Structural design and biomechanical analysis of anti- subsidence gradient porous artificial vertebrae combined with a...

In total disc replacement, mechanical failure and implant subsidence are significant complications after vertebral body replacement. Therefore, the design of a new artificial vertebral implant(AVI)that can ensure safety and improve prosthesis's subsidence has become a key challenge for spinal reconstruction.

This study involved designing a new AVI. Its exterior is a topological entity framework, and its interior is a gradient triply periodic minimal surface (TPMS) gyroid structure, which simulates cortical bone and cancellous bone, respectively. To enhance the safety and stability of the prosthesis. The biomechanical properties of AVIs under different physiological postures were analysed using the finite element method(FEM). The samples were prepared using selective laser melting (SLM), and the quasi-static compression and subsidence experiments were carried out for evaluation.

The peak stress of the topological gradient gyroid AVI was significantly lower than that of the traditional titanium mesh cage (TMC) and the truss + fluorite AVI, with a maximum reduction of 69.7%. Under all working conditions, the peak stress at the bone-implant interface of the vertebrae was 5.9% -14.1% lower than that of the truss + fluorite AVI and much lower than that of the TMC, with a decrease of 44.3%. Quasi-static compression experiments show that the maximum compression load of the topological gradient gyroid AVI is approximately 1.12 times greater than that of the truss + fluorite AVI and significantly greater than that of the TMC. This indicates that topological gradient gyroid AVI meets safety requirements. Additionally, its anti-subsidence ability is 20.4% higher than that of traditional porous AVI.

Compared with traditional AVIs, the combination of topology optimization framework and gradient gyroid structure significantly improves the mechanical strength and subsidence resistance of the AVI, and can effectively reduce the stress concentration, which is expected to become the preferred scheme for spinal reconstruction.