A photoelastic study of ligament strain.
A photoelastic study of ligament strain.
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DOI：
10.1109/86.712228
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发表时间：
1998-09-01
期刊：
影响因子：
--
通讯作者：
Kawada, T
中科院分区：
文献类型：
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作者：
Hirokawa, S;Yamamoto, K;Kawada, T
人类膝关节的前十字韧带(ACL)在屈膝时表现出高达10%-20%的应变，而通常的Hookean弹性材料表现出最多0.3%的应变。此外，由于膝关节屈曲时附着体的复杂三维(3-D)运动，形状复杂的前交叉韧带以高度可变的方式变形。这种大的和高度可变的前交叉韧带变形不能通过一维(1-D)和/或局部化测量来充分量化。为了测量前交叉韧带整个区域的应变，我们在应变的基础上采用光弹涂布法进行应力分析。一种具有光学高条纹灵敏度的特殊类型的聚氨酯被发现最适合用于测量目的。初步实验发现，PU薄膜的双折射级数与应变之间的相关系数为99%，线性相关系数可达45%。这项研究分两步进行。在第一步中，利用制作的独特的膝关节模型进行研究，该模型允许通过光弹性涂层方法直接观察和测量模型ACL中的变形和应变分布。结果表明，该膜对某些生物软组织的力学性能影响不大，能较好地反映组织的应变行为。因此，在第二步中，使用光弹性方法测量了膝关节自由屈伸时实际前交叉韧带上的应变。一种特殊设计的器械被用来允许膝盖的自然运动。光弹性测量表明，该方法不仅可用于测量模型韧带上的应变分布，还可用于测量实际韧带上的应变分布。对实际前交叉韧带的测量得出了以下结果：主应变线很好地描述了其纤维方向。观察到前束和后束之间的相互作用。在靠近胫骨附着点的中央和后侧有一个零应变区。
The anterior cruciate ligament (ACL) in the human knee is known to exhibit as large as 10-20% of strain in association with knee flexion, while usual Hookean elastic materials exhibit at most 0.3%. Furthermore the complex ACL in shape deforms in highly variable manners due to the complicated three-dimensional (3-D) movements of the insertions in association with knee flexion. Such large and highly variable deformations of the ACL cannot be adequately quantified by one-dimensional (1-D) and/or localized measurements. In order to measure strains over the entire area of the ACL, we employed the photoelastic coating method to analyze stress on the basis of the strains. A specific kind of polyurethane possessing optically high fringe-sensitivity was found to be most suitable for measurement purposes. From the preliminary experiments, it was found that a linear relation with 99% of correlation coefficient between the birefringence order and the strain on the polyurethane film continued up to 45% of strain. This study was done in two steps. In the first step, a study was done using a unique model of a knee joint fabricated in a way which allowed deformation and strain distribution in the model ACL to be directly observed and measured by means of the photoelastic coating method. It was confirmed that the film, having negligible effect on the mechanical properties of some biological soft tissues, closely reflected the strain behavior of the tissue. Thus in the second step, the photoelastic method was employed to measure the strains on an actual ACL during free flexion-extension of the knee. A specially designed apparatus was used to allow a natural motion of the knee. The photoelastic measurements demonstrated the potential utility of the application to measuring strain distributions not only on a model ligament but also on an actual ligament. The measurement of an actual ACL led the following results; The principal strain lines well depicted its fiber directions. A reciprocal function between the anterior and posterior bundles was observed. And there was a zero-strain area on the central and posterior sides near the tibial insertion.