Abstract: BACKGROUND: The biomechanical stability of basal femoral neck fracture is poor, and the treatment plan is different from the traditional femoral neck fracture. At present, there is still no consensus on the surgical plan for the treatment of basal femoral neck fracture in young adults.
OBJECTIVE: To compare the biomechanical characteristics of proximal femoral nail antirotation and femoral neck system in the treatment of basal femoral neck fractures by finite element analysis.
METHODS: First, Mimics Medical 21.0 software was used to extract the right femur CT data of healthy young female volunteers to establish a preliminary model. Secondly, the model was imported into Geomagic Wrap 2021 software for further smoothing. SOLIDWORKS 2021 software was used to establish and assemble the femoral neck base fracture model, proximal femoral nail antirotation model, and femoral neck system model. Finally, the assembled model was imported into Workbench 2021 R1 software for biomechanical analysis. 
RESULTS AND CONCLUSION: (1) Stress distribution: the stress distribution of the proximal femoral nail antirotation group was mainly near the fracture line and the medial side of the femur, and the peak stress was 151.90 MPa. In the femoral neck system group, the stress distribution of the femoral model was mainly near the fracture line, and the peak stress was 290.74 MPa. The proximal femoral nail antirotation internal fixation stress was mainly distributed at the proximal end of the helical blade and the main nail, and the peak stress was 102.95 MPa. The stress distribution of internal fixation in femoral neck system mainly extended to both sides of the support rod, and the peak stress was 184.69 MPa. (2) Total displacement: the maximum displacement of the femoral model in the proximal femoral nail antirotation group was 4.032 3 mm, and the maximum displacement of the femoral model in the femoral neck system group was 4.648 9 mm. The maximum displacement was located in the femoral head. The peak displacement of internal fixation in the proximal femoral nail antirotation group and the femoral neck system group was 2.709 4 mm and 3.130 3 mm, respectively. The displacement of internal fixation in the two groups was mainly concentrated in the proximal end of internal fixation, and gradually decreased to the distal end. (3) It is concluded that in the femoral neck base fracture model, whether it is the femoral model or the internal fixation model, the proximal femoral nail antirotation group has more dispersed stress distribution, lower stress peak, smaller femoral head displacement, and better biomechanical stability than the femoral neck system group.

Key words: fracture at the base of the femoral neck, finite element analysis, proximal femoral nail antirotation, femoral neck system, biomechanics