Background

Expandable titanium implants have proven their suitability as vertebral body replacement device in several clinical and biomechanical studies. Potential stabilizing features of personalized 3D printed titanium devices, however, have never been explored. This in vitro study aimed to prove their equivalence regarding primary stability and three-dimensional motion behavior in the mid-thoracic spine including the entire rib cage.

Methods

Six fresh frozen human thoracic spine specimens with intact rib cages were loaded with pure moments of 5 Nm while performing optical motion tracking of all vertebrae. Following testing in intact condition (1), the specimens were tested after inserting personalized 3D printed titanium vertebral body replacement implants (2) and the two standard expandable titanium implants Obelisc™ (3) and Synex™ (4), each at T6 level combined with posterior pedicle screw-rod fixation from T4 to T8.

Findings

No significant differences (P < .05) in primary and secondary T1-T12 ranges of motion were found between the three implant types. Compared to the intact condition, slight decreases of the range of motion were found, which were significant for Synex™ in primary flexion/extension (−17%), specifically at T3-T4 level (−46%), primary lateral bending (−18%), and secondary lateral bending during primary axial rotation (−53%). Range of motion solely increased at T8-T9 level, while being significant only for Obelisc™ (+35%).

Interpretation

Personalized 3D printed vertebral body replacement implants provide a promising alternative to standard expandable devices regarding primary stability and three-dimensional motion behavior in the mid-thoracic spine due to the stabilizing effect of the rib cage.

中文翻译：

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使用整个肋骨标本对胸椎中部的个性化3D打印与标准可扩展钛椎体置换植入物进行体外比较。

背景

在一些临床和生物力学研究中，可膨胀钛植入物已证明其适合作为椎体置换装置。但是，从未探索过个性化3D打印钛设备的潜在稳定功能。这项体外研究旨在证明它们在包括整个胸廓的胸中脊柱的主要稳定性和三维运动行为方面的等效性。

方法

在对所有椎骨进行光学运动跟踪的同时，对六个具有完整肋骨笼的新鲜冷冻人胸椎标本加载5 Nm的纯弯矩。在完好无损的条件下进行测试（1）之后，在插入个性化的3D打印的钛椎骨置换植入物（2）和两个标准的可扩展钛植入物Obelisc™（3）和Synex™（4）后分别对标本进行测试，两者均处于T6级椎弓根螺钉从T4固定到T8。

发现

 在这三种植入物类型之间，在主要和次要T1-T12的运动范围内没有发现显着差异（P <.05）。与完整状态相比，发现运动范围略有减少，这对于Synex™在主要屈曲/伸展度（−17％），特别是在T3-T4水平（−46％），主要横向弯曲（− 18％），以及一次轴向旋转时的二次侧向弯曲（-53％）。运动范围仅在T8-T9级别增加，而仅对Obelisc™有意义（+ 35％）。

解释

个性化的3D打印椎体置换植入物由于肋骨笼的稳定作用，为胸椎中段的主要稳定性和三维运动行为提供了一种可替代标准可扩展装置的有希望的选择。