Kothe Ralph, Rüther Wolfgang, Schneider Erich, Linke Berend
Department of Orthopedics, University Hospital Hamburg-Eppendorf, Hamburg, Germany.
Spine (Phila Pa 1976). 2004 Sep 1;29(17):1869-75. doi: 10.1097/01.brs.0000137287.67388.0b.
An in vitro biomechanical study to compare 2 different dorsal screw fixation techniques in the cervical spine with respect to primary stability and stability after cyclic loading.
To investigate if the biomechanical stability is better in pedicle screw or in lateral mass fixation.
In patients with poor bone quality who require multisegmental fixations, the current dorsal stabilization procedures in the subaxial cervical spine using lateral mass screws are often insufficient. Cervical pedicle screw fixation has been suggested as an alternative procedure, but there are still limited data available on the biomechanical differences between pedicle screw and lateral mass fixation.
A severe multilevel discoligamentous instability was created in 8 human cervical spine specimens (C2-C7). Dorsal stabilization was performed with the assistance of computer navigation (SurgiGate, Medivison, Switzerland) using either lateral mass or pedicle screw fixation. In the first part of the study, primary stability was measured by means of a multidirectional flexibility test. Then, specimens were divided into 2 groups, randomized for bone mineral density. Cyclic loading was applied with sinusoidal loads in flexion/extension (1000 cycles, +/-1.5 Nm, 0.1 Hz). Mechanical behavior of the specimens was determined by a flexibility test before and after the application of cyclic loads. Data analysis was performed by calculating the ranges of motion, and statistical differences were determined with the t test for group comparison.
Pedicle screw fixation showed a significantly higher stability in lateral bending (pedicle screw range of motion 0.86 +/- 0.31 degrees; lateral mass range of motion 1.43 +/- 0.62 degrees; P = 0.037). No significant differences were seen in flexion/extension and axial rotation. After cyclic loading, the decrease in stability was less with pedicle screw fixation in all load directions. Differences in the decrease of stability were statistically significant in flexion/extension (pedicle screw 95.4 +/- 9.4%; lateral mass 70.5 +/- 9.8%; P = 0.010) and lateral bending (pedicle screw 105.3 +/- 5.0%; lateral mass 84.2 +/- 13.6%; P = 0.046), whereas there was no significant difference in axial rotation.
The major finding of the current study was the higher stability of pedicle screws over lateral mass fixation with respect to primary stability and stability after cyclic loading. From a biomechanical point of view the use of pedicle screws in the subaxial cervical spine seems justified in patients with poor bone quality and need for multisegmental fixation.
一项体外生物力学研究，旨在比较颈椎两种不同的后路螺钉固定技术在初始稳定性和循环加载后的稳定性。
探讨椎弓根螺钉或侧块固定的生物力学稳定性是否更好。
在骨质较差且需要多节段固定的患者中，目前在颈椎下颈椎节段使用侧块螺钉的后路稳定手术往往不足。颈椎椎弓根螺钉固定已被建议作为一种替代手术，但关于椎弓根螺钉和侧块固定之间生物力学差异的数据仍然有限。
在8个人类颈椎标本（C2-C7）上制造严重的多节段椎间盘韧带不稳定。在计算机导航（SurgiGate，Medivison，瑞士）辅助下，使用侧块或椎弓根螺钉固定进行后路稳定手术。在研究的第一部分，通过多方向柔韧性测试测量初始稳定性。然后，将标本分为2组，根据骨密度进行随机分组。在屈伸（1000个周期，+/-1.5 Nm，0.1 Hz）中施加正弦载荷进行循环加载。在施加循环载荷前后，通过柔韧性测试确定标本的力学行为。通过计算运动范围进行数据分析，并使用t检验进行组间比较以确定统计学差异。
椎弓根螺钉固定在侧方弯曲时显示出明显更高的稳定性（椎弓根螺钉运动范围0.86 +/- 0.31度；侧块运动范围1.43 +/- 0.62度；P = 0.037）。在屈伸和轴向旋转方面未观察到显著差异。循环加载后，在所有加载方向上，椎弓根螺钉固定的稳定性下降较少。在屈伸（椎弓根螺钉95.4 +/- 9.4%；侧块70.5 +/- 9.8%；P = 0.010）和侧方弯曲（椎弓根螺钉105.3 +/- 5.0%；侧块84.2 +/- 13.6%；P = 0.046）方面，稳定性下降的差异具有统计学意义，而在轴向旋转方面没有显著差异。
本研究的主要发现是，在初始稳定性和循环加载后的稳定性方面，椎弓根螺钉比侧块固定具有更高的稳定性。从生物力学角度来看，在骨质较差且需要多节段固定的颈椎下颈椎节段患者中使用椎弓根螺钉似乎是合理的。
