Construction of Organic-Inorganic Composite Degradable Bone Cement and Its Hydration Mechanism

Bone cement， widely used in orthopedic clinical applications as a filling and supporting material， plays a crucial role in the treatment of vertebral compression fractures and bone defect repair. Traditional methacrylate-based bone cements exhibit high modulus and poor degradability， while inorganic phosphate-based bone cements， though degradable， are brittle and prone to early disintegration. Therefore， developing a bone cement material system with both excellent mechanical properties and degradability is a challenging task. In this study， an innovative strategy for constructing organic-inorganic composite bone cement is proposed by combining an in-situ free radical ring-opening polymerization system with a self-setting phosphate hydration system. The resulting composite bone cement material （PMH-MPC） demonstrates both superior mechanical performance and degradability. When the mass-to-volume ratio of inorganic phosphate to organic monomer liquid phase is 1 g/mL， the resulting composite bone cement exhibits optimal comprehensive properties： an initial compressive strength of 66.7 MPa， and after immersion in water for 48 h， the compressive strength decreases by only 33.3% compared to the pure polymer group PMH. Additionally， the composite material shows good injectability and degradability. Scanning electron microscopy （SEM） and X-ray diffraction （XRD） results confirm that the composite bone cement forms struvite mineral phases in water， and the hydration layer formed by cementation effectively protects the material matrix. The composite bone cement also exhibits excellent cell and blood compatibility. This study demonstrates that the organic-inorganic composite strategy significantly enhances the mechanical strength of bone cement while maintaining its degradability， providing a new solution to overcome the clinical limitations of traditional bone cement materials.