Integrating 4D printing technology in medical implants offers promising advancements for minimally invasive delivery (MID) and personalized orthopedic solutions. This study presents a 4D-printed shape memory nickel-titanium (NiTi) mesh implant for cavitary bone defect reconstruction, enabling a time-dependent shape transformation. Fabricated through selective laser melting (80 W laser power, 600 mm/s scanning speed, 70 μm hatch spacing, 25 μm layer thickness), the implant can be compressed during implantation and recover its original shape. Micro-computed tomography analysis confirmed high geometric fidelity (D50 = 58 μm), while scanning electron microscopy-energy dispersive spectroscopy analysis revealed a uniform microstructure and confirmed the homogeneous distribution of Ni/Ti across the mesh implant. Phase transformation testing showed that the austenite finish temperatures (austenite finish) of the as-built sample and the acid-washed sample were below the 37°C physiological threshold. Compression testing indicated that a force of 156 N was required for 30% deformation, with complete recovery to its pre-defined shape. Clinically, the implant reduced cortical bone fenestration by 20%. Post-operative imaging at 6 and 12 months showed excellent osseointegration and minimal residual cavities. Functional assessments at 12 months indicated excellent recovery, with a Musculoskeletal Tumor Society score of 29. In the present study, the clinical use of the 4D-printed mesh implant demonstrated not only satisfactory osteointegration but also a practical advantage in surgical handling. The shape recovery of the implant from a compressed state to its pre-designed shape allowed for MID and precise fit to the defect contour.
Li et al. (Thu,) studied this question.