Shono Y, Kaneda K, Abumi K, McAfee P C, Cunningham B W
Department of Orthopaedic Surgery, Hokkaido University School of Medicine, Sapporo, Japan.
Spine (Phila Pa 1976). 1998 Jul 15;23(14):1550-8. doi: 10.1097/00007632-199807150-00009.
An in vitro biomechanical analysis of three anterior instability patterns was performed using calf lumbosacral spines. Stiffness of the constructs was compared, and segmental motion analyses were performed.
To clarify the factors that alter the stability of the spinal instrumentation and to evaluate the influence of instrumentation on the residual intact motion segments.
Recently, many adverse effects have been reported in fusion augmented with rigid instrumentation. Only few reports are available regarding biomechanical effects of stability provided by spinal instrumentation and its effects on residual adjacent motion segments in the lumbar-lumbosacral spine.
Eighteen calf lumbosacral spine specimens were divided into three groups according to instability patterns--one-level, two-level, and three-level disc dissections. Six constructs were cyclically tested in rotation, flexion-extension, and lateral bending of intact spines, of destabilized spine, and of spines with four segmental posterior instrumentation systems used to extend the levels of instability (Cotrel-Dubousset compression hook and three transpedicular screw fixation systems). During each test, stiffness values and segmental displacements were measured.
The rigidity of the instrumented construct increased as the fixation range became more extensive. Although application of the instrumentation effectively reduced the segmental motion of the destabilized vertebral level, the motion at the destabilized level tended to increase as the number of unstable vertebral levels increased, and the fixation range of the instrumentation became more extensive. Instrumented constructs produced higher segmental displacement values at the upper residual intact motion segment when compared with those of the intact spine. In contrast, the instrumented constructs decreased their segmental displacement values at the lower residual intact motion segment with higher magnitude of the translational (shear) motion taking place compared with the intact spine in flexion-extension and lateral bending. These changes in the motion pattern became more distinct as the fixation range became more extensive.
As segmental spinal instrumentation progresses from one level to three levels, the overall torsional and flexural rigidity of the system increases. However, segmental displacement at the site of simulated instability becomes more obvious. Application of segmental instrumentation changes the motion pattern of the residual intact motion segments, and the changes in the motion pattern become more distinct as the fixation range becomes more extensive and as the rigidity of the construct increases.
使用小牛腰骶椎脊柱对三种前侧不稳定模式进行体外生物力学分析。比较了不同结构的刚度，并进行了节段运动分析。
阐明改变脊柱内固定稳定性的因素，并评估内固定对剩余完整运动节段的影响。
最近，有许多关于刚性内固定增强融合术的不良反应的报道。关于脊柱内固定提供的稳定性的生物力学效应及其对腰骶椎脊柱剩余相邻运动节段的影响的报道很少。
18个小牛腰骶椎脊柱标本根据不稳定模式分为三组——单节段、双节段和三节段椎间盘切除术。对六个结构在完整脊柱、不稳定脊柱以及使用四种节段性后路内固定系统来延长不稳定节段水平（Cotrel-Dubousset加压钩和三种椎弓根螺钉固定系统）的脊柱的旋转、屈伸和侧方弯曲中进行循环测试。在每次测试中，测量刚度值和节段位移。
随着固定范围扩大，内固定结构的刚度增加。尽管内固定的应用有效降低了不稳定椎体节段的节段运动，但随着不稳定椎体节段数量增加以及内固定的固定范围扩大，不稳定节段的运动趋于增加。与完整脊柱相比，内固定结构在上方剩余完整运动节段产生更高的节段位移值。相反，内固定结构在下方剩余完整运动节段降低了其节段位移值，与完整脊柱在屈伸和侧方弯曲时相比，平移（剪切）运动幅度更大。随着固定范围扩大，这些运动模式的变化变得更加明显。
随着脊柱节段性内固定从单节段发展到三节段，系统的整体扭转和弯曲刚度增加。然而，模拟不稳定部位的节段位移变得更加明显。节段性内固定的应用改变了剩余完整运动节段的运动模式，并且随着固定范围扩大和结构刚度增加，运动模式的变化变得更加明显。
