Effect of Foot Structural Morphology on Biomechanical Characteristics during Ambulation

• Main Authors: Chi-Wen Lung, 龍希文
• Other Authors: Sai-Wei Yang
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/64518108188595958627

博士 === 國立陽明大學 === 醫學工程研究所 === 96 === Medial longitudinal arch is composed of bones and soft tissues. It also played the one of important roles in the ambulation. The arch provides not only for the stability during stance phase of walking, but also for the connecting with the posterior and the anterior center-of-gravity position. The use of radiography to determine the high-arch foot and flatfoot has certain drawbacks such as exposure of radiations. Arch index (AI) can solve the problems; however, it does not allow clinicians to examine the bone alignment in the foot. On the other hand, the change of arch height of the human foot can change the contact times and region forces of plantar regions during walking, and finally lead to musculoskeletal injury. Understanding the arch bone alignments and plantar variables during ambulation could suggest new diagnostic and preventive method of foot injury. To investigate the correlations between the AI and bony alignments, this study comprised 57 young subjects (28 men and 29 women). Footprints were scanned using a flatbed scanner and the AI was then calculated. Radiographs were taken and the x-ray coordinate system was used to determine the position of the bones in the foot. Results showed that the measured AI averaged at 0.255 ± 0.067 (ranged from 0.050 to 0.407). The navicular height/foot breadth showed the strongest correlaions with the AI (r = 0.626). Therefore, AI was found to provide a simple quantitative mean of assessing the bone angles, especially in the calcaneal pitch angle inclination (r = 0.699). To show the spatio-temporal distribution of center of pressure (CoP) under high-arch, normal, and flatfoot subjects during walking, this study comprised three groups of young subjects who were the same condition of arch type in left and right foot. Each subject walked through the 10-meter walkway including a pressure plate which was used to calculate the CoP data. Results showed that the stance time of CoP on the mid-foot area of normal feet was significantly shortened comparing with both the high-arch and flatfoot feet; in the metatarsal region, the high-arch foot and flatfoot could be generating the different velocity to compensate the foot structure effect during walking. In the high-arch group, the heel off time was delayed during walking. In the flatfoot group, the initial contact time was also delayed. However, the regional force in the 3rd metatarsal of flatfoot group was increased during walking. Therefore, flatfoot could be at the higher risk for 3rd metatarsal stress fractures, indicating that foot type should be assessed when determining an individual's risk for metatarsal stress fractures. The finding of this study can help clinicians to determine an appropriate conservative treatment and to evaluate the treatment outcomes for people with high-arch and flat foot.