Introduction

Flatfoot deformity is commonly characterized by a subtalar valgus, a low medial longitudinal arch, and abduction of the forefoot. Although flatfoot deformity has been associated with lower first (KAM1) and second (KAM2) peak knee adduction moments during walking, the biomechanical connection remains unknown.

Research question

We hypothesized that hindfoot eversion, lateral calcaneal shift correlate with KAM1 and forefoot abduction and arch height with KAM2, due to the lateralization of the ground reaction force vector resulting from shifted heel and forefoot in flatfoot deformity.

Methods

Gait data from 103 children with flatfoot deformity who underwent three-dimensional gait analysis with the Oxford Foot Model were retrospectively included. Children with knee varus/valgus, in- and out-toeing were excluded. Fifteen healthy children with a rectus foot type were also collected from the database. Lateral calcaneal shift was defined as the distance between the projection of the ankle joint center onto the calcaneal axis and the midpoint of the calcaneal axis formed by the medial and lateral calcaneal markers. A subgroup of children with idiopathic flatfoot deformity that had received corrective surgery was also identified. Statistical analysis included Pearson’s correlations and independent and paired t-tests (α < .05).

Results

When compared to a norm cohort, flatfooted children had significant lower KAM1 and KAM2 (t-test, P < .001). Lateral calcaneal shift correlated with KAM1 and KAM2 (r = 0.42, p < .001 and r = 0.32, P < .001, respectively). Arch height correlated with KAM2 (r = 0.23, p = 0.017). KAM1 and KAM2 normalized after surgery and the change in KAM1 correlated with the change in lateral calcaneal shift for children who underwent corrective surgery.

Significance

Lateral calcaneal shift explains the reduction of KAM1 by lateralization of the point of force application in flatfooted children. It is recommended to consider the lateral calcaneal shift when investigating KAM in gait analysis research.

中文翻译：

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特发性扁平足畸形对行走过程中膝盖内收力矩的影响

介绍

扁平足畸形的特征通常是距下外翻，内侧纵弓低和前足外展。尽管扁平足畸形与行走过程中较低的第一（KAM1）和第二（KAM2）峰值内收力矩有关，但生物力学连接仍然未知。

研究问题

我们假设后脚外翻，跟骨横向移位与KAM1和前足外展以及KAM2与足弓高度有关，这是由于平足畸形中脚跟和前脚移位导致地面反作用力矢量的横向化。

方法

回顾性分析了103名扁平足畸形儿童的步态数据，这些儿童通过牛津脚模型进行了三维步态分析。排除膝内翻/外翻，脚尖和脚趾的儿童。还从数据库中收集了15名健康的直肌型儿童。跟骨外侧移位定义为踝关节中心向跟骨轴上的投影与内侧和外侧跟骨标记形成的跟骨轴中点之间的距离。还确定了接受矫正手术的特发性扁平足畸形儿童亚组。统计分析包括Pearson的相关性以及独立和成对的t检验（α<.05）。

结果

与正常人群相比，措手不及的儿童的KAM1和KAM2明显较低（t检验，P <.001）。跟骨横向跟移与KAM1和KAM2相关（r = 0.42，p <.001和r = 0.32，P <.001）。足弓高度与KAM2相关（r = 0.23，p = 0.017）。手术后，KAM1和KAM2正常化，而KAM1的变化与进行矫正手术的儿童的跟骨外侧移位相关。

意义

跟骨外侧移位解释了平足儿童受力点的侧向化可以降低KAM1。建议在步态分析研究中调查KAM时，应考虑跟骨横向移位。