醫療用鞋之力學分析

Analysis of the mechanical properties of medical footwear

張庭凱(Ting-Kai Chang)

指導教授 ： 邵耀華

國立臺灣大學/工學院/應用力學研究所/碩士(2021年)

https://doi.org/10.6342/NTU202103972

摘要

人的足型有分成正常足、扁平足和高弓足，其中扁平足是一種由內側縱向足弓塌陷所導致的足部畸形，而這種足部畸形具有相當高的患病率，在一般的人群中大約為3%-25%之間。對於症狀較輕微的扁平足患者而言，非手術治療具有良好的效果，其中就包括具有足弓支撐的鞋具或鞋墊，然而，在判別鞋具或鞋墊的療效時，往往需要透過患者的主觀感受進行評估，而評估的過程不但耗時，對患者而言也是一種折磨。因此本研究欲針對用於扁平足的鞋具建立一套量測與分析系統，提供該鞋具之效果評估依據。
本研究透過文獻回顧扁平足的選鞋建議，隨後針對以乙烯醋酸乙烯酯共聚物(EVA)發泡成型並且具有足弓支撐的鞋具進行壓縮試驗和足底壓力分佈量測。其中壓縮試驗是將鞋具裝配到具有標準足的壓縮試驗機上並以四個不同的加載速度進行，隨後將獲得的負載變形曲線用於評估鞋具的剛性和能量耗散率(Energy dissipation ratio，EDR)。而壓力分佈量測是由一名正常足和兩名扁平足參與者在赤腳和穿鞋的情況下以站立和走路的方式進行，結果則是以壓力分佈圖探討足底壓力的變化。除了評估足弓支撐效果探討外，還使用2mm的EVA墊片以五種方式墊高鞋墊，以探討修改鞋墊對壓力分佈的影響。壓力分佈的量測是以一名扁平足較為嚴重的參與者在穿著修改前和修改後鞋具的情況下以站立和走路的方式進行，結果則是以壓力分佈圖和壓力中心線的變化探討修改鞋墊的效果。
在研究結果顯示，使用的EVA鞋具會隨著壓縮速度增加而變硬，而能量耗散率則是會隨著壓縮速度增加而減少。對於正常足參與者，鞋具的足弓支撐設計在站立和走路時，能夠減少前足和足跟的壓力，但同時中足的壓力和接觸面積也會增加。而對於扁平足的參與者，足弓支撐設計能夠減少足跟的最大壓力，但同時中足的壓力和接觸面積也會增加，而中足的壓力會增加可能是因為鞋具的鞋底具有弧形設計所導致。在評估鞋具或修改鞋墊對壓力分佈的影響時，使用壓力分佈圖僅能了解壓力變化的趨勢，因此建議使用圖形配合數值的分析，以提供更加精確且一目瞭然的結果。而在修改鞋墊對行進壓力中心的內外側偏移的影響時，若使用的墊片較薄，壓力中心線的偏移較不明顯。

關鍵字

扁平足 ； 鞋具 ； 足弓支撐 ； 能量耗散率 ； 足底壓力 ； 壓力中心

並列摘要

The foot is classified as normal foot, flatfoot, and high arch foot. Flatfoot is a foot deformity caused by the collapse of the medial longitudinal arch. Its prevalence is rather high, which is about 3-25%. Non-surgical treatment is effective for flatfoot patients with mild symptoms, including footwear or insoles with arch support. However, the effect of footwear or insoles usually needs to be evaluated through the patient's subjective assessments. The process is not only time-consuming but also torture for the patient. Therefore, this study intends to establish a measurement and analysis system to provide a reference for evaluating the effects of footwear for the flatfoot.
This study reviewed the recommendations for selecting footwear for flatfoot through the literature. Then, footwear with arch support formed by foaming ethylene vinyl acetate(EVA) be used for compression tests and measurement of plantar pressure distribution. The procedure of the compression test was to put the footwear on the compression testing machine that was mounted a last and then carried out at four loading speeds. Last, the obtained load-deformation curve was used to analyze the stiffness and the energy dissipation ratio(EDR) of the footwear. The participants of the pressure distribution measurement include a normal foot and two flatfoot. The test conditions include standing with barefoot, walking with barefoot, standing with footwear, and walking with footwear. Last, the changes in plantar pressure were explored by the pressure distribution chart to evaluate the effect of the arch support. In addition to evaluating the effect of arch support, a 2mm EVA pad was used to modify the insole in five ways to explore the influence of modifying the insole on the pressure distribution. The pressure distribution was measured by a flatfoot participant with severe symptoms wearing the footwear before and after the modification while standing and walking. Last, evaluating the effect of modifying the insole through the changes in the pressure distribution chart and the progress line.
The results showed that the EVA footwear used would harden and the energy dissipation ratio would decrease as the loading speed increases. For the participant with normal foot, the arch support could reduce the pressure on the forefoot and heel when standing and walking, but the pressure and contact area of the midfoot would also increase. For participants with flatfoot, the arch support could reduce the maximum pressure on the heel, but the pressure and contact area of the midfoot would also increase. The cause of the increased pressure on the midfoot may be the rocker bottom. When evaluating the influence of footwear or modifying insoles on the pressure distribution, the pressure distribution chart only shows the trend of pressure changes. Therefore, to provide accurate and intuitive results, it is recommended to use the chart with numerical analysis. When evaluating the influence of the modifying insole on the shift of the center of pressure in the medial-lateral direction in movement, if a thinner pad is used, the shift of the progress line is less obvious.

並列關鍵字

Flatfoot ； Footwear ； Arch support ； Energy dissipation ratio ； Plantar pressure ； Center of pressure

參考文獻

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