人工膝關節所用超高分子量聚乙烯磨耗分析

Abstract

本文探討人工膝關節的磨耗型態，以試驗機模擬人體一個步態週期中人工膝關節磨耗情形，包括其正向受力，前後移動及彎曲伸直的各項運動。在本文中採用兩種不同接觸壓應力大小作磨耗試驗，分別為16.5MPa和9.76MPa。 實驗結果顯示在較大應力作用下，在前半段區域由於受到高應力及滑動的影響，產生明顯的刮痕，其磨耗的深度也大於其他區域。而在縱剖面的影響也較為顯著，在應力較大的試片中，可以觀察到縱剖面的疲勞發生處會伴隨垂直表面的裂縫，在壓應力16.5MPa週期數100萬次以及200萬次之試片皆可觀察到有貫穿試片的垂直裂縫。在9.76MPa壓應力作用下的試片，表面磨耗型態皆較為平坦，前半段區域並無明顯刮痕，整體的磨耗深度也較小，在縱剖面的觀察下，垂直表面的裂縫也大大減少，說明由於壓應力的減少，可以改變磨屑型態，進而降低磨耗的速度。 臨床取下來的聚乙烯試片中，可以觀察到和人工膝關節磨耗試驗機所模擬之試片具有相似的磨耗型態，大體上和較高應力的試片結果較為類似，其因滑動產生的刮痕和片狀脫落的磨屑以及多層重疊的結果都和本文實驗結果相似。

The wear patterns of ultra high molecular weight polyethylene (UHMWPE) used in artificial knee joint were studied in this research. A knee joint simulator was used to simulate the vertical load, anterior-posterior translation, flexion-extension and internal-external rotation in a complete walking cycle. Two different contact compressive stresses of 16.5MPa and 9.76MPa were set in this experiment. The experimental results show that obvious wear print would be observed in anterior area, it was caused by bearing high stress and relative sliding. The wear depth in this area was also deeper than that in other area. Subjected to the higher stress (i.e. 16.5MPa), fatigue cracks occurred in axial section perpendicular to the wear surface of the specimens subjected to 1x106 cycle and 2x106 cycle-tests. Subjected to the compressive stress of 9.76MPa, wear situation of the UHMWPE specimen was mild, and no obvious scrape in anterior area. The total wear depth was smaller, only some perpendicular cracks were observed. The similar wear patterns were observed on both the clinically used polyethylene and simulated one, especially on the specimens subjected to higher stress. The wear phenomena of delamination wear、stacks of wear debris and scratched marks on the simulated specimens were similar to those on the clinically used UHMWPE.