Quantification of microdamage formation during fatigue testing of individual trabeculae

Abstract

siehe EN

Osteoporosis is a widespread skeletal disease, which is a major problem of today's society. The current diagnosis and treatment of osteoporosis is based on the quantity of bone. Nevertheless, there is a growing awareness of the importance of the bone quality. Microdamage accumulation in bone may contribute to a loss in the quality of osteoporotic bone. The role of microdamage in fatigue fractures is widely unknown and the formation of microdamage in individual trabeculae under a dened uni-axial loading has not been performed so far. Therefore, this thesis investigated the quantication of microdamage formation in individual trabeculae under fatigue testing conditions in tension. A fatigue test protocol was developed and a stop criterion was dened to ensure microdamage formation without breaking the trabeculae. Several criteria were tested for this purpose. The decrease in elastic modulus, stress and strain amplitude and monitoring the whitening effect were excluded for various reasons. Nevertheless, with usage of a system with a higher resolution of the strain recording (temporal and local) it would be worthy to test these parameters further of their applicability. The number of cycles for which the samples were loaded and unloaded were chosen as stop criterion. Individual trabeculae were tested for 1500 (n=6), 2100 (n=6) and 3000 (n=7) cycles with a frequency of 1 Hz and an amplitude of 0.05 mm (whole sample). An adjusted preload was used to account for the variation in site of dierent sizes of trabeculae. The samples were stained with chelating agent Alizarin Red S before testing and with Calcein afterwards to show the formation of microdamage. Confocal laser scanning microscopy (CLSM) was used to investigate the samples and to visualize microdamage. Linear cracks and diuse damaged were detected in individual trabeculae after testing. By testing trabeculae for the mentioned dierent numbers of cycles the formation of microdamage was shown and the development of t