Wang Xiaoyu, Yeung Kelvin, Cheung Jason Pui Yin, Lau Johnson Yiu-Nam, Qi Weichen, Cheung Kenneth Man-Chee, Aubin Carl-Eric
Department of Mechanical Engineering, Polytechnique Montreal, Downtown Station, P.O. Box 6079, Montreal, QC, H3C 3A7, Canada.
Sainte-Justine University Hospital Center, 3175, Cote Sainte-Catherine Road, Montreal, QC, H3T 1C5, Canada.
Spine Deform. 2020 Jun;8(3):369-379. doi: 10.1007/s43390-020-00075-8. Epub 2020 Feb 24.
Biomechanical analysis of scoliosis instrumentation using superelastic Nickel-titanium shape memory (SNT) rods.
To compare SNT with conventional Titanium (Ti) and Cobalt-chrome (Co-Cr) rods. A clinical trial has documented comparable efficacy between two adolescent idiopathic scoliosis (AIS) cohorts instrumented using SNT versus conventional Ti rods. The shape memory and superelasticity of the SNT rod are thought to allow easy rod insertion, progressive curve correction, and correction from spinal tissue relaxation, but study is yet to be done to assess the effects of the shape memory and superelasticity.
Instrumentations of AIS patients from the clinical trial were computationally simulated using SNT, Ti and Co-Cr rods (5.5 or 6 mm; 30°, 50° or 60° sagittal contouring angles; 0°, 25° or 50° coronal over-contouring angles). Curve correction, its improvement from stress relaxation in the spine, and loads in the instrumentation constructs were computed and compared.
The simulated main thoracic Cobb angles (MT) and thoracic kyphosis with the SNT rods were 4°-7° higher and 1°-2° lower than the Ti and Co-Cr rods, respectively. Bone-implant forces with Ti and Co-Cr rods were higher than the SNT rods by 84% and 130% at 18 °C and 35% and 65% at 37 °C, respectively (p < 0.001). Further corrections of the MT from the simulated stress relaxation in the spine were 4°-8° with the SNT rods versus 2°-5° with the Ti and Co-Cr rods (p < 0.001).
This study concurs with clinical observation that the SNT rods are easier to insert and can result in similar correction to the conventional rods. The SNT rods allow significantly lower bone-implant forces and have the ability to take advantage of post-instrumentation correction as the tissues relax.
使用超弹性镍钛形状记忆（SNT）棒对脊柱侧弯器械进行生物力学分析。
将SNT与传统钛（Ti）棒和钴铬（Co-Cr）棒进行比较。一项临床试验记录了使用SNT棒与传统Ti棒治疗的两个青少年特发性脊柱侧弯（AIS）队列之间具有相当的疗效。SNT棒的形状记忆和超弹性被认为有助于棒的轻松插入、逐步矫正曲线以及通过脊柱组织松弛进行矫正，但尚未进行研究来评估形状记忆和超弹性的效果。
使用SNT棒、Ti棒和Co-Cr棒（5.5或6毫米；矢状面轮廓角度为30°、50°或60°；冠状面过度轮廓角度为0°、25°或50°）对来自该临床试验的AIS患者的器械植入进行计算机模拟。计算并比较曲线矫正、其因脊柱应力松弛而产生的改善以及器械结构中的负荷。
模拟的使用SNT棒时的主胸弯Cobb角（MT）和胸椎后凸分别比Ti棒和Co-Cr棒高4° - 7°和低1° - 2°。在18°C时，Ti棒和Co-Cr棒与骨的植入力分别比SNT棒高84%和130%，在37°C时分别高35%和65%（p < 0.001）。通过模拟脊柱应力松弛，SNT棒对MT的进一步矫正为4° - 8°，而Ti棒和Co-Cr棒为2° - 5°（p < 0.001）。
本研究与临床观察结果一致，即SNT棒更容易插入，并且可以产生与传统棒类似的矫正效果。SNT棒可使骨-植入物的力显著降低，并能够在组织松弛时利用器械植入后的矫正作用。
