Drillable magnesium phosphate cements in biomechanical evaluation: bone adhesive and bone substitute at same time.

• Applicant: Professorin Dr. Stefanie Hölscher-Doht
• Subject Area: Biomaterials ; Orthopaedics, Traumatology, Reconstructive Surgery
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 524554701

Mineral ceramics as bone substitutes have been in clinical use for some time. The current commercially available standard for bone void fillers are hydroxyapatite cements, which can be injected into bony defects and after a short setting time already become so strong that surgical fracture treatment can be continued. However, these cements show a lack of remodeling to bone, even over years, which is why magnesium phosphate-based cements represent an exciting alternative. In recent years, these cements demonstrated convincing performance in loading tests as pure material tests, in realistic fracture models and in in vivo animal models with regard to their mechanical properties, their biocompatibility and their remodeling to bone. Using phytic acid (IP-6) as a liquid component, two compositions of magnesium phosphate cements could be detected in the preliminary study for this research project, which, in addition to these desirable properties, are optimized for clinical use: In addition to being injectable at different temperatures, they are drillable and further exhibit, even after the drilling process and placement of a screw, a high axial load-bearing capacity. An interesting side effect that was noticed when testing different compositions of the magnesium phosphate cements with phytic acid was the adhesive effect on all surfaces of these cements. This is a side-effect that is extremely interesting for further clinical application of the cements. The aim of this project is now to further characterize these drillable and adhesive cements as "all-rounders" for application to bone, as an adhesive and filler in one. If both properties can be combined in one cement, this would revolutionize surgical fracture treatment, especially for articular multi-fragment fractures. In order to investigate this highly interesting new aspect of potential clinical application in more detail, a close to clinic fracture model is first established, which has beside a bony defect and a gap component for bonding. Using porcine tibia bones, this fracture model will be evaluated and a new surgical technique of filling and gluing this fracture with primary anatomic reduction will be analyzed. Using biomechanical tests of combinations of bone cements and plate osteosyntheses, the new surgical method will be evaluated for strength differences from the previously used, established method. In addition, the properties of the new adhesive and drillable magnesium phosphate cements will be investigated in the fracture model on human bone. Valuable results for the transferability and clinical application of magnesium phosphate cement with phytic acid are expected from the findings.

• DFG Programme: Research Grants