CT引导下经皮纤维环穿刺建立兔腰椎间盘退变模型

Establishment of rabbit lumbar intervertebral disc degeneration model induced by penetration under CT guidance

中文关键词:  椎间盘退变  纤维环穿刺  螺旋CT  MRI  兔

英文关键词:Intervertebral disc degeneration  Anular fibrosus stabbing  Spiral CT  Magnetic resonance imaging  Rabbit

中文摘要:

  【摘要】 目的：在CT引导下经皮纤维环穿刺建立兔腰椎间盘退变模型，并通过影像学和病理学验证其退变过程及效果。方法：3月龄新西兰大白兔18只，体重2.7~3.3kg，雌雄不限，术前均行X线及MRI检查。每只兔在螺旋CT引导下，用18G穿刺针经侧方皮下穿刺兔L5/6椎间盘（穿刺组），确认刺入椎间盘纤维环深度约为5mm，并对L4/5椎间盘进行假性穿刺（穿刺达椎间盘边缘，但不刺入纤维环内；假穿刺组），L3/4椎间盘作为对照椎间盘（对照组）。术后4周、8周、12周随机选取6只兔行X线片及MRI检查，观察各组椎间隙高度、邻近骨质改变及椎间盘信号改变，以“术后椎间隙高度/术前椎间隙高度×100”计算椎间盘高度相对值(DHRV)，并进行椎间盘改良Thompson分级法分级；X线片及MRI检查结束24h内处死动物，选取对照、假穿刺和穿刺组椎间盘进行组织形态学及免疫组织化学分析。结果：对照组及假穿刺组术后4、8、12周，X线片示椎间隙高度无降低，无终板骨质硬化与骨赘形成；MRI T2加权成像图像示各椎间盘均呈高信号；组织学检查见髓核细胞数量较多，分布均匀，纤维环排列呈同心圆层状；免疫组化分析髓核呈Ⅰ型胶原染色强阳性，Ⅱ型胶原染色阴性，在各时间点表现无明显差别。穿刺组椎间盘在术后4周X线片即可见椎间隙高度轻度降低（DHRV=70.78±4.55），MRI示椎间盘信号强度轻度下降，组织学上见纤维环结构紊乱、髓核细胞轻度减少；术后8周椎间隙高度明显降低（DHRV=50.63±4.04），开始出现终板骨质硬化，MRI示椎间盘信号强度明显下降，组织学上髓核被胶原组织分裂为含较多椭圆形细胞的细胞岛，出现纤维软骨细胞，纤维环层状结构变形、部分断裂；术后12周椎间隙高度继续下降（DHRV=44.78±2.61），骨赘形成、终板骨质硬化明显，MRI示椎间盘信号强度继续减弱，组织学上见髓核被纤维软骨组织所代替，纤维环层状组织碎裂、解体；免疫组织化学分析示术后4、8、12周髓核Ⅰ型胶原染色逐渐增强，Ⅱ型胶原染色逐渐减弱。各时间点对照组椎间盘的DHRV及改良Thompson分级与假穿刺组比较均无统计学差异（P＞0.05）；穿刺组在术后不同时间点的DHRV降低、改良Thompson分级增高与对照组及假穿刺组比较均有统计学差异（P<0.05）；随着穿刺时间的延长，穿刺组DHRV呈进行性降低趋势，改良Thompson分级进行性升高，两者在术后4、8、12周间均有统计学差异（P<0.05）。结论：CT引导下经皮纤维环穿刺法诱导兔椎间盘退变模型构建成功，操作方法简单、创伤小，经影像学及病理学证实其退变过程为渐进性。

英文摘要:

  【Abstract】 Objectives: To establish a rabbit model of disc degeneration by induced annulus fibrosus penetration under CT guidance, and to verify its degenerative procedure radiology and pathology. Methods： Eighteen New Zealand white rabbits aged about 3 months and weighing 2.7-3.3kg were used in our experiment, all of them were taken radiographic and MRI examinations preoperatively. The L5/6 discs(stabbed group) were punctured by 18-gauge needle into a depth of about 5mm inthe lateral annulus fibrosus guided by spiral CT. The L3/4 discs(sham group) were punctured at the margin of the disc with no injury to the annulus fibrosus, while the L4/5 discs were taken as control group. Each six rabbits were executed randomly at 4, 8 and 12 weeks postoperatively after radiographic and MRI examinations at 24 hours. The intervertebral space, the changes of vertebrae on radiography and signal intensity of discs on MR images in all groups were analyzed. The disc height relative value(DHRV) was calculated based on intervertebral space of pre- and post- operation(DHRV=postoperative intervertebral space/preoperative intervertebral space ×100), and modified Thompson scoring based on MRI were performed in all groups. Histological and immunohistochemical analysis was assessed in each group. Results: At 4, 8, 12 weeks postoperatively, the discs in control and sham groups showed no decrease of the intervertebral space, no endplate sclerosis and formation of osteophyte of vertebrae on radiography. On MR T2 weighted images, the discs in both control and sham groups showed high signal intensity. Histologically, nucleus pulposus contained a great number of cells with even distribution, and annulus fibrosus presented as concentric lamellae shape. Immunohistochemistry demonstrated strong positive type Ⅰ and negative type Ⅱ collagen in nucleus pulposus of control and sham groups at each time point. At 4 weeks postoperatively, disc height decreased slightly(DHRV=70.78±4.55), and MRI showed lower signal intensity in stabbed discs. Histologically, cell count of nucleus pulposus decreased slightly, while annulus fibrosus became disorganized. At 8 weeks postoperatively, significant decrease of intervertebral space was evidenced(DHRV=50.63±4.04), and endplate osteosclerosis was seen either. MRI revealed a moderate decrease of T2 weight signal intensity images. Histologically, nucleus pulposus was separated by proteoglycan matrix into multiple elliptical shape of cell islands, and the concentric fibrous lamellae distorted, or even fractured. Fibrochondrocyte was found in nucleus pulposus. At 12 weeks postoperatively, successional decrease of intervertebral space(DHRV=44.78±4.55) was found, with obvious endplate sclerosis and formation of vertebrae osteophyte. The T2 weighted signal intensity of the stabbed discs decreased continuously. Histologically, nucleus pulposus was replaced by fibrocartilage tissue, while the fibrous lamellae was induced into fragmentation, and its architecture disintegrated. Immunohistochemical analysis exhibited a progressive increase of type Ⅰ collagen and a progressive decrease of type Ⅱ collagen at 4, 8, 12 weeks postoperatively. The statistic analysis revealed that there was no significant difference of DHRV and modified Thompson scoring between control and sham groups at each time point. But the stabbed group demonstrated decrease of DHRV and increase of modified Thompson scoring, showing significant difference compared with those of control and sham groups at each time point(P<0.05). There was a progressive decrease of DHRV and a progressive increase of modified Thompson scoring in stabbed group, respectively. Both DHRV and modified Thompson scoring in stabbed group showed statistic differences between 4, 8, 12 weeks postoperatively(P<0.05). Conclusions： The percutaneous puncture of annulus fibrosus under CT guidance can induce disc degeneration in rabbit. The procedure is feasible and minimal invasive, which can be confirmed by radiology and pathology.