Abstract

Objective To quantify the amount of the screw head thread and the plate hole thread connection in two 3.5 mm locking plates: Locking Compression Plate (LCP) and Polyaxial Locking System (PLS).

Materials and Methods A micro - CT scan of a screw head - plate hole connection was performed pre- and post destructive tests. Tests were performed on bone surrogates in a fracture gap model. The 3.5 LCP and 3.5 PLS plates, with 3 perpendicular screws per segment were used in a destructive static test. The 3.5 PLS plates with mono- and polyaxial screws were compared in a cyclic fatigue tests in two orthogonal directions. Pre - and post - test scan datasets were compared. Each dataset was converted into serial images depicting sections cut orthogonally to locking screw axis. The amount of engagement was detected through automated image postprocessing.

Results The mean amount of the thread connection for the LCP was 28.85% before and 18.55% after destructive static test. The mean amount of the connection for the PLS was 16.20% before and 14.55% after destructive static test. When inserted monoaxially, the mean amount of the connection for the PLS screws was 14.4% before and 19.24% after destructive cyclic test. The mean amount of the connection for the polyaxial inserted PLS screws when loaded against plate thickness was 2.99% before and 2.08% after destructive cyclic test. The mean amount of the connection for the polyaxial inserted PLS screws when loaded against plate width was 3.36% before and 3.93% after destructive cyclic test. The 3D visualization of the thread connection showed that the initial interface points between screw head and plate hole are different for both LCP and PLS after the destructive testing. Depending on the type of applied force, there was either loss or increase of the contact.

Clinical Relevance Micro-CT offers news possibilities in locking implant investigation. It might be helpful in better understanding the nature of locking mechanism and prediction of possible mode of failure in different systems.

Authors' Contributions

Jakub Kaczmarek, Tomasz Bartkowiak and Martin Unger contributed to conception of study, study design, acquisition of data and data analysis and interpretation. Bartosz Gapinski, Piotr Paczos and Hanna Jąder contributed to acquisition of data, data analysis and interpretation. All authors drafted, revised and approved the submitted manuscript.

中文翻译：

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锁定螺丝如何锁定？3.5毫米锁紧螺丝机构的Micro-CT研究。

摘要

目的 要量化两个3.5毫米锁定板（锁定压缩板（LCP）和多轴锁定系统（PLS））中的螺钉头螺钉和板孔螺纹连接的数量。

材料和方法 在破坏性测试之前和之后，对螺钉头-板孔连接进行了微CT扫描。在骨折间隙模型中对骨替代物进行了测试。在破坏性静态测试中使用了3.5 LCP和3.5 PLS板，每节带有3个垂直螺钉。在两个正交方向上的循环疲劳测试中比较了带有单轴和多轴螺钉的3.5 PLS板。比较测试前和测试后的扫描数据集。每个数据集都转换为序列图像，该图像描述了与锁定螺钉轴正交切开的部分。通过自动图像后处理检测参与度。

结果 LCP的平均螺纹连接量在破坏性静态测试之前为28.85％，在破坏性静态测试之后为18.55％。PLS的平均连接量在破坏性静态测试之前为16.20％，之后为14.55％。单轴插入时，PLS螺钉的平均连接量在破坏性循环测试之前为14.4％，而在破坏性测试之后为19.24％。多轴插入的PLS螺钉在按板厚加载时的平均连接量在破坏性循环试验之前为2.99％，而在破坏性循环试验之后为2.08％。多轴插入的PLS螺钉在按板宽度加载时的平均连接量在破坏性循环试验之前为3.36％，而在破坏性试验之后为3.93％。螺纹连接的3D可视化显示，在破坏性测试之后，LCP和PLS的螺钉头和板孔之间的初始界面点是不同的。根据所施加的力的类型，接触的丢失或增加。

临床相关性 Micro-CT为锁定植入物研究提供了新的可能性。这可能有助于更好地了解锁定机制的性质以及预测不同系统中可能的故障模式。

作者的贡献

Jakub Kaczmarek，Tomasz Bartkowiak和Martin Unger为研究构想，研究设计，数据获取以及数据分析和解释做出了贡献。Bartosz Gapinski，Piotr Paczos和HannaJąder为数据采集，数据分析和解释做出了贡献。所有作者都起草，修改和批准了提交的手稿。