Evaluation of different hindfoot kinematics according to various shoe-types during walking using bi-planar fluoroscopy

Abstract

INTRODUCTION: Dynamics of the foot can be affected by shoe wears [1, 2]. Various factors of the shoe including sole stiffness, heel height, and shape of the bottom surface can change the kinematics of the foot and ankle joints [3]. While a plethora of shoe types exists, the mechanism of different kinematics of the foot by different shoe types have not been well understood due to a lack of measurement tools. Recent development of high-speed bi-planar fluoroscopic imaging technique allowed direct imaging and three-dimensional (3D) reconstruction of skeletal movements [4, 5]. Previously, we reported temporal rotational patterns in the ankle (tibiotalar) and subtalar (talocalcaneal) joints separately during barefoot walking using the bi-planar fluoroscopic imaging technique [6]. Understanding the change of hindfoot kinematics according to different shoe types would help clinicians find right shoe wears for patients with a specific foot and ankle problem. This study aimed to investigate change of hindfoot (ankle and subtalar) kinematics according to various shoe-types during walking using a bi-planar fluoroscopic system.

METHODS: The study was approved by the institutional review board at the Korean Anam University Hospital and obtained an informed consent from each participant. Ten healthy subjects (five males and five females; mean age 23.4 (±1.2) years and 25.2 (±1.9) years, respectively) were enrolled in the study and divided into a male group and a female group. Both groups performed normal walking at barefoot (BF) and with running shoes (RS) and climbing shoes (CS). Additionally, the male group was tested with rocker bottom shoes (RBS) and the female group was tested with 7 cm high-heeled shoes (HHS). Bi-planar fluoroscopic images were captured during the walking trials at the speed of 100 frames per second with a 0.1 ms exposure time, 1024 × 1024-pixel resolution, and 14-bit depth image. All subjects underwent computed tomography examination to reconstruct 3D polygonal bone models using the Seg3D software. The 3D bone models of the tibia, talus and calcaneus were registered to the bi-planar fluoroscopic images using our custom 2D/3D registration software at every 10%-th frame from 0 to 90% of the stance phase, total 10 frames per a gait trial. Rotational kinematics (dorsiflexion/plantar-flexion, inversion/eversion, and internal/external rotations) in the ankle and subtalar joints were calculated using the anatomical coordinate systems of the three bones which were determined as described in our previous study [6]. Mean rotation, range of motion (ROM), and peak rotations in positive and negative directions were calculated. Nonparametric statistical tests were performed for male (N=5) and female (N=5) groups, separately, using the SPSS (Ver. 25, IBM Corp., Armonk, NY). Friedman’s 2-way ANOVA by ranks was performed at the significance level of 0.05 followed by multiple comparisons between all pairs to understand the effect of shoe type on the four kinematic parameters.

RESULTS: In the female group, only the HHS showed significantly different hindfoot kinematics from the three other shoe types. While the ankle ROM was not different by shoe types, the ankle was significantly plantar-flexed in HHS than BF by 14.4° in average throughout the stance phase (p = 0.02). The subtalar was also significantly plantar-flexed in HHS than CS by 3.2° in average (p=0.04). In the male group, the peak ankle dorsiflexion was significantly smaller in RBS than BF by 8.6° in average (p=0.01) though the peak ankle plantar flexion was not different. The ankle ROMs along the dorsiflexion/plantar-flexion in RBS and BF were 8.2° and 17.0° (p=0.02), respectively. The subtalar was significantly plantar-flexed and internally rotated in RBS than BF by 1.4° (p=0.04) and 1.7° (p=0.04) in average, respectively. The subtalar ROM along the internal/external rotation was significantly higher in CS than BF by 7.6° in average (p=0.02).