髂骨不同置钉方式在腰-髂重建结构中稳定性的生物力学研究

Biomechanical advantages of dual iliac screws over single ones in lumbo-iliac fixation construct

目的评价髂骨单枚短钉、单枚长钉和双枚短钉技术对腰一髂固定结构稳定性的生物力学影响。方法7具成人新鲜尸体L2-骨盆标本用于实验。于L3-5间行椎弓根钉固定，并将该结构定义为本研究的完整状态。完整状态测试后，制作骶骨全切的失稳模型，并进行三种髂骨钉技术的L3-髂骨间钉-棒稳定重建，A组：双侧单枚髂骨短钉；B组：双侧单枚髂骨长钉；C组：双侧双枚髂骨短钉。三种髂骨置钉技术均在同一标本上按随机顺序建立，短钉和长钉的长度分别为70mm和130mm。在MTS材料实验机上，给标本施加800N压缩和7N·m扭转载荷，记录L3-髂骨间的结构刚度并比较。结果A、B、C组的结构压缩刚度分别是完整状态的73％、76％和108％，A组与B组间差异无统计学意义（P〉0．05），然而A和B组的结构压缩刚度低于完整状态和C组，差异有统计学意义（P〈0．05）。A、B、C组的结构扭转刚度分别占初始状态的72％、79％和109％，A、B两组间、完整状态与c组间差异均无统计学意义（P〉0．05）；但是，A、B组的结构扭转刚度低于完整状态和c组，差异有统计学意义（P〈0．05）。结论骶骨完全切除后，单枚髂骨长钉难以恢复局部的初始稳定性，双侧双枚髂骨短钉在抗压缩和扭转方面均显著高于双侧单枚髂骨钉结构，并且可获得与初始状态同等的稳定性。

Objective To evaluate the biomechanical effects of single short, single long and dual short iliac screws on the stability of lumbo-iliac fixation construct. Methods L2-pelvic specimens were harvested from 7 fresh human cadavers. Following the test of the intact state simulated by L3-L5 pedicle screw fixation, the destabilization by total sacrectomy and L3-iliac screw-rod reconstructions with 3 placements of iliac screws were conducted as follows： bilateral single short iliac screws in Group A; bilateral single long iliac screws in Group B; bilateral dual short iliac screws in Group C. The 3 iliac screw fixations were preformed in the same specimens in a random order, and the lengths of short and long iliac screws were 70 mm and 130 mm, respectively. Biomechanical testing was performed on a material testing machine under 800 N compression and 7 Nm torsion loading modes for construct stiffness evaluation. Results In compression, the constructs in Groups A, B, C obtained 73%, 76%, and 108% of the initial compression stiffness, respectively. No significant differences were demonstrated between Groups A and B （ P 〉 0.05）, but the 2 groups showed obviously lower construct compression stiffness than the intact state and Group C （ P 〈 0.05） . In torsion, Groups A, B, C acquired 72%, 79%, and 109% of the initial torsion stiffness, respectively. No significant differences were detected not only between Groups A and B, but also between Group C and the intact condition （ P 〉 0. 05）. However, Groups A and B provided markedly lower construct torsion stiffness than the other 2 conditions （ P 〈 0.05）. Conclusions Following total saerectomy, it is rather difficult to restore the initial local stability by using bilateral single long iliac screws. However, the dual iliac screws when compared with the single ones can provide much higher construct stability comparable to the initial state.