Medizinische Universität Graz Austria/Österreich - Forschungsportal - Medical University of Graz
Gewählte Publikation:
Schmoeller, G.
In vivo and ex vivo microCT evaluations of biodegradable poly(3-hydroxybutyrate) implants in a rat model
Humanmedizin; [ Diplomarbeit ] Medical University of Graz; 2014. pp. 61
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- Autor*innen der Med Uni Graz:
- Betreuer*innen:
- Kraus Tanja
- Weinberg Annelie-Martina
- Altmetrics:
- Abstract:
- Introduction: Biodegradable materials have first been introduced to medicine in the form of resorbable sutures and small fixation devices. By now, a widespread range of materials enables even complex and heavy load applications. The advantages of biodegradable materials are obvious: reduction of secondary surgeries, avoidance of common complications known from conventional metallic devices and potential for optimization for special applications, i.e. pediatric fracture fixation. At present, biodegradable materials can be divided into polymers, metals and ceramics, of which polymers are the most versatile group due to the great variety of materials and diverse mechanical and chemical properties. Polyhydroxyalcanoates and poly(3- hydroxybutyrate) (PHB) in special belong with the most promising polymeric materials available for biodegradable applications in medicine today. Methods, materials and animals: Three blends of PHB, featuring varying amounts of the heavy metal zirkonium and the resorbable bone substitute Herafill® were established and shaped as cylindric pins (1,6mm diameter, 8mm length). These pins were transcortically implanted in 5 week old Sprague-Dawley rats ´ femora and their surface and volume monitored in vivo over a 9 month period using micro computed tomography (microCT). Several explanted pins were also scanned using microCT in an ex vivo setting for validation reasons. Results: Due to 3D-processing issues of in vivo microCT scans, only ex vivo scans produced validly quantifiable data. Though, in vivo scans showed no obvious signs of degradation even after 9 months of dwelling time, which was confirmed by ex vivo evaluations. Actually, both volume and surface of the pins had even increased in relation to calculated preimplantational values and degradational behavior was thus denied. Discussion: PHB already possesses good properties for pediatric osteosynthesis that can even be enhanced by techniques such as blending. Still, important factors must be taken into account, i.e. slow degradation, sterilization issues, general biocompatibility and fibrous encapsulation of implants. For in vivo evaluations of degradable implants, microCT has proven to deliver adequate results, though the used composites presented density properties too similar to those of bone to be certainly differentiated from surrounding tissue in vivo. Hence, only ex vivo scans could be regarded as valid data. Also, some pins appeared to be inhomogeneously blended, yet this had no effect on degradation properties. Conclusion: The exceptionally slow degradation of all three blends of PHB cannot meet the requirements modern osteosynthesis puts on a biodegradable implant in a growing skeleton. Hence, without major progress in material sciences and enhancement of degradation properties, PHB cannot be recommended for the use in biodegradable pediatric fracture fixation devices.