Clarke Gabriel, Johnson Joshua E, de Cesar Netto Cesar, Anderson Donald D
Department of Orthopedics and Rehabilitation, The University of Iowa, Iowa City, IA, USA.
Department of Biomedical Engineering, The University of Iowa, Iowa City, IA, USA.
Foot Ankle Int. 2024 Dec;45(12):1414-1421. doi: 10.1177/10711007241281294. Epub 2024 Oct 6.
Implant survivorship in uncemented total ankle replacement (TAR) is dependent on achieving initial stability. This is because early micromotion between the implant and bone can disrupt the process of osseointegration, leading to poor long-term outcomes. Tibial implant fixation features are designed to resist micromotion, aided by bony sidewall retention and interference fit. The goal of this study was to investigate design-specific factors influencing implant-bone micromotion in TAR tibial components with interference fit.
Three implant designs with fixation features representative of current TAR tibial components (ARC, SPIKES, KEEL) were virtually inserted into models of the distal tibias of 2 patients with end-stage ankle arthritis. Tibia models were generated from deidentified patient computed tomography scans, with material properties for modeling bone behavior and compaction during press-fit. Finite element analysis (FEA) was used to simulate 2 fixation configurations: (1) no sidewalls or interference fit, and (2) sidewalls with interference fit. Load profiles representing the stance phase of gait were applied to the models, and implant-bone micromotions were computed from FEA output.
Sidewalls and interference fit substantially influenced implant-bone micromotions across all designs studied. When sidewalls and interference fit were modeled, average micromotions were less than 11 µm, consistent across the stance phase of gait. Without sidewalls or interference fit, micromotions were largest near either heel strike or toe-off. In the absence of sidewalls and interference fit, the amount of micromotion generally aligned inversely with the size of implant fixation features; the ARC design had the largest micromotion (540 µm average), whereas the KEEL design had the smallest micromotion (15 µm).
This study presents new insights into the effect of TAR fixation features on implant-bone micromotion. With sidewalls and interference fit, micromotion is predicted to be minimal for implants, whereas with no sidewalls and no interference fit, micromotion depended primarily on the implant design.
This study presents new insights into the effect of TAR primary fixation features on implant-bone micromotion. Although design features heavily influenced implant stability in the model, their influence was greatly diminished when interference fit was introduced. The results of this study show the relative importance of design features and interference fit in the predicted initial stability of uncemented TAR, potentially a key factor in implant survivorship.
非骨水泥型全踝关节置换术（TAR）中植入物的存活率取决于能否实现初始稳定性。这是因为植入物与骨骼之间的早期微动会破坏骨整合过程，导致长期效果不佳。胫骨植入物固定特征的设计旨在抵抗微动，借助骨侧壁固定和压入配合辅助。本研究的目的是调查影响具有压入配合的TAR胫骨部件中植入物 - 骨微动的特定设计因素。
将三种具有代表当前TAR胫骨部件固定特征的植入物设计（ARC、SPIKES、KEEL）虚拟插入2例终末期踝关节关节炎患者的胫骨远端模型中。胫骨模型由匿名患者的计算机断层扫描生成，具有用于模拟压入配合过程中骨行为和压实的材料特性。有限元分析（FEA）用于模拟两种固定配置：（1）无侧壁或压入配合，（2）有侧壁和压入配合。将代表步态站立期的载荷曲线应用于模型，并根据FEA输出计算植入物 - 骨微动。
侧壁和压入配合对所有研究设计的植入物 - 骨微动有重大影响。当对侧壁和压入配合进行建模时，平均微动小于11微米，在步态站立期保持一致。没有侧壁或压入配合时，微动在足跟撞击或足趾离地附近最大。在没有侧壁和压入配合的情况下，微动的量通常与植入物固定特征的大小成反比；ARC设计的微动最大（平均约540微米），而KEEL设计的微动最小（约15微米）。
本研究为TAR固定特征对植入物 - 骨微动的影响提供了新的见解。有侧壁和压入配合时，预计植入物的微动最小，而没有侧壁和压入配合时，微动主要取决于植入物设计。
本研究为TAR主要固定特征对植入物 - 骨微动的影响提供了新的见解。尽管设计特征在模型中对植入物稳定性有很大影响，但引入压入配合后其影响大大减弱。本研究结果显示了设计特征和压入配合在预测非骨水泥型TAR初始稳定性中的相对重要性，这可能是植入物存活率的关键因素。
