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Description
The study presents an approach to the optimisation of the thickness field of surgical implants used in the treatment of abdominal hernias in humans, a medical condition with a high recurrence rate. Building upon previous research, this investigation aims to enhance the mechanical compatibility between native tissues of the human abdominal wall and implants reducing the likelihood of hernia recurrence. The primary objective is to achieve reduced and uniformly distributed reaction forces at the interface between the patient's tissue and the implant through optimization of the implant's topology by changing thickness along the surface of the implant. The research employs a combination of commercial finite element software (Marc Hexagon) and custom-developed Python code for optimisation and control. Four distinct implant materials are analysed and compared. The shape of the implant is a decagonal membrane. The implant model is constructed with 6108 4-node membrane finite elements, each node having three degrees of freedom. The first model of the implant is isotropic and the other three are ortothropic with different ortotropy ratios: 3.19, 2.02, and 18.84 representing the commercial implants Parietex, Bard, and DynaMesh, respectively. The loading conditions are simulated through forced displacements of the model supports located in ten places on the implant where it's connected to the abdominal wall. The displacements are different in 5 of the supports and are symmetrical on the Y axis ranging between 2-5.75 mm and correspond to deformation of the abdominal wall during human physiological activities. The optimisation process utilizes a surface equation to describe thickness in the spatial coordinates of the implant instead of using separate elements. This allowed to reduce of the quantity of unknown variables during optimisation. This approach provides a balance between computational efficiency and the ability to generate complex optimised surfaces. For the implants with different material properties, the optimisation achieved slightly different thickness fields. In all of them, we can see better reaction force distribution than before the thickness optimisation.
