Department of Chemical and Materials Engineering, University of Auckland, Auckland, New Zealand.
Spine (Phila Pa 1976). 2009 Oct 1;34(21):2288-96. doi: 10.1097/BRS.0b013e3181a49d7e.
Hydrostatically induced disruption of flexed lumbar intervertebral discs followed by microstructural investigation.
To investigate how flexion affects the anulus' ability to resist rupture during hydrostatic loading, and determine how the characteristics of the resulting disc failures compare with those observed clinically.
While compression of neutrally positioned motion segments consistently causes vertebral failure, compression of flexed segments can induce herniation. Why flexion has this effect remains unclear. A vast range of herniation characteristics have been documented clinically; whether flexion-related herniations are likely to possess a subset of these is unknown.
Forty-two ovine lumbar motion segments, dissected from the same 3 levels of 14 spines, were each flexed 7 degrees or 10 degrees from the neutral position. While maintained at one of these angles, the nucleus of each segment was gradually injected with a viscous radio-opaque gel via an injection screw placed longitudinally within the inferior vertebra, until failure occurred. Each segment was then inspected using microcomputed tomography and oblique illumination microscopy in tandem. RESULTS.: Eighteen segments suffered disc failure; 14 of these were caused by direct radial rupture of the anular wall. All radial ruptures were located in the central posterior anulus. Nine radial ruptures contained nuclear material, which had breached the posterior longitudinal ligament in 1 disc, and reached it in 5 others forming transligamentous and subligamentous nuclear extrusions, respectively. The most common radial rupture route, occurring in 10 discs, involved a systematic anulus-endplate-anulus failure pattern.
Flexion places the anulus at risk by facilitating nuclear flow, limiting circumferential disruption while promoting radial rupture, and rendering the endplate/vertebra junction vulnerable to failure. Flexion may play a developmental role in those herniations possessing a central posterior radial rupture that incorporates a short span of endplate disruption along the apex of the vertebral rim.
水静压诱导弯曲腰椎间盘破裂，随后进行微观结构研究。
研究弯曲如何影响环在水静压加载下抵抗破裂的能力，并确定由此产生的椎间盘破裂的特征与临床上观察到的相比如何。
虽然中性位置运动节段的压缩始终会导致椎体失效，但弯曲节段的压缩会导致突出。为什么弯曲会产生这种效果尚不清楚。临床上已经记录了广泛的突出特征；是否与弯曲相关的突出更有可能具有其中的一部分尚不清楚。
从 14 个脊柱的相同 3 个水平解剖出 42 个羊腰椎运动节段，每个节段从中立位置弯曲 7 度或 10 度。在保持在这些角度之一的同时，通过纵向放置在下位椎体中的注射螺钉逐渐将粘性放射可透凝胶注入每个节段的核，直到发生故障。然后使用微计算机断层扫描和斜向照明显微镜同时对每个节段进行检查。
18 个节段发生椎间盘破裂；其中 14 个是由环壁的直接放射状破裂引起的。所有放射状破裂均位于中央后环。9 个放射状破裂包含核材料，其中 1 个椎间盘的核材料已突破后纵韧带，另外 5 个椎间盘的核材料已到达后纵韧带，分别形成经韧带和韧带下核突出。最常见的放射状破裂途径发生在 10 个椎间盘上，涉及一种系统性的环-终板-环破裂模式。
弯曲通过促进核流、限制周向破裂同时促进放射状破裂以及使终板/椎体交界处易发生故障，使环处于危险之中。在那些具有中央后放射状破裂的突出中，弯曲可能发挥了发育作用，该破裂包含沿着椎体边缘顶点的短段终板破坏。
