Finite Element Analysis of Six Internal Fixations in the Treatment of Pauwels Type III Femoral Neck Fracture

• Published in: Orthopaedic surgery Vol. 16; no. 7; pp. 1695 - 1709
• Main Authors: Sun, Xiang, Han, Zhe, Cao, Dongdong, Han, Chao, Xie, Mengqi, Zeng, Xiantie, Dong, Qiang
• Format: Journal Article
• Language: English
• Published: Melbourne John Wiley & Sons Australia, Ltd 01-07-2024; John Wiley & Sons, Inc; Wiley
• Subjects: Analysis; Biomechanical Phenomena; Biomechanical study; Biomechanics; Bone Nails; Bone Plates; Bone Screws; Care and treatment; Clinical medicine; Fatigue; Femoral Neck Fractures - surgery; Finite Element Analysis; Finite element method; Fracture Fixation, Internal - methods; Fractures; Humans; Internal fixation; Internal fixation in fractures; Life expectancy; Medical technology; Neck; Orthopedics; Pauwels type III femoral neck fracture; Risk factors; Stress; Stress, Mechanical; Transplants & implants; Weight-Bearing; United States > US; Internal fixation; Pauwels type III femoral neck fracture; Biomechanical study; Finite element analysis
• ISSN: 1757-7853; 1757-7861
• DOI: 10.1111/os.14069

Objective
The current investigation sought to utilize finite element analysis to replicate the biomechanical effects of different fixation methods, with the objective of establishing a theoretical framework for the optimal choice of modalities in managing Pauwels type III femoral neck fractures.
Methods
The Pauwels type III fracture configuration, characterized by angles of 70°, was simulated in conjunction with six distinct internal fixation methods, including cannulated compression screw (CCS), dynamic hip screw (DHS), DHS with de‐rotational screw (DS), CCS with medial buttress plate (MBP), proximal femoral nail anti‐rotation (PFNA), and femoral neck system (FNS). These models were developed and refined using Geomagic and SolidWorks software. Subsequently, finite element analysis was conducted utilizing Ansys software, incorporating axial loading, torsional loading, yield loading and cyclic loading.
Results
Under axial loading conditions, the peak stress values for internal fixation and the femur were found to be highest for CCS (454.4; 215.4 MPa) and CCS + MBP (797.2; 284.2 MPa), respectively. The corresponding maximum and minimum displacements for internal fixation were recorded as 6.65 mm for CCS and 6.44 mm for CCS + MBP. When subjected to torsional loading, the peak stress values for internal fixation were highest for CCS + MBP (153.6 MPa) and DHS + DS (72.8 MPa), while for the femur, the maximum and minimum peak stress values were observed for CCS + MBP (119.3 MPa) and FNS (17.6 MPa), respectively. Furthermore, the maximum and minimum displacements for internal fixation were measured as 0.249 mm for CCS + MBP and 0.205 mm for PFNA. Additionally, all six internal fixation models showed excellent performance in terms of yield load and fatigue life.
Conclusion
CCS + MBP had the best initial mechanical stability in treatment for Pauwels type III fracture. However, the MBP was found to be more susceptible to shear stress, potentially increasing the risk of plate breakage. Furthermore, the DHS + DS exhibited superior biomechanical stability compared to CCS, DHS, and PFNA, thereby offering a more conducive environment for fracture healing. Additionally, it appeared that FNS represented a promising treatment strategy, warranting further validation in future studies.
In this study, the three CCS + MBP showed the best biomechanical stability compared with the other five internal fixation models. The biomechanical stability of DHS + DS was second only to that of the three CCS + MBP, and both could be considered as a treatment for Pauwels III femoral neck fracture based on biomechanical stability alone. However, after considering the biomechanical stability, the stability of the internal fixation model, the difficulty of surgery and surgical trauma, FNS showed some advantages, so we believe that FNS can be considered as an effective method for treating Pauwels type III femoral neck fracture. CCS, cannulated compression screw; DHS, dynamic hip screw; DS, DHS with de‐rotational screw; FNS, femoral neck system; MBP, CCS with medial buttress plate; PFNA, proximal femoral nail anti‐rotation.