Injectable Bismuth‐Based Composite Enable Bone Defect Repair for Osteosarcoma Treatment and Mild Magnetothermal Bone Regeneration

Abstract Bone implant materials are essential for treating bone defects in clinical, however, current options face challenges in minimally invasive implantation, precise in situ molding, and long surgical times with large incisions. To address these drawbacks, the newly‐emerging low‐melting‐point bismuth‐based alloys as injectable bone implants, combined with clinically applied polymethyl methacrylate (PMMA) bone cement are proposed here to innovatively design the multifunctional bismuth‐PMMA composites (BPCs) for effective bone repair. The as‐prepared BPCs offer excellent injectability, enhanced mechanical properties (≈252% increase in compressive strength), and favorable magnetothermal effects, enabling minimally invasive, in situ bone molding via easygoing injection for orthopedic surgeries. The introduction of PMMA in BPCs significantly improves mechanical strength while maintaining the injectability of bismuth alloys, and reduces exothermic heat during curing to prevent thermal damage to bone tissue. In vivo experiments demonstrate that under an alternating magnetic field, BPCs exhibit outstanding tumor cell killing capability and inhibit osteosarcoma growth through efficient magnetic hyperthermia. Further, long‐term in vivo implantation results coupled with histological analysis display stable bone filling and evident bone regeneration, attributed to the collaborative efficacy of BPC implant and mild magnetothermal therapy. This study promises to revolutionize bone repair and provide a versatile surgical strategy for in situ 3D‐printed orthopedics in the future.