Department of Biomedical Engineering, National Yang-Ming University, Taipei, Taiwan.
Department of Orthopedics, Shuang Ho Hospital, Taipei Medical University, New Taipei City, Taiwan.
BMC Musculoskelet Disord. 2020 Feb 14;21(1):100. doi: 10.1186/s12891-020-3111-1.
Lumbar spinal fusion with rigid spinal fixators as one of the high risk factors related to adjacent-segment failure. The purpose of this study is to investigate how the material properties of spinal fixation rods influence the biomechanical behavior at the instrumented and adjacent levels through the use of the finite element method.
Five finite element models were constructed in our study to simulate the human spine pre- and post-surgery. For the four post-surgical models, the spines were implanted with rods made of three different materials: (i) titanium rod, (ii) PEEK rod with interbody PEEK cage, (iii) Biodegradable rod with interbody PEEK cage, and (iv) PEEK cage without pedicle screw fixation (no rods).
Fusion of the lumbar spine using PEEK or biodegradable rods allowed a similar ROM at both the fusion and adjacent levels under all conditions. The models with PEEK and biodegradable rods also showed a similar increase in contact forces at adjacent facet joints, but both were less than the model with a titanium rod.
Flexible rods or cages with non-instrumented fusion can mitigate the increased contact forces on adjacent facet joints typically found following spinal fixation, and could also reduce the level of stress shielding at the bone graft.
腰椎融合术联合刚性脊柱固定器是导致邻近节段失败的高风险因素之一。本研究旨在通过有限元方法探讨脊柱固定杆的材料特性如何通过仪器和邻近水平影响生物力学行为。
本研究构建了五个有限元模型来模拟脊柱术前和术后的状态。对于四个术后模型，使用三种不同材料的杆进行脊柱植入：（i）钛杆、（ii）带椎间 PEEK cage 的 PEEK 杆、（iii）带椎间 PEEK cage 的可生物降解杆和（iv）无椎弓根螺钉固定的 PEEK cage（无杆）。
在所有情况下，使用 PEEK 或可生物降解杆融合腰椎后，在融合和邻近水平上具有相似的 ROM。PEEK 和可生物降解杆的模型还显示出相邻小关节接触力的相似增加，但均低于钛杆模型。
灵活的杆或无仪器融合的 cage 可以减轻脊柱固定后通常在相邻小关节上发现的增加的接触力，并可以降低骨移植物的应力屏蔽水平。
