Abstract: BACKGROUND: Pauwels type III femoral neck fractures may be subjected to more shear and bending forces, and may be prone to complications such as internal fixation failure, bone nonunion, or femoral head necrosis. There is no consensus on the optimal selection of internal fixation devices.
OBJECTIVE: To compare the biomechanical properties of four types of internal fixation methods for Pauwels type III femoral neck fracture by finite element analysis
METHODS: Femur CT data of a healthy young volunteer were imported into Mimics software to construct a three-dimensional model of normal femur. Pauwels type III femoral neck fracture was simulated based on 70° fracture line. Four types of fracture internal fixation models were optimized and constructed using Geomagic and UG software: conventional inverted triangle hollow screw, femoral neck fixation system, femoral neck fixation system plus anterior or posterior hollow screw treatment. Finally, Ansys software was used to analyze the stress distribution, peak stress, and peak displacement of proximal femur fracture block in four types of different internal fixation models. The displacement distribution and peak displacement of internal fixation device and femoral neck fracture were observed. 
RESULTS AND CONCLUSION: (1) The peak stress of proximal fracture fragments in the four groups was concentrated near the fracture line. The peak stress in the femoral neck fixation system group was the largest, and that in the conventional inverted triangle hollow screw group was the smallest. (2) The peak displacement of fracture fragments was located at the top of the femoral head. The peak displacement of the conventional inverted triangle hollow screw group was the largest, and that in the femoral neck fixation system + hollow screw (posterior) group was the smallest. (3) The peak displacement of the internal fixation model was located at the top of the model. The peak displacement was maximum in the conventional inverted triangle hollow screw group and minimum in the femoral neck fixation system + hollow screw (posterior) group. (4) The displacement of the fracture surface in the femoral neck fixation system + hollow screw (posterior) group was at the upper part of the fracture end. The peak displacement was the largest in the conventional inverted triangle hollow screw group and the smallest in the femoral neck fixation system + hollow screw (posterior) group. (5) It is indicated that compared with the other three internal fixation methods, femoral neck fixation system + hollow screw (posterior) group showed good biomechanical stability. When Pauwels type III femoral neck fracture occurs in a young person, from the point of view of finite element analysis, it may be a more favorable choice to treat the Pauwels type III femoral neck fracture.

Key words: femoral neck fracture, femoral neck fixation system, hollow screw, Pauwels type III fracture, finite element analysis, biomechanics