Porous Biodegradable Lumbar Interbody Fusion Cage Design and Fabrication Using Integrated Global-Local Topology Optimization With Laser Sintering
Porous Biodegradable Lumbar Interbody Fusion Cage Design and Fabrication Using Integrated Global-Local Topology Optimization With Laser Sintering
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DOI：
10.1115/1.4025102
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发表时间：
2013-10-01
影响因子：
1.7
通讯作者：
Lin, Chia-Ying
中科院分区：
文献类型：
--
作者：
Kang, Heesuk;Hollister, Scott J.;Lin, Chia-Ying
生物可降解融合器因其在脊柱手术中的应用而受到越来越多的关注，这些手术涉及椎间融合术，以解决与使用不可降解融合器相关的并发症，例如应力遮挡和长期异物反应。然而，与永久性材料相比，相对较弱的初始材料强度以及随后由于降解而导致的降低可能是有问题的。为了设计用于临床前大型动物研究的多孔生物可降解椎间融合器，该融合器可以承受生理载荷，同时具有足够的互连孔隙率用于骨桥接和融合，我们开发了一种多尺度拓扑优化技术。宏观尺度的拓扑优化提供了确保机械强度的最佳结构布局，而替代宏观材料布局的最佳设计的微结构确保了最大的渗透性。使用聚（ε-己内酯）与羟基磷灰石混合的固体自由成型制造优化设计的融合器。压缩试验显示，优化融合器的屈服强度是典型人体腰椎载荷的两倍。计算分析进一步证实了人体腰椎内的机械完整性，尽管孔隙结构局部承受的应力高于屈服应力。当使用生物可降解材料用于融合器时，这种优化技术可用于平衡承重、应力屏蔽和互连孔隙率的复杂要求。
Biodegradable cages have received increasing attention for their use in spinal procedures involving interbody fusion to resolve complications associated with the use of nondegradable cages, such as stress shielding and long-term foreign body reaction. However, the relatively weak initial material strength compared to permanent materials and subsequent reduction due to degradation may be problematic. To design a porous biodegradable interbody fusion cage for a preclinical large animal study that can withstand physiological loads while possessing sufficient interconnected porosity for bony bridging and fusion, we developed a multiscale topology optimization technique. Topology optimization at the macroscopic scale provides optimal structural layout that ensures mechanical strength, while optimally designed microstructures, which replace the macroscopic material layout, ensure maximum permeability. Optimally designed cages were fabricated using solid, freeform fabrication of poly(epsilon-caprolactone) mixed with hydroxyapatite. Compression tests revealed that the yield strength of optimized fusion cages was two times that of typical human lumbar spine loads. Computational analysis further confirmed the mechanical integrity within the human lumbar spine, although the pore structure locally underwent higher stress than yield stress. This optimization technique may be utilized to balance the complex requirements of load-bearing, stress shielding, and interconnected porosity when using biodegradable materials for fusion cages.