Abstract

A 3D-printed Ti-6Al-4V tubular implant improved initial stability via extended intramedullary and lateral fixation. • Microporous mid-segment topology promoted stronger bone-implant interface integration. • The porous mid-segment showed compliant fixation behavior. Large tubular bone defects remain difficult to reconstruct because limited fixation length compromises initial mechanical stability, whereas suboptimal implant microarchitecture hinders long-term biological integration. To address these dual challenges, this study developed an application-oriented dual-optimization framework for Ti-6Al-4 V tubular implants by integrating established fixation principles with microscopic pore-topology regulation. At the macroscopic level, finite element analysis (FEA) showed that an unfavorable exposure-to-fixation ratio increased mid-segment stress concentration and interfacial shear, which guided the design of a tubular implant with extended intramedullary fixation and lateral cortical anchoring wings. A single proof-of-concept clinical application in an ultra-long femoral defect provided preliminary support for the early technical feasibility of this fixation concept. At the microscopic level, three representative mid-segment architectures—Porous, Truss, and Solid—were comparatively evaluated. In vitro, the Porous architecture promoted superior cell adhesion, proliferation, osteogenic activity, and angiogenic response while limiting fibroblast infiltration. In a rabbit femoral defect model, the Porous implant also achieved greater fixation stability and enhanced cortical bone integration. Overall, these findings support a mechanically and biologically integrated reconstruction strategy for large tubular bone defects. However, the current evidence remains preclinical and proof-of-concept in nature. Larger clinical cohorts, longer follow-up, and dedicated fatigue testing are still required to evaluate clinical generalizability, long-term safety, and the fatigue durabilit