Abstract: BACKGROUND: At present, there is still controversy in clinical practice about the choice of internal fixation of Pauwels type III femoral neck fracture, and the selection of internal fixation that provides stable fixation strength is the key basis for achieving Pauwels type III fracture fixation.
OBJECTIVE: The three-dimensional finite element analysis method was used to test the difference in biomechanical strength of three types of internal fixation in Pauwels type III femoral neck fracture, which provided a reference for its clinical treatment.
METHODS: Using the CT data of the left femur of a healthy male volunteer, a complete femur and its cancellous bone were reconstructed in Mimics software, and Geomagic studio software was used for reverse modeling. Cannulated compression screw, dynamic hip screw, and femoral neck system were created in UG-NX software. Three kinds of internal fixation models were assembled on the femur model, and Pauwels type III femoral neck fracture was simulated by Hypermesh software. Finally, Abaqus software was used to carry out finite element experimental analysis to analyze and compare the stress distribution, stress peak, strain, and displacement distribution caused by fixed femoral neck fracture of different internal fixation systems.
RESULTS AND CONCLUSION: (1) The stress of the proximal femur bone mass was mainly distributed in the area below the femoral neck near the fracture end, with the highest stress peak in the dynamic hip screw group and the smallest in the femoral neck system group. (2) The stress distribution of the internal fixation device was mainly concentrated on the screw surface near the fracture line, with the highest stress peak in the femoral neck system group and the smallest in the dynamic hip screw group. (3) The main strain field of the proximal femur bone mass was distributed in the upper surface area where the bone and screw contacted, and the yield strain was the smallest in the femoral neck system group and the largest in the cannulated compression screw group. (4) The main strain field of the internal fixation device model was distributed on the upper surface of the femoral neck screw, with the yield strain being the smallest in the femoral neck system group and the largest in the cannulated compression screw group. (5) The displacement distribution values of femur, proximal bone mass, distal bone block, internal fixation device and internal fixation with the femur as a whole in the three femoral neck fracture internal fixation models decreased gradually from proximal to distal, and the peak displacement of the femoral neck system group was the largest and the lowest in the dynamic hip screw group. (6) The results showed that when the Pauwels type III femoral neck fracture was fixed, the stress distribution of femoral neck system was more uniform, the mechanical conduction characteristics were better, and it was subjected to lower yield strain, higher stress and higher displacement. It has relatively better biomechanical stability and can provide a superior mechanical environment for fracture healing.

Key words: fracture, femoral neck fracture, internal fixation, biomechanics, finite element analysis