Trauma Research Center Ulm (ZTF), Institute of Orthopedic Research and Biomechanics, Ulm University, Helmholtzstraße 14, 89081, Ulm, Germany.
Department of Internal Medicine II, University Hospital Ulm, Ulm, Germany.
Eur Spine J. 2022 Jun;31(6):1487-1500. doi: 10.1007/s00586-022-07132-y. Epub 2022 Feb 16.
Both posture and loading rate are key factors in the herniation process and can determine the mechanism of disc failure. The aim of this study was to test the hypothesis that disruption visible with HR-MRI post-testing corresponds with microstructural features and further elucidate the mechanism by which this disruption weakens the disc. This will enable us to gain new insights into the herniation process.
Thirty ovine lumbar spinal segments were subjected to combinations of four loading conditions (0-12° flexion, 0-9° lateral bending, 0-4° axial rotation, 0-1500 N axial compression) for 1000 loading cycles at 2 Hz in a dynamic disc loading simulator. The discs were scanned in an ultra-high field MRI (11.7 T) then examined using brightfield microscopy to examine their microstructure.
Four discs herniated and seven discs suffered nucleus displacement. These discs contained pre-existing defects in the central posterior annulus. Generally, following testing discs contained more posterior annulus disruption, Microstructural investigation revealed there was clear correspondence between HR-MRI and microstructural observations, and that the mid-outer annular-endplate junction had failed in all discs examined in this study.
While all discs suffered outer annulus damage, only the discs containing pre-existing defects herniated. These pre-existing defects weakened the inner and mid annulus, allowing herniation to occur once the mid and outer annular wall was compromised. We propose this can occur during the degenerative cascade.
姿势和加载速率都是椎间盘突出过程中的关键因素，它们可以决定椎间盘失效的机制。本研究旨在验证以下假设，即 HR-MRI 后测试中的破坏与微观结构特征相对应，并进一步阐明破坏使椎间盘变弱的机制。这将使我们能够深入了解椎间盘突出过程。
30 个绵羊腰椎节段在动态椎间盘加载模拟器中以 2 Hz 的频率进行 1000 次循环，承受 4 种加载条件（0-12°前屈、0-9°侧屈、0-4°轴向旋转、0-1500 N 轴向压缩）的组合。在超高场 MRI（11.7 T）中对椎间盘进行扫描，然后使用明场显微镜检查其微观结构。
4 个椎间盘突出，7 个椎间盘发生核移位。这些椎间盘的中央后环有预先存在的缺陷。一般来说，经过测试后，椎间盘的后环破坏更严重。微观结构研究表明，HR-MRI 与微观结构观察之间存在明显对应关系，而且在本研究中检查的所有椎间盘的中-外环形-终板交界处都已经失效。
虽然所有的椎间盘都有外环形损伤，但只有含有预先存在缺陷的椎间盘突出。这些预先存在的缺陷削弱了内环形和中环形，一旦中环形和外环形壁受损，就会导致椎间盘突出。我们提出，这种情况可能发生在退行性级联反应中。
