µXRF Elemental Mapping of Bioresorbable Magnesium-Based Implants in Bone

This study investigated the distribution of the elemental constituents of Mg-based implants at various stages of the degradation process in surrounding bone tissue, with a focus on magnesium (Mg), as the main component of the alloy, and yttrium (Y), due to its potential adverse health effects. The measurements were performed on the implant-bearing thin sections of rat bone in a time series of implant degradation between one and 18 months. Micro X-ray fluorescence analysis (μXRF) with a special spectrometer meeting the requirements for the measurements of low-Z elements was used. It was found that the migration and accumulation behaviour of implant degradation products is element-specific. A sharp decrease in Mg was observed in the immediate vicinity of the interface and no specific accumulation or aggregation of Mg in the adjacent bone tissue was detected. By contrast, Y was found to migrate further into the bone over time and to remain in the tissue even after the complete degradation of the implant. Although the nature of Y accumulations must still be clarified, its potential health impact should be considered.ISSN:1996-194

Long-term in vivo degradation behavior and near-implant distribution of resorbed elements for magnesium alloys WZ21 and ZX50

We report on the long-term effects of degrading magnesium implants on bone tissue in a growing rat skeleton using continuous in vivo micro-Computed Tomography, histological staining and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). Two different magnesium alloys—one rapidly degrading (ZX50) and one slowly degrading (WZ21)—were used to evaluate the bone response and distribution of released Mg and Y ions in the femur of male Sprague-Dawley rats. Regardless of whether the alloy degrades rapidly or slowly, we found that bone recovers restitutio ad integrum after complete degradation of the magnesium implant. The degradation of the Mg alloys generates a significant increase in Mg concentration in the cortical bone near the remaining implant parts, but the Mg accumulation disappears after the implant degrades completely. The degradation of the Y-containing alloy WZ21 leads to Y enrichment in adjacent bone tissues and in newly formed bone inside the medullary space. Locally high Y concentrations suggest migration not only of Y ions but also of Y-containing intermetallic particles. However, after the full degradation of the implant the Y-enrichment disappears almost completely. Hydrogen gas formation and ion release during implant degradation did not harm bone regeneration in our samples.ISSN:1742-7061ISSN:1878-756