Finite element analysis of the three and four cannulated screws for Pauwels III femoral neck fractures / 中国组织工程研究

ABSTRACT

BACKGROUND:Femoral neck fracture is mainly fixed by three inverted triangle cannulated screws. Scholars have proposed to add a cannulated screw to enhance the fixation strength of femoral neck fracture of Pauwels III type based on three cannulated screw fixation, but the stability is not verified. OBJECTIVE:To analyze the biomechanical stability and stress of the three and four cannulated screws for the treatment of the Pauwels III femoral neck fractures. METHODS:The CT imaging results of the fourth generation of artificial bone sawbones were imported into the Mimics software wherein a three-dimensional finite element model of the proximal femur was prepared and introduced in the 3-matic software. Models of middlesegment of femoral neck with Pauwels III fractures were established. Cannulated screw models were established with UG 8.0 software and introduced in the fractures models. Finally, finite element models of Pauwels III femoral neck fractures fixed with three and four screws were established. In the same condition, an axial load of 411 N was applied on the femoral head with Abaqus software. The displacement of two markers of the broken ends and internal fixation system Von Mises stress distribution were compared between the two models. RESULTS AND CONCLUSION:(1) The displacement was 0.42 mm in three screws model, and 0.17 mm in the four screws model. (2) Von Mises stress peak was 547 MPa and 27.8 MPa in both models. The peak value was lower in models of fourscrews than that of three screws. Stress concentration position was at the fracture site in both models. The stress range of models of four screws was more extensive and scattered. (3) Finite element analysis results demonstrated that four-screw implantation for Pauwels III femoral neck fractures had strong anti-shearing force and biomechanical stability. Clinical advantages need further clinical comparative study.