Schinagl R M, Ting M K, Price J H, Sah R L
Department of Bioengineering, University of California, San Diego 92093-0412, USA.
Ann Biomed Eng. 1996 Jul-Aug;24(4):500-12. doi: 10.1007/BF02648112.
The objectives of this study were to develop a method to quantitate the displacement and strain fields within articular cartilage during equilibrium confined compression, and to use the method to determine the variation of the equilibrium confined compression modulus with depth from the articular surface in bovine cartilage. The method made use of fluorescently labeled chondrocyte nuclei as intrinsic fiducial markers. Articular cartilage was harvested from the patellofemoral groove of adult bovines and trimmed to rectangular blocks 5 mm long, 0.76 mm wide, and 500 microns deep with the articular surface intact. Test specimens were stained with the DNA binding dye Hoechst 33258, placed in a custom confined compression chamber, and viewed with an epifluorescence microscope equipped for video image acquisition. Image processing was used to localize fluorescing chondrocyte nuclei in uncompressed and compressed (approximately 17%) specimens, allowing determination of the intra-tissue displacement profile. Strain was determined as the slope of linear regression fits of the displacement data in four sequential 125-microns-thick layers. Equilibrium strains varied 6.1-fold from the articular surface through 500 microns of cartilage depth, with the greatest compressive strain in the superficial 125-microns layer and the least compressive strain in the two deepest 125-microns layers. Thus, the four successive 125-microns layers have moduli that are 0.44 (superficial), 1.07, 2.39, and 2.67 (deep) times the apparent modulus for a 500-microns thick cartilage sample assumed to be homogeneous.
本研究的目的是开发一种方法，用于定量关节软骨在平衡受限压缩过程中的位移和应变场，并使用该方法确定牛软骨中平衡受限压缩模量随距关节表面深度的变化。该方法利用荧光标记的软骨细胞核作为内在基准标记。从成年牛的髌股沟采集关节软骨，并修剪成长5mm、宽0.76mm、深500微米且关节表面完整的矩形块。测试样本用DNA结合染料Hoechst 33258染色，置于定制的受限压缩室中，并用配备视频图像采集功能的落射荧光显微镜观察。图像处理用于在未压缩和压缩（约17%）的样本中定位荧光软骨细胞核，从而确定组织内的位移分布。应变被确定为四个连续的125微米厚层中位移数据线性回归拟合的斜率。从关节表面到500微米的软骨深度，平衡应变变化了6.1倍，在最浅的125微米层中压缩应变最大，在最深的两个125微米层中压缩应变最小。因此，对于假设为均匀的500微米厚软骨样本，这四个连续的125微米层的模量分别为表观模量的0.44（浅表层）、1.07、2.39和2.67（深层）倍。
