Kallemeyn Nicole A, Grosland Nicole M, Magnotta Wincent A, Martin James A, Pedersen Douglas R
Department of Orthopaedics and Rehabilitation, The University of Iowa, Iowa City, IA 52242, USA.
Iowa Orthop J. 2007;27:52-7.
It is difficult to study the deformation of articular cartilage because it is an inhomogenous material with depth dependent constituents. In many experimental studies, cartilage is assumed to behave homogeneously and is subjected to only static or quasi-static loads. In this study, a thick walled, mechanically active culture device (TRIAX) was used to apply cyclic loading to cartilage explants at physiological stress levels. An arthroscope was fitted into the wall of the TRIAX to monitorand record the cyclic compressive behavior of the cartilage and to measure depth dependent cartilage strains. A common concern with arthroscopy systems is that the images obtained are radially distorted about a central point ("fisheye" view); therefore it is necessary to correct this distortion in order to accurately quantify distances between objects within the images. To do this, an algorithm was developed which used a calibration pattern to create an image transform. Digital video of the cyclic cartilage compression was recorded, and the distortion algorithm was applied to the images to measure the cartilage as it deformed. This technique will provide valuable and practical insight into cartilage mechanics and viability (via calcein AM-stained chondrocytes) during multiday cyclic loading of living cartilage explants. The implementation of an arthroscopy system provides the advantage of bringing microscope-level resolution into a cartilage compression device to allow for digital visualization of the entire explant at the whole-tissue level.
研究关节软骨的变形很困难，因为它是一种成分随深度变化的非均质材料。在许多实验研究中，软骨被假定为均质材料，并且仅承受静态或准静态载荷。在本研究中，使用了一种厚壁、机械活性培养装置（TRIAX），在生理应力水平下对软骨外植体施加循环载荷。将一个关节镜安装到TRIAX的壁上，以监测和记录软骨的循环压缩行为，并测量随深度变化的软骨应变。关节镜系统的一个常见问题是，所获得的图像会围绕中心点呈径向扭曲（“鱼眼”视图）；因此，有必要校正这种扭曲，以便准确量化图像中物体之间的距离。为此，开发了一种算法，该算法使用校准图案来创建图像变换。记录了软骨循环压缩的数字视频，并将扭曲算法应用于图像，以测量软骨变形时的情况。这项技术将为活软骨外植体在多天循环加载过程中的软骨力学和活力（通过钙黄绿素AM染色的软骨细胞）提供有价值的实用见解。关节镜系统的应用具有将显微镜级分辨率引入软骨压缩装置的优势，从而能够在全组织水平上对整个外植体进行数字可视化。
