Edwards装置中套棒位置对Harrington分离棒应力分布影响的研究

The Influences of Edwards Rod-sleeve Site to the Stress Distribution of Harrington Rod by Photoelasticiy

Edwards套棒装置可显著提高胸腰椎骨折复位率,但套棒的不同位置对Harrington棒的应力分布有明显影响。利用光弹性实验技术在实验载荷下可直观地观测到Harrington棒模型各部的应力情况。当套棒位于Harrington棒的齿棘区,光滑区交界处时,齿棘区应力集中最为严重,平均应力值分别高于套棒在Harrington棒工作长度内中点及远端1/4点时的23.9％,32.9％(棒前侧点)及31.3％、43.6％(棒后侧点)(P<0.01)。无论套棒位置如何。Harrington棒前侧点的应力值均高于棒后侧相应点(P<0.01)。实验结果提示使用Edwards装置时应尽量使套棒远离齿棘区,或选用齿棘区短的Harrington棒以减少应力集中造成的Harrington棒疲劳断裂。

The anatomic reduction rates were improved very much by Edwards devices, but the site of Edwards rodsleeve influenced the stress distribution of Harrington rod obviously. The stress distribution on the Harrington photoelastic model could be observed directly on experimental loads by photoelastic technique. When the rodsleeve was on the ratchet-shait junction there was severe stress coucentration on the ratchet parts, the average stress was 23.9% (anterior) and 34.3% (posterior) higher than the one when rod-sleeve on 1/2 point of Harrington rod length and were 32.9% (anterior) and 43.6% (posterior) higher than the one when rod-sleeve on the 1/4 point of Harrington rod (P(0.01). The stress was higher on the Harrington rod auteucrly than on the posteriorly (P(0.01). The experimental results recommended that the rodsleeve should be placed as farther away from ratchet part as possible, or used the rod with short ratchet segment in order to reduce the risk of mechanical failure of Harringtong rod.