Objective:This study examines the biomechanical stability of distal tibial epiphyseal injuries in children, focusing on the influence of fracture fragment size and fixation. Methods:A three-dimensional finite element model of a Salter-Harris II (SH-II) epiphyseal injury was constructed using computed tomography (CT) data from the lower limb of a 10-year-old volunteer. Fracture fragments of varying sizes were simulated, and bone-internal fixation assemblies were created with 1-3 screws and metal bone pins. The model was subjected to gravitational forces, posterior drawer forces, and external rotation. Displacement and stress distributions across fracture fragments and fixation devices were analyzed. Results:Maximum displacement in each model was primarily localized at the distal end of the fracture fragment. Screw fixation produced similar overall displacement across models, with larger fragments showing significantly lower displacement than smaller fragments. Increasing screw count enhanced fixation stability and distributed local bone stress more effectively. Compared to screws, Kirschner wire fixation exerted less stress on the epiphyseal plate, with screws generating higher stress at the epiphyseal plate and fracture line, while Kirschner wires concentrated stress along the plate’s edge. Conclusions: In treating distal tibial epiphyseal fractures in children, ensuring sufficient connection area between the fracture fragment and epiphyseal plate is critical when using screws. Kirschner wire fixation offer biomechanical advantages over screw fixation.