Analysis of tissue-material characteristics at the bone-magnesium interface built by biodegradable implants

对于活跃的青少年患者群体和表现出创伤性骨折的成年人，例如在体育活动后，需要最佳的医疗护理。在目前阶段，这种骨折是用不可降解的金属植入物治疗的，有时必须移除，例如，植入物与生长中的骨之间的大小和形状可能不匹配，特别是在儿童生长过程中。这样的第二次手术干预伴随着额外的愈合期，潜在的并发症和对患者的副作用。由镁合金制成的可降解植入物为骨愈合提供了很高的潜力，因为这种植入物在恢复过程中随时间溶解。镁合金的生物相容性可能进一步有利于愈合过程，因为镁在体内自然存在，镁合金的机械性能更接近人骨。由于种植体的降解，骨与种植体的界面不能再被认为是恒定的，因为它随着化学环境的变化而受到稳定的重塑。到目前为止，还没有完全了解这种转变是如何影响骨整合的。因此，我们的目的是研究降解植入物对骨组织力学性能的影响，并将其与不同层次骨结构的变化联系起来。我们设计了一项研究计划，通过加入提供综合骨表征（UKE）和生物可降解镁植入物专业知识的相关工作组的能力，测量镁植入物所需的纳米结构、化学和生物力学特性，以破译由降解引起的不同层次长度尺度的变化。我们将利用组织学、元素映射、纳米压痕和小角度x射线散射实验来获得化学成分、机械性能和微观和纳米结构行为的信息。因此，将生成一个综合数据集，将围绕Mg植入物的机械、结构和化学参数汇集在一起。对该多模态数据集进行相关分析将使我们更好地了解在稳定重塑植入物与骨界面的情况下，哪些关键因素决定骨整合，以及骨基质的最终特性如何依赖于此。将骨组织的生物力学变化与种植体降解过程中的结构适应、降解产物的形成以及骨-种植体界面的动态变化联系起来是可能的。

Optimal medical care is required for active juvenile patient groups and adults exhibiting traumatic fractures, e.g., following sports activities. At the current stage, such fractures are treated with non-degradable metal implants that sometimes must be removed as, e.g., a mismatch in size and shape between the implant and growing bone can occur especially for children during growth. Such a second surgical intervention comes along with additional healing periods, potential complications, and side effects for the patient. Degradable implants made of magnesium (Mg) alloys provide a high potential for bone healing as such an implant dissolves with time during recovery. Magnesium alloys may further benefit the healing process due to their biocompatibility as Mg is naturally occurring in the body and Mg alloys mechanical properties are closer to those of human bone. Due to the degradation of the implant, the bone to implant interface can no longer be regarded as constant as it is subject to a steady remodelling alongside a changing chemical environment. Up to now, it is not fully understood how this transition impacts osseointegration. Therefore, we aim to examine the influence of degrading implants on the mechanical properties of the bone tissue and connect it to changes in the different hierarchical bone structures. We have designed a research program to measure the needed nanostructural, chemical, and biomechanical properties around Mg implants to decipher changes at different hierarchical length scales induced by degradation through joining the competencies of the involved workgroups providing the expertise of comprehensive bone characterization (UKE) and biological degradable magnesium implants (Hereon). We will utilize histology, elemental mapping, nanoindentation, and small-angle X-ray scattering experiments to obtain information on the chemical composition, mechanical properties, and micro- and nanostructural behaviour. As a result, a comprehensive dataset will be generated, bringing together mechanical, structural, and chemical parameters around Mg implants. Performing a correlative analysis on this multimodal dataset will allow us to understand better which key factors determine the osseointegration in the presence of a steadily remodelling implant to bone interface and how the resulting properties of the bone matrix depend on this. It will be possible to connect the bone tissue's biomechanical changes to structural adaptations during implant degradation, formation of degradation products, and dynamically changing bone-implant interface.