腰椎形状记忆合金椎间融合器的研制和生物力学评价

The Design and Biomechanical Evaluation of a Shape Memory Alloy Lumbar Interbody Fusion Cage

目的 介绍记忆合金椎间融合器的设计原理和构型 ,并对其进行生物力学评价。方法 采用镍钛合金研制一种具有独特构型的腰椎椎间融合器。在 8具新鲜L3、4节段标本上测试正常 (完整状态 )组、失稳 (椎间盘摘除 )组和融合器 (固定 )组 3种状态的各向运动范围 (ROM)。然后将 8个标本分成 2组 ,比较记忆合金椎间融合器和螺纹状融合器两者的抗拔出能力。结果 与正常组相比 ,椎间盘摘除后腰椎节段明显失稳 (P <0 0 5 )。植入融合器后 ,其前屈和侧屈方向的ROM分别为正常的6 6 %和 6 5 % ;两者差别显著 (P <0 0 5 ) ;后伸方向的ROM值为正常的 84 % ,两者无统计学差别 (P =0 15 ) ;旋转方向ROM值较正常组提高了 2 5 % ,两者差别明显 (P <0 0 5 )。记忆合金椎间融合器和螺纹状椎间融合器的平均最大拔出力分别为75 0± 2 0 5N和 6 95± 175N ,两者之间无明显统计学差异 (P =0 5 4 )。结论 记忆合金椎间融合器设计独特、具有良好的三维运动稳定性和抗拔出能力 ,能够进一步应用于临床。

Objective To introduce the design and comformation of a shape memory alloy interbody fusion cage(SMACAGE) and evaluate its biomechanical properties. Methods Eight human cadaver lumbar spine specimens was designed to compare stability of L 3、4 segment after being inserted with SMACAGE. They were test in three models: ①control (intact);②destabilized(after discetomy);③SMACAGE fixed. All groups were tested for range of motion(ROM) using a spinal three dimensional anlysis system. The specimen were then divided into two groups for the test of pull-out strength of SMACAGE and a threaded cage using a biomechanical test machine.Results Statistically significant difference was observed between intact and destabilized models(P<0.05) as well as between destabilized and SMACAGE models(P<0.05).The SMACAGE used significantly decreased the intervertebral movement in flexion and lateral bending with a range of motion of 66% and 65% to intact model respectively(P<0.05). The median cage movement of extension were 84% of intact movement which was not a significant difference(P=0.15 ).The ROM in torsion was increased 25% to intact,which was significantly different from control group(P<0.05).The maximum pullout strength of SMACAGE and threaded cages were 750±205N and 695±175N,respectively. There were no statistic difference between them(P=0.54 ).Conclusion The SMACAGE has a unique design and demonstrate good biomechanical stability and pullout resistance.It can be apply to clinical use, especially in the minimal invasive surgery.