Finite Element Analysis of Osteosynthesis Screw Fixation in the Bone Stock: An Appropriate Method for Automatic Screw Modelling

Abstract

The use of finite element analysis (FEA) has grown to a more and more important method in the field of biomedical engineering and biomechanics. Although increased computational performance allows new ways to generate more complex biomechanical models, in the area of orthopaedic surgery, solid modelling of screws and drill holes represent a limitation of their use for individual cases and an increase of computational costs. To cope with these requirements, different methods for numerical screw modelling have therefore been investigated to improve its application diversity. Exemplarily, fixation was performed for stabilization of a large segmental femoral bone defect by an osteosynthesis plate. Three different numerical modelling techniques for implant fixation were used in this study, i.e. without screw modelling, screws as solid elements as well as screws as structural elements. The latter one offers the possibility to implement automatically generated screws with variable geometry on arbitrary FE models. Structural screws were parametrically generated by a Python script for the automatic generation in the FE-software Abaqus/CAE on both a tetrahedral and a hexahedral meshed femur. Accuracy of the FE models was confirmed by experimental testing using a composite femur with a segmental defect and an identical osteosynthesis plate for primary stabilisation with titanium screws. Both deflection of the femoral head and the gap alteration were measured with an optical measuring system with an accuracy of approximately 3 µm. For both screw modelling techniques a sufficient correlation of approximately 95% between numerical and experimental analysis was found. Furthermore, using structural elements for screw modelling the computational time could be reduced by 85% using hexahedral elements instead of tetrahedral elements for femur meshing. The automatically generated screw modelling offers a realistic simulation of the osteosynthesis fixation with screws in the adjacent bone stock and can be used for further investigations.

Strength analysis of clavicle fracture fixation devices and fixation techniques using finite element analysis with musculoskeletal force input

“…In further work, customized plates designed based on these guidelines will be compared to commercial plates regarding mechanical response. Another interesting continuation is to study the screw-bone interaction more in detail, as in [46] and to find a way to include the risk of screw loosening in the model. The purpose with plate osteosynthesis is to achieve proper healing of the fracture, and hence, the best plate is a plate that contributes to fracture healing with minimized negative side effects.…”

Comparative study of three models of extra-articular distal humerus fracture osteosynthesis using the finite element method on an osteoporotic computational model

“…24,26 The Poisson's ratio for osteoporotic bone was set to be 0.4 27 and the moduli of elasticity used for the cortical bone in axial compression, posterior deflection and varus loading were 3400 MPa, 1150 MPa and 660 MPa, respectively. As there was no information from the manufacturer about the bone material properties, these moduli of elasticity were determined by comparing linear elastic displacements obtained numerically by finite element analysis and experimentally on identical synthetic osteoporotic humeri.…”

Finite element analysis of the effect of cannulated screw placement and drilling frequency on femoral neck fracture fixation

“…1) to establish the finite element model. Ten-node tetrahedral three-dimensional elements (solid 92) were applied to a selection of unit types, similar to a model studied by Wielding et al [4]. Our models presumed that the bone was an isotropic, linear, elastic material.…”

“…Three different numerical modelling techniques for implant fixation were investigated in a FE analysis performed on CAD models of a composite femur and an angular-stable osteosynthesis plate generated from CT data [4]. Analysis without screw modelling, using screws as solid elements, as well as using screws as structural elements were all compared to experimental testing.…”

“…Analysis without screw modelling, using screws as solid elements, as well as using screws as structural elements were all compared to experimental testing. Results revealed that screw modelling with FE analysis offers a realistic simulation of osteosynthesis fixation with screws [4].…”