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

• Applicants: Professor Dr. Björn Busse; Dr. Florian Wieland
• Subject Area: Orthopaedics, Traumatology, Reconstructive Surgery
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 526239533

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.

• DFG Programme: Research Grants