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Title: [Finite element analysis of artificial ankle elastic improved inserts].
Author: Xu Z, Li Y, Zou G, Jin Y, Rao J, Tian S.
Journal: Zhongguo Xiu Fu Chong Jian Wai Ke Za Zhi; 2023 Nov 15; 37(11):1361-1369. PubMed ID: 37987045.
Abstract:
OBJECTIVE: To discuss the influence of artificial ankle elastic improved inserts (hereinafter referred to as "improved inserts") in reducing prosthesis micromotion and improving joint surface contact mechanics by finite element analysis. METHODS: Based on the original insert of INBONE Ⅱ implant system (model A), four kinds of improved inserts were constructed by adding arc or platform type flexible layer with thickness of 1.3 or 2.6 mm, respectively. They were Flying goose type_1.3 elastic improved insert (model B), Flying goose type_2.6 elastic improved insert (model C), Platform type_1.3 elastic improved insert (model D), Platform type_2.6 elastic improved insert (model E). Then, the CT data of right ankle at neutral position of a healthy adult male volunteer was collected, and finite element models of total ankle replacement (TAR) was constructed based on model A-E prostheses by software of Mimics 19.0, Geomagic wrap 2017, Creo 6.0, Hypermesh 14.0, and Abaqus 6.14. Finally, the differences of bone-metal prosthesis interface micromotion and articular surface contact behavior between different models were investigated under ISO gait load. RESULTS: The tibia/talus-metal prosthesis interfaces micromotion of the five TAR models gradually increased during the support phase, then gradually fell back after entering the swing phase. The improved models (models B-E) showed lower bone-metal prosthesis interface micromotion when compared with the original model (model A), but there was no significant difference among models A-E ( P>0.05). The maximum micromotion of tibia appeared at the dome of the tibial bone groove, and the micromotion area was the largest in model A and the smallest in model E. The maximum micromotion of talus appeared at the posterior surface of the central bone groove, and there was no difference in the micromotion area among models A-E. The contact area of the articular surface of the insert/talus prosthesis in each group increased in the support phase and decreased in the swing phase during the gait cycle. Compared with model A, the articular surface contact area of models B-E increased, but there was no significant difference among models A-E ( P>0.05). The change trend of the maximum stress on the articular surface of the inserts/talus prosthesis was similar to that of the contact area. Only the maximum contact stress of the insert joint surface of models D and E was lower than that of model A, while the maximum contact stress of the talar prosthesis joint surface of models B-E was lower than that of model A, but there was no significant difference among models A-E ( P>0.05). The high stress area of the lateral articular surface of the improved inserts significantly reduced, and the articular surface stress distribution of the talus prosthesis was more uniform. CONCLUSION: Adding a flexible layer in the insert can improve the elasticity of the overall component, which is beneficial to absorb the impact force of the artificial ankle joint, thereby reducing interface micromotion and improving contact behavior. The mechanical properties of the inserts designed with the platform type and thicker flexible layer are better. 目的: 通过有限元分析探讨人工踝关节弹性化改良衬垫（以下简称“改良衬垫”）在减少假体微动和改善关节面接触力学方面的影响。. 方法: 基于INBONE Ⅱ植入物系统原始衬垫（模型A），通过添加弧形或平台型及层厚分别为1.3、2.6 mm的柔性层，构建4种改良衬垫，分别为雁飞型_1.3弹性化改良衬垫（模型B）、雁飞型_2.6弹性化改良衬垫（模型C）、平台型_1.3弹性化改良衬垫（模型D）、平台型_2.6弹性化改良衬垫（模型E）。然后，采集1名健康成年男性志愿者右踝关节中立位CT扫描数据，通过Mimics 19.0软件、Geomagic wrap 2017软件、Creo 6.0软件、Hypermesh 14.0软件、Abaqus 6.14软件，构建基于模型A～E假体的人工全踝关节置换术（total ankle replacement，TAR）有限元模型。最后，在ISO步态载荷下检验不同模型之间的骨-金属假体界面微动和关节面接触行为的差异。. 结果: 各组模型胫骨/距骨-金属假体界面微动均在支撑相时逐渐增大，进入摆动相后减小；完整步态周期中，模型B～E骨-金属假体界面微动与模型A相比均下降，但组间差异无统计学意义（ P>0.05）；最大微动胫骨出现在骨槽穹顶处且微动区域面积模型A最大、模型E最小，而距骨出现在中央骨槽后表面且微动区域面积组间无明显差异。各组模型衬垫/距骨假体关节面接触面积均呈在支撑相上升、在摆动相下降的总体趋势。其中，模型B～E与模型A相比关节面接触面积更大，但组间差异无统计学意义（ P>0.05）。各组衬垫/距骨假体关节面最大接触应力变化趋势与接触面积相似；其中，模型D、E衬垫关节面最大接触应力小于模型A，模型B～E距骨假体关节面最大接触应力均小于模型A，组间差异无统计学意义（ P>0.05）。改良型衬垫外侧关节面高应力区面积明显缩小，距骨假体表面应力分布更均匀。. 结论: 在衬垫中增加柔性层可以提高整体部件弹性，有利于吸收人工踝关节冲击力，从而降低界面微动和改善接触行为，其中平台构型和柔性层较厚的改良衬垫机械性能更好。.

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