Imaging magnesium-based implants and their biological surroundings

This doctoral thesis investigates the clinical potential of biodegradable magnesium (Mg)-based orthopaedic implants, focusing on their effects on bone remodelling, MRI artefacts, and RF-induced heating. A literature review on Mg alloy behaviour in MRI complements the work.

The first study examines how Mg implants influence the lacuno-canalicular network (LCN), essential for bone remodelling. Using synchrotron-based X-ray microscopy, it compares untreated and plasma electrolytic oxidation (PEO)-treated WE43 screws in sheep bone. PEO-treated implants promote healthier lacunar shapes, while untreated ones yield a more connected LCN, potentially enhancing trauma response.

The second study assesses MRI artefacts caused by Mg implants through in vitro, ex vivo, and clinical imaging. Artefacts decrease as the implant degrades, especially when imaging is perpendicular to the implant axis. Compared to titanium, Mg-based implants consistently produce fewer artefacts, supporting their use in post-operative MRI.

The third study explores RF-induced heating during MRI. WE43 screws were degraded in vitro, and temperature changes were measured. The highest heating occurred before degradation, with reduced heating as the degradation layer formed. Heating levels were comparable to titanium, highlighting the need for MRI safety standards to include biodegradable materials.

Together, these studies advance understanding of Mg-based implants, supporting their safe and effective use in orthopaedic surgery and imaging.

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