Kääb M J, Ito K, Clark J M, Nötzli H P
AO Research Institute, Davos, Switzerland.
J Orthop Res. 1998 Nov;16(6):743-51. doi: 10.1002/jor.1100160617.
Relatively little is known about the morphology of articular cartilage under conditions of normal use, yet a more profound knowledge is both critical to the understanding of cartilage function and helpful for the validation of tissue-engineered cartilage. In this study, the deformation of the articular cartilage of the tibial plateau under compressive static and cyclic loading is characterized. Whole knee joints of rabbits were loaded ex vivo while the knee was held statically or allowed to move against resistance. Load magnitudes of quadriceps were maintained at either three (high) or one (low) times body weight for 30 minutes. For cyclic loading, the tibia was flexed between 70 and 150 degrees relative to the femur at 1 Hz with either a cyclic or constant force. The recovery of cartilage after unloading was examined for each loading condition. At the end of the loading, specimens were cryofixed while under load, freeze-substituted, and prepared for scanning electron microscopy. Morphological examination demonstrated significantly higher deformation of the collagen structure throughout all cartilage zones under static loading conditions compared with cyclic loading conditions in which deformation was limited to the superficial regions. The minimum thickness of the cartilage that remained after loading was dependent on the magnitude of load and was significantly smaller with static loads (54% of the thickness of the unloaded controls) than after cyclic loading or constant-force cyclic loading (78 or 66% of the thickness of the unloaded controls, p < 0.05). Acute bending of the collagen fibers was observed under both loading conditions: in the superficial half of the articular cartilage after static loading and in the superficial quarter after cyclic loading. Complete recovery of all deformation occurred within 30 minutes but was significantly faster after cyclic loading. These data suggest that the structure of the collagen of articular cartilage exhibits a zone-specific deformation that is dependent on the magnitude and type of load.
在正常使用条件下，人们对关节软骨形态的了解相对较少，然而更深入的认识对于理解软骨功能至关重要，也有助于验证组织工程软骨。在本研究中，对胫骨平台关节软骨在静态和循环压缩载荷下的变形进行了表征。兔的全膝关节在体外加载，膝关节保持静止或抵抗运动。股四头肌的载荷大小维持在体重的三倍（高）或一倍（低），持续30分钟。对于循环加载，胫骨以1Hz的频率在相对于股骨70至150度之间弯曲，施加循环力或恒力。检查每种加载条件下卸载后软骨的恢复情况。在加载结束时，标本在加载状态下进行冷冻固定，冷冻置换，并制备用于扫描电子显微镜检查。形态学检查表明，与循环加载条件相比，静态加载条件下所有软骨区域的胶原结构变形明显更高，在循环加载条件下变形仅限于表层区域。加载后剩余软骨的最小厚度取决于载荷大小，静态载荷后的厚度（为未加载对照厚度的54%）明显小于循环加载或恒力循环加载后的厚度（分别为未加载对照厚度的78%或66%，p<0.05）。在两种加载条件下均观察到胶原纤维的急性弯曲：静态加载后在关节软骨的表层一半，循环加载后在表层四分之一。所有变形在30分钟内完全恢复，但循环加载后恢复明显更快。这些数据表明，关节软骨胶原结构表现出区域特异性变形，这取决于载荷的大小和类型。
