循环加载下关节软骨的棘轮应变及理论预测

Ratcheting strain and theoretical prediction of articular cartilage under cyclic loading

目的获得不同加载条件下关节软骨的棘轮应变,建立预测棘轮应变的理论模型,并对软骨的棘轮应变进行预测。方法将猪股骨远端滑车部的新鲜关节软骨作为研究对象,采用非接触式数字图像技术,测试循环压缩载荷下关节软骨的棘轮应变;建立预测棘轮应变的理论模型,对不同应力幅值和加载率下软骨的棘轮应变进行预测,并比较预测结果与实验结果。结果随循环圈数的增加,软骨的棘轮应变先快速增长然后趋于稳定;定加载率下,软骨的棘轮应变随应力幅值的增大而增大;定应力幅值下,棘轮应变随加载率的增大而减小。实验结果与建立的理论模型预测结果吻合良好。结论关节软骨的棘轮应变与应力幅值成正比,与加载率成反比。建立的理论模型可以预测软骨的棘轮行为,同时为组织工程软骨的构造提供指导。

Objective To obtain the ratcheting strain of articular cartilage under different loading conditions, and construct the theoretical model so as to predict the ratcheting strain of cartilage. Methods The fresh articular car- tilage obtained from the trochlear of distal femur was used as experimental subject. The ratcheting strain of articu- lar cartilage was tested under cyclic compressive loads by applying the non-contact digital image correlation tech- nique. The theoretical model was constructed to predict the ratcheting strain of articular cartilage with different stress amplitudes and stress rates. The results from predictions were compared with the experimental results. Results The ratcheting strain of cartilage increased rapidly at initial stage and then showed the slower increase with cycles increasing. The ratcheting strain increased with stress amplitude increasing when the stress rate was constant. However, the ratcheting strain decreased with stress rate increasing when the stress amplitude was constant. When the stress rate increased, the ratcheting stain decreased. The prediction results of the estab- lished theoretical model were in good agreement with experimental results. Conclusions The ratcheting strain of articular cartilage is proportional to the stress amplitude, and inversely proportional to the stress rate. The estab- lished theoretical model can predict the ratcheting strain of articular cartilage and provide guidance for the con- struction of tissue engineered artificial cartilage.