Finite element analysis of 3 internal fixations for distal type C3 femur fractures with medial wall bone defects

Abstract

Objectives: Managing 33-C3 femur fractures with medial wall bone defects poses a significant challenge for orthopedic surgeons. The gold standard treatment for arbeitsgemeinschaftfür osteosynthesefragen (AO)/orthopedic trauma association (OTA) 33-C3 distal femur fractures with medial wall bone defects remains elusive. This study employs finite element analysis to compare the stability and mechanical behavior of 3 internal fixation patterns (single lateral distal locking plate, retrograde intramedullary nail, and dual plates) for 33-C3 femur fractures with medial wall bone defects. The aim is to provide a theoretical basis for the selection of internal fixation modalities in clinical practice.

Methods: Enrollment included a 43-year-old male volunteer weighing 60 kg, without a history of femur fracture. Bilateral femur normality was verified through X-ray and CT scan assessments. A finite element simulation model of AO/OTA 33-C3 distal femur fracture with medial wall bone defect was established. Three fixation methods, named single lateral locking plate (single-plate group), retrograde intramedullary nail (retrograde intramedullary nail group), and dual plates (dual-plate group), were evaluated using finite element analysis under an axial load of 300 N. The assessment included an examination of von Mises stress distribution, shear stress, and displacement patterns at the internal fixation and femur fracture sites.

Results: The finite element analysis revealed that dual-plate fixation effectively reduced the concentration of von Mises stress at the plate on the fracture site. Under full weight-bearing conditions, the maximum von Mises stress in the implants occurred at the distal femur defect level, with values of 149.30, 59.281, and 58.03 MPa for single-plate fixation, retrograde intramedullary nail, and dual-plate fixation methods, respectively. Similarly, the maximum shear stress in the implants was 77.867, 30.136, and 33.505 MPa for single-plate fixation, retrograde intramedullary nail, and dual-plate fixation methods, respectively, all presenting at the distal femur defect level. The maximum relative displacements of implants during compressive loading were 1.34, 1.25, and 0.83 mm for the single-plate , retrograde intramedullary nail, and dual-plate groups, respectively. Consistently, the maximum loading-point displacements of fracture sites were 1.529, 1.264, and 0.880 mm for the single-plate fixation group, retrograde intramedullary nail group, and dual-plate fixation group, respectively. Furthermore, at the distal femur defect level, the maximum von Mises stress was 72.682, 112.430, and 40.716 MPa for the single-plate, retrograde intramedullary nail, and dual-plate fixation groups, respectively.

Conclusions: Dual-plate fixation demonstrates superior biomechanical outcomes and exhibites the lowest maximum von Mises stress and shear stress, along with minimal relative movements between fracture fragments. This configuration offers optimal mechanical stability for managing AO/OTA 33-C3 distal femur fractures with medial wall bone defects. Consequently, dual-plate fixation emerges as a better treatment strategy for patients presenting with comminuted intra-articular distal femur fractures accompanied by medial wall bone defects.

Keywords: comminuted intra-articular distal femur fracture; dual plate fixation; finite element analysis; medial wall bone defect.

图1

Mimics软件重建的股骨全长三维模型 Figure 1 Construction of three-dimensional model for femur via Mimics software A: Coronal view of femur bone; B: Axial view of femur bone; C: Sagittal view of femur bone; D: Three-dimensional model femur.

图2

3种不同内植物固定伴有内侧骨缺损股骨远端C3型骨折的三维模型 Figure 2 Geometric three-dimensional models of 3 internal fixation patterns for distal type C3 femur fracture with medial wall bone defects A: Single lateral distal femoral locking plate fixation model; B: Distal femoral retrograde intramedullary nail fixation model; C: Dual plates fixation model.

图3

接触设置 Figure 3 Contact settings Bonded contact was used to simulate the contact properties in the femur and single plate (A), retrograde intramedullary nail (B), and dual plates (C) fixation.

图4

边界条件及载荷设置 Figure 4 Boundary conditions and loading force settings Freedom of all nodes at the proximal femur was set to zero. A preload of 300 N force was applied vertically on the distal femur.

图5

网格划分 Figure 5 Mesh distribution A: Appearance diagram in single lateral distal femur locking plate fixation model; B: Retrograde intramedullary nail fixation model; C: Dual plates fixation model.

图6

3种不同内固定模型中内植物的应力分布 Figure 6 Von Mises stress distribution on models fixed with the indicated implant A: Single lateral distal femur locking plate fixation model; B: Retrograde intramedullary nail fixation model; C: Dual plates fixation model.

图7

3种不同内固定模型中内植物的位移分布 Figure 7 Displacement patterns of implants in 3 internal fixations models A: Single lateral distal femur locking plate fixation model; B: Retrograde intramedullary nail fixation model; C: Dual plates fixation model.

图8

3种不同内固定模型中骨折端的位移分布 Figure 8 Displacement patterns of the femur in 3 internal fixation models A: Single lateral distal femur locking plate fixation model; B: Retrograde intramedullary nail fixation model; C: Dual plates fixation model.

图9

3种不同内固定模型中股骨应力分布 Figure 9 Stress distribution of the femur in 3 internal fixation models A: Single lateral distal femur locking plate fixation model; B: Retrograde intramedullary nail fixation model; C: Dual plates fixation model. The arrow indicats the position of femur with max stress during finite element analysis.

图10

3种不同内固定模型中内植物的剪切力分布 Figure 10 Shear stress distribution fixed with the indicated implant in 3 internal fixation models A: Single lateral distal femur locking plate fixation model; B: Retrograde intramedullary nail fixation model; C: Dual plates fixation model.