Available online 2 May 2025

This study compared the biomechanical properties of three cannulated screws (3-CSs) and a fixed angle device (FAD) for treating undisplaced femoral neck fracture (FNF) Pauwels types I and III, using finite element analysis (FEA) models created with nonlinear material properties; accurately reflecting the bone quality of osteoporotic patients.

FEA involved three patients with a history of undisplaced FNF. Mesh generation was performed using the preoperative CT data. Two internal fixation models:3-CSs and FAD were created for Pauwels type I and III models with a fracture angle of 30° and 70°, respectively. Compression force and relative displacement of the fracture site, and von Mises stress (VMS) of the implants were evaluated. Data analysis involved paired t-test at p < 0.05 statistical level of significance.

No significant difference was seen in the compression force between the two implants for Pauwels 30° and 70°models. There was no significant difference in the relative displacement and VMS between the two implants for Pauwels 30° model. However, both relative displacement and VMS were significantly higher in 3-CSs than in FAD for Pauwels 70° model.

Results indicate the need for FAD when treating Pawels Type III FNF with osteoporosis, since FAD fixation exhibited superior mechanical stability compared to 3-CSs. However, for the Pauwels Type I FNF, both fixation methods provided comparable stability. When considering the implant's simple and minimally invasive features, the clinical use of 3-CSs may be applicable. These findings highlight the importance of evaluating the Pauwels angle when determining the optimal fixation method for undisplaced FNF.

Finite element analysis

Undisplaced femoral neck fracture

Pauwels classification

Cannulated screws

Fixed angle device

Pauwels type Ⅲ

© 2025 The Authors. Published by Elsevier B.V. on behalf of The Japanese Orthopaedic Associationé