Wang Libing, Pan Hehai, Yu Binsheng, Xie Chaofan, Xu Yinfeng, Zheng Zhaomin
Department of Spinal Surgery, Research Center of Orthopaedics, the First Affiliated Hospital of Sun Yat-sen University, Guangzhou Guangdong, 510700, PR China.
Zhongguo Xiu Fu Chong Jian Wai Ke Za Zhi. 2013 May;27(5):606-11.
To evaluate the biomechanical effect of a self-made iliac screw plate on the stability of lumbo-iliac fixation construct before and after fatigue loading.
Twelve fresh lumbo-pelvic specimens from donated adult cadavers with formalin embalm were used in the study. According to whether use the iliac screw plate or not, the specimens were randomly assigned into group A (with iliac screw plate, n=6) and group B (without iliac screw plate, n=6). The bone mineral density (BMD) of L(t-4) was measured using dual-energy radiograph absorptiometry. The pedicle screw and iliac screw fixation were given at L3-5, and bilateral facetectomy and diskectomy at L5, S1 level were performed to prepare the model of the intervertebral destabilization. The biomechanical testing was conducted on a material testing machine under 0-600 N compression and -7-7 N.m torsion loading modes for the initial compressive stiffness and torsional stiffness evaluation. And then 20 000 cyclic compressive loading of 40-400 N was given to the specimen, the stiffness evaluation was repeated. Then the maximum pull-out strength of screws at every level was measured and compared. Gross observation and radiological observation were performed during experiment.
The BMD values of groups A and B were (1.15 +/-0.13) g/cm(2) and (1.12 +/-0.11) g/cm(2) respectively, showing no significant difference between 2 groups (t=0.428, P=0.678). All pedicle screws and iliac screws were inserted in good position; no loosening or breaking of screw was observed during loading. After fatigue loading, the incidence of halo ring around the iliac screws of groups A and B was 16.7% (1/6) and 50.0% (3/6), respectively. The compressive stiffness and torsional stiffness after fatigue loading were significantly lower than those in initial state in groups A and B (P < 0.05); there was no significant difference in compressive stiffness and torsional stiffness between groups A and B before fatigue loading (P > 0.05). However, group A had higher compressive stiffness than group B (t=2.664, P=0.024) after fatigue loading, and there was no significant difference in torsional stiffness between 2 groups (t=0.410, P=0.690). No significant difference was found in screw pull-out strength of pedicle screws at L3, L4, and L5 levels between groups A and B (P > 0.05); however, the pull-out strength of the iliac screws in group A was significantly higher than that in group B (t=3.398, P=0.007). In groups A and B, the pull-out strength of L3 screw was significantly lower than that of L4 and L5 screws (P < 0.05). In group A, pull-out strength of the iliac screws was significantly higher than that of L3, L4, and L5 screws (P < 0.05); in group B, the pull-out strength of iliac screws was significantly lower than that of L4 and L5 screws (P < 0.05).
In the lumbo-iliac reconstruction, the use of iliac screw plate could resist iliac screw loosening, therefore, it has the potential to increase the stability oflumbo-iliac fixation construct.
评估自制髂骨螺钉钢板对腰骶髂固定结构在疲劳加载前后稳定性的生物力学影响。
本研究使用12个来自成年捐赠尸体、经福尔马林防腐处理的新鲜腰骶骨盆标本。根据是否使用髂骨螺钉钢板，将标本随机分为A组（使用髂骨螺钉钢板，n = 6）和B组（未使用髂骨螺钉钢板，n = 6）。采用双能X线吸收法测量L（t - 4）的骨密度（BMD）。在L3 - 5进行椎弓根螺钉和髂骨螺钉固定，并在L5、S1水平进行双侧关节突切除和椎间盘切除以制备椎间失稳模型。在材料试验机上以0 - 600 N压缩和 - 7 - 7 N·m扭转加载模式进行生物力学测试，以评估初始压缩刚度和扭转刚度。然后对标本施加20000次40 - 400 N的循环压缩加载，再次进行刚度评估。随后测量并比较各水平螺钉的最大拔出强度。实验过程中进行大体观察和影像学观察。
A组和B组的BMD值分别为（1.15±0.13）g/cm²和（1.12±0.11）g/cm²，两组间差异无统计学意义（t = 0.428，P = 0.678）。所有椎弓根螺钉和髂骨螺钉均置入位置良好；加载过程中未观察到螺钉松动或断裂。疲劳加载后，A组和B组髂骨螺钉周围晕圈发生率分别为16.7%（1/6）和50.0%（3/6）。A组和B组疲劳加载后的压缩刚度和扭转刚度均显著低于初始状态（P < 0.05）；疲劳加载前A组和B组的压缩刚度和扭转刚度差异无统计学意义（P > 0.05）。然而，疲劳加载后A组的压缩刚度高于B组（t = 2.664，P = 0.024），两组间扭转刚度差异无统计学意义（t = 0.410，P = 0.690）。A组和B组在L3、L4和L5水平的椎弓根螺钉拔出强度差异无统计学意义（P > 0.05）；然而，A组髂骨螺钉的拔出强度显著高于B组（t = 3.398，P = 0.007）。在A组和B组中，L3螺钉的拔出强度显著低于L4和L5螺钉（P < 0.05）。在A组中，髂骨螺钉的拔出强度显著高于L3、L4和L5螺钉（P < 0.05）；在B组中，髂骨螺钉的拔出强度显著低于L4和L5螺钉（P < 0.05）。
在腰骶髂重建中，使用髂骨螺钉钢板可抵抗髂骨螺钉松动，因此，它有可能增加腰骶髂固定结构的稳定性。
