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Description
Background: Femoral fractures are common injuries in orthopaedic trauma surgery that usually require surgical intervention with internal fixation devices such as intramedullary nails or implants. In the implant case studied here, the number of screws, their positioning and the corresponding angle of insertion can significantly influence the mechanical environment at the fracture site, which in turn can affect healing outcomes. A better understanding of how screw configurations affect local micromechanics and interfragmentary motion can be used to optimize patient-specific implant setups.
Methods: 3D computer models were generated based on clinical image data of several femurs from body donations. These models were virtually provided with different fractures that would be treated with implants in everyday clinical practice and then virtually treated accordingly. To investigate the influence of the screw configuration, a series of configurations was then created for each model and analyzed using biomechanical FEM. To ensure realistic boundary conditions, physiological loading conditions were applied as hip forces and moments corresponding to those of normal healing progression from partial to full weight bearing. The key parameters evaluated included the von Mises stress distribution of the implant and the associated screws as well as the degree of interfragmentary movement and the strain-state of the fracture gap.
Results: The simulations showed that there are combinations of fractures and screw configurations where the influence on the micro-mechanics is greater than in other cases where the screw variation exerts only a minor influence. In addition, the result is influenced by the quality of the bone, comparing healthy bone versus osteoporosis patients.
Conclusion: The study shows that there is an influence of the screw configuration, which can be of great relevance in individual cases. The mechanical stability of the bone-implant system also influences the interfragmentary movement depending on the level of the partial weight bearing.
