Orthopaedic Institute, Department of Orthopaedics, The First Affiliated Hospital of SooChow University, 708 Renmin Rd, SuZhou, Jiangsu 215007, PR China; Department of Orthopedics, The Affiliated Peace Hospital of Changzhi Medical College, 110 Yan'an Rd, Changzhi, Shanxi 046000, PR China.
Orthopaedic Institute, Department of Orthopaedics, The First Affiliated Hospital of SooChow University, 708 Renmin Rd, SuZhou, Jiangsu 215007, PR China.
Spine J. 2019 Jul;19(7):1242-1253. doi: 10.1016/j.spinee.2019.01.008. Epub 2019 Jan 30.
Pfirrmann grading can be used to assess intervertebral disc degeneration (IVDD). There is growing evidence that IVDD is not simply a structural disorder but also involves changes to the substructural characteristics of the disc. Whether Pfirrmann grade can accurately represent these micro-nano environmental changes remains unclear.
We aimed to assess the micro-nano structural characteristics of the degenerative disc to provide more specific biomechanical information than the Pfirrmann score.
A micro- and nano-level structural analysis of degenerative discs of rat tails.
In this study, 12-week-old adult male Sprague-Dawley rats were divided randomly into five groups: control (no intervention to the intervertebral disc of the tail) and four intervention groups that all had caudal vertebrae immobilized using a custom-made external device to fix four caudal vertebrae (Co7-Co10) but with variable subsequent compression of Co8 and Co9 for 2, 4, 6, or 8 weeks. Magnetic resonance imaging detection of rat coccygeal vertebrae was conducted at each time node of the experiment, and the T2 signal intensity and disc space were evaluated. Animals were euthanized and the caudal vertebrae were harvested for further analysis. Histopathology, glycosaminoglycan (GAG) content, histologic score, end plate structure, and elastic modulus of the intervertebral discs were evaluated.
IVDD was observed at an earlier Pfirrmann grade (Pfirrmann II) under the microscope. With an increase in Pfirrmann grade to III-V, the pore structure of the bony end plate changed significantly and the number of pores decreased gradually. Furthermore, the total GAG content of the nucleus pulposus decreased from an average of 640.33 μg GAG/ng DNA in Pfirrmann grade I to 271.33 μg GAG/ng DNA in Pfirrmann grade V (p < .0001). At the early stage of clinical degeneration of intervertebral discs (Pfirrmann grades II and III), there were significant changes in mechanical properties of the outer annulus fibrosus compared with the inner layer (p < .05). Further, the fibril diameters exhibited significant changes compared with the control group (p < .05).
Our study found that the Pfirrmann grading system combined with intervertebral disc micro-nano structural changes more comprehensively reflected the extent of disc degeneration. These data may help improve our understanding of the pathogenesis and process of clinical disc degeneration.
Pfirrmann 分级可用于评估椎间盘退变（IVDD）。越来越多的证据表明，IVDD 不仅仅是一种结构紊乱，还涉及椎间盘亚结构特征的改变。Pfirrmann 分级是否能准确反映这些微观-纳米环境变化尚不清楚。
本研究旨在评估退变椎间盘的微观-纳米结构特征，为 Pfirrmann 评分提供更具体的生物力学信息。
大鼠尾椎退行性椎间盘的微观和纳米结构分析。
本研究中，将 12 周龄成年雄性 Sprague-Dawley 大鼠随机分为 5 组：对照组（尾椎椎间盘无干预）和 4 个干预组，通过定制的外部装置固定 4 个尾椎（Co7-Co10），但随后对 Co8 和 Co9 施加不同的压缩，持续 2、4、6 或 8 周。在实验的每个时间节点，通过磁共振成像（MRI）检测大鼠尾骨椎骨，评估 T2 信号强度和椎间盘间隙。动物被安乐死后，收获尾骨进行进一步分析。评估椎间盘的组织病理学、糖胺聚糖（GAG）含量、组织学评分、终板结构和弹性模量。
在显微镜下，IVDD 较早出现 Pfirrmann 分级（Pfirrmann II）。随着 Pfirrmann 分级增加到 III-V，骨终板的孔结构发生显著变化，孔数逐渐减少。此外，从 Pfirrmann 分级 I 的平均 640.33μg GAG/ng DNA 到 Pfirrmann 分级 V 的 271.33μg GAG/ng DNA，核髓总 GAG 含量显著降低（p<0.0001）。在椎间盘临床退变的早期（Pfirrmann 分级 II 和 III），与内层相比，外层纤维环的力学性能发生了显著变化（p<0.05）。此外，与对照组相比，纤维直径也发生了显著变化（p<0.05）。
本研究发现，Pfirrmann 分级系统结合椎间盘微观-纳米结构变化更全面地反映了椎间盘退变的程度。这些数据可能有助于提高我们对临床椎间盘退变发病机制和过程的认识。
