Dar F H, Aspden R M
Department of Bio-Medical Physics, University of Aberdeen, Foresterhill, Aberdeen, UK.
Proc Inst Mech Eng H. 2003;217(5):341-8. doi: 10.1243/095441103770802504.
The stiffness of articular cartilage increases dramatically with increasing rate of loading, and it has been hypothesized that increasing the stiffness of the subchondral bone may result in damaging stresses being generated in the articular cartilage. Despite the interdependence of these tissues in a joint, little is understood of the effect of such changes in one tissue on stresses generated in another. To investigate this, a parametric finite element model of an idealized joint was developed. The model incorporated layers representing articular cartilage, calcified cartilage, the subchondral bone plate and cancellous bone. Taguchi factorial design techniques, employing a two-level full-factorial and a four-level fractional factorial design, were used to vary the material properties and thicknesses of the layers over the wide range of values found in the literature. The effects on the maximum values of von Mises stress in each of the tissues are reported here. The stiffness of the cartilage was the main factor that determined the stress in the articular cartilage. This, and the thickness of the cartilage, also had the largest effect on the stresses in all the other tissues with the exception of the subchondral bone plate, in which stresses were dominated by its own stiffness. The stiffness of the underlying subchondral bone had no effect on the stresses generated in the cartilage. This study shows how stresses in the various tissues are affected by changes in their mechanical properties and thicknesses. It also demonstrates the benefits of a structured, systematic approach to investigating parameter variation in finite element models.
关节软骨的刚度会随着加载速率的增加而急剧增大，并且据推测，增加软骨下骨的刚度可能会导致关节软骨中产生损伤应力。尽管这些组织在关节中相互依存，但对于一个组织的这种变化对另一个组织中产生的应力的影响却知之甚少。为了对此进行研究，建立了一个理想化关节的参数化有限元模型。该模型包含了代表关节软骨、钙化软骨、软骨下骨板和松质骨的各层。采用田口因子设计技术，运用二级全因子设计和四级部分因子设计，在文献中发现的广泛数值范围内改变各层的材料属性和厚度。本文报告了这些变化对各组织中冯·米塞斯应力最大值的影响。软骨的刚度是决定关节软骨应力的主要因素。除了软骨下骨板（其应力主要由自身刚度决定）外，软骨的刚度及其厚度对所有其他组织中的应力也有最大影响。下方软骨下骨的刚度对软骨中产生的应力没有影响。这项研究展示了各组织中的应力如何受到其力学性能和厚度变化的影响。它还证明了采用结构化、系统的方法来研究有限元模型中参数变化的益处。
