A comparison of intervertebral ligament properties utilized in a thoracic spine functional unit through kinematic evaluation

Ligament properties in the literature are variable, yet scarce, but needed to calibrate computational models for spine clinical research applications. A comparison of ligament stiffness properties and their effect on the kinematic behavior of a thoracic functional spinal unit (FSU) is examined in this paper. Six unique ligament property sets were utilized within a volumetric T7–T8 finite element (FE) model developed using computer-aided design (CAD) spinal geometry. A 7.5 Nm moment was applied along three anatomical planes both with and without costovertebral (CV) joints present. Range of Motion (RoM) was assessed for each property set and compared to published experimental data. Intact and serial ligament removal procedures were implemented in accordance with experimental protocol. The variance in both kinematic behavior and comparability with experimental data among property sets emphasizes the role nonlinear characterization plays in determining proper kinematic behavior in spinal FE models. Additionally, a decrease in RoM variation among property sets was exhibited when the model setup incorporated the CV joint. With proper assessment of the source and size of each ligament, the material properties considered here could be expanded and justified for implementation into thoracic spine clinical studies.

现有文献中关于韧带特性的报道不仅稀缺，且结果差异较大，但脊柱临床研究应用中的计算模型校准亟需此类数据。本文针对胸椎功能性脊柱单元（FSU）的韧带刚度特性及其对运动学行为的影响展开对比分析。研究采用基于计算机辅助设计（CAD）脊柱几何模型构建的容积式T7-T8有限元（FE）模型，共设置6组独特的韧带特性参数。分别在存在与不存在肋椎关节（CV）的两种工况下，沿三个解剖平面施加7.5 Nm的弯矩。针对每组特性参数评估其活动度（RoM），并与已发表的实验数据进行对比。本研究严格遵循实验方案，设置了完整韧带与依次切除韧带的对照组别。不同韧带特性参数组在运动学行为表现及与实验数据的匹配一致性上均存在明显离散差异，这凸显了非线性特性表征在确定脊柱有限元模型合理运动学行为中的关键作用。此外，当模型纳入肋椎关节后，各组参数间的活动度差异有所减小。若能对每条韧带的起源与尺寸进行充分评估，本研究中采用的材料特性可得到进一步拓展，并为其应用于胸椎脊柱临床研究提供合理性依据。