Department of Neurosurgery, University of Utah School of Medicine, Salt Lake City, UT, USA.
Spine (Phila Pa 1976). 2011 Mar 15;36(6):448-53. doi: 10.1097/BRS.0b013e3181fd5d7c.
Biomechanical study.
To determine biomechanical forces exerted on intermediate and adjacent segments after two- or three-level fusion for treatment of noncontiguous levels.
Increased motion adjacent to fused spinal segments is postulated to be a driving force in adjacent segment degeneration. Occasionally, a patient requires treatment of noncontiguous levels on either side of a normal level. The biomechanical forces exerted on the intermediate and adjacent levels are unknown.
Seven intact human cadaveric cervical spines (C3-T1) were mounted in a custom seven-axis spine simulator equipped with a follower load apparatus and OptoTRAK three-dimensional tracking system. Each intact specimen underwent five cycles each of flexion/extension, lateral bending, and axial rotation under a ± 1.5 Nm moment and a 100-Nm axial follower load. Applied torque and motion data in each axis of motion and level were recorded. Testing was repeated under the same parameters after C4-C5 and C6-C7 diskectomies were performed and fused with rigid cervical plates and interbody spacers and again after a three-level fusion from C4 to C7.
Range of motion was modestly increased (35%) in the intermediate and adjacent levels in the skip fusion construct. A significant or nearly significant difference was reached in seven of nine moments. With the three-level fusion construct, motion at the infra- and supra-adjacent levels was significantly or nearly significantly increased in all applied moments over the intact and the two-level noncontiguous construct. The magnitude of this change was substantial (72%).
Infra- and supra-adjacent levels experienced a marked increase in strain in all moments with a three-level fusion, whereas the intermediate, supra-, and infra-adjacent segments of a two-level fusion experienced modest strain moments relative to intact. It would be appropriate to consider noncontiguous fusions instead of a three-level fusion when confronted with nonadjacent disease.
生物力学研究。
确定治疗非连续节段时，两到三节段融合后对中间和相邻节段施加的生物力学力。
融合脊柱节段相邻节段的运动增加被认为是相邻节段退变的驱动力。偶尔，患者需要在正常节段两侧治疗非相邻节段。中间和相邻节段所受的生物力学力尚不清楚。
将 7 个完整的人体颈椎（C3-T1）标本安装在配备跟随力装置和 OptoTRAK 三维跟踪系统的定制七轴脊柱模拟器中。每个完整标本在±1.5Nm 扭矩和 100Nm 轴向跟随力下进行 5 次屈伸、侧屈和轴向旋转循环。记录每个运动轴和节段的施加扭矩和运动数据。在 C4-C5 和 C6-C7 椎间盘切除术并使用刚性颈椎板和椎间间隔器融合后，以相同的参数重复测试，并再次从 C4 到 C7 进行三水平融合后，再次重复测试。
在跳跃式融合结构中，中间和相邻节段的活动范围适度增加（35%）。在九个扭矩中有七个达到了显著或接近显著差异。在三水平融合结构中，在所有施加的扭矩下，上下相邻节段的运动在完整和双水平非连续结构中均显著或接近显著增加。这种变化的幅度很大（72%）。
在三水平融合时，所有扭矩下，下-上相邻节段都经历了明显的应变增加，而双水平融合时，中间、上-下相邻节段相对于完整节段的应变扭矩适中。在遇到非相邻疾病时，考虑非连续融合而不是三水平融合是合适的。
