Hakało Jerzy, Wroński Jerzy, Ciupik Lechosław
Oddziału Neurochirurgii Szpitala Wojewódzkiego w Zielonej Górze.
Neurol Neurochir Pol. 2003;37(4):903-15.
A definition of subsidence in terms of spinal biomechanics is presented in the paper. Subsidence is defined as sinking of a body with a higher elasticity modulus (e.g. graft, cage, spacer) in a body characterized by a lower elasticity modulus (e.g. vertebral body), resulting in 3D changes of the spinal geometry. Magnitude of subsidence is directly proportional to the load pressure and to the difference between the elasticity modules, but inversely proportional to the area of the graft-bed interface. Both biological and mechanical qualities of the graft-bed interface are important for the subsidence process. Any excessive subsidence decreases the interbody space and produces both local and general kyphotization of the spine. This may cause destabilization of the screw-plate and/or screw-bone interfaces (e.g. pulling-out, altered angulation or breakage of the screws). A method is proposed of radiological estimating the absolute magnitude of subsidence, based on the real known length of the implanted stabilizer (e.g. plate). Clinical examples of an excessive subsidence and its impact on the stabilizing plate system are presented. Subsidence is inherent in the interbody fusion process. Endplate preservation and a dynamic modification of cervical plates may enables us to control subsidence and reduce the number of complications.
本文给出了一个从脊柱生物力学角度对下沉的定义。下沉定义为弹性模量较高的物体（如移植物、椎间融合器、间隔器）在弹性模量较低的物体（如椎体）中下沉，从而导致脊柱几何形状的三维变化。下沉的程度与负载压力以及弹性模量之间的差值成正比，但与移植物-骨床界面的面积成反比。移植物-骨床界面的生物学和力学特性对下沉过程都很重要。任何过度下沉都会减小椎间空间，并导致脊柱局部和整体后凸。这可能会导致螺钉-钢板和/或螺钉-骨界面失稳（如螺钉拔出、角度改变或断裂）。本文提出了一种基于植入的稳定器（如钢板）实际已知长度进行放射学评估下沉绝对程度的方法。文中给出了过度下沉及其对稳定钢板系统影响的临床实例。下沉是椎间融合过程中固有的现象。保留终板以及对颈椎钢板进行动态调整或许能使我们控制下沉并减少并发症的数量。
