Abnormalities in the ankle contact pressure are related to the onset of osteoarthritis. In vivo measurements are not possible with currently available techniques, so computational methods such as the finite element analysis (FEA) are often used instead. The discrete element method (DEM), a computationally efficient alternative to time-consuming FEA, has also been used to predict the joint contact pressure. It describes the articular cartilage as a bed of independent springs, assuming a linearly elastic behaviour and absence of relative motion between the bones. In this study, we present the extended DEM (EDEM) which is able to track the motion of talus over time. The method was used, with input data from a subject-specific musculoskeletal model, to predict the contact pressure in the ankle joint during gait. Results from EDEM were also compared with outputs from conventional DEM. Predicted values of contact area were larger in EDEM than they were in DEM (4.67 and 4.18 cm2, respectively). Peak values of contact pressure, attained at the toe-off, were 7.3 MPa for EDEM and 6.92 MPa for DEM. Values predicted from EDEM fell well within the ranges reported in the literature. Overall, the motion of the talus had more effect on the extension and shape of the pressure distribution than it had on the magnitude of the pressure. The results indicated that EDEM is a valid methodology for the prediction of ankle contact pressure during daily activities.

中文翻译：

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一种扩展的离散元方法，用于评估站立阶段踝关节的接触压力。

踝关节接触压力异常与骨关节炎的发作有关。目前可用的技术无法进行体内测量，因此通常使用诸如有限元分析（FEA）之类的计算方法来代替。离散元素方法（DEM）是费时的FEA的一种计算有效替代方法，也已用于预测关节接触压力。它将关节软骨描述为独立的弹簧床，假设其具有线性弹性行为并且骨骼之间没有相对运动。在这项研究中，我们提出了扩展的DEM（EDEM），它能够跟踪距骨随着时间的运动。该方法与来自对象特定的肌肉骨骼模型的输入数据一起用于预测步态期间踝关节的接触压力。EDEM的结果也与传统DEM的结果进行了比较。EDEM中的接触面积预测值比DEM中的预测值大（分别为4.67和4.18 cm2）。脚趾断开时达到的接触压力峰值对于EDEM为7.3 MPa，对于DEM为6.92 MPa。由EDEM预测的值很好地落在文献报道的范围内。总体而言，距骨的运动对压力分布的延伸和形状的影响大于对压力大小的影响。结果表明，EDEM是预测日常活动中踝关节接触压力的有效方法。EDEM为3 MPa，DEM为6.92 MPa。由EDEM预测的值很好地落在文献报道的范围内。总体而言，距骨的运动对压力分布的延伸和形状的影响大于对压力大小的影响。结果表明，EDEM是预测日常活动中踝关节接触压力的有效方法。EDEM为3 MPa，DEM为6.92 MPa。由EDEM预测的值很好地落在文献报道的范围内。总体而言，距骨的运动对压力分布的延伸和形状的影响大于对压力大小的影响。结果表明，EDEM是预测日常活动中踝关节接触压力的有效方法。