此研究建立一三維KBM膝下殘肢與義肢之有限元素網格模組，此模組具有精確的幾何形狀和面對面的界面模擬，觀察殘肢滑動過程的生物力學反應，且特別強調摩擦係數及內襯材料對滑動過程的影響。在骨頭構造上面的三節點給予相同向下位移量來模擬滑動過程。結果顯示：KBM承套設計的起始主要荷重部分是在前面，然而，當殘肢滑進承套，主要支撐位置將轉移至後面，此乃由於後面接觸面積增加，此非線性效應可能來自非線性模擬模組的滑動過程。
隨著摩擦係數數值增加，殘肢滑動距離和平均界面壓力減少，而最大和平均摩擦應力隨之增加，此現象與摩擦力的一般力學行為一致。然而，最大界面壓力不只受摩擦係數影響，且受承套形狀影響，即決定於殘肢平衡位置之軟組織壓縮量，此平衡位置與殘肢滑動距離相關，而反應出摩擦係數的效應。因此，摩擦係數增加，能減少滑動距離和增加摩擦應力，但不能確定最大接觸壓力的減少。
反觀內襯硬度與摩擦效應的比較，殘肢滑動距離和界面應力對內襯硬度呈現中度靈敏，但內襯硬度效應並非正相關。一般而言，隨著彈性模量減少，會造成內襯硬度的的減少，此現象將增加滑動距離和接觸面積，然而，接觸面積的增加未必引發界面應力的減少，除非接觸面積足夠大。
為了進一步檢測荷重效應，本研究將建立單一荷重節點的五個模組。模擬結果顯示荷重位置在殘肢承套評估是一重要因子，荷重位置可能只因兩公分的改變，將會造成最大界面應力增加為兩倍，而殘肢滑動距離和平均界面應力改變量卻小於25%。一般而言，荷重的彎曲力矩越小(在中心位置)，產生的最大界面壓力將越小，此現象可看出承套校正的重要性，更重要的，此將可解釋在同一人進行不同次數的實驗量測，因站立姿勢些微不同，會引發荷重中心的改變，進而引起最大界面應力的改變。
討論: 本研究顯示殘肢承套系統的荷重傳導機制呈現高非線性，並非由於可能的非線性材料特性，而是殘肢滑動過程所造成。此滑動現象是由材料、形狀、及荷重等很多設計參數所共同引發，因此，欲評估像PTB設計可能具有較大的滑動行為，不能進行單一參數的檢測，而須整體考慮。

This study established a three-dimensional below-knee (BK) stump/liner finite element (FE) model for Kondylen Betrung Münster (KBM) socket with accurate tomography-based stump geometry and improved surface-to-surface contact interface conditions to investigate the biomechanical response during the stump slip process, with particular emphasis on the effects of the coefficient of friction (CoF), and liner stiffness. Three nodes at the superior surface of the bone structure were assigned with the same downward displacement to simulate the slip process. The results showed that the major loading portion for the KBM socket was initially at the anterior region. However, as the stump slip into the socket, the major supporting region shifted to the posterior region, due to the increasing contact area in the posterior region. This nonlinear effect could only be identified from nonlinear simulation models, which emphasize the slip process.
With increasing of CoF value, the stump slip distance as well as the average interface pressure decreased and the peak friction stress as well as the average friction stress increased, which are consistent with general mechanical behavior of the friction force. Nevertheless, the peak interface pressure depends not only on the CoF but also on the socket shape, that is, the amount of compression on soft tissue at the equivalent position. This equivalent position is related to the stump slip distance, which back to the CoF effect. Hence, an increasing of CoF could reduce the slip distance and increase the friction stress but does not ensure a decreasing in peak contact pressure.
As for the liner stiffness, the stump slip distance and interface stresses are moderately sensitive to the liner stiffness, comparing with the CoF effect. But the effect of liner stiffness is not straightforward. In general, a decreasing of liner stiffness, by decreasing its elastic modulus, would increase the stump slip distance and total contact area. However, the increasing of contact area would not necessary induce a decreasing of interface stress unless the enlarging of contact area is large enough.
To further examine the effects of loading, five models with one loading node were also established in this study. Their simulation results indicated that the loading position (or loading mode) is a vital factor for stump/socket evaluation. With the loading position differed by only 2cm the peak interface pressure could increase by almost 200%, while for the stump slip distance, the average interface stress only varied by less than 25%. In general, the loading with less bending moment (at the centroid) would produce smaller peak interface pressure, which indicated the significance of socket alignment. More importantly, this might explain the variations of interface stresses from experimental measurement on the same subject at different trail sessions, because a little difference in the standing posture would cause variations in loading center thus causing variations in the peak interface stresses.
In conclusion, this study demonstrated that the load transfer mechanism of a stump/socket system is highly nonlinear not just because of the possible nonlinear material property but more prominently from the stump slip process. This slip phenomenon further complicates the other design parameters, e.g. material, shape and loading. Therefore, to evaluate a socket with possible large slip behavior, such as PTB design, the design parameter could not be examined alone and should be considered as a whole.

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