Kazunori Okamura1, Kohei Egawa2, Tomohiro Ikeda3, Kengo Fukuda4, Shusaku Kanai5. 1. Department of Physical Therapy, Faculty of Health and Welfare, Prefectural University of Hiroshima, 1-1 Gakuen-cho, Mihara-shi, Hiroshima, 723-0053, Japan. Electronic address: k-okamura@pu-hiroshima.ac.jp. 2. Graduate School of Comprehensive Scientific Research, Prefectural University of Hiroshima, 1-1 Gakuen-cho, Mihara-shi, Hiroshima, 723-0053, Japan. Electronic address: egawakohei1024@yahoo.co.jp. 3. Graduate School of Comprehensive Scientific Research, Prefectural University of Hiroshima, 1-1 Gakuen-cho, Mihara-shi, Hiroshima, 723-0053, Japan. Electronic address: lirfranjitte@yahoo.co.jp. 4. Graduate School of Comprehensive Scientific Research, Prefectural University of Hiroshima, 1-1 Gakuen-cho, Mihara-shi, Hiroshima, 723-0053, Japan. Electronic address: 511kengofukuda@gmail.com. 5. Department of Physical Therapy, Faculty of Health and Welfare, Prefectural University of Hiroshima, 1-1 Gakuen-cho, Mihara-shi, Hiroshima, 723-0053, Japan. Electronic address: kanai@pu-hiroshima.ac.jp.
Abstract
BACKGROUND: The morphology of foot muscles that support the medial longitudinal arch differs between normal and pronated feet. The degree to which the difference depends on the severity of the pronated foot deformity is unclear. In the clinical setting, however, to reduce the pronated deformity, muscle-strengthening exercises are performed. RESEARCH QUESTION: Does a relationship exist between foot muscle morphology and severity of the pronated foot deformity and foot kinematics during gait? METHODS: Using the six-item foot posture index (FPI-6), 26 study participants were assessed for their foot posture and divided into two groups of 13 participants each based on the FPI-6 score: pronated foot group (with a score of 6-9) and highly pronated foot group (with a score of 10-12). Select foot muscles were scanned with ultrasonography, and muscle thicknesses were measured. The following were the muscles of interest: abductor hallucis, flexor hallucis brevis and longus, flexor digitorum brevis and longus, and peroneus longus. Foot kinematic data during gait was collected using a three-dimensional motion capture system as a dynamic navicular drop. RESULTS: No between-group differences were noted for muscle thickness and dynamic navicular drop. However, the abductor hallucis and flexor hallucis brevis thicknesses were correlated with the dynamic navicular drop, but not with the severity of the pronated foot deformity. SIGNIFICANCE: In individuals with pronated foot deformity, more developed abductor hallucis and flexor hallucis brevis muscles may reduce the dynamic navicular drop that represents the degree of medial longitudinal arch deformation during the stance phase of gait.
BACKGROUND: The morphology of foot muscles that support the medial longitudinal arch differs between normal and pronated feet. The degree to which the difference depends on the severity of the pronated foot deformity is unclear. In the clinical setting, however, to reduce the pronated deformity, muscle-strengthening exercises are performed. RESEARCH QUESTION: Does a relationship exist between foot muscle morphology and severity of the pronated foot deformity and foot kinematics during gait? METHODS: Using the six-item foot posture index (FPI-6), 26 study participants were assessed for their foot posture and divided into two groups of 13 participants each based on the FPI-6 score: pronated foot group (with a score of 6-9) and highly pronated foot group (with a score of 10-12). Select foot muscles were scanned with ultrasonography, and muscle thicknesses were measured. The following were the muscles of interest: abductor hallucis, flexor hallucis brevis and longus, flexor digitorum brevis and longus, and peroneus longus. Foot kinematic data during gait was collected using a three-dimensional motion capture system as a dynamic navicular drop. RESULTS: No between-group differences were noted for muscle thickness and dynamic navicular drop. However, the abductor hallucis and flexor hallucis brevis thicknesses were correlated with the dynamic navicular drop, but not with the severity of the pronated foot deformity. SIGNIFICANCE: In individuals with pronated foot deformity, more developed abductor hallucis and flexor hallucis brevis muscles may reduce the dynamic navicular drop that represents the degree of medial longitudinal arch deformation during the stance phase of gait.