BACKGROUND 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. METHODS 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). RESULTS 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. CONCLUSIONS 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.

中文翻译：

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单层椎间融合器与不同内固定杆材料的生物力学分析：有限元分析。

背景技术腰椎融合与刚性脊柱固定器是与相邻节段衰竭相关的高风险因素之一。这项研究的目的是通过使用有限元方法研究脊柱固定棒的材料特性如何在仪器水平和邻近水平上影响生物力学行为。方法在我们的研究中，构建了五个有限元模型来模拟人体脊柱手术前后。对于这四个术后模型，将脊柱植入由三种不同材料制成的棒：（i）钛棒，（ii）带主体PEEK固定架的PEEK杆，（iii）带主体PEEK固定架的可生物降解的杆和（iv） PEEK笼，无椎弓根螺钉固定（无杆）。结果使用PEEK或可生物降解的棒融合腰椎可以在所有情况下在融合和邻近水平获得相似的ROM。带有PEEK和可生物降解棒的模型在相邻的小关节上也显示出相似的接触力增加，但是两者都比带有钛棒的模型小。结论具有非器械融合的柔性杆或笼可以减轻在脊柱固定后通常在相邻小关节上产生的增加的接触力，并且还可以降低骨移植物的应力屏蔽水平。