中文摘要

後穿式踝足裝具（Posterior Ankle Foot Orthoses posterior AFO）常用來矯正異常步態及在行走時維持足踝部於正常姿勢。研究指出不同疾病的病人應給予其個別的踝足裝具，因為不適當的踝足裝具將影響病人的步態流暢性或增加足底面的壓力而導致足部壓瘡。現今踝足裝具的製造，仍然是靠義肢裝具師的經驗及其主觀判斷，然後在經由不斷地修改，才能得到較佳的結果。以往學者僅針對踝足裝具本身作力學分析或是以感測器量測足底界面之壓力分佈，因此對整個足部與踝足裝具的界面力學瞭解很有限，所以本研究期望藉由實驗量測與有限元素模型分析探討踝足裝具本身以及患者在穿戴踝足裝具時界面力學行為。本研究根據電腦斷層掃瞄影像建構出接近真實幾何外型的足部與踝足裝具三維有限元素模型，並以此模型探討踝足裝具本身的力學行為，及足部穿戴踝足裝具後之界面力學表現。在實驗的部分以EMED-PEDAR量測足部與踝足裝具間的足底壓力，用實驗量測來驗證有限元素模擬的結果。其結果顯示站立時在前足區為界面應力發生之最大值，與實驗相符。而在模擬heel strike及toe off時，界面最大剪應力分別增加1.6及5.9倍，此結果指出行走時不僅造成踝足裝具與足部間界面壓力的增加，界面剪應力的增加也是必須觀察的一個重點。在踝足裝具本身的力學表現上，踝足裝具的厚度與其裁線大小會對裝具的勁度造成影響。其中裁線越小則勁度越大，厚度越厚勁度也越大，且做蹠曲所需的力矩比做背曲來得大，其結果數據可提供臨床人員設計踝足裝具之參考。

Abstract

Posterior AFO are often used to correct abnormal gait and maintain ankle and foot in neutral position during ambulation. Unsuitable prescription will cause the increasing of plantar pressure and even ulceration. Currently, a suitable the correct prescription still relies on the orthotist’s experience and subjective judgments. This often induced a costly “trail and error” approach to obtain an acceptable AFO. In this study, 3-D finite element models of AFO and foot, based the CT images, were established to investigate the interface stress between the AFO and foot as well as the stiffness of AFO for different trimline and thickness designs. Experimental measurements of the contact pressure between the foot and AFO were also carried to valid the finite element simulation. The simulated result showed that the peak contact pressure was founded in the forefoot during foot flat. This outcome was consistent with the experimental result. The peak shear stress increased by 1.6 and 5.9 times during the heel strike and toe off respectively compared with the foot flat stage. This indicated that not only the contact pressure but also the shear stress should be considered during the evaluation of the AFO. As for the mechanical behavior of the AFO, the increasing of the radius of the trimline could decrease the stiffness of AFO while the increasing of AFO thickness would increase the stiffness. The thickness effect was large than the trimline effect.

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