Table_1_Biomechanical study of two-level oblique lumbar interbody fusion with different types of lateral instrumentation: a finite element analysis.docx

ObjectiveThe aim of this study was to verify the biomechanical properties of a newly designed angulated lateral plate (mini-LP) suited for two-level oblique lumbar interbody fusion (OLIF). The mini-LP is placed through the lateral ante-psoas surgical corridor, which reduces the operative time and complications associated with prolonged anesthesia and placement in the prone position.
MethodsA three-dimensional nonlinear finite element (FE) model of an intact L1–L5 lumbar spine was constructed and validated. The intact model was modified to generate a two-level OLIF surgery model augmented with three types of lateral fixation (stand-alone, SA; lateral rod screw, LRS; miniature lateral plate, mini-LP); the operative segments were L2–L3 and L3–L4. By applying a 500 N follower load and 7.5 Nm directional moment (flexion-extension, lateral bending, and axial rotation), all models were used to simulate human spine movement. Then, we extracted the range of motion (ROM), peak contact force of the bony endplate (PCFBE), peak equivalent stress of the cage (PESC), peak equivalent stress of fixation (PESF), and stress contour plots.
ResultsWhen compared with the intact model, the SA model achieved the least reduction in ROM to surgical segments in all motions. The ROM of the mini-LP model was slightly smaller than that of the LRS model. There were no significant differences in surgical segments (L1–L2, L4–L5) between all surgical models and the intact model. The PCFBE and PESC of the LRS and the mini-LP fixation models were lower than those of the SA model. However, the differences in PCFBE or PESC between the LRS- and mini-LP-based models were not significant. The fixation stress of the LRS- and mini-LP-based models was significantly lower than the yield strength under all loading conditions. In addition, the variances in the PESF in the LRS- and mini-LP-based models were not obvious.
ConclusionOur biomechanical FE analysis indicated that LRS or mini-LP fixation can both provide adequate biomechanical stability for two-level OLIF through a single incision. The newly designed mini-LP model seemed to be superior in installation convenience, and equally good outcomes were achieved with both LRS and mini-LP for two-level OLIF.

研究目的：本研究旨在验证一款专为双节段斜外侧腰椎椎间融合术（two-level oblique lumbar interbody fusion, OLIF）设计的新型成角侧方钢板（mini-LP）的生物力学性能。该mini-LP经腰大肌前方手术通路置入，可缩短手术时长，减少因延长麻醉时间及俯卧位操作引发的相关并发症。

研究方法：本研究构建并验证了完整L1~L5腰椎的三维非线性有限元（finite element, FE）模型。以该完整模型为基础，修改得到双节段OLIF手术模型，并分别植入三类侧方固定装置：单纯融合器（stand-alone, SA）、侧方棒螺钉系统（lateral rod screw, LRS）以及微型侧方钢板（mini-LP）；手术节段设定为L2~L3与L3~L4。通过施加500 N的跟随载荷与7.5 N·m的定向力矩（模拟屈伸、侧屈及轴向旋转运动），对所有模型开展人体脊柱运动仿真。随后提取各项力学指标，包括活动度（range of motion, ROM）、终板峰值接触力（peak contact force of the bony endplate, PCFBE）、融合器峰值等效应力（peak equivalent stress of the cage, PESC）、固定装置峰值等效应力（peak equivalent stress of fixation, PESF）以及应力云图。

研究结果：相较于完整模型，单纯融合器组（SA）对手术节段活动度的降低幅度最小。微型侧方钢板组（mini-LP）的活动度略小于侧方棒螺钉组（LRS）。所有手术模型与完整模型在非手术节段（L1~L2、L4~L5）的活动度均无显著差异。侧方棒螺钉组（LRS）与微型侧方钢板组（mini-LP）的终板峰值接触力（PCFBE）及融合器峰值等效应力（PESC）均低于单纯融合器组（SA），但LRS与mini-LP两组间的PCFBE及PESC差异无统计学意义。在所有载荷工况下，LRS与mini-LP两组的固定装置峰值等效应力（PESF）均显著低于材料屈服强度。此外，LRS与mini-LP两组的PESF波动幅度均不明显。

研究结论：本生物力学有限元分析结果表明，侧方棒螺钉系统（LRS）与微型侧方钢板（mini-LP）均可通过单一切口为双节段OLIF提供充足的生物力学稳定性。本研究设计的新型mini-LP在安装便利性上更具优势，而LRS与mini-LP应用于双节段OLIF均可取得同等良好的临床效果。