Polyurethane/Tricalcium Phosphate Bone Adhesives and Substitutes for Load Bearing Applications

The large mechanical forces throughout the sternum and upon the tibia, impact healing capacities following sternotomies and upper tibia osteotomies, respectively. In these fields, there remains a need for materials with a strong adhesive capacity, high mechanical strength when set and sufficient porosity to allow osteointegration. The present work investigates castor oil-based polyurethanes synthesized and combined with β-tricalcium phosphate (β-TCP) granules for use as bone graft substitutes or adhesives in load-bearing regions. The material is produced via a reaction involving castor oil, caprolactone monomers, an aliphatic diamine-based catalyst and water, with the CO₂ gas product creating pores throughout the structure. β-TCP particles 1000–2000 μm in diameter that were added to the mixture compose the ceramic phase of the material. Setting completely after 24 hours, the adhesive cubic bone grafts exhibited a 97% structural porosity, Young's Modulus of around 44 MPa, biocompatibility, cell attachment and tissue ingrowth and no apoptotic or necrotic effects. With a fully interconnected porous structure and adhesive qualities, this adhesive bone graft material holds potential for the reconstruction of challenging regions such as the sternum, upper tibia and mandible. Furthermore, the bone grafts can be offered as pre-formed, off-the-shelf products.