Hydrogels for Bone Repair: Construction Strategies and Applications

Bone injuries, particularly those associated with an aging global population, pose a persistent and complex clinical challenge. Current gold-standard treatments such as autografts, allografts, and metal implants, are often limited by immune rejection and mechanical mismatch. In this context, hydrogels are promising biomaterials for bone regeneration, due not only to inherent biocompatibility, high hydration, and tunable elasticity but also to the ability to mimic the native bone micro environment. This review presents a critical and comprehensive analysis of how hydrogels for bone repair are designed, constructed, and functionalized to achieve the desired regenerative performance. It systematically examines multiple hydrogel types, centering on the design of their strength and biodegradation features to better align with the functional demands of bone healing. Furthermore, the review summarizes that by incorporating bioactive molecules, nanomaterials, or cells, advanced functionalization can orchestrate osteogenesis and angiogenesis. In vitro and in vivo studies evidenced the performance of hydrogels' applications ranging from bone fracture repair to smart, stimuli-responsive platforms for personalized regenerative medicine. This review finally identifies the prevailing translational challenges and suggests future research trajectories.