Medizinische Universität Graz Austria/Österreich - Forschungsportal - Medical University of Graz
Gewählte Publikation:
Martinelli, E.
Intramedullary application of novel modified bioresorbable implants in the growing rat for osteosynthesis
Doktoratsstudium der Medizinischen Wissenschaft; Humanmedizin; [ Dissertation ] Graz Medical University; 2015. pp. 99
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- Autor*innen der Med Uni Graz:
- Martinelli Elisabeth
- Betreuer*innen:
- Kühn Klaus-Dieter
- Leithner Andreas
- Weinberg Annelie-Martina
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- Abstract:
- Introduction In the development of biodegradable implants for children several special features have to be addressed: Fracture healing in children is faster and the bone takes over weight-bearing earlier than adults permitting fast degradation of the implant material. So biodegradable implants would be of substantial benefit in paediatric patients. But due to the special conditions of the children’s bone, several steps regarding materials, biomechanics, the degradation in the bone and the bony answer have to be considered. Materials & Methods Cylindrical pins made of Poly(3-hydroxybutyrate) (PHB) with different additives were analysed: pure PHB, PHB with 3w% Zircondioxid, PHB with 3w% Zircondioxid and 30w% Herafill®, an alternative bone material, PHB only with 30w% Herafill® and PHB with 40w% Magnesium powder. Two identical pins were implanted in the femoral bones of growing Spraque Dawley® rats. Continuous micro computed tomography scans were performed to asses the degradation performance and new bone adherence after 1, 3, 6 and 9 months of implantation of the composite materials. Additionally, push out tests, histological slides and high resolution scans ex vivo were made to compare bone reaction. Blood examinations evaluated the response of the innate immune system during the study period. Results Added Magnesium powder was degrading faster and dissolved of the PHB network, but remaining PHB showed no enhanced degradation process. The whole implant was too brittle for proper handling during the implantation process and the push out tests after 1 month showed the lowest forces of all tested PHB implants. Also the additives Zircondioxide and Herafill® could not accelerate the degradation process. Again with new additives, the resolution between implant and surface was not high enough to get valid volume and surface values with µCT scans. But it was possible to compare bone reactions and new bone formations within the different PHB groups. The high tolerance of tissue and bone to the implant in histological slices is promising. Over the time and the healing process, the bone fused with the implant and no inflammatory or adverse tissue reaction was observed. Compared to Sham group with bone injury and trauma, the implant material shows no further immune reactions. The negative immunological effects of anaesthesia and surgery are seen in the first week after surgery in the sham and experimental group. After 4 weeks, the drill hole is healed and the bone remodelling started. This study confirms that PHB as a bioresorbable implant does not provide any significant further adverse effects compared to the Sham group, a good bone adherence and new bone formation can be observed in the µCT pictures. Discussion Although PHB is a natural material produced by bacteria, the use as an implant for children in its native composition seems to be inappropriate due to its long degradation process. Because of the low degradation rate at the one side and the good tissue and bone tolerance on the other side, other fields of application should be considered. Coatings of permanent implants should be mentioned and it is also an alternative to PLA which is used for sutures, stents, dialysis, scaffolds and drug delivery devices.