臂丛神经的力学性质实验

背景:臂丛神经上干是新生儿分娩过程中臂丛神经损伤的好发部位。目的:对新鲜胎儿尸体臂丛神经上干进行拉伸实验、应力松弛实验以及蠕变实验,分析其拉伸力学性质和黏弹性力学性质。设计:随机对照实验,多变量分析。单位:吉林大学中日联谊医院放射线科,吉林大学南岭校区工程力学系。材料:实验标本为死亡的新鲜6.5～8月龄胎儿30具,男16具,女14具。方法:①常温解冻后取出臂丛神经上干,沿标本纵向切取100个试样,分别用于拉伸实验32个,应力松弛实验32个,蠕变实验32个,预实验4个。②拉伸实验、应力松弛实验、蠕变实验各自独立,均分为4组:男性6.5～7月胎龄组、男性8月以上胎龄组、女性6.5～7月胎龄组、女性8月以上胎龄组,各8个试样。③对臂丛神经上干进行单向拉伸实验,得出破坏载荷、强度极限、最大应变;对臂丛神经上干进行应力松弛实验和蠕变实验,得出应力松弛、蠕变实验数据和曲线。对实验数据进行归一化处理,得出归一化应力松弛函数、归一化蠕变函数及曲线。以一元线性回归分析的方法对实验数据进行回归分析,得出回归系数,拟合实验曲线。主要观察指标:臂丛神经上干的拉伸力学性质和黏弹性力学性质。结果:①6.5～7月龄胎儿臂丛神经上干的破坏载荷、强度极限、最大应变均小于8月龄以上胎儿(P<0.05)。男、女胎儿臂丛神经之间拉伸力学性质差异无显著性意义(P>0.05)。②女性8月以上胎龄组7200s蠕变量大于男性8月以上胎龄组(10.2±1.1)%,(7.2±1.08)%,P<0.05]。女性6.5～7月胎龄组7200s蠕变量与男性6.5～7月胎龄组基本相近(16.7±1.6)%,(15.1±1.2)%,P>0.05]。③男性8月以上胎龄组7200s应力松弛量与女性8月以上胎龄组基本相似(P>0.05)。男性6.5～7月胎龄组7200s应力松弛量大于女性6.5～7月胎龄组(P<0.05)。结论:分娩过程中相同外力作用下,只有少数抵抗外力能力差的胎儿会产生臂丛神经损伤,这种臂丛神经上干拉伸力学性质个体差异可能是由于遗传、营养不良等因素造成的。此外,在相同应力作用下男、女小月龄组的蠕变量均大于大月龄组,分析认为是由于小月龄胎儿臂纵神经发育不如大月龄胎儿成熟。

Mechanical characters of the brachial plexus nerve

BACKGROUND: Superior trunk of brachial plexus nerve is the part where brachial plexus nerve injury occurred easily during the process of delivery.OBJECTIVE: To perform elongation test, stress relaxation and creeping test on superior trunk of brachial plexus nerve of fresh fetal corpses, and to analyze the mechanical characters of elongation and mechanical characters of visco-elasticity.DESIGN: A randomized and controlled experiment, multiple variable analysis.SETTING: Department of Radiology, China-Japan Union Hospital, Jilin University, Department of Engineering Mechanics, Nanling Campus, Jilin niversity.MATERIALS: The specimens were 30 dead and fresh fetuses aged 6.5 to 8 months, including 16 male and 14 female.METHODS: ①After efrosting at ordinary temperature, superior trunk of brachial plexus nerve was taken out, and 100 samples were cut out along the length wise of specimen. 32 samples were used in elongation test, 32 in stress relaxation test and 32 in creeping test and 4 in pre-test. ②Elongation test, stress relaxation test and creeping test were separate and each test was subdivided into 4 groups: male fetus group of 6.5 to 7 months ,male fetus group of over 8 months, female fetus group of 6.5 to 7 months and female etus group of over 8 months, with 8 samples in each group. ③Superior trunk of brachial plexus nerve was performed one-way elongation test ,and destroy load , intensity limit, maximum strain were obtained; Superior trunk of brachial plexus nerve as performed stress relaxation test and creeping test, and data and curve of stress relaxation test and creeping test were obtained. Experimental data were given normalized treatment and normalized stress relaxation function and normalized creeping function and curve were derived. The experimental data were performed regression analysis with one-dimensional linear regression analysis, then regression coefficient was obtained and experimental curve was fitted.MAIN OUTCOME MEASURES: Mechanical characters of elongation and mechanical characters of visco-elasticity of superior trunk of brachial plexus nerve.RESULTS: ①Destroy load, intensity limit and maximum strain of superior trunk of brachial plexus nerve were all less in fetus group of 6.5 to 7 months than in the fetus group of over 8 months (P ＜ 0.05). There was no significant difference of mechanical characters of elongation among brachial plexus nerves between male and female (P ＞ 0.05). ② 7 200 s creeping quantity was larger in female fetus group of over 8 months than in the male fetus group of over 8 months (10.2±1.1)%, (7.2±1.08)% ,P ＜ 0.05].7 200 s creeping quantity was basically close in female fetus group of 6.5 to 7 months group to male fetus group of 6.5 to 7 months (16.7± 1.6)%,(15.1±1.2)%,P ＞ 0.05]. ③ 7 200 s stress relaxation quantity was basically similar in male fetus group of over 8 months to female fetus group of over 8 months (P ＞ 0.05). 7 200 s stress relaxation quantity was larger in male fetus group of 6.5 to 7 months than in female fetus group of 6.5 to 7 months (P ＜ 0.05).CONCLUSION: In the process of delivery, at the same external force, only fewer fetuses with poor ability to resist external force present brachial plexus nerve injury. The individual difference of mechanical characters of elongation of superior trunk of brachial plexus nerve might be caused by heredity, dystrophy and other factors. In addition, at the same strain, the creeping quantity is larger in the female group of small month than in the female group of large month, which might be due to that the development of brachial plexus nerve is not mature in the fetus of small months as that in the fetus of large months.