Influence of biodegradable Mg-based implants on bone nanoadaptation
Identifying the ideal material for bone fracture treatment is challenging due to mechanical, medical, and financial factors. Traditional implants like titanium or stainless steel often require costly removal surgeries. Biodegradable implants allow to avaid the secondary surgery, as, with time, it fully dissolves in a body. Magnesium (Mg) -based implants show good degradation behavior and bone integration, but their effects on bone ultrastructure and mechanical properties are not fully understood. This dissertation investigates bone nanoadaptation around Mg-based implants—Mg-5Gd, Mg-10Gd, Mg-Ca-Zn (ZX00), Mg- rare earth elements (WE43), and pure Mg—compared to titanium, using synchrotron techniques (XRD, SAXS, XRF, XRD-CT), along with histology and mechanical testing. ZX00 altered the hydroxyapatite lattice, reducing crystallite size and platelet thickness near the implant, likely due to magnesium ion incorporation. These changes were linked to lower bone maturity and mechanical strength. Mg-10Gd caused no significant structural changes, while Mg-5Gd led to decreased d-spacing over time. Although Ca/P ratios at the implant surface remained stable, bone near blood vessels showed a decrease, suggesting magnesium accumulation in vessel walls. WE43 caused no early changes in bone structure, while pure Mg altered bone only after 28 days. Titanium consistently reduced d-spacing and increased crystallite size, likely reflecting early healing responses like woven bone formation. This research sheds light on nanoscale bone healing over 3 days to 8 months. Mg-10Gd stands out as the most promising implant, showing minimal impact on bone and no gadolinium accumulation. Other alloys, like Mg-5Gd, WE43, and ZX00, affected crystallite structure and, as shown with ZX00, may influence bone mechanics.
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