Biomechanical load sharing in the foot during dynamic, load-bearing activity

脚在结构上是多余的。与大腿或小腿不同，大腿或小腿只有一到两块大骨头，生物力学载荷的传递实际上只有一种方式。相反，脚是一个由26块骨头组成的复杂结构，每块骨头都承担着生物力学载荷。一个有趣的事实是，整个人体大约四分之一的骨骼在两只脚上。这使得脚在身体和地面之间传递载荷的方式具有极大的灵活性。但人们对脚是如何做到这一点的知之甚少。将脚踝关节连接到地面的是五根射线或柱状骨，它们始于脚跟(跟骨)，终止于每个脚趾。第一条射线也称为内侧纵弓，第五条射线为外侧纵弓。每条射线将总生物力学载荷的一部分从身体传递到地面。但由于脚的结构冗余，每条射线承担的总载荷的比例无法确定地计算出来。每条射线上有多少载荷，载荷的分担是否总是相同，是否一步一步地变化，一步中是否变化，不同人之间是否相同，这仍然是一个悬而未决的问题。这项研究计划解决了脚部负荷分担的问题。它使用两种互补的方法，对执行动态任务的健康测试对象进行直接测量，以及对足部解剖、鞋类和矫形术进行有限元(FE)建模。采用荧光放射立体分析(FRSA)技术对健康受试者足部骨骼的运动进行测量。当测试对象执行动态任务时，该系统使用X光对骨骼进行成像，例如向前直走和改变方向。在鞋内，使用鞋内压力传感系统直接测量鞋与脚的顶部和底部之间的压力。使用光学运动捕捉来测量身体的整体运动。这三个系统以前从未被结合起来用于脚的研究。这项研究项目将显著提高我们对脚如何保持直立和移动的理解，以及鞋类和矫形器如何促进我们的行动能力。**

The foot is structurally redundant. It is unlike the thigh or the lower leg where there are only one or two large bones and really only one way for biomechanical loads to be transmitted. The foot is instead a complex structure of 26 bones that each bear biomechanical load. An interesting fact is that about one quarter of the bones in the entire human body are in the two feet. This gives the foot a tremendous flexibility in how it transmits loads between the body and the ground. But how the foot does so is poorly understood. Connecting the ankle joint to the ground are five rays', or columns, of bones that start at the heel (calcaneus) and terminate at each of the toes. The first ray is also known as the medial longitudinal arch, the fifth ray is the lateral longitudinal arch. Each ray transmits a portion of the total biomechanical load from the body to the ground. But what proportion of the total load each ray bears cannot be calculated deterministically due to the foot's structural redundancy. It remains an open question how much load goes through each ray, whether the sharing of load is always the same, whether it changes from step to step, whether it changes during a step and whether it is the same between different people. This research program addresses the question of load sharing in the foot. It uses two complementary approaches, direct measurement on healthy test subjects performing dynamic tasks and finite element (FE) modeling of the foot anatomy, footwear and orthotics. The motion of the bones of the foot in healthy subjects is measured using the technique of fluoroscopic radio-stereometric analysis (fRSA). This system uses x-rays to image the bones while the test subject is performing dynamic tasks such as walking straight ahead and change directions. Within the shoe, the pressure between the footwear and the top and bottom of the foot is measured directly using an in-shoe pressure sensing system. The overall motion of the body is measured using optical motion capture. These three systems have never been combined for the study of the foot before. This program of research will significantly improve our understanding of how the feet keep us upright and mobile, and how footwear and orthotics can facilitate our mobility.**