Finite element analysis investigation of positive reduction in the femoral neck fracture
by Xiang Zhou
Date of Examination:2025-02-13
Date of issue:2025-02-05
Advisor:Prof. Dr. Wolfgang Lehmann
Referee:Prof. Dr. Wolfgang Lehmann
Referee:Prof. Dr. Jochen Gaedcke
Sponsor:This work was supported by a scholarship from the China Scholarship Council (No. 202308080019)
Persistent Address:
http://dx.doi.org/10.53846/goediss-11070
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Abstract
English
Aim Gotfried positive reduction offers an alternative strategy for femoral neck fracture (FNF) when achieving anatomical reduction is challenging. However, quantifying positive reduction and assessing the potential issues from excessive positive reduction remain unclear. The purpose of this study was to investigate the biomechanical behavior of positive reduction across different Pauwels classification, providing a reference for quantifying positive reduction in clinical practice. Methods Three-dimensional (3D) models representing negative, anatomical, and positive FNF reductions, each associated with distinct Pauwels groups (Type I, II, and III), were generated based on computed tomography (CT) dataset. These models were stabilized using dynamic hip screws (DHS) and cannulated screws (CS). A 2100 N load was systematically applied to the femoral head, precisely aligned with the mechanical axis of the femur. Our investigation encompassed five parameters, namely the maximum von-Mises stress of internal fixators and the proximal femur, displacement of the proximal femoral head fragment, and displacement of the femur fixed with DHS and CS. Furthermore, we considered the maximum von-Mises strain at the fracture site of the proximal fragment. When evaluating the stability of FNF reduction post-internal fixation, the efficacy of the internal fixation device predominantly influences the stability of the fractured site. In this study, we prioritized the maximum von-Mises stress of the internal fixation as pivotal indicators for assessing the stability across different reduction models. Results Within each Pauwels group, the anatomical reduction model exhibited the lowest maximum von-Mises stress on both the internal fixator and proximal femur, and the maximum von-Mises strain at the fracture site of the proximal femur fragment was also lowest in the anatomical reduction model. In the Pauwels I group, positive reduction exceeding 3mm resulted in the maximum von-Mises stress on the internal fixators surpassing that of the negative reduction model. For the Pauwels II group, positive reduction beyond 2mm led to the maximum von-Mises stress on the internal fixators exceeding that of the negative reduction model. In the Pauwels III group, positive reduction beyond 1mm caused the maximum von-Mises stress on the internal fixators to be higher than that of the negative reduction model. The maximum von-Mises stress on the proximal femur increased with positive reduction in Pauwels II and III but decreased in Pauwels I group. The maximum von-Mises strain at the fracture site of proximal femur fragment increased with positive reduction, focusing on the cancellous bone of the CS. Femoral displacement decreased with positive reduction across all Pauwels groups. However, varus displacement increased in positive reduction models as the Pauwels angle rose, potentially exacerbating rotation deformity in Pauwels III. Conclusions Excessive positive reduction may increase the risk of FNF failure after internal fixation. From a biomechanical stability perspective, positive reduction should be limited to 3mm or below in the Pauwels I group, restricted to not exceed 2mm in the Pauwels II group, and should not exceed 1mm in the Pauwels III group. Negative reduction should be avoided in all Pauwels groups.
Keywords: Finite Element Analysis; Positive reduction; Femoral neck fracture
Schlagwörter: Finite Element Analysis; Positive reduction; Femoral neck fracture
