Reachout Orthopedics - Issue 1
defined [6, 9, 12, 19]. This study investigated the indirect effect on the physeal plate during the interfragmentary compression of SH type 4 distal femoral fractures. The aim of the study was to define the biomechanical effects on the epiphyseal plate while compressing the fracture line with partially threaded screws after reduction and decide whether a probability of iatrogenic injury to the physeal plate existed. Computer-aided Finite Element Analysis and Modeling A 3D of biologic models is very popular in nowadays. Data such as magnetic resonance imaging (MRI) and multislice computed tomography (CT) can be processed by using 3D modeling. The computer-aided numerical analysis to the distal femoral fracture line and physeal plate after reduction during fixation was performed using ANSYS Workbench software based on finite element method (FEM). FEM is very important in the development of new surgical techniques. It is also used as a reliable technique for validation of experimental or analytical results. In addition, several scientists similarly examined the optimal configuration, implant materials, fatigue behavior of implant materials, metal turning, bone drilling and bone screwing process using the computer-aided FEA tool [22–28]. Surgery Procedure The bone screwing processes were performed on the sawbones samples. A CNC machine with 2.5 kW power was used for the bone screwing processes. M4×1.75×22 screw was used for parallel configuration of SH type 4 fractures. Generally, in orthopedic surgery, a drilling process (2.5-mm drill bit) was applied to screwing zone before the bone screwing processes. A Kistler 9257B dynamometer was used to measure the screwing moment and thrust force. The bone screwing process parameters are given in Table 1. 3D Modeling A 3D scanner was used to obtain the point cloud of child human femoral model. Geomagic Studio 10 software was modeled as 3D using point cloud data. The diameter of partially threaded screw used Fig. 2: Ø 4×1.75×22 screw. Fig. 3: Mesh structure of screw configuration. Fig. 4: The loading types for parallel screw configurations. in configuration was M4×1.75×22 screw (Fig. 2). The bone screws were provided via orthopaedic-implants.com. Tapping process was not applied before the screwing process. Loading and Boundary Conditions The mesh process was performed using tetrahedrons finite element for FEAmodeling after importing single configuration of 3D models into ANSYS Workbench software (Fig. 3). FEA model has 264,697 nodes and 166,285 elements. While the mesh density for femur and femur fragments was aided as 1 mm, that for the physeal plate and screw was inputted as 0.5 mm. A moment of 810 Nmm around the Z axis in CW of the screw was applied to the screw head, and a force of 182 N was applied to the screw head. Both screws applied the boundary conditions (Fig. 4). It was fixed from the distal femoral condyles. Transient structural analysis type was selected for the parallel screws configuration for SH type 4 fracture. The force of 182 N was applied at the end of the screwing process to apply the actual surgical process. The contact types between bone and bone interaction, and screw and bone interaction were defined as a frictional contact. Friction coefficients were taken as 0.46 for bone and bone interactions and 0.42 for screw and bone interaction, respectively [29]. The frictionless contact type was selected among the physeal plates. Besides, the bonded contact type was selected, i.e., between bone and physeal plates [30]. Finally, convergent analysis was performed. This is very important for correct analyses. Material Model Table 2 shows the mechanical properties of bone and physeal plates. The stainless steel was used for screws used in FEA. ANSYS Workbench Material Library used the mechanical properties of screw [31]. The material model of the mechanical behaviors of bone, physeal plate and screw was selected as linear isotropic material model in this analysis. The physeal plate was assumed as soft tissue. Results and Discussion In the literature, behavioral loads under ductile materials such as cartilage have been calculated according to the vonMises damage 4 reachOut Orthopedics
Made with FlippingBook
RkJQdWJsaXNoZXIy NjQyMzE5