Finite element study on the influence of pore size and structure on stress shielding effect of additive manufactured spinal cage

The stress shielding effect occurs when the orthopedic implant reduces the load delivered to the bone, causing inefficient stress transfer to the host bone. The usage of porous additive manufactured (AM) cages reduces the stress shielding effect and promotes bone ingrowth also. The purpose of this work is to study the stress and deformation on porous hybrid spinal cages under different loading conditions using Finite Element Analysis (FEA). The spinal cages consisting of three porous structures with pore sizes ranging from 0.4 to 0.6 mm were investigated for stress shielding and fatigue strength. The results showed a significant reduction in stress shielding for the studied designs and conclude that the pore size has a greater significant effect on stress shielding than the porous structure in spinal cages.

应力遮挡效应（stress shielding effect）指当骨科植入物（orthopedic implant）降低传递至骨骼的载荷时，引发宿主骨应力传递效率低下的现象。采用多孔增材制造（additive manufactured, AM）的脊柱融合器，可降低应力遮挡效应，同时促进骨长入（bone ingrowth）。本研究旨在通过有限元分析（Finite Element Analysis, FEA），探究不同载荷条件下多孔混合式脊柱融合器的应力与变形情况。本次研究针对孔径范围为0.4~0.6 mm的三种多孔结构脊柱融合器，就其应力遮挡效应与疲劳强度（fatigue strength）展开分析。研究结果表明，所设计的融合器的应力遮挡效应得到显著降低；同时得出结论：相较于多孔结构类型，孔径对脊柱融合器的应力遮挡效应具有更为显著的影响。