全踝关节置换术后对线不良会增加骨-假体界面的峰值接触应力：有限元分析。

INTRODUCTION: Malalignment of the Total Ankle Replacement (TAR) has often been postulated as the main reason for the high incidence of TAR failure. As the ankle joint has a small contact area, stresses are typically high, and malalignment may lead to non-homogeneous stress distributions, including stress peaks that may initiate failure. This study aims to elucidate the effect of TAR malalignment on the contact stresses on the bone-implant interface, thereby gaining more understanding of the potential role of malalignment in TAR failure. METHODS: Finite Element (FE) models of the neutrally aligned as well as malaligned CCI (Ceramic Coated Implant) Evolution TAR implant (Van Straten Medical) were developed. The CCI components were virtually inserted in a generic three-dimensional (3D) reconstruction of the tibia and talus. The tibial and talar TAR components were placed in neutral alignment and in 5° and 10° varus, valgus, anterior and posterior malalignment. Loading conditions of the terminal stance phase of the gait cycle were applied. Peak contact pressure and shear stress at the bone-implant interface were simulated and stress distributions on the bone-implant interface were visualized. RESULTS: In the neutral position, a peak contact pressure and shear stress of respectively 98.4 MPa and 31.9 MPa were found on the tibial bone-implant interface. For the talar bone-implant interface, this was respectively 68.2 MPa and 39.0 MPa. TAR malalignment increases peak contact pressure and shear stress on the bone-implant interface. The highest peak contact pressure of 177 MPa was found for the 10° valgus malaligned tibial component, and the highest shear stress of 98.5 MPa was found for the 10° posterior malaligned talar model. High contact stresses were mainly located at the edges of the bone-implant interface and the fixation pegs of the talar component. CONCLUSIONS: The current study demonstrates that TAR malalignment leads to increased peak stresses. High peak stresses could contribute to bone damage and subsequently reduced implant fixation, micromotion, and loosening. Further research is needed to investigate the relationship between increased contact stresses at the bone-implant interface and TAR failure.

引言：全踝关节置换术（TAR）的对线不良通常被认为是 TAR 失败发生率高的主要原因。由于踝关节的接触面积较小，因此通常会产生较高的应力，对线不良可能导致非均匀的应力分布，包括可能引发失效的应力峰值。本研究旨在阐明 TAR 对线不良对骨-假体界面接触应力的影响，从而更深入地了解对线不良在 TAR 失效中的潜在作用。

方法：开发了中性对线和 CCI（陶瓷涂层植入物）Evolution TAR 植入物（Van Straten Medical）对线不良的有限元（FE）模型。CCI 组件被虚拟插入胫骨和距骨的通用三维（3D）重建中。将胫骨和距骨 TAR 组件分别放置在中立对线位置以及 5°和 10°内翻、外翻、前向和后向对线不良位置。施加步态周期终末站立阶段的加载条件。模拟了骨-假体界面的最大接触压力和剪切应力，并可视化了骨-假体界面上的应力分布。

结果：在中立位置，胫骨骨-假体界面上的最大接触压力和剪切应力分别为 98.4 MPa 和 31.9 MPa。距骨骨-假体界面上的最大接触压力和剪切应力分别为 68.2 MPa 和 39.0 MPa。TAR 对线不良会增加骨-假体界面上的最大接触压力和剪切应力。胫骨对线不良 10°外翻的最大接触压力为 177 MPa，距骨对线不良 10°后倾的最大剪切应力为 98.5 MPa。高接触应力主要位于骨-假体界面的边缘和距骨组件的固定钉上。

结论：本研究表明，TAR 对线不良会导致峰值应力增加。高峰值应力可能导致骨损伤，随后导致植入物固定不良、微动和松动。需要进一步研究以探讨骨-假体界面接触应力增加与 TAR 失效之间的关系。