纵向生理加压外固定器的生物力学分析

Biomechanical analysis on vertical physiological external pressure fixator

背景:目前骨外固定器大多为刚性结构,对骨折端存在过多的应力遮挡,影响骨折愈合速度及骨痂质量,甚至骨折发生不愈合。目的:观察纵向生理加压外固定器固定胫骨中段横断骨折后与人体正常胫骨生物力学强度的差异。方法:选取12根新鲜胫骨标本随机分为试验组和对照组,试验组分别用线锯造成胫骨中段横断骨折,纵向生理加压外固定器固定;对照组即正常胫骨。分别进行轴向载荷、弯曲载荷、扭转载荷作用下的力学实验,记录每一级加载后胫骨的位移及扭转角度,计算出轴向压缩刚度、弯曲刚度及扭转刚度。结果与结论:在生理范围内加载下,试验左右应变略大于对照组,但其固定后整体刚度与对照组无显著性差异(P>0.05);试验组的弯曲应变大于对照组,但其整体刚度与对照组无显著性差异(P>0.05);两组整体扭转刚度无明显差异(P>0.05);试验组极限弯曲载荷明显大于对照组(P<0.05)。提示纵向生理加压外固定器能够达到足够的生物力学强度,有良好的稳定性,对骨折能起到生物学固定。

BACKGROUND： Most of the external fixator is a rigid structure with too much stress shielding on the fracture end which can affect the fracture healing speed and quality of callus, and even lead to fracture nonunion. OBJECTIVE： To compare the difference of biomechanical strength between normal tibia and the tibia with middle transverse fracture after treated with vertical physiological external pressure fixator. METHODS： Twelve fresh tibial specimens were obtained and randomly divided into experimental group and control group, tibia with middle transverse fracture caused by wire saw and fixed with vertical physiological external pressure fixator was the experimental group; the tibias in the control group were the normal tibias. The mechanical loading experiment was performed on the axial load, bending load and torsional load, and the displacement of the tibia and the torsion angle were recorded after each level of load, the axial compression stiffness, bending stiffness and torsional stiffness were calculated. RESULTS AND CONCLUSION： Loading within the physiological range, the left and right strain in the experimental group were slightly larger than those in the control group, but there was no significant difference of overall stiffness after fixation between two groups （P 〉 0.05）; the bending strain in the experimental group was larger than that in the control group, but there was no significant difference of overall stiffness after fixation between two groups （P 〉 0.05）; there was no significant difference of overall torsional stiffness between two groups （P 〉 0.05）; the ultimate bending load in the experimental group was significantly larger than that in the control group （P 〈 0.05）. The vertical physiological external pressure fixator has a sufficient biomechanical strength and good stability, and plays an important role in the biological fixation of fracture.