Browsing by Author "Thurner, Philipp J."

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Effects of anti-resorptive treatment on the material properties of individual canine trabeculae in cyclic tensile tests
    (Elsevier, 2021) Frank, Martin; Grabos, Andreas; Reisinger, Andreas G.; Burr, David B.; Pahr, Dieter H.; Allen, Matthew R.; Thurner, Philipp J.; Anatomy and Cell Biology, School of Medicine
    Osteoporosis is defined as a decrease of bone mass and strength, as well as an increase in fracture risk. It is conventionally treated with antiresorptive drugs, such as bisphosphonates (BPs) and selective estrogen receptor modulators (SERMs). Although both drug types successfully decrease the risk of bone fractures, their effect on bone mass and strength is different. For instance, BP treatment causes an increase of bone mass, stiffness and strength of whole bones, whereas SERM treatment causes only small (4%) increases of bone mass, but increased bone toughness. Such improved mechanical behavior of whole bones can be potentially related to the bone mass, bone structure or material changes. While bone mass and architecture have already been investigated previously, little is known about the mechanical behavior at the tissue/material level, especially of trabecular bone. As such, the goal of the work presented here was to fill this gap by performing cyclic tensile tests in a wet, close to physiologic environment of individual trabeculae retrieved from the vertebrae of beagle dogs treated with alendronate (a BP), raloxifene (a SERM) or without treatments. Identification of material properties was performed with a previously developed rheological model and of mechanical properties via fitting of envelope curves. Additionally, tissue mineral density (TMD) and microdamage formation were analyzed. Alendronate treatment resulted in a higher trabecular tissue stiffness and strength, associated with higher levels of TMD. In contrast, raloxifene treatment caused a higher trabecular toughness, pre-dominantly in the post-yield region. Microdamage formation during testing was not affected by either anti-resorptive treatment regimens. These findings highlight that the improved mechanical behavior of whole bones after anti-resorptive treatment is at least partly caused by improved material properties, with different mechanisms for alendronate and raloxifene. This study further shows the power of performing a mechanical characterization of trabecular bone at the level of individual trabeculae for better understanding of clinically relevant mechanical behavior of bone.
  • Thumbnail Image
    Item
    Simultaneous visualisation of calcified bone microstructure and intracortical vasculature using synchrotron X-ray phase contrast-enhanced tomography
    (Nature Publishing group, 2017-10-16) Núñez, Juan A.; Goring, Alice; Hesse, Eric; Thurner, Philipp J.; Schneider, Philipp; Clarkin, Claire E.; Anatomy and Cell Biology, School of Medicine
    3D imaging of the bone vasculature is of key importance in the understanding of skeletal disease. As blood vessels in bone are deeply encased in the calcified matrix, imaging techniques that are applicable to soft tissues are generally difficult or impossible to apply to the skeleton. While canals in cortical bone can readily be identified and characterised in X-ray computed tomographic data in 3D, the soft tissue comprising blood vessels that are putatively contained within the canal structures does not provide sufficient image contrast necessary for image segmentation. Here, we report an approach that allows for rapid, simultaneous visualisation of calcified bone tissue and the vasculature within the calcified bone matrix. Using synchrotron X-ray phase contrast-enhanced tomography we show exemplar data with intracortical capillaries uncovered at sub-micrometre level without the need for any staining or contrast agent. Using the tibiofibular junction of 15 week-old C57BL/6 mice post mortem, we show the bone cortical porosity simultaneously along with the soft tissue comprising the vasculature. Validation with histology confirms that we can resolve individual capillaries. This imaging approach could be easily applied to other skeletal sites and transgenic models, and could improve our understanding of the role the vasculature plays in bone disease.