定量分析钢板及椎弓根钉固定脊柱骨折脱位后的应力松弛

背景：正常范围的应力松弛有利于各种骨折内外固定之后的再造和重建，一定的应力松弛可缓解过度的坚强固定而产生的应力遮挡效应。目的：通过模拟脊柱L1~2骨折脱位，以钢板和髓内钉固定后对标本进行轴向压缩应力松弛实验，从流变学角度对临床治疗脊柱骨折脱位的2种固定器进行定量分析。设计、时间及地点：配对检验设计实验，于2006-06/2007-02在吉林大学力学实验中心完成。材料：实验所用8个正常国人尸体T8~L4脊柱标本由白求恩医科大学解剖教研室提供。方法：将8个标本在椎体锯开，模拟L1椎体骨折脱位。分为2组，即钢板固定组及椎弓根钉固定组，n=4。分别将2组标本放入装有生理盐水的有机玻璃缸内，置于电子万能实验工作台上，驱动机器以50%/min的应变增加速度进行实验，设定时间为7 200 s，采集100个数据，达到设定时间后计算机自动输出实验数据和曲线。主要观察指标：应力松弛数据和曲线，应力与时间的变化规律。结果：得出了2组标本的应力松弛数据及归一化应力松弛函数数据和曲线，建立了归一化应力松弛函数方程。钢板组、椎弓根钉组的7 200 s应力松弛量分别为0.62，0.629 MPa，椎弓根钉组大于钢板组，但差异无显著性意义(P > 0.05)。结论：回归分析的方法能准确地处理应力松弛实验数据，钢板及椎弓根钉的7 200 s应力松弛量差异不显著。

Stress relaxation following plate or pedicle screw fixation for spinal fracture and dislocation: A quantitative analysis

BACKGROUND: Stress relaxation of normal range aids reconstruction of fracture after internal or external fixation; certain stress relaxation can alleviate stress shielding effect due to over-fixation. OBJECTIVE: From the rheological point of view to quantitatively analyze the two fixators in clinical application of the treatment of spinal fracture-dislocation through simulation of spinal L1-2 fracture-dislocation and axial compression test after plate and intramedullary nail fixation. DESIGN, TIME AND SETTING: Paired observation experiment was performed at the Experimental Center of Mechanics in Jilin University between June 2006 and February 2007.MATERIALS: Eight spinal specimens of T8-L4 from normal cadavers were provided by Teaching and Research Section of Bethune Medical University.METHODS: Eight specimens were sawed to simulate L1 fracture dislocation. The specimens were divided into two groups (n=4): plate fixation and pedicle screw fixation groups. All specimens were placed into the plexiglass cylinder containing normal saline, and put on an electronic universal testing machine table. The test was performed at strain increase of 50%/min for 7 200 seconds. 100 data were collected, and the experimental data and curves were output automatically by computer.MAIN OUTCOME MEASURES: Stress relaxation data and curve, stress and time changes.RESULTS: Stress relaxation data, normalized stress relaxation function of data and curve of two groups of specimens were obtained; the normalized stress relaxation function of equation was established. The amount of 7 200s stress relaxation of the plate fixation group was 0.62 Mpa, and the pedicle screw fixation group was 0.629 Mpa. The difference was not significant (P > 0.05).CONCLUSION: The method of regression analysis can accurately process the stress relaxation experimental data. The amount of 7 200s stress relaxation between plate and pedicle screw fixation groups was not statistically significant.