腰骶椎带锁轴向融合内固定的生物力学测试

Biomechanical testing of the locking axial lumbosacral interbody fusion

背景:21世纪以来国内外学者对L5-S1单纯轴向融合内固定进行了大量基础及临床研究,证实其技术微创,利于植骨的成功融合,并能够满足人体生理需求,但其抗旋转固定不够。因此需要一种既能微创操作、又能达到稳定固定的新内固定器械。目的:通过对团队前期研制的腰骶椎带锁轴向融合内固定螺钉进行生物力学评价,为进一步加以改进及应用于临床提供实验数据。方法:选取5具新鲜成人脊柱标本,截取腰骶椎运动节段(L3-S5),分为以下5组顺次进行生物力学测试:①正常组:结构完整;②峡部裂组:双侧峡部裂;③锁定组:带锁轴向固定螺钉固定+双侧峡部裂;④螺钉组:轴向固定螺钉固定+双侧峡部裂;⑤复合固定组:轴向固定螺钉固定+双侧峡部裂+双侧椎弓根螺钉固定。分别测试各个标本在屈伸、左右侧弯、左右旋转各个不同运动状态下L5/S1节段的活动度及轴向抗压刚度;其中在屈伸状态下,另外测试各组标本在施加300N轴向跟随力时的运动范围。实验方法得到医院伦理委员会批准。结果与结论:①峡部裂组在屈伸及旋转方向上的活动度均显著大于正常组(P<0.05),在侧弯方向上与正常组差异无显著性意义(P>0.05);②在屈伸及侧弯方向上,3种内固定方式的活动度均显著小于正常组(P<0.05),其中在屈伸方向上复合固定组及锁定组的活动度均显著小于螺钉组(P<0.05),轴向螺钉+椎弓根钉组(复合固定组)与锁定组差异无显著性意义(P>0.05);③在侧弯方向上锁定组的活动度与其他2种内固定方式差异无显著性意义(P>0.05),复合固定组的活动度显著小于螺钉组(P<0.05);④在旋转方向上,轴向锁定组与轴向螺钉+椎弓根钉组(复合固定组)的活动度均显著小于正常组(P<0.05),轴向螺钉组与正常组差异无显著性意义(P>0.05),复合固定组活动度显著小于锁定组(P<0.05);锁定组中左旋与右旋的活动度比较差异无显著性意义(P>0.05);⑤在轴向抗压刚度方面,3种内固定方式均显著大于正常组(P<0.05),3种内固定方式间差异均无显著性意义(P>0.05);⑥提示腰骶椎带锁轴向融合内固定系统可以显著提高腰骶椎后柱失稳情况下各个运动方向的稳定性,为腰骶椎后柱结构失稳情况下单纯行轴向融合内固定抗旋转稳定性差的问题提供了有效的解决办法。

BACKGROUND: In the 21^st century, domestic and foreign scholars have carried out a lot of basic and clinical researches on L5-S1 simple axial fusion internal fixation, which prove that its technology is minimally invasive, is conducive to the successful fusion of bone grafting and can meet the physiological needs of human body, but its anti-rotation fixation is poor. Therefore, a new internal fixation device that is both minimally invasive and stable is needed. OBJECTIVE: To evaluate the biomechanical stability of the locking axial lumbosacral interbody fusion, so as to provide experimental data for future clinical usage. METHODS: Five fresh human lumbar spines (L3-S5) were tested by applying pure moments. Each specimen was tested for the following order: normal control group;bilateral spondylolysis;locking AxiaLIF and bilateral spondylolysis;AxiaLIF and bilateral spondylolysis;AxiaLIF, bilateral pedicle screws and bilateral spondylolysis. The L5/S1 range of motion was obtained by applying pure moments in flexion, extension, lateral bending, axial rotation and axial compression loaded with 300 N force. The study was approved by the ethics committee of the hospital. RESULTS AND CONCLUSION:(1) Spondylolysis significantly increased the range of motion in flexion-extension and axial rotation compared with the normal control group (P < 0.05). The two groups showed no significant difference in the lateral bending (P > 0.05).(2) Three kinds of fixation ways significantly reduced the range of motion in flexion-extension and lateral bending compared with the normal control group (P < 0.05). In flexion-extension, the combined fixation and locking AxiaLIF groups significantly reduced the range of motion compared with the screw group (P < 0.05), and there was no significant difference between combined fixation and locking AxiaLIF groups (P > 0.05).(3) In lateral bending, the range of motion in the locking AxiaLIF ROM group had no significant difference compared with the other fixation groups (P > 0.05), but the combined group significantly reduced the range of motion compared with the screw group (P < 0.05).(4) Locking AxiaLIF and combined groups significantly reduced the range of motion in axial rotation compared with the normal control group (P < 0.05), and there was no significant difference between screw and normal control groups (P > 0.05). Screw group significantly increased the range of motion in axial rotation compared with the combined group (P < 0.05). In the locking group, there was no significant difference between left axial rotation and right axial rotation (P > 0.05).(5) Three fixation groups significantly increased the axial compressive stiffness compared with the normal control group (P < 0.05), but there was no significant difference among three fixation groups (P > 0.05).(6) These results indicate that the locking axial lumbosacral interbody fusion can significantly enhance the stability of lumbosacral vertebral instability in all loading modes. It provides an effective solution for the question that the AxaiLIF has a poor stability in axial rotation.