正常足部之三維動態有限元素分析

Three-Dimensional Dynamic Finite Element Analysis of a Normal Foot

林師誠(Shih-Cherng Lin)

指導教授 ： 陳文斌

中原大學/工學院/醫學工程研究所/碩士(2004年)

https://doi.org/10.6840/cycu200400599

摘要

摘 要

使用電腦計算模擬的方式從事足部生物力學之研究，不僅能夠排除進行體內實驗之限制，完成體內實驗所無法施行之研究，更能夠降低體內實驗所需耗費之龐大設備資源與經費。綜觀各項有關足部之有限元素分析研究可知，唯有較為符合人體解剖學之足部幾何外型及其軟硬組織之建構，配合施予適當之邊界條件，並根據研究重點適當且合理地簡化有限元素模型，才能有效的提高模擬分析之效率，精確的展現靜態站立或步態週期期間正常足底與足部內部應力及應變之分佈情形。進而配合各種輔具模型之建構，完成輔具之功能性評估與結構分析。本研究採用泛用型網格建立系統 Gridgen V14 建構一區分各關節之足部骨骼與部分軟組織三維六面體有限元素模型。並利用進階型有限元素結構分析軟體 LS-DYNA 970，配合步態分析之運動學參數，進行人體步態之動態分析，探討站立期間（stance phase）足跟著地期（heel strike）跟骨（calcaneum）之應力與距下關節（subtalar joint）之壓力分佈狀態。此外，亦分別進行五位正常男性左足之足底壓力量測實驗十次，比較模擬分析與實驗之結果，作為有限元素分析結果之驗證。
分析結果顯示，跟骨於足跟著地期之應力分佈由跟骰關節附近逐漸往跟骨後端傳遞，von Mises應力分佈值約為30 ~ 180 KPa。而距下關節於足跟著地期，前與後關節面承受壓力，中關節面則承受張力。此現象證實距下關節於足跟著地期具有維持人體自然姿勢之功用。本研究完成之三維六面體有限元素模型建立與分析，不僅結果獲得足底壓力量測實驗之驗證，亦證實利用動態有限元素分析從事足部生物力學之可行性。未來可藉由本模型之改良與運用，完成整體步態週期之動態有限元素分析，並運用於臨床醫學，提供臨床醫師量化之數據作為術前規劃之參考，與術後輔具之製作。達成工程科技與醫學臨床結合之終極目標。

關鍵字

足底壓力 ； 動態分析 ； 足部模型 ； 有限元素分析 ； 足部生物力學

並列摘要

Abstract

Computational analysis of the foot biomechanics has its advantage in providing an overall stress distribution of the foot. It is also more economical than in vitro cadaver experiments. In view of the previously existed computational models, only a detailed representation of the foot geometry and joint characteristics together with realistic loading conditions can depict the internal stress and strain distributions of the foot complex. Functional evaluation as well as structure analysis of foot orthoses via construction of various foot orthoses finite element models will be completed based on the computational analysis. A general mesh generation software, Gridgen V14, was used to establish the three-dimensional hexahedral foot finite element model with detailed joint characteristics and partial plantar soft tissue. In addition, an advanced finite element analysis software, LS-DYNA 970, was utilized with the kinematic data of gait analysis for the dynamic finite element analysis of human motion. Also, the stress distributions of calcaneus and subtalar joint during heel strike in the stance phase were investigated. Furthermore, in order to validate the results of the finite element analysis, the plantar pressures of five normal male subjects’ left foot were obtained.

Results showed that during heel strike, calcaneal stress distribution was transferred gradually from calcaneocuboid joint nearby to posterior calcaneus. Thus, the mean von Mises stress was around 30 ~ 180 KPa. However, anterior and posterior joint surfaces of the subtalar joint sustained compressive stress, and medium joint surface of subtalar joint received tensile stress. These significant findings demonstrated that subtalar joint provided the function for keeping the human in neutral position. A three-dimensional hexahedral finite element model was established and analyzed in this study. The simulation results proved that the plantar pressures obtained from the dynamic finite element analysis were feasible for clinical use. With the application of this model, dynamic finite element analysis for a full gait cycle can be completed in future studies. This model can also provide useful information for pre-surgical planning and post-surgical orthotic design and fabrication. We hope this computational foot model can be beneficial both to the fields of engineering technologies, and clinical medicine.

並列關鍵字

finite element analysis ； foot biomechanics ； foot model ； plantar pressure ； dynamic analysis

參考文獻

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