Abstract
Despite the presence of biodegradable Magnesium implants in the clinics, their widespread use remain limited due to persisting inquiries regarding their biological interactions. The first understanding of the impact of Mg-based materials on bone structure, ranging from the tissue level to the lacunar-canaliculi network (LCN) has been studied. First, tissue level information was obtained by studying different biodegradable Mg-based screws (Mg-10Gd, Mg-4Y-3RE and Mg-2Ag) which were implanted into rabbit femur for 6 and 9 months. The bone implant contact, bone volume fraction and implant morphology were studied using high-resolution synchrotron radiation micro-computed tomography and histology. In addition, the elemental traces of the degradation products were studied using micro X-ray fluorescence. At the microscale, the LCN architecture was studied within the interfacial bone of Mg-10Gd implanted in rat tibia in comparison to Titanium (Ti) at 4, 8, 10, 12 and 20 weeks using synchrotron radiation-based transmission X-ray microscopy in conjunction with image-based finite element modelling. The result showed that mature bone formation occurred around all the implant types. Calcium and Phosphorus, were distributed within the degradation layer of all implant types. Also, the implants containing Yttrium and Gadolinium remained intact after 9 months, whereas those containing Silver had severely disintegrated. In the microscale domain, the degradation of Mg-10Gd did not significantly impact on the morphology of the LCN and its fluid flow dynamics. But, there was a significant decrease in lacunar density compared to Ti from 4 to 12 weeks. Altogether, despite the distinct degradation dynamics of Mg-10Gd, Mg-4Y-3RE, and Mg-2Ag, they elicited comparable long-term bone healing responses. Also, the degradation of Mg-10Gd influenced the lacunar distribution rather than morphology, indicating potential variations in bone remodeling rate when compared to Ti.
