Department of Orthopaedics and Rehabilitation, University of Vermont, Burlington, VT 05405, USA.
Eur Spine J. 2011 Oct;20(10):1735-44. doi: 10.1007/s00586-011-1868-5. Epub 2011 Jun 26.
The intervertebral discs become wedged and narrowed in scoliosis, and this may result from altered biomechanical environment. The effects of four permutations of disc compression, angulation and reduced mobility were studied to identify possible causes of progressive disc deformity in scoliosis. The purpose of this study was to document morphological and biomechanical changes in four different models of altered mechanical environment in intervertebral discs of growing rats and in a sham and control groups.
External rings were attached by percutaneous pins transfixing adjacent caudal vertebrae of 5-week-old Sprague-Dawley rats. Four experimental Groups of animals underwent permutations of the imposed mechanical conditions (A) 15° disc angulation, (B) angulation with 0.1 MPa compression, (C) 0.1 MPa compression and (R) reduced mobility (N = 20 per group), and they were compared with a sham group (N = 12) and control group (N = 8) (total of 6 groups of animals). The altered mechanical conditions were applied for 5 weeks. Intervertebral disc space was measured from micro-CT images at weeks 1 and 5. Post euthanasia, lateral bending stiffness of experimental and within-animal control discs was measured in a mechanical testing jig and collagen crimp was measured from histological sections.
After 5 weeks, micro-CT images showed disc space loss averaging 35, 53, 56 and 35% of the adjacent disc values in the four intervention groups. Lateral bending stiffness was 4.2 times that of within-animal controls in Group B and 2.3 times in Group R. The minimum stiffness occurred at an angle close to the in vivo value, indicating that angulated discs had adapted to the imposed deformity, this is also supported by measurements of collagen crimping at concave and convex sides of the disc annuli.
Loss of disc space was present in all of the instrumented discs. Thus, reduced mobility, that was common to all interventions, may be a major source of the observed disc changes and may be a factor in disc deformity in scoliosis. Clinically, it is possible that rigid bracing for control of scoliosis progression may have secondary harmful effects by reducing spinal mobility.
脊柱侧凸患者的椎间盘变窄，这可能是由于生物力学环境改变所致。本研究探讨了椎间盘受压、成角和活动度降低的四种组合方式，以确定脊柱侧凸患者椎间盘进行性变形的可能原因。本研究的目的是记录生长大鼠椎间盘在四种不同机械环境改变模型中的形态和生物力学变化，并与假手术组和对照组进行比较。
通过经皮穿针固定相邻尾骨，将外环固定在 5 周龄 Sprague-Dawley 大鼠的尾骨上。四组动物（A：15°椎间盘成角；B：0.1 MPa 压缩下的成角；C：0.1 MPa 压缩；R：活动度降低）接受了不同的机械条件组合处理，每组 20 只，并与假手术组（12 只）和对照组（8 只）进行比较（共 6 组动物）。施加改变的机械条件 5 周。在第 1 周和第 5 周，通过 micro-CT 图像测量椎间盘间隙。处死动物后，在机械测试夹具中测量实验和动物内对照椎间盘的侧向弯曲刚度，并从组织学切片中测量胶原卷曲。
5 周后，micro-CT 图像显示，4 个干预组的椎间盘间隙平均丢失量为相邻椎间盘值的 35%、53%、56%和 35%。B 组的侧向弯曲刚度是动物内对照组的 4.2 倍，R 组为 2.3 倍。最小刚度出现在接近体内值的角度，这表明成角的椎间盘已经适应了施加的变形，这也得到了椎间盘环凸侧和凹侧胶原卷曲测量的支持。
所有仪器化椎间盘均出现椎间盘间隙丢失。因此，活动度降低可能是观察到的椎间盘变化的主要原因，并且可能是脊柱侧凸中椎间盘变形的一个因素。临床上，为控制脊柱侧凸进展而进行的刚性支具固定可能会通过降低脊柱活动度而产生继发性有害影响。
