Impact of design optimization on cyclic loading performance of novel pedicle screw and comparison with control device: a bilayer model simulation study

This study investigates the fatigue behaviour of a novel pedicle screw design, comparing its performance with a control device using the finite element (FE) method. Pedicle screw-based treatments are standard methods in spinal fusion procedures. However, complications such as screw loosening and breakage occur in both osteoporotic and non-osteoporotic patients, often due to high bone-implant interface stress and fatigue failure. A novel pedicle screw was designed, and its performance was compared with a control device. A cylindrical bone model of human vertebrae was developed with lamina and cortico-cancellous properties, and the screws were assigned properties of medical grade titanium alloy. The outer surfaces of the screw head model were constrained, and a time varying moment simulating clinical conditions was applied at a distance from the screw head. Stress and strain on the bone model, safety factor, life, and fatigue sensitivity on the screws were determined. Results indicate that the von Mises stress on the bone models was reduced for the novel design, and it performed better in terms of life than the control device. The novel design also provided a greater safety factor than the control device, which is likely to improve pedicle screw life. These findings suggest that the novel screw design enhances performance, potentially leading to better patient outcomes. The study offers valuable insights for researchers developing spinal pedicle screws and evaluating their cyclic performance using FE analysis.