PEEK颈椎融合器的拓扑优化设计

Topological optimization and design of cervical interbody fusion cage made of PEEK

为了提高聚醚醚酮(polyether ether ketone,PEEK)材料颈椎椎间融合器的融合率,本研究利用有限元方法对其进行三维结构的拓扑优化设计。首先建立C3~C7节段的颈椎有限元模型并验证,然后创建C5~C6节段椎间融合器植入和前路钢板内固定的模型。将PEEK融合器设置为椭圆盘型和箱型两种初始设计域。先后进行单工况和多工况下融合器拓扑优化,并结合加权柔度优化。经过两次拓扑优化后,再对融合器的构型提取分析。研究结果表明:PEEK融合器的优化结构为环形,前方缺失,材料集中分布于后部及两侧;当体积分数分别为50%和30%时,融合器优化为多孔径和单一大孔径的形状,前者比后者增加了与终板的接触面积;优化后的融合器通过降低自身应力,增加了内部植骨块所受的应力。本研究通过加权柔度的方法构建的颈椎融合器优化模型,不受初始设计域变化的影响,且可以有效减少应力遮挡,增加植骨块的应力传导,将有助于促进融合。

The three-dimensional topological optimization of cervical interbody fusion cage was developed by the finite element method to enhance the fusion rate of the cervical interbody cage.The finite element(FE)model of C3-C7 segments was constructed and validated.The fusion FE model was developed by inserting the cage into the C5-C6 disc space and internal fixation used anterior plate-screw system.The initial structures of cages made of polyether ether ketone(PEEK)were set up into two types of elliptic cage and box.Topological optimization and weighted compliance optimization were developed under single and multiple loading conditions.The structural configuration analysis of the cage was carried out after two times of topological optimization.The results showed that the optimal structure of the cage is annular,and the materials of the cage are concentrated in the back and both sides;the cage is optimized for multi-pore shape and single large-pore shape when the volume fraction is set to 50%and 30%,respectively,and the former has more contact area with the endplate than the latter;the optimized cage increases the stress on the internal bone graft by reducing its own stress under loading.In this study,the optimal PEEK cage was designed by topological and weighted compliance optimization method,which was not affected by the change of initial structures of cage.It can effectively reduce the stress shielding and increase the stress stimulation of internal bone graft,which will help to promote the cervical fusion.