髂骨双钉在腰-髂重建结构中的生物力学优势

目的 评价髂骨单钉与髂骨双钉技术对腰-髂重建结构稳定性的影响.方法 7具成人新鲜尸体L2-骨盆标本,于L3-L5行椎弓根钉固定,将该结构定义为完整状态.对完整状态进行测试后制作骶骨全切失稳模型,每一标本均应用四种髂骨钉技术行L3-髂骨钉-棒稳定重建:A组,髂骨单枚短钉;B组,髂骨单枚长钉;C组,置入髂骨上、下柱的髂骨双枚短钉;D组,置入髂骨下柱的髂骨双枚短钉.髂骨钉的安装及测试顺序随机产生.在MTS材料试验机上,对标本施加800 N压缩和7 N·m扭转载荷,记录L3-髂骨的结构刚度.结果 (1)轴向压缩下,四组的压缩刚度依次为完整状态的73%、76%、98%和112%,A组和B组低于完整状态及C组和D组(P<0.05).其中A组与B组差异无统计学意义,D组与C组差异有统计学意义(P<0.05).(2)在扭转测试中,四组的扭转刚度依次为完整状态的72%、79%、105%和109%,A组和B组低于其他三组(P<0.05).其中A组与B组,完整状态、C组与D组间的差异无统计学意义.结论 对骶骨完全切除所导致的失稳,单枚髂骨短钉与长钉均难以恢复局部的初始稳定性;而双枚髂骨短钉在抗压缩与抗扭转能力方面均高于单枚髂骨钉,可获得与初始状态等同的稳定性.

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

Objective To evaluate the biomechanical effects of single and dual iliac screws on the stability of lumbo-iliac fixation construct. Methods L2-pelvic specimens were harvested from 7 fresh hu-man cadavers. Following the test of the intact state simulated by L3-L5pedicle screw fixation, the destabi-lization by total sacrectomy and L3-iliac screw-rod reconstructions with four placements of iliac screws were conducted as follows: Group A, single short iliac screw; Group B, single long iliac screw; Group C, dual short iliac screws (respectively placed in the upper and lower iliac columns); Group D, dual short iliac screws (all placed in the lower iliac column). The establishment and testing of iliac screw technique were performed in random order. Biomechanical testing was performed on a material testing machine under 800 N compression and 7 N·m torsion loading modes for construct stiffness evaluation. Results In compression, the constructs of Group A-D obtained the initial compression stiffness of 73%, 76%, 98% and 112%, respectively. Group A and B were obviously lower than the intact state, and Group C and D (P<0.05). No significant differences were demonstrated between Group A and B (P>0.05), however, the difference between Group C and D was significant (P<0.05). In torsion, Group A-D acquired 72%, 79%, 105% and 109% torsion stiffness of the ini-tial condition, respectively. Group A and B were markedly lower than the other three groups (P<0.05). No significant differences were detected not only between the Group A and B, but also among Group C, D, and the intact condition (P>0.05). Conclusion For the instability followed by total sacrectomy, single short and long iliac screws do not help in restoring the local stability to the intact condition. However, dual iliac screws provided much higher anti-compression and torsion resistance properties than using single iliac screw tech-niques, and the construct stability could compare to the initial state.