Adapting bioresorbable Mg-Fe Implants in bone healing

To stabilize fractures of the lower extremities, particularly the femur and tibia, load-bearing implants are required to support the patients body weight and enable early mobilization. This promotes bone regeneration and helps to prevent secondary complications such as thrombosis or embolism. Currently, permanent metals such as plates, intramedullary nails, screws, wires, and plates made of titanium or stainless steel are used for fracture fixation. However, these materials do not fully meet biological requirements, as they have a high e-modulus compared to human bone. As a result, only minimal load is transferred to the bone, which can lead to bone resorption beneath the materials. This may cause pain or new fractures (e.g., above or below a plate), sometimes requiring surgical removal. Implants made from resorbable materials offer an excellent alternative to avoid these disadvantages and complications. Implants made from magnesium (Mg)-based alloys can completely dissolve within the human body and exhibit a mechanical stiffness similar to that of bone allowing the bone to bear load again quickly and become trained. Clinical studies in humans have shown that magnesium implants dissolve completely and without side effects after approximately three years. However, the strength of Mg-based implants is currently still too low to fix fractures of load-bearing bones (such as the femur or ankle). Therefore, the goal of this project is to develop resorbable metallic materials with sufficient strength to stabilize load-bearing bones and to investigate their compatibility within the body. To achieve the required strength, instead of Mg alloys, we will develop Mg-Fe composite materials and test their biocompatibility, degradation behavior, and mechanical strength in both cell and animal studies. We will evaluate the composites with regard to their material properties and degradation behavior. Clinical applicability will be simulated in a small animal model, in which a bone fracture will be stabilized using the Mg/Fe composites, followed by analysis of the healing capability and quality of the bone. In addition, potential inflammatory reactions and side effects will be examined. The resulting data will be compared to established Mg alloys as well as permanent implant materials. The project involves researchers and surgeons from university hospitals (clinicians and researchers: Stange, Weinberg), molecular biologists (Timmen, Sommer), and materials scientists (Renk, Eckert) to carry out the necessary work for developing the first bioresorbable, load-bearing implant made from a Mg/Fe composite material.