Department of Anatomy and Cell Biology, Temple University School of Medicine, Philadelphia, PA 19140, USA.
J Anat. 2013 Jun;222(6):598-607. doi: 10.1111/joa.12050. Epub 2013 Apr 19.
The modern human foot is a complex biomechanical structure that must act both as a shock absorber and as a propulsive strut during the stance phase of gait. Understanding the ways in which foot segments interact can illuminate the mechanics of foot function in healthy and pathological humans. It has been proposed that increased values of medial longitudinal arch deformation can limit metatarsophalangeal joint excursion via tension in the plantar aponeurosis. However, this model has not been tested directly in a dynamic setting. In this study, we tested the hypothesis that during the stance phase, subtalar pronation (stretching of the plantar aponeurosis and subsequent lowering of the medial longitudinal arch) will negatively affect the amount of first metatarsophalangeal joint excursion occurring at push-off. Vertical descent of the navicular (a proxy for subtalar pronation) and first metatarsophalangeal joint dorsal excursion were measured during steady locomotion over a flat substrate on a novel sample consisting of asymptomatic adult males and females, many of whom are habitually unshod. Least-squares regression analyses indicated that, contrary to the hypothesis, navicular drop did not explain a significant amount of variation in first metatarsophalangeal joint dorsal excursion. These results suggest that, in an asymptomatic subject, the plantar aponeurosis and the associated foot bones can function effectively within the normal range of subtalar pronation that takes place during walking gait. From a clinical standpoint, this study highlights the need for investigating the in vivo kinematic relationship between subtalar pronation and metatarsophalangeal joint dorsiflexion in symptomatic populations, and also the need to explore other factors that may affect the kinematics of asymptomatic feet.
现代人的脚是一种复杂的生物力学结构，在步态的站立阶段，它既要起到减震器的作用，又要起到推进支柱的作用。了解足段之间相互作用的方式可以阐明健康和病理人群中足功能的力学原理。有人提出，内侧纵弓变形值的增加可以通过足底腱膜的张力限制跖趾关节的伸展。然而，这种模型尚未在动态环境中得到直接验证。在这项研究中，我们假设在站立阶段，距下关节内翻（足底腱膜的拉伸和随后内侧纵弓的降低）会对第一跖趾关节在蹬离时的伸展量产生负面影响。在一个由无症状的成年男性和女性组成的新型样本中，在平坦的基质上进行稳定的运动时，我们测量了舟骨的垂直下降（距下关节内翻的代理指标）和第一跖趾关节背屈的背屈。最小二乘法回归分析表明，与假设相反，舟骨下降并不能解释第一跖趾关节背屈的大量变化。这些结果表明，在无症状的受试者中，足底腱膜和相关的足部骨骼可以在距下关节内翻的正常范围内有效发挥作用，而距下关节内翻发生在步行步态中。从临床角度来看，这项研究强调了在有症状人群中研究距下关节内翻和跖趾关节背屈之间的运动学关系的必要性，也需要探索可能影响无症状足部运动学的其他因素。
