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Diplom- und Master-Arbeiten (eigene und betreute):

C. Karl:
"Mechanical Anisotropy of Human Vertebral Bone Measured by the Means of Microindentation with Special Focus on Osteophyte Structures";
Betreuer/in(nen): D. H. Pahr, P.K. Zysset; Institut für Leichtbau und Struktur-Biomechanik, TU Wien, 2013; Abschlussprüfung: 16.10.2013.



Kurzfassung englisch:
The anisotropic behavior of human vertebral bone is postulated all over the literature, but the quantification of it is still debated. Moreover, most of the vertebrae of patients older than 50 years present abnormal calcifications (called osteophytes) with unknown mechanical properties. Therefore, the present study was meant to expand an existing database of vertebral mechanical properties at tissue level measured by means of microindentation (indentation modulus E; and hardness HV) to evaluate the degree of anisotropy in the human vertebral body and to better understand the mechanical properties of osteophytes.
Indentation is an experimental technique where a hard tip (usually made of black diamond) penetrates the tested material under continuous measurement of the load (P) and the penetration depth (h). A complete measuring cycle (loading and unloading) leads to a full load-displacement-curve from which the indentation modulus, the hardness and other mechanical material parameters can be calculated. If such a test is performed at a micrometer scale (for example with a maximal penetration depth of 2500 nm) this procedure is called microindentation.
This technique has been already used extensively to determine the mechanical properties of hone. Moreover, if indentations are performed in different directions, it can be used to evaluate its anisotropic behavior.
In this study four vertebral bodies were cleaned from the soft tissue and were cut with a diamond coated band saw in five slices perpendicular to the vertical body axis.
Afterwards, the five slices were cut into eleven samples for indentation of the cortical shell, cortical endplates and trabecular bone in different directions. In particular, the samples extracted from the cortical shell were indented in axial, circumferential and radial directions according to a cylindrical coordinate system. The samples extracted from the two endplates were tested in lateral and anterior/posterior directions. The samples extracted from the trabecular bone were tested in axial and transverse directions. Furthermore, the trabeculae were indented both in the center (IN) and closer to their perimeter (OUT). In addition five large osteophytes isolated from five human vertebrae were prepared for microindentation to better characterize the mechanic al properties of such calcifications; different sub-regions of each osteophyte were indented along the axial direction. Approximately 30 indentations were performed on each sample, which provided a total number of 2405 indentations (630 of these indentations on osteophytes).
All the indentation data from this study and the data from Mazza were pooled, statistically analyzed and compared with the results found in the literature.

Erstellt aus der Publikationsdatenbank der Technischen Universität Wien.