Review on lower limb bone fracture fixation: biomechanics, design, and advancements in additive manufacturing for implants

• Porous bone plates reduce stress shielding and enhance load sharing at fracture site. • FEM and mechano-regulation models can predict implant response. • Topology-optimized and porous implants improve stiffness–flexibility balance. • AI-driven designs can suggets patient-specific implants with superior performance. Bone fractures in the lower limbs, pose significant challenges in orthopaedic treatment due to the need for effective stabilization and healing. To contextualize recent advances, data indicate that lower limb fractures account for 20.2 % of all fractures. Conventional metallic implants show a mismatch in stiffness, with cortical bone exhibiting a Young’s modulus of 7–30 GPa, compared to 110 GPa for titanium (Ti-6Al-4V) and 200–230 GPa for stainless steel (SS) and cobalt-chromium (Co-Cr) alloys, leading to stress shielding. By contrast, additively manufactured porous and topology-optimized designs have demonstrated reductions in implant stiffness of up to 40–70 %, while maintaining mechanical stability and enhancing callus formation. This review examines the biomechanics, design considerations, and advancements in additive manufacturing (AM) for bone plates and intramedullary nails. The fundamental aspects of bone fractures and the healing process highlight the importance of biomechanical environments for implant performance. While tracing the evolution of bone plates and intramedullary nails, the review discusses modern innovations and advancements in fracture stabilization and healing outcomes. The review concludes the biomechanical performance of optimized implants through experimental, clinical, and computational studies, emphasizing the benefits of AM for fracture fixation. Future directions include integrating artificial intelligence into implant design