[A new exploration and consideration of Type A fracture of distal femur based on finite element biomechanical analysis].

Abstract

<b>Objective:</b> To investigate the changes of internal fixation stress under different angles of interior fracture line and different screw placement modes in the case of A-type distal femoral fracture. <b>Methods:</b> A 24-year-old healthy male volunteer was recruited to collect the right femur data. CATIA V5R21 software produced a 10 mm fracture gap at the external side of the femur 6.5 cm proximal to the joint line and different angle fracture lines were generated on the internal of the femur at the same height. Based on the actual measured dimensions, the three-dimensional (3D) model of the locking plate and screw was reconstructed using CATIA V5R21 software, ignoring the screw surface threads and then the assembly of the internal fixation of the titanium plate, screws and femur was done. All models were meshed using Hypermesh 13.0 software. The assembled 3D model was input into ABAQUS 6.14 to generate a finite element model. Preliminary finite element biomechanical analysis was performed using the four medial fracture line angles and the stress distribution of the internal fixation under the three screw placement modes, and then the analysis was continued after the optimal screw placement method was re-determined. <b>Results:</b> Under an axial loading of 700 N, with the increase of the angle of the fracture line, the stress of the lateral internal fixation gradually increased, and the displacement of the proximal end of the fracture gradually increased. The sequential screw placement method was superior to the leaping screw placement method. The placement of the first screw at the proximal end of the fracture was critical to the distribution of the internal fixation stress. <b>Conclusions:</b> The operation plan of the type A of distal femoral fracture needs to be confirmed according to the internal and external fracture's condition. When the fracture line is at a excessive positive angle or a negative angle, a simple lateral fixation may not provide a stable fracture fixation so that other fixation methods are needed.

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