以拉力参数构建兔腰骶神经牵拉损伤模型

Establishing rabbit models of lumbar-sacral nerve stretch injury based on tensile force

背景:神经根牵拉损伤是腰椎手术失败综合征的近期发病原因之一,但确切的病理机制尚未经证实。目的:建立一种不同程度的腰骶神经根牵拉损伤动物模型,探讨脊髓、神经根牵拉损伤后光镜和电镜改变。设计、时间及地点:随机对照,形态学动物实验,于2004-04/2006-10在南通大学第二附属医院中心实验室和南通大学江苏省神经再生重点实验室完成。材料:清洁级健康12周龄雄性大白兔40只,随机分为对照组、轻度牵拉组、中度牵拉组、重度牵拉组4组,每组10只。方法:轻、中、重度牵拉组动物全椎板切除显露双侧S1神经根,用测力神经根拉钩分别以0.4,1和1.8N的拉力水平牵拉左侧S1神经根造成神经根和脊髓的牵拉性损伤,分别定义为轻、中和重度牵拉,时间持续10min。对照组不牵拉。主要观察指标:术后2周对受牵拉节段脊髓,两侧S1神经根行光镜和透射电镜检测神经元和髓鞘。结果:轻度牵拉组牵拉侧前角个别神经元稍肿胀,神经元及神经纤维形态基本上正常,个别白质小片状脱髓鞘样改变,神经根髓鞘和轴索轻度水肿,脱髓鞘不明显;中度牵拉组白质有脱髓鞘改变,神经纤维排列紊乱,轴索崩解、断裂;灰质神经元水肿明显加重,前角运动神经原细胞尼氏体消失,核固缩、深染,神经根髓鞘和轴索水肿,局部轻度脱髓鞘改变;重度牵拉组牵拉侧白质为不规则的大片脱髓鞘区,前角运动神经元胞体固缩、变形、核深染,神经根有髓神经纤维萎缩、数目减少,重度脱髓鞘改变。结论:以拉力为参数可以稳定地建立不同程度的腰骶神经根牵拉性损伤动物模型,术后神经根和脊髓的病理分级改变与牵拉损伤程度一致。

BACKGROUND： Stretch injury of nerve root is one of reasons for recent onset of failed back surgery syndrome, but precise pathological mechanism has not been verified. OBJECTIVE： To establish an animal model of graded tractive lumbar-sacral nerve root injury, and to discuss the morphology of spinal cord and nerve root with an optical microscope and an electron microscope after lumbar-sacral nerve root injury. DESIGN, TIME AND SETTING： Randomized controlled morphological animal trial was performed at the Central Laboratory, Second Hospital Affiliated to Nantong University and Jiangsu Provincial Key Laboratory of Neural Regeneration, Nantong University between April 2004 and October 2006. MATERIALS： Forty clean-grade 12-week-old healthy male rabbits were randomly divided into control, mild, moderate and heavy traction groups, with 10 rabbits for each group. METHODS： Bilateral $1 nerve root was exposed using total laminectomy in the mild, moderate and heavy traction groups. The model of nerve root and spinal cord traction injury was induced by dragging the left $1 nerve root in 0.4,1 and 1.8 N using nerve root retracto, which was named mild, moderate and severe traction for 10 minutes. Rabbits in the control group were without traction. MAIN OUTCOME MEASURES： Bilateral s1 nerve root of the dragged spinal cord was observed under the optical microscope and the electron microscope to detect neurons and the myelin sheath at 2 weeks after surgery. RESULTS： The mild traction group showed angulus anterior individual neuron slightly engorged, neuron and nerve fiber morphous was normal essentially; individual substantia alba demyelinates in fragmentis; medullary sheath and auxiliary fibers of nerve root were hydropsia slightly without conspicuous myelinolysis. The moderate traction group demonstrated myelinolysis change in the spinal cord, and neurofibras lined up chaos, auxiliary fibers disaggregated, neuron dropsy, tigroid body disappeared with karyopycnosis and anachromasis in neurons; nerve root showed myelinolysis. The severe traction group displayed a great demyelination region; anterior motor neurons with karyopycnosis and anachromasis; myelinated nerve fiber of nerve root shrinked, decreased in number, with severe demyelination changes. CONCLUSION： Animal models of tractive lumbar-sacral nerve root injury can be stably established using tensile strength as a reference. Pathological grading changes of nerve root and spinal cord is accorded with traction injury degree after surgery.