Injectable hydrogels for bone regeneration: from materials design to clinical translation

Clinical repair of bone defects has long faced challenges including the limited availability of autografts, immunological rejection of allografts, and mechanical mismatch of traditional implants. Injectable hydrogels have emerged as highly promising strategies in bone tissue engineering due to their unique advantages: minimally invasive implantation, the ability to conform to irregular defect cavities, excellent biocompatibility, and high functional tunability. This review systematically outlines recent advances in injectable hydrogels for bone regeneration. It comprehensively outlines material classifications and fundamental properties. Specifically, it analyzes key design strategies, including enhancing mechanical support through cross-linking optimization and the incorporation of reinforcing phases, reconstructing the regenerative microenvironment via bioactive factor loading, and enabling synchronized degradation and tissue regeneration. Furthermore, this review summarizes current applications for different bone defect types, identifies current technical bottlenecks such as balancing mechanical strength with minimally invasive delivery, and anticipates future directions, including stimuli-responsive design and multifunctional integration.