Medizinische Universität Graz Austria/Österreich - Forschungsportal - Medical University of Graz
Gewählte Publikation:
Eichler, J.
Optimized imaging and post-imaging technologies for the evaluation of biodegradable implants
Doktoratsstudium der Medizinischen Wissenschaft; Humanmedizin; [ Dissertation ] Graz Medical University; 2016. pp. 171
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- Autor*innen der Med Uni Graz:
- Betreuer*innen:
- Kraus Tanja
- Sorantin Erich
- Weinberg Annelie-Martina
- Altmetrics:
- Abstract:
- Biodegradable implant materials are subject of intensive research during the last years. Fracture healing after clinical application of biodegradable implants is an important goal to avoid an operation for metal removal and simultaneously improve bone healing through adapted implant rigidity. Acceptance of those materials by bone cells like osteoblasts and osteoclasts is crucial, as well as suitable degradation characteristics and a low and homogeneous hydrogen gas formation, which can not be completely avoided for Magnesium implants. Clinical devices for radiological diagnostics were adapted to pre-clinical imaging methods in case of the well known CT method for high resolution small animal imaging, which was used for implant characterisation during the following studies. Also standard clinical CT method was used successfully with special protocol settings in a large animal model. Another method for tomographic imaging of molecular processes by near infrared fluorescence in vivo was also used within this work. The in vivo characterisation of biodegradable polymers, iron alloys and the latest and very promising Magnesium-Zinc-Calcium alloys by pre-clinical and clinical imaging was conducted and evaluated for applicability of those imaging methods. Optimisations of imaging protocol parameters were applied which increased the evaluation accuracy for the different materials. Cylindrical pins were machined of the polymer Polyhydroxybutyrate (PHB) and composites, pure Iron and Iron-Manganese-(Carbon)-Palladium alloys and the Magnesium-Gadolinium alloy Mg10Gd, as well as the extra high purified Magnesium-Zinc-Calcium alloy BRI.Mag. Implants were inserted into rat tibiae and observed with in vivo and ex vivo imaging methods in CT and fluorescence molecular tomography. Imaging protocols were adapted to best performance with different implant characteristics like radiological density and bone ingrowth. Furthermore, full-size ESIN implants and interlocking systems, made of conventional Ti were implanted into sheep tibiae and imaged ex vivo in CT, to evaluate the resulting internal bone damage after mechanical loading. Similar shaped ESIN implants were manufactured from the observed Mg-Zn-Ca materials and implanted into sheep tibiae, to examine degradation, fracture healing and hard- and soft tissue reactions by radiological imaging in a clinical CT device. As a last step, biodegradable screws were manufactured from the Mg-Zn-Ca alloy and tested in sheep tibiae. To ensure a detailed visualisation of the thread-bone interface area, high resolution imaging was performed with the explanted tibiae in CT.