Medizinische Universität Graz Austria/Österreich - Forschungsportal - Medical University of Graz
Gewählte Publikation:
Marek, R.
In vivo characterization of designated full size magnesium implants by clinical CT and µCT in a juvenile sheep model
PhD-Studium (Doctor of Philosophy); Humanmedizin; [ Dissertation ] Medizinische Universität Graz; 2023. pp. 143
- Autor*innen der Med Uni Graz:
- Betreuer*innen:
- Schindl Rainer
- Sommer Nicole
- Weinberg Annelie-Martina
- Altmetrics:
- Abstract:
- Patient treatment aims to achieve the optimal outcome at high efficiency. In pediatric fracture treatment, additional factors have to be considered compared to adults. A major challenge in children presents the risk for growth disturbances, which may result from any trauma occurring around the physis. The active physis comprises highly chronological processes, which are responsible for longitudinal bone growth. A disruption of these sensitive mechanisms is often accompanied by limb length discrepancies or axis deviations. Growth alterations potentially cause significant discomfort, requiring medical therapies. It is known that implanting non-resorbable materials such as titanium (Ti) through the physis mostly provokes growth discrepancies. As a result, implantation via the physis is commonly avoided in pediatric fracture treatment, taking reduced fracture stability into account. In addition, concerns about the long-term consequences of non-resorbable materials are increasing among researchers and medical professionals alike. Especially in children, where the implant remains longer in the body than in adults, the occurrence of late-stage side effects, such as hypersensitivities, or diminished bone tissue due to stress-shielding effects, would be devastating. Consequently, non-resorbable implants in pediatrics are mostly removed in a second operation, thereby repeatedly exposing child and parents to the stresses of the procedure. Bioresorbable magnesium (Mg) implants offer new possibilities for fracture treatment in children. In a previous study, Mg - zinc (Zn) - calcium (Ca) screws broke several weeks after implantation through the physis of growing sheep, without affecting longitudinal bone growth. The possibility to stabilize fractures via the physis without intervening with bone elongation processes could open up new options as well as facilitate and improve existing techniques in pediatric orthopedics. Moreover, hardware removal after fracture consolidation is obviated when using resorbable osteosynthesis devices, which additionally constitutes a significant advantage over gold standard materials. To allow use of these materials in children, an enduring high acceptance by the surrounding tissue must be given, which persists over the complete life-span of the device. Thereby, fibrous encapsulations, often associated with stagnating implant resorption and tissue inflammation, are prevented. Thus, long-term investigations on the degradation behavior and bone response are essential before their application in children. The aim of this work was therefore to evaluate the short- and long-term influence of trans-epiphyseally inserted Mg–Zn–Ca implants on the physis of the growing skeleton as well as their general suitability for use in pediatric fracture treatment. For this purpose, longitudinal growth of tibiae after trans-epiphyseal implantation of Mg–Zn–Ca osteosynthesis devices (screws and elastic stable intramedullary nails (ESIN)) was examined over a period of up to 3.5 years in a growing sheep model. A comparison was made to the gold standard material Ti. Furthermore, the degradation behavior and bone response of Mg–Zn–Ca implants in different regions of the tibia of growing sheep was determined. In addition, the benefit of an implant-surface-treatment by plasma-electrolytic-oxidation (PEO), to decrease the degradation rate, was evaluated in juvenile sheep and compared to untreated Mg–Zn–Ca and Ti implants. The results show that trans-epiphyseal implantation of Mg–Zn–Ca osteosynthesis devices with the used techniques has no influence on longitudinal growth of the bones. Furthermore, no physeal bone bridges were found which could possibly induce growth disorders at later time points. In contrast, trans-epiphyseal implantation of Ti screws led to physeal bone bridge formation and permanent growth disorders (leg length shortening and axis deviations). Moreover, the results suggest that Mg–Zn–Ca implants feature suitable deg