The growing incidence of skeletal fractures poses a significant challenge to ageing societies. Since a major part of physiological loading in the lower limbs is carried by cortical bone, it would be desirable to better understand the structure-mechanical property relationships and scale effects in this tissue. This study aims at assessing whether micro-mechanical properties measured by microindentation combined with morphological information may be used to predict macroscopic elastic and strength properties in a donor- and site-matched manner.Specimens for microindentation and quasi-static macroscopic tests in tension, compression, and torsion were prepared from a cohort of 19 male and 20 female donors (46 to 99 years of age). All tests were performed under fully hydrated conditions. The results of the micro-mechanical tests were combined with morphological properties such as porosity and cement line density using a power law relationship to predict the macroscopic properties.Microindentation properties were not gender dependent, remarkably constant over age, and showed an overall small variation with standard deviations of approximately 10 %. Macro-mechanical stiffness and strength were significantly related to porosity for all load cases (p < 0.05). In cases of macroscopic yield strain and work-to-failure this was only true in torsion and compression, respectively. The correlations of macro-mechanical with micro-mechanical and morphological properties showed no significance for cement line density or variations in the microindentation results and were dominated by porosity with a moderate explanatory power of most often less than 50 %. The results confirm that gender and age have negligible effect on the tissue microindentation properties of human lamellar bone. Furthermore, our findings suggest that a microindentation experiment is not suitable to predict macroscopic mechanical properties. The presented data may help to form a better understanding of the mechanisms of ageing in bone tissue and of the length scale at which they are active. This may be used for prediction of fracture risk in the elderly in the future.
|Title of host publication||American Society for Bone and Muscle Research - ASBMR Annual Meeting|
|Publication status||Published - 2015|