Background

Current implants for clavicle fractures are known to cause poor cosmesis and irritation, which may require implant removal. Low-profile shape-memory staples provide an attractive alternative, but their biomechanical utility in clavicle reconstruction is unknown. We hypothesized that shape-memory reconstructions would be more compliant compared to traditional constructs but would also outperform conventional plates during cyclic loading to failure.

Methods

This study was performed with 36 synthetic clavicles and 12 matched pairs of cadaveric specimens. The synthetic study tested four reconstructions: a single superiorly placed staple (n = 6), a single anteroinferiorly-placed staple (n = 6), a 3.5 mm reconstruction plate (n = 12), and two orthogonally placed staples (n = 12). The cadaveric study tested three constructs: reconstruction plate (n = 8), two orthogonal staples (n = 8), and a 2.7 mm reconstruction plate combined with a superior staple (n = 8). Non-destructive 4-point bending, compression, and torsion assays were performed prior to destructive cantilever bending and cyclic torsion tests.

Findings

The single staple and double staple groups demonstrated significantly decreased resistance to bending (p < 0.001) and torsion (p ≤ 0.027) when compared to reconstruction plate groups. The double staple group sustained significantly fewer cycles to failure than the reconstruction plate group in cyclic torsional tests (p = 0.012). The synthetic models produced higher stiffness and failure mechanisms that were completely different from cadaveric specimens.

Interpretation

Shape memory alloy implants provided inadequate stiffness for clavicle fixation but may have utility in other orthopaedic applications when used as a supplementary compression device in conjunction with traditional plated constructs. Synthetic bones have limited capacity for modeling fragility fractures.

中文翻译：

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检查连续压缩植入物在锁骨重建中的新用途：生物力学研究

背景

已知目前用于锁骨骨折的植入物会导致美容效果不佳和刺激，这可能需要移除植入物。低调形状记忆钉提供了一种有吸引力的替代方案，但它们在锁骨重建中的生物力学效用尚不清楚。我们假设形状记忆重建与传统结构相比更符合要求，但在循环加载至失效期间也将优于传统板。

方法

这项研究是用 36 个合成锁骨和 12 对匹配的尸体标本进行的。综合研究测试了四种重建：单个上方放置的钉 ( n  = 6)、单个前下方放置的钉 ( n  = 6)、3.5 mm 重建板 ( n  = 12) 和两个正交放置的钉 ( n  = 12 ）。尸体研究测试了三种结构：重建板 ( n  = 8)、两个正交钉 ( n  = 8) 和一个 2.7 mm 的重建板与上级钉 ( n  = 8) 结合。在破坏性悬臂弯曲和循环扭转试验之前进行了无损 4 点弯曲、压缩和扭转试验。

发现

 与重建板组相比，单钉组和双钉组的抗弯曲 ( p  < 0.001) 和抗扭转 ( p ≤ 0.027)显着降低。在循环扭转试验中，双钉组的失效周期明显少于重建板组 ( p  = 0.012)。合成模型产生了与尸体标本完全不同的更高刚度和失效机制。

解释

形状记忆合金植入物为锁骨固定提供了不足的刚度，但当与传统的镀层结构一起用作辅助压缩装置时，可能在其他骨科应用中有用。合成骨模拟脆性骨折的能力有限。