Lucie Hucke (Frankfurt a. M.; Cádiz / ES; Graz / AT), Dr. Andreas Wittek (Frankfurt a. M.), Prof. Dr. Antonio Gámez (Cádiz / ES), Prof. Dr. Armin Huß (Frankfurt a. M.), Univ.-Prof. Dr.med. Niels Hammer (Graz / AT), Dr. techn. MSc. Justyna A. Niestrawska (Graz / AT)
Abstract-Text (inkl. Referenzen und Bildunterschriften)
Introduction: Finite element methods are used to simulate length growth on long bones [1]. In these models, the growth rate depends, indirectly through the principal and shear stresses, on the geometry of the model, the boundary conditions and the material properties. In this study, shear tests were conducted to investigate the material properties, which have been poorly studied to date.
Objectives: Shear tests are carried out and evaluated to investigate the material properties. The statistical evaluation of the results will help to understand inter- and individual differences (growth plate (GP) types, location of the samples within the GP) and the influence of the shear rate.
Methods: Rectangular bone-GP-bone samples were created from the proximal and distal femoral GP and the proximal tibial GP obtained from 5 porcine individuals. Only specimens with GPs straight and parallel to the top and bottom edges of the specimen were used for testing. For each of the chosen 302 test samples the anatomical location within the respective GP was known. For the experiments, the specimens were securely fastened above and below the GP and subjected to cyclic deformation at shear rates of either 0.04 °/s, 0.2 °/s or 0.5°/s, reaching a maximum deflection angle of 8° to 10° (Fig 1). After cyclic testing, the samples were allowed to relax for 5 minutes before being destroyed using an increasing amplitude up to 25° at the respective shear rate.
Results: To analyse the results, the hysteresis as well as the tangent moduli at the beginning and end of the elastic region are examined and investigated in relation to the individual, GP type, anatomical location of the sample and shear rate.
Conclusion: The shear test measurements indicate that a linear description of the material is not appropriate (Fig 2). The shear test results will be used to determine the material parameters for a more accurate material model in the future.
References
[1] Sadeghian (2023); J Biomech;157