Department of Neurosurgery, Spinal Column Biomechanics and Surgical Outcomes Laboratory, The Johns Hopkins Hospital, Baltimore, Maryland 21218, USA.
Neurosurgery. 2009 Dec;65(6 Suppl):167-72; discussion 172. doi: 10.1227/01.NEU.0000345642.50726.A3.
The first in vitro biomechanical investigation comparing the immediate and postcyclical rigidities of thoracic translaminar versus pedicle screws in posterior constructs crossing the cervicothoracic junction (CTJ).
Ten human cadaveric spines underwent C4-C6 lateral mass screw and T1-T2 translaminar (n = 5) versus pedicle (n = 5) screw fixation. Spines were then potted in polymethylmethacrylate bone cement and placed on a materials testing machine. Rotation about the axis of bending was measured using passive retroreflective markers and infrared motion capture cameras. The motion of C6 relative to T2 in flexion-extension and lateral bending was assessed uninstrumented, immediately after instrumentation, and after 40,000 cycles of 4 N.m flexion-extension and lateral bending moments at 1 Hz. The effect of instrumentation and cyclical loading on rotational motion across the CTJ was analyzed for significance.
Compared with preinstrumented spines, pedicle and translaminar screw constructs significantly (P < 0.001) decreased motion during flexion-extension and lateral bending. After cyclical loading, rotational motion at the CTJ was significantly increased (P < 0.05) during flexion-extension and lateral bending in both groups. With flexion-extension, the mean rotational motion across the CTJ was similar in the translaminar and pedicle constructs immediately after fixation, but slightly greater (P = 0.03) after cyclical loading in the translaminar versus the pedicle screw constructs (0.39 degrees versus 0.26 degrees). Nevertheless, after cyclical loading, the mean angular motion across the CTJ remained less than one half of a degree in both groups. With lateral bending, the mean rotational motion was similar in both translaminar and pedicle screw constructs.
Both upper thoracic translaminar and pedicle screws allow for rigid fixation at the CTJ. Although translaminar screw constructs demonstrated one eighth of a degree more motion at the CTJ after cycling, this minimal difference is likely less than would influence the biological fusion process. Upper thoracic translaminar screws are a biomechanically effective option to rigidly stabilize the CTJ.
首次对穿过颈胸交界区（CTJ）的后路构建体中胸椎间层和椎弓根螺钉的即刻和循环后刚度进行体外生物力学比较。
10 个人体脊柱标本进行 C4-C6 侧块螺钉和 T1-T2 经椎板（n = 5）与椎弓根（n = 5）螺钉固定。然后将脊柱用聚甲基丙烯酸甲酯骨水泥盆栽，并放置在材料试验机上。使用被动反射标记和红外运动捕捉摄像机测量围绕弯曲轴的旋转。在无器械、器械后即刻以及在 1Hz 下 4N.m 屈伸和侧屈力矩 40000 次循环后，评估 C6 相对于 T2 的屈伸和侧屈运动。分析器械和循环加载对 CTJ 旋转运动的影响是否有统计学意义。
与未固定的脊柱相比，椎弓根和经椎板螺钉固定结构在屈伸和侧屈时明显（P < 0.001）减少了运动。循环加载后，两组在屈伸和侧屈时 CTJ 处的旋转运动均明显增加（P < 0.05）。在屈伸时，固定后即刻，经椎板与椎弓根螺钉固定结构之间的 CTJ 旋转运动相似，但经椎板螺钉固定结构的旋转运动略大（P = 0.03）（0.39 度对 0.26 度）。然而，循环加载后，两组 CTJ 处的平均角运动均小于 0.5 度。在侧屈时，经椎板和椎弓根螺钉固定结构之间的平均旋转运动相似。
上胸椎经椎板和椎弓根螺钉均可在 CTJ 处实现刚性固定。尽管经椎板螺钉固定结构在循环后 CTJ 处的运动增加了 1/8 度，但这种微小差异可能小于对生物融合过程的影响。上胸椎经椎板螺钉是一种有效的刚性稳定 CTJ 的生物力学选择。
