Biomechanical study of pedicle screw construct and locking compression plate fixation for the treatment of posterior pelvic ring injuries: A finite element analysis

Abstract

Objective The pedicle screw construct and locking compression plate have been clinically investigated for the treatment of posterior pelvic ring injuries. However, few studies are available that evaluate the biomechanical performance of these two pelvic fixation techniques. The aim of this study was to compare the construct stability, model displacement and stress distribution of two implants with a finite element (FE) method. Methods A three-dimensional FE model of spine-pelvis-femur complex with ligaments was reconstructed from computed tomography images. The unstable posterior pelvic ring injury was created, which was fixed with the pedicle screw construct or locking compression plate. A follower load of 400 N was applied to the upper surface of the vertebrae to simulate upper body weight, while the ends of the proximal femurs were fixed. Results The construct stiffness of the pedicle screw model was 2 times that of the plate fixation. The maximum displacement of the pedicle screw model decreased by 51.2% compared with the plate fixation. The peek stresses of the implant and pelvis in the pedicle screw model decreased by 80.4% and 25% when compared with the plate model (44.57 MPa and 34.48 MPa in the pedicle screw model, and 227.47 MPa and 45.97 MPa in the plate model). Conclusions The study suggested that the pedicle screw construct could provide better fixation stability compared with locking compression plate, and serves as the recommended fixation method for the treatment of posterior pelvic ring injuries.