Biomechanical evaluation of X-ray permeable CF/PEEK composite versus conventional titanium alloy for tibial external fixation plates: a finite element analysis

This study aimed to evaluate the mechanical performance of CF/PEEK composite plates for external fixation through finite element analysis (FEA), and to explore the impact of different screw placement patterns on fixation stability. A proximal tibial fracture model treated with external fixation was constructed using FEA. Longitudinal loading was applied to simulate walking stress, with additional internal and external rotational torques to mimic load-bearing movement. Mechanical responses of titanium alloy and CF/PEEK plates were compared under three loading conditions: longitudinal, longitudinal with internal rotation, and longitudinal with external rotation. Screw alignment was also varied between linear and non-linear configurations to assess its biomechanical influence. Compared to titanium alloy group, the linear CF/PEEK plate exhibited a mild increase in displacement of 0.232-0.386 mm (8.23-11.14%), accompanied by a substantial reduction in plate stress of 46.03-80.84%. At the fracture site, interfragmentary displacement increased slightly by 0.105-0.132 mm (5.56-6.74%), while fracture-site stress increased by 3.119-18.029 MPa (18.30-63.20%). The non-linear CF/PEEK plate demonstrated a similar biomechanical performance, with no significant differences compared with the linear configuration. For external plate fixation, CF/PEEK represents a promising alternative to conventional titanium alloy plates. By allowing an acceptable level of local micromotion, CF/PEEK plates significantly reduce stress in the plate and screws while increasing stress transfer at the fracture site. This load-sharing behavior may mitigate stress shielding associated with traditional metallic plates and thereby promote early biological fracture healing.