Finite element comparative analysis of three different internal fixation methods in the treatment of Pauwels type III femoral neck fractures

Background: Comparison of 4 cannulated lag screws (3 inverted triangular cannulated screws + anti-rotating screws;4 CLS), dynamic hip screws + derotational screws (DHS + DS), and femoral neck fixation system (FNS) in the treatment of Biomechanical properties of middle-aged Pauwels type III femoral neck fractures. Methods: The femur CT data of a healthy young volunteer was selected and imported into Mimics software to construct a three-dimensional model of a normal femur. Pauwels type III femoral neck fractures were simulated according to the 70 degrees fracture line. Use Geomagic and SolidWorks software to optimize and build CLS, DHS + DS, and FNS fracture internal fixation models. Finally, Ansys software was used to analyze the stress distribution, peak value, and maximum displacement of the proximal fracture fragment and internal fixation; the displacement distribution, and peak value of the fracture surface at the fracture end. Results: (1) The stress peaks of the proximal fracture fragments in the three groups were concentrated near the femoral calcar. The peak stress of the FNS group was the largest, and the DHS + DS group was the smallest.(2)The displacement of the fracture fragments was all located at the top of the femur. The peak displacement of the FNS group was the largest, and the DHS + DS group was the smallest.(3) The internal fixation stress of the three groups is concentrated in the middle part of the device. The stress distribution of the first two groups of models is more uniform than that of FNS. The peak stress of FNS is the largest and the CLS is the smallest.(4) The internal fixed displacements are all located at the top of the model. The peak displacement of the CLS is the largest, and the DHS + DS is the smallest. (5) The displacement of the fracture surface is in the upper part of the fractured end. The peak displacement of the FNS group was the largest, and the DHS + DS group was the smallest. Conclusion: Compared with the other two internal fixation methods, dynamic hip screw + derotational screw (DHS + DS) showed good biomechanical stability. When Pauwels type III femoral neck fracture occurs in young adults, DHS + DS can be given priority as the preferred treatment for this type of fracture.