Analysis of the performance of different screws in the presence of bone density variability.

With the advancement of minimally invasive spinal surgery, pedicle screw fixation is a key approach for spinal disease treatment. However, achieving reliable fixation in osteoporotic bone remains challenging. This study evaluates the pullout performance of eight pedicle screw types across different bone densities using 3D-printed screws and rigid polyurethane foam models. Pullout strength, equivalent force, and maximum deflection were assessed via mechanical testing and finite element analysis. Cement-Augmented (CA) and Expandable (EPS) screws exhibited superior pullout resistance in osteoporosis, while Double Pitch (DP) and Double Threaded (DT) screws performed best in healthy bone, and Double Double Core (DDC) and New Double Threaded (NDT) screws excelled in osteopenia. Finite element results closely matched experimental data, confirming reliability. The findings highlight the significant influence of bone density on screw fixation and provide guidance for clinical selection. Future research will focus on novel screw designs to enhance surgical outcomes.