for minimizing the slippage of medical screws.