Skelley Nathan W, Castile Ryan M, Cannon Paul C, Weber Christian I, Brophy Robert H, Lake Spencer P
Department of Orthopaedic Surgery, Barnes-Jewish Hospital/Washington University in St Louis School of Medicine, St Louis, Missouri, USA.
Department of Mechanical Engineering and Materials Science, Washington University in St Louis, St Louis, Missouri, USA.
Am J Sports Med. 2016 Nov;44(11):2892-2899. doi: 10.1177/0363546516654480. Epub 2016 Jul 25.
The anteromedial (AM) bundle of the anterior cruciate ligament (ACL) has a higher modulus and failure stress than does the posterolateral (PL) bundle. However, it is unknown how these properties vary within each bundle.
To quantify mechanical and microstructural properties of samples within ACL bundles to elucidate any regional variation across the ligament. We hypothesized that there are no differences within each bundle in contrast to cross-bundle variation.
Descriptive laboratory study.
Sixteen human ACLs were dissected into AM and PL bundles. Three samples were taken from each bundle in an ordered sequence from AM (region 1 AM bundle) to PL (region 6 PL bundle). Each sample was tested in uniaxial tension, using quantitative polarized light imaging (QPLI) to quantify collagen fiber alignment. After preconditioning, samples were subjected to a stress-relaxation (SR) test followed by quasistatic ramp-to-failure (RF). Peak and equilibrium stress values were computed from the SR test and modulus quantified in the toe- and linear-regions of the RF. QPLI values describing collagen orientation (angle of polarization [AoP]) and strength of alignment (degree of linear polarization [DoLP]) were computed for the SR test and at points corresponding to the zero, transition point, and linear region of the RF.
Toe- and linear-region modulus values decreased from region 1 to 6. Slopes of regression lines increased for the average DoLP during RF, with significance at higher strains. The standard deviation of AoP values decreased during RF, indicating tighter distribution of orientation angles, with significant correlations at all points of the RF. During SR, stress values uniformly decreased but did not show significant linear regression by region. DoLP and AoP values changed slightly during SR and demonstrated significant linear variation by region at both peak and equilibrium points.
Most microstructural and material properties evaluated in this study appear to follow a linear gradient across the ACL, rather than varying by bundle.
This AM-to-PL variation provides a more accurate description of functional tissue anatomy and can be used to assess and guide techniques of ACL reconstruction.
前交叉韧带（ACL）的前内侧（AM）束比后外侧（PL）束具有更高的模量和破坏应力。然而，这些特性在每个束内如何变化尚不清楚。
量化ACL束内样本的力学和微观结构特性，以阐明整个韧带的任何区域差异。我们假设与跨束差异相反，每个束内不存在差异。
描述性实验室研究。
将16条人ACL解剖为AM束和PL束。从AM（区域1 AM束）到PL（区域6 PL束）按顺序从每个束中取三个样本。每个样本进行单轴拉伸测试，使用定量偏振光成像（QPLI）量化胶原纤维排列。预处理后，样本进行应力松弛（SR）测试，然后进行准静态斜坡至破坏（RF）测试。从SR测试中计算峰值和平衡应力值，并在RF的趾部和线性区域量化模量。计算SR测试以及对应于RF的零、转变点和线性区域的点处描述胶原取向（偏振角[AoP]）和排列强度（线性偏振度[DoLP]）的QPLI值。
趾部和线性区域模量值从区域1到6降低。RF期间平均DoLP的回归线斜率增加，在较高应变时具有显著性。RF期间AoP值的标准差降低，表明取向角分布更紧密，在RF的所有点均具有显著相关性。SR期间，应力值均匀下降，但各区域未显示出显著的线性回归。DoLP和AoP值在SR期间略有变化，在峰值和平衡点均显示出各区域的显著线性变化。
本研究中评估的大多数微观结构和材料特性似乎在整个ACL中呈线性梯度变化，而非因束而异。
这种从AM到PL的变化提供了对功能性组织解剖结构更准确的描述，可用于评估和指导ACL重建技术。
