Background

The clinical outcomes of total ankle replacement are limited by prosthesis component malpositioning during surgery. The goal of this study is to assess the mechanical impact of this malpositioning in a validated computer model.

Methods

In a previously developed multi-body dynamic model of the human ankle complex three different artificial implants were designed, each one presenting a different approximation of the natural articular surfaces of the corresponding specimen. The most common implant translational and rotational malpositionings were defined and mimicked. Dynamic simulations of joint motion were run for the various surfaces and malpositionings. The same input loading conditions derived from a previous in-vitro experiment on the corresponding natural specimen were applied.

Findings

From load-displacement graphs it was observed that all three artificial surfaces reproduced well physiological motion between the calcaneus and the tibia/fibula, with a maximum difference of 2°. It was found that antero-posterior translation of either the tibial or the talar component and inclination of the tibial component in the sagittal plane led to considerable increases in the range of motion. Antero-posterior and dorsiflexion of the tibial component resulted in an increased internal-external rotation by up to 3.5° and 4.0°, respectively. The corresponding increase of inversion-eversion was 5.0° and 6.5°.

Interpretation

This study showed that relatively small surgical errors have great consequences in replaced joint mechanics. The present model can be used in future studies to analyse the effect of malpositioning with any specific current total ankle prosthesis.

中文翻译：

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人工表面形状及其错位对置换踝关节力学的影响，以实现更好的假肢设计

背景

全踝关节置换术的临床结果受到手术期间假体组件错位的限制。本研究的目的是在经过验证的计算机模型中评估这种错位的机械影响。

方法

在先前开发的人体踝关节复合体的多体动力学模型中，设计了三种不同的人工植入物，每一种都呈现出相应标本自然关节表面的不同近似值。定义和模拟了最常见的种植体平移和旋转错位。对各种表面和错位进行了关节运动的动态模拟。应用了从先前对相应天然样本进行的体外实验得出的相同输入加载条件。

发现

从载荷-位移图可以看出，所有三个人造表面都能很好地再现跟骨和胫骨/腓骨之间的生理运动，最大差异为 2°。发现胫骨或距骨组件的前后平移以及胫骨组件在矢状面上的倾斜导致运动范围的显着增加。胫骨组件的前后和背屈分别导致内外旋转增加高达 3.5° 和 4.0°。倒转-外翻的相应增加分别为5.0°和6.5°。

解释

这项研究表明，相对较小的手术错误对更换关节力学有很大的影响。本模型可用于未来的研究，以分析当前任何特定全踝关节假体的错位效果。