Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907, United States.
Osteoarthritis Cartilage. 2009 Nov;17(11):1461-8. doi: 10.1016/j.joca.2009.04.021. Epub 2009 May 7.
Cartilage displacement and strain patterns were documented noninvasively in intact tibiofemoral joints in situ by magnetic resonance imaging (MRI). This study determined the number of compressive loading cycles required to precondition intact joints prior to imaging, the spatial distribution of displacements and strains in cartilage using displacement-encoded MRI, and the depth-dependency of these measures across specimens.
Juvenile porcine tibiofemoral joints were cyclically compressed at one and two times body weight at 0.1 Hz to achieve a quasi-steady state load-displacement response. A 7.0 T MRI scanner was used for displacement-encoded imaging with stimulated echoes and a fast spin echo acquisition (DENSE-FSE) in eight intact joints. Two-dimensional displacements and strains were determined throughout the thickness of the tibial and femoral cartilage and then normalized over the tissue thickness.
Two-dimensional displacements and strains were heterogeneous through the depth of femoral and tibial cartilage under cyclic compression. Strains in the loading direction were compressive and were maximal in the middle zone of femoral and tibial cartilage, and tensile strains were observed in the direction transverse to loading.
This study determined the depth-dependent displacements and strains in intact juvenile porcine tibiofemoral joints using displacement-encoded imaging. Displacement and strain distributions reflect the heterogeneous biochemistry of cartilage and the biomechanical response of the tissue to compression in the loading environment of an intact joint. This unique information about the biomechanics of cartilage has potential for comparisons of healthy and degenerated tissue and in the design of engineered replacement tissues.
通过磁共振成像（MRI）非侵入性地原位记录完整的胫股关节中的软骨位移和应变模式。本研究确定了在成像前对完整关节进行预处理所需的压缩加载循环次数，使用位移编码 MRI 确定软骨中的位移和应变的空间分布，以及这些测量值在标本中的深度依赖性。
在 0.1 Hz 下以 1 倍和 2 倍体重对幼年猪的胫股关节进行周期性压缩，以达到准稳态的载荷-位移响应。在 7.0 T MRI 扫描仪上使用受激回波和快速自旋回波采集（DENSE-FSE）进行位移编码成像，对 8 个完整关节进行成像。在整个胫骨和股骨软骨厚度上确定二维位移和应变，然后相对于组织厚度进行归一化。
在周期性压缩下，股骨和胫骨软骨的深度存在二维位移和应变的异质性。加载方向上的应变是压缩的，在股骨和胫骨软骨的中间区域最大，在与加载方向相反的方向上观察到拉伸应变。
本研究使用位移编码成像确定了完整的幼年猪胫股关节中的深度依赖性位移和应变。位移和应变分布反映了软骨的异质生化特性和组织在完整关节的加载环境下对压缩的生物力学响应。这种关于软骨生物力学的独特信息有可能对健康和退化组织进行比较，并用于设计工程化替代组织。
