Zastosowanie modelowania metodą elementów skończonych do optymalizacji właściwości klamer do osteosyntezy

Abstract

The subject of the presented dissertation is modelling by the finite element method to optimize the clinical properties of the NiTi staples currently used for osteosynthesis. The assumed goal was achieved through: 1. measurement of selected properties of the NiTi alloy, 2. modelling the series of real staples, 3. measurement of selected staples properties, 4. comparing the modelling results with the experimental results, 5. implementation of the staple modification in order to improve its clinical properties, 6. a numerical verification of the improvement of the clinical properties of the modified staple. The first stage of the modelling showed that the values of the compressive force exerted by the arms of the staple on the bone, calculated for individual staples, were consistent with the measured data. By the modelling it was possible to determine the volume of the staples in the superelastic state. In order to optimize the properties of the staples, which would increase the volume of the superelastic phase and “reserve of superelastic”, it was proposed to increase the stress inside the staple. This was achieved by reducing the bend angle of the staple arms. The reduction of the bend angle, in addition to the intended increase in the volume of the staple in the plateau range and in the “reserve of superelastic” range, also caused an unfavourable increase in the value of the force exerted by the staple arms on the bone. To maintain the original compressive force, it was necessary to reduce the staple diameter. After this modification, in some cases, there was a slight decrease in the volume of the staple in the range of superelasticity, but the volume of the "reserve of superelastic" increased significantly in all analyzed cases (except for the staple with a span length of 15,9 mm for the FEM 1.5 parameter set). Moreover, by reducing the diameter of the staples, the original impact of the staple arms on the bone fragments was maintained. Thus, the modified superelasticity staples for osteosynthesis will work in the appropriate stress range, which will allow to use better the unusual properties of the applied material and thus increase their clinical functionality.