Galvis Sarah, Arnold Josh, Mannen Erin, Wong Benjamin, Sis Hadley, Cadel Eileen, Anderson John, Anderson Dennis, Arnold Paul, Friis Elizabeth
University of Kansas, 1450 Jayhawk Blvd Mechanical Engineering and Bioengineering, 1530 W. 15th St., 3138 Learned Hall, Lawrence, KS 66045, USA.
Tufts University, 419 Boston Ave, Medford, MA 02155, USA.
Spine Deform. 2017 Jan;5(1):11-17. doi: 10.1016/j.jspd.2016.09.003.
Distraction-type rods mechanically stabilize the thorax and improve lung growth and function by applying distraction forces at the rib, spine, pelvis, or a combination of locations. However, the amount of stability the rods provide and the amount the thorax needs is unknown.
Five freshly frozen and thawed cadaveric thoracic spine specimens were tested for lateral bending, flexion/extension, and axial rotation in displacement control (1°/sec) to a load limit of ±5 Nm for five cycles after which a growth-friendly unilateral rod was placed in a simulated rib-to-lumbar attachment along the right side. The specimens were tested again in the same modes of bending. From the seven Optotrak Orthopedic Research Pin markers (Northern Digital Inc., Waterloo, Ontario, Canada) inserted into the top potting to denote T1, and the right pedicles at T2, T4, T5, T8, T9, and T11 and the Standard Needle Tip Pressure Transducers (Gaeltech, Isle of Skye, Scotland) inserted into the T4/T5 and T8/T9 discs, motion, stiffness, and pressure data were calculated. Parameters from the third cycle of the intact case and the construct case were compared using two-tailed paired t tests with 0.05 as the level of significance.
With the construct attached, the T1-T4 segment showed a 30% increase in neutral zone stiffness during extension (p = .001); the T8-T12 segment experienced a 63% reduction in the in-plane range of motion during flexion (p = .04); and the T8/T9 spinal motion unit had a significant decrease of 24% in elastic zone stiffness during left axial rotation (p = .04).
It is clear the device as tested here does not produce large biomechanical changes, but the balance between providing desired changes while preventing complications remains difficult.
撑开式棒通过在肋骨、脊柱、骨盆或这些部位的组合处施加撑开力，机械性地稳定胸廓并促进肺的生长和功能。然而，这些棒所提供的稳定性程度以及胸廓所需的稳定性程度尚不清楚。
对五个新鲜冷冻并解冻的尸体胸椎标本进行测试，在位移控制（1°/秒）下进行侧弯、屈伸和轴向旋转测试，直至达到±5牛米的载荷极限，共进行五个循环，之后将一个有利于生长的单侧棒沿右侧放置在模拟的肋骨至腰椎附着处。再次以相同的弯曲模式对标本进行测试。从插入顶部灌封材料以标记T1的七个Optotrak骨科研究销钉标记物（加拿大安大略省滑铁卢市北方数字公司），以及插入T2、T4、T5、T8、T9和T11右侧椎弓根的标记物，和插入T4/T5和T8/T9椎间盘的标准针尖压力传感器（苏格兰斯凯岛盖尔泰克公司），计算运动、刚度和压力数据。使用双侧配对t检验比较完整病例和植入器械病例第三个循环的参数，显著性水平为0.05。
植入器械后，T1 - T4节段在伸展过程中的中性区刚度增加了30%（p = 0.001）；T8 - T12节段在屈曲过程中的平面内运动范围减少了63%（p = 0.04）；T8/T9脊柱运动单元在向左轴向旋转过程中的弹性区刚度显著降低了24%（p = 0.04）。
很明显，此处测试的装置不会产生大的生物力学变化，但在提供所需变化的同时预防并发症之间保持平衡仍然困难。
