Hislop Brady D, Heveran Chelsea M, June Ronald K
Department of Mechanical & Industrial Engineering, Montana State University, United States.
Department of Mechanical & Industrial Engineering, Montana State University, United States; Department of Microbiology & Cell Biology, Montana State University, United States; Department of Orthopaedics and Sports Medicine, University of Washington, United States.
J Biomech. 2021 Jun 23;123:110497. doi: 10.1016/j.jbiomech.2021.110497. Epub 2021 May 18.
Fluid transport is critical to joint health. In this study we evaluate an unexplored component of joint fluid transport -fluid transport between cartilage and bone. Such transport across the cartilage-bone interface could potentially provide chondrocytes with an additional source of nutrients and signaling molecules. A biphasic viscoelastic model using an ellipsoidal fiber distribution was created with three distinct layers of cartilage (superficial zone, middle zone, and deep zone) along with a layer of subchondral bone. For stress-relaxation in unconfined compression, our results for compressive stress, radial stress, and effective fluid pressure were compared with established biphasic analytical solutions. Our model also shows the development of fluid pressure gradients at the cartilage-bone interface during loading. Fluid pressure gradients that develop at the cartilage-bone interface show consistently higher pressures in cartilage following the initial loading to 10% stain, followed by convergence of the pressures in cartilage and bone during the 400 s relaxation period. These results provide additional evidence that fluid is transported between cartilage and bone during loading and improves upon estimates of the magnitude of this effect through incorporating a realistic distribution and estimate of the collagen ultrastructure. Understanding fluid transport between cartilage and bone may be key to new insights about the mechanical and biological environment of both tissues in health and disease.
液体运输对关节健康至关重要。在本研究中，我们评估了关节液体运输中一个未被探索的部分——软骨与骨之间的液体运输。这种跨软骨 - 骨界面的运输可能为软骨细胞提供额外的营养物质和信号分子来源。使用椭圆形纤维分布创建了一个双相粘弹性模型，该模型包含三层不同的软骨（表层、中层和深层）以及一层软骨下骨。对于无侧限压缩中的应力松弛，我们将压缩应力、径向应力和有效流体压力的结果与已有的双相解析解进行了比较。我们的模型还显示了加载过程中软骨 - 骨界面处流体压力梯度的发展。在初始加载至10%应变后，软骨 - 骨界面处形成的流体压力梯度在软骨中始终显示出更高的压力，随后在400秒的松弛期内软骨和骨中的压力趋于一致。这些结果提供了额外证据，表明加载过程中软骨与骨之间存在液体运输，并且通过纳入胶原蛋白超微结构的实际分布和估计，改进了对这种效应大小的估计。了解软骨与骨之间的液体运输可能是深入了解健康和疾病状态下两种组织的力学和生物学环境的关键。
