How to choose the suitable FNS specification in young patients with femoral neck fracture: A finite element analysis

Background: Consensus regarding the optimal approach for the treatment of femoral neck fractures remains lacking. A new internal fixation femoral neck system (FNS) was developed and used in clinical practice. We aimed to investigate the biomechanical outcomes of different types of FNS in the treatment of unstable femoral neck fractures. Method: In this study, we constructed three different types of unstable femoral neck fractures of Pauwels classification with angles of 50 degrees, 60 degrees, and 70 degrees. We set up four test groups, namely, the one-hole plated FNS group, two-hole plated FNS group, inverted cannulated screw group and triangle cannulated screw group. Under 2100 N axial loads, displacements and the von Mises stress of the femur and internal fixation components were measured for each fracture group. Results: When the Pauwels angle was 50 degrees or 60 degrees, the one-hole locking plated FNS was as superior as the two-hole plated FNS in terms of femur and internal fixation displacement, and the inverted cannulated screw had slightly better stability than the triangular cannulated screw. However, when the angle increases to 70 degrees, the two-hole locking plate has the minimum displacement, followed by the triangular cannulated screw and inverted cannulated screw, which is the worst displacement for the single-hole locking plate. Regardless of the angle, the two sets of FNS have higher internal fixation stress than the two sets of cannulated screws, which is approximately 1.6-3.0 times that of the cannulated screw group. Conclusion: From the perspective of biomechanics, we suggest that when the angle of the fracture line is less than 60 degrees, both single-hole locking plated or double-hole locking plated FNS can be used to treat unstable femoral neck fractures. However, when the angle of the fracture line is greater than 70 degrees, we recommend using a double-hole locking plated FNS. This result needs further verification in further clinical studies. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

The optimal approach for the treatment of femoral neck fractures remains debated. A new internal fixation femoral neck system (FNS) was developed and tested for biomechanical outcomes in unstable fractures. Results indicate that single-hole or double-hole locking plated FNS can be used for fractures with angles less than 60 degrees, while a double-hole locking plated FNS is recommended for angles greater than 70 degrees.