Osteointegration and remodeling of a novel mineral magnesium phosphate-based bone glue in-vivo

Background Bone adhesives represent a major challenge in the field of materials science. Magnesium phosphate-based mineral bone cements exhibit high biocompatibility, particularly for the use as bone substitutes. In combination with calcium ions and phytic acid as liquid components, these cements demonstrate adhesive properties and potentially represent a promising new type of bone glue. Two of these first cement-adhesives were further investigated for their in vivo properties on distal femoral defects in rabbits in this study. Materials and methods In 4.5-month-old New Zealand White rabbits, distal lateral femoral defects in the metaphyseal region were grafted with two different magnesium phosphate-based bone adhesives (MgO, Mg2 _,75 Ca _0,25 (PO ₄ ) ₂ , phytic acid 22,5/25%wt). After 6 weeks in vivo, the adhesives were evaluated by histologic examination, biomechanical testing, imaging, XRD, and porosimetry measurements for biocompatibility and remodeling to bone. Results While the bone adhesives showed a higher density on pQCT than the surrounding cancellous bone the biomechanical testing revealed a significantly lower initial stiffness of the adhesives 6 weeks after implantation compared to both the cancellous bone and the cuboid testing before implantation. The decrease in stability was confirmed by the degradation demonstrated histologically as well as by imaging morphology. Remodeling to bone was not yet complete. Conclusion Both bone adhesives exhibited high biocompatibility without foreign body reactions. Imaging and histology presented a homogeneous picture of degradation of both adhesives and remodeling to bone, which was not yet complete 6 weeks after the implantation.