Biomechanical comparison of triangle supporting fixation system and Gamma nail fixation in the treatment of intertrochanteric fractures of the femur: finite element analysis / 中华骨科杂志

ABSTRACT

Objective:To compare the biomechanical properties of triangular supporting fixation and Gamma nail fixation for intertrochanteric fractures of the femur.Methods:The femoral CT imaging data provided by a healthy adult male volunteer aged 40 years, height 172 cm, and weight 75 kg were used to reconstruct the femur model using Mimics 21.0 software and Geomagics 2013 software. Evans type I intertrochanteric fracture models were established using UG12.0 software, and Gamma nail and triangular supporting intramedullary nail models were reconstructed to simulate intertrochanteric fracture internal fixation, respectively. In Abaqus software, two internal fixation models of Gamma nail and triangular supporting intramedullary nail in standing state are simulated, and the stress peaks of the main nail, fixation screw and bone substance were collected, also the stress peak of supporting screw of the triangular supporting intramedullary nail is obtained. Additionally, the maximum displacement of the fracture model fixed by Gamma nail and triangular supporting intramedullary nail is measured.Results:Under the load of 1 200 N, the peak stress of the two fracture internal fixation models was located in the main nail, in which the peak stress of the triangular supporting intramedullary nail was 233.73 MPa, which was 11.9% lower than that of the Gamma nail (265.21 MPa); the peak stress of the fixation screw was located in the contact area between the pressure screw and the main nail, which was 23.2% lower in triangular supporting intramedullary nail than that of the Gamma nail (138.86 MPa vs. 180.75 MPa); the peak stress of the bone model was located in the medial cortex of the femur, which was 61.67 MPa and 32.38 MPa, respectively, 47.5% lower in the triangular supporting intramedullary nail than that of the Gamma nail; the peak stress of the supporting screw in the triangular supporting intramedullary nail was 92.04 MPa. The maximum displacement of the fracture model fixed with triangular supporting intramedullary nail was 17.34 mm, which was 10.5% less than the maximum displacement of the fracture model fixed with Gamma nail (19.37 mm). Conclusion:Compared with Gamma nail, triangular supporting intramedullary nail fixation can significantly improve the stability of intertrochanteric fractures and stress distribution as well as reduce stress peak and stress concentration area, which is helpful to improve the efficacy of intertrochanteric fractures.