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O. Kabbani:
"Quantification of microdamage formation during fatigue testing of individual trabeculae";
Supervisor: P.J. Thurner, M. Frank; Institut für Leichtbau und Struktur-Biomechanik, TU Wien, 2019.

Osteoporosis is a skeletal disease which decreases the bone mass density and has a big effect on
humans´ health all over the globe. There is no agreement on the disease diagnosis or treatment.
However, the importance of bone quality is not questioned. Microdamage accumulation might
have an effect on the decrease of mechanical properties of osteoporotic bones. Considering that
most of the fractures due to osteoporosis are located in trabecular bone regions and that most of
the existing researches focus on cortical bone or whole trabecular bone cores, it is of interest to
develop a mechanical test procedure that allows testing on individual trabeculae. This project
improves the mechanical test protocol developed by Julia Fischer. Modifications in order to
make the protocol more sample independent and better controlled in terms of load conditions.
Due to individual trabecula´s dimensions and shape diversity the number of different conditions
and variables is considerable, which implies that a compromise between precision and
practicality has to be found. A difference in mechanical properties presented by two different
specimens of the same race and age was observed and a solution is given. The importance of the
relaxation of the sample during the test is discussed and practically removed. Other
improvements were applied and the result is a protocol which allows fatigue testing on individual
trabeculae controlling the load conditions during the whole test. A decrease of Young´s modulus
with increasing accumulated number of cycles is observed using this protocol. Some issues
concerning the fluorescent labelling of microdamage was detected and is discussed in this thesis.
The resulting protocol of this thesis is still very time consuming and the success rate
(successfully tested samples / total attempts of sample obtainment) is very low. Thus, an
alternative for the used sample preparation is suggested. Although, due to time reasons it could
not be applied and tested, but finite element simulations are cause for optimism. This
modification would radically change the sample preparation reducing the elapsed time and
increasing the success rate.