Hwang Soo-Hyun, Kayanja Mark, Milks Ryan A, Benzel Edward C
Department of Neurosurgery, College of Medicine, Gyeonsang National University, 90 Chilamdong, Jinju, South Korea, 660-702.
Spine J. 2007 Mar-Apr;7(2):216-21. doi: 10.1016/j.spinee.2006.05.018.
Complications, such as graft subsidence and adjacent segment degeneration, are not uncommon after ventral cervical fusion. It has been theorized, but not proven, that sagittal alignment may affect this process. It is therefore hypothesized that increasing lordosis during anterior cervical fusion decreases adjacent segment motion (ASM) and thus decreases the rate of adjacent disc degeneration. A study was designed to test the first portion of this hypothesis; ie, that increasing lordosis during anterior cervical fusion decreases ASM.
To determine the effect on the adjacent segment motion (ASM) after ventral cervical spine fusion obtained by varying the angle of lordosis using interbody spacers with different heights (small: 6-mm interbody spacer; large: 9-mm interbody spacer).
A biomechanical study comparing the segmental motion at adjacent disc levels after cervical fusion with varying angles of lordosis. Sample and outcome measures: six human cadaveric spines C2-C7, range of motion (ROM).
Six fresh human cadaveric cervical spines (C2-C7) were embedded at C2 and C7 and biomechanically tested to 0.7 Nm flexion and 0.5 Nm extension. Lordosis was measured at C4-C5 from radiographs; range of motion (ROM) at C3-C4, C4-C5, and C5-C6 was measured using markers during flexion and extension in the intact state, after ventral cervical fixation at C4-C5 with a small (6-mm) and with a large (9-mm) interbody spacer. A repeated measures analysis of variance was used to compare lordosis and the ROM for the different states.
Six cervical spines with a mean age of 55.3+/-1.6 years were studied. The mean sagittal angles of the specimens measured at C4-C5 using the Cobb angle method were -6.4+/-1.3 degrees intact, -8.8+/-1.4 degrees with small interbody spacer (intact vs. small spacer p=.02), and -12.4+/-0.9 degrees with large interbody spacer fixation (intact vs. large spacer p=.005). The lordotic angle of the specimens was lowest in the intact state, higher with the small spacer, and highest with the large spacer. The greatest ROM in the intact state testing was at C4-C5 (10.6+/-1.3 degrees), followed by at C5-C6 (7.2+/-1.5 degrees), and then at C3-C4 (7.1+/-0.9 degrees). After C4-C5 fusion, the ROM at C3-C4 and C5-C6 was significantly increased with the small spacer only. No significant change in ROM was observed with the large spacer. The greatest overall ROM (all three motion segments) was observed in the intact state (24.9+/-1.8 degrees), followed by the small spacer (21.4+/-2.0 degrees) and the large spacer (15.1+/-1.7 degrees).
Under the conditions of this study, there is a significant increase in ASM with the achievement of a modest increase in lordosis (small spacer) that is not observed with a greater increase in lordosis (large spacer).
颈椎前路融合术后，诸如植骨沉降和相邻节段退变等并发症并不少见。有理论认为矢状位对线可能影响这一过程，但尚未得到证实。因此，有人提出假设，在前路颈椎融合术中增加前凸可减少相邻节段运动（ASM），从而降低相邻椎间盘退变的发生率。本研究旨在验证该假设的第一部分，即在前路颈椎融合术中增加前凸可减少ASM。
通过使用不同高度的椎间融合器（小：6毫米椎间融合器；大：9毫米椎间融合器）改变前凸角度，确定其对颈椎前路融合术后相邻节段运动（ASM）的影响。
一项生物力学研究，比较不同前凸角度的颈椎融合术后相邻椎间盘水平的节段运动。样本和结果测量：6具人类尸体颈椎C2-C7，运动范围（ROM）。
将6具新鲜人类尸体颈椎（C2-C7）固定于C2和C7，并进行生物力学测试，屈伸力矩分别为0.7牛米和0.5牛米。通过X线片测量C4-C5的前凸；在完整状态下、C4-C5前路固定使用小（6毫米）和大（9毫米）椎间融合器后，通过标记物测量C3-C4、C4-C5和C5-C6在屈伸过程中的运动范围（ROM）。采用重复测量方差分析比较不同状态下的前凸和ROM。
研究了6具平均年龄为55.3±1.6岁的颈椎。使用Cobb角法在C4-C5测量的标本矢状角，完整状态下为-6.4±1.3度，使用小椎间融合器时为-8.8±1.4度（完整状态与小融合器相比，p = 0.02），使用大椎间融合器固定时为-12.4±0.9度（完整状态与大融合器相比，p = 0.005）。标本的前凸角在完整状态下最低，使用小融合器时较高，使用大融合器时最高。完整状态下测试时，最大ROM在C4-C5（10.6±1.3度），其次是C5-C6（7.2±1.5度），然后是C3-C4（7.1±0.9度）。C4-C5融合后，仅使用小融合器时C3-C4和C5-C6的ROM显著增加。使用大融合器时ROM无显著变化。整体最大ROM（所有三个运动节段）在完整状态下观察到（24.9±1.8度），其次是小融合器（21.4±2.0度）和大融合器（15.1±1.7度）。
在本研究条件下（适度增加前凸（小融合器）时ASM显著增加，而更大程度增加前凸（大融合器）时未观察到这种情况）。
