Background

Four-corner arthrodesis, which involves fusing four carpal bones while removing the scaphoid bone, is a standard surgery for the treatment of advanced stages of wrist arthritis. Nowadays, it can be performed using a dorsal approach by fixing a plate to the bones and a new radial approach is in development. To date, there is no consensus on the biomechanically optimal and most reliable surgical construct for four-corner arthrodesis.

Methods

To evaluate them biomechanically and thus assist the surgeon in choosing the best implant orientation, radial or dorsal, the two different four-corner arthrodesis surgical constructs were virtually simulated on a 3D finite element model representing all major structures of the wrist. Two different realistic load sets were applied to the model, representing common tasks for the elderly.

Findings

Results consistency was assessed by comparing with the literature the force magnitude computed on the carpal bones. The Von Mises stress distribution in the radial and dorsal plates were calculated. Stress concentration was located at the plate-screw interface for both surgical constructs, with a maximum stress value of 413 MPa for the dorsal plate compared to 326 MPa for the radial plate, meaning that the stress levels are more unfavourable in the dorsal approach.

Interpretation

Although some bending stress was found in one load case, the radial plate was mechanically more robust in the other load case. Despite some limitations, this study provides, for the first time, quantified evidence that the newly developed radial surgical construct is mechanically as efficient as the dorsal surgical construct.

中文翻译：

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通过腕背和radial骨入路对比两种手腕四角关节固定术的力学性能

背景

四角关节固定术涉及融合四个腕骨，同时去除舟骨骨，是治疗腕关节炎晚期的标准手术。如今，可以通过将背板固定在骨骼上使用背侧入路来进行，目前正在开发一种新的放射状入路。迄今为止，关于四角关节固定术的生物力学最佳和最可靠的手术结构尚无共识。

方法

为了对其进行生物力学评估，从而帮助外科医生选择最佳的植入物方向（径向或背面），在代表腕部所有主要结构的3D有限元模型中虚拟模拟了两种不同的四角关节固定术手术构造。该模型应用了两种不同的实际负荷集，代表了老年人的常见任务。

发现

通过与文献比较在腕骨上计算出的力大小来评估结果的一致性。计算了plates骨板和背板中的冯·米塞斯应力分布。两种手术构造的应力集中都位于板螺钉界面，背板的最大应力值为413 MPa，而radial骨板的最大应力值为326 MPa，这意味着在背侧入路时应力水平更为不利。

解释

尽管在一个载荷情况下发现了一些弯曲应力，但在另一种载荷情况下，径向板在机械上更坚固。尽管有一些限制，但这项研究首次提供了量化的证据，表明新开发的radial骨外科手术结构在机械方面与背侧外科手术结构一样有效。