使用三維動態有限元素分析探討步行速度與鞋具對於足底壓力的影響

Using Three-Dimensional Dynamic Finite Element Analysis to Study the Effects of Walking Speed and Footwear on Plantar Pressures

葉齊偉(Chi-Wei Yeh)

指導教授 ： 陳文斌 ； 鄧復旦

中原大學/工學院/醫學工程研究所/碩士(2005年)

https://doi.org/10.6840/cycu200500819

摘要

有限元素分析是一項實用的電腦計算工具，並具有容易改變模型之幾何外型、材料性質、邊界與負載條件等優點。在過去文獻中研究人員多採取靜態或者準靜態之分析探討足部生物力學，而動態分析則較為少見。本研究之目的在於採取動態有限元素分析探討步行速度於步態週期站立期之足跟著地期到足底平貼期階段對於足底壓力之影響，以及穿著不同幾何外型與材料之鞋具於步態週期站立期之足跟著地期階段對於足底壓力之影響。
本研究建構一組包含骨骼、關節軟骨與完整軟組織之左足三維六面體有限元素模型，並分別建構平板式鞋內墊、全觸式鞋內墊與平板式鞋內墊加上足跟墊之簡易鞋具三維六面體有限元素模型。在鞋內墊材料方面，則選用plastazote、blue plastazote與pink plastazote三種材料。此外，在足部有限元素模型邊界條件方面，則利用步態分析設備所測量一名正常男性受測者左足於三種步行速度下（1.79 m/s、1.55 m/s與1.09 m/s）之運動學參數做為設定。然而，有限元素模型邊界與負載條件必須進行驗證以確認是否介於合理之範圍。因此，將有限元素分析與步態分析中測力板兩者所獲得之垂直方向地面反作用力相互比較，做為驗證之方式。
有限元素分析成功模擬出左足於足跟著地期到足底平貼期階段在矢狀面上之運動行為。此外，步態分析中測力板與有限元素分析兩者所獲得之垂直方向地面反作用力對時間曲線呈現符合之趨勢。因此，有限元素模型邊界與負載條件設定可視為介於合理之範圍。另一方面，由有限元素分析結果中可發現步行速度愈快會導致地面對於足部產生愈高之衝擊力，進而造成足跟之壓力上升率與平均壓力峰値愈高。在九種鞋具之有限元素分析中，可發現在平板式鞋內墊之上放置足跟墊以及選用材質較軟之pink plastazote材料，對於降緩足跟著地期階段足跟壓力峰値之效果較佳。
本研究所建立之左足三維六面體有限元素模型可提供臨床醫學進行應用，並提供足部輔具製作人員在進行開發與設計之工作時，做為參考之依據。在未來的研究中，可針對完成足部步態行為之模擬以及足部輔具設計等方面進行深入探討。

關鍵字

足部有限元素模型 ； 足底壓力 ； 鞋具 ； 步行速度 ； 動態模擬

並列摘要

Finite element analysis is a useful computational tool. It has the advantage to easily change the geometry, material properties, boundary and loading conditions. In previous literature that used finite element method to study the foot biomechanics are mostly static or quasi-static analyses and dynamic analyses are rare. The purpose of the current research is first to study the effects of walking speed on the plantar pressures during heel strike to foot flat phase in the stance phase of gait cycle, and second to study the effects of different geometries and materials of footwear on the plantar pressures during heel strike phase in the stance phase of gait cycle by using 3-D dynamic finite element analysis.
In this research, a 3-D hexahedral finite element model of left foot including bones, cartilages, and soft tissues was developed. Besides, three finite element models of footwear including flat insole, total contact insole, and flat insole combined heel pad were also built, respectively. The three materials of insoles, plastazote, blue plastazote and pink plastazote, were chosen. In addition, the kinematic gait data of a normal male subject measured in three walking velocities were used to set the boundary conditions of the finite element models. The finite element model needs to be validated before the results can be interpreted. Therefore, the vertical ground reaction force predicted by the finite element analysis was compared to that measured by a force plate in gait analysis.
In the finite element analysis, the left foot motion in the sagittal plane during heel strike to foot flat phase was simulated successfully. Besides, the vertical ground reaction force versus time curves acquired by a force plate in gait analysis and finite element analysis presented a similar trend. Therefore, the set of boundary and loading conditions for the finite element models is considered acceptable. Furthermore, the results in the finite element analysis showed that walking with faster velocities would result in higher impact force to the foot, and then the higher value of plantar pressures were found at the heel. In addition, the flat insole combined heel pad with pink plastazote insole material had the better effect in reducing the peak plantar pressure during heel strike phase.
The 3-D hexahedral finite element model of a left foot developed in this research may provide useful information for footwear design and other foot biomechanics applications. In future research, the simulation of whole gait cycle and the design of footwear can be considered.

並列關鍵字

walking velocity ； plantar pressure ； footwear ； finite element foot model ； dynamic simulation

參考文獻

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