Biomechanical evaluation of femoral neck system versus non-sliding fixation in the treatment of young patients with Pauwels type III femoral neck fractures: a finite element analysis.

Objective: This study aimed to compare the biomechanical performance of the femoral neck system (FNS) and four cannulated screws (FCS) on treating young patients with Pauwels type III femoral neck fractures.

Methods: The model of a young Pauwels type III femoral neck fracture with 70° inclination, FNS, and FCS were established, and the fixations were set up. Under an axial load of 2100 N, the finite element anaysis was performed, and the shear force distribution, von Mises stress (VMS), and displacement of each group of models were recorded to analyze the biomechanical effects.

Results: The FNS group exhibited localized shear stress, with a peak value of 181.96 MPa, whereas the FCS group displayed a more dispersed shear stress distribution. In the FCS group, the maximum shear stress values were 71.21 MPa, 66.65 MPa, 59.22 MPa, and 84.23 MPa for the upper anterior parallel, upper posterior parallel, transverse, and lower parallel screws, respectively. The maximum shear stress observed in the femur were 113.98 MPa in the FNS group and 89.39 MPa in the FCS group. VMS in the FNS group was predominantly concentrated at the plate-screw junction, reaching a peak of 326.24 MPa, whereas in the FCS group, it was primarily localized near the fracture site in the mid-screw region, with a maximum value of 166.77 MPa. In the femur, VMS was concentrated at the stress application site on the femoral head, with peak values of 197.54 MPa and 154.85 MPa in the FNS and FCS groups, respectively. The greatest displacement of the internal fixators was observed at the screw heads and the two upper parallel screws, measuring 3.36 mm in the FNS group and 3.28 mm in the FCS group. The maximum displacement of the femur occurred at the stress application site on the femoral head, measuring 3.41 mm and 3.33 mm in the FNS and FCS groups, respectively.

Conclusion: Comparative finite element analysis demonstrates superior biomechanical stability of FCS over FNS, indicating its greater suitability for managing young Pauwels type III femoral neck fractures.

Clinical trial number: Not applicable.