Backgrounds

Trigonometric formulae have been derived to correlate the distraction angle (height) and tibial specifications. However, the assumption-induced simplifications are inherent in the formulae such as the rigid tibia and the specific orientations of cutting plane and lateral hinge. This study aimed to evaluated the accuracy of the trigonometric formulae.

Methods

The 3D printed tibiae were used as the specimens for which the hinge orientations and distraction sites were systematically varied. Hinge orientation was determined by wedge inclination of the bone saw into the medial tibia and saw progression near the lateral cortex. The specimens were distracted at different distraction sites to measure the distraction angles that were compared with literature formulae.

Findings

In cases of the same distraction height, the wedge inclination, saw progression, and distraction site had various impacts on the coronal angles, indicating that the ideal formula should consider these parameters. Averagely, the predicted angles of the literature formulae were 15% higher than the testing results. The differences in these results may be attributed to the deformable property of the specimen material, non-ideal hinge orientation, and differences in distraction sites. Saw progression and distraction site had greater impacts than wedge inclination on the distraction angle.

Interpretation

Variations in three surgical indices constitute a complicated mechanism that affects the 3D hinged rotation of the distracted plateau. The non-middle distraction further deforms the tibial rotation and reduces the accuracy of the trigonometric formulae. The trigonometric formulae might underestimate the distraction angle; thus. Appropriate corrections are necessary for clinical application.

中文翻译：

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截骨术和牵引力如何影响楔形高位胫骨截骨术的牵引角？

背景资料

已经推导了三角公式，以将撑开角（高度）和胫骨规格关联起来。但是，假设引起的简化在公式中是固有的，例如刚性胫骨以及切割平面和横向铰链的特定方向。这项研究旨在评估三角公式的准确性。

方法

3D打印的胫骨被用作标本，其铰链方向和撑开部位有系统地变化。铰链的方向是由锯片向内胫骨的楔形倾斜和锯片在外侧皮质附近的进展确定的。将标本在不同的撑开部位撑开，以测量撑开角度，并与文献公式进行比较。

发现

在相同的撑开高度的情况下，楔形倾斜度，锯切进度和撑开位置会对冠状角产生不同的影响，这表明理想公式应考虑这些参数。平均而言，文献公式的预测角度比测试结果高15％。这些结果的差异可能归因于样本材料的可变形性，非理想的铰链方向以及牵引部位的差异。锯的前进和牵引位置对楔角的影响比楔形倾斜更大。

解释

三种手术指标的变化构成了影响分散高原的3D铰接旋转的复杂机制。非中间分散会进一步使胫骨旋转变形，并降低三角公式的准确性。三角公式可能会低估牵引角。从而。对于临床应用而言，必须进行适当的更正。