脊柱-骨盆固定系统的生物力学研究

目的:研究髂骨钉在脊柱-骨盆固定系统中对腰骶稳定性及螺钉应力分布的影响。方法:6具成人腰椎-骨盆防腐标本,分别按照三种不同的固定方式完成置钉连接操作,制成3个实验组:单纯腰椎后路长节段固定组(L2-L5组)、腰骶固定组(L2-S1组)、髂骨钉固定组(L2-S1-I组)。生物力学测试采用8 N·m纯力矩执行前屈、后伸、左右侧弯、左右旋转6个工况运动,比较各固定组L2、L5水平活动度以及L5椎弓根钉、S1螺钉应力。结果:L2-S1组、L2-S1-I组内固定系统以及腰骶关节活动度均明显降低(P0.05),L2-S1-I组的优势更加显著,尤其在抵抗固定系统旋转活动以及腰骶关节前屈活动时作用更明显。L2-S1-I组、L2-S1组L5椎弓根钉应力均较L2-L5组明显减小(P0.05);L2-S1-I组S1螺钉应力较L2-S1组显著减小(P0.05)。结论:髂骨钉技术能够提供良好的脊柱-骨盆固定效果,在维持腰骶稳定性方面优势明显;对近端固定螺钉有保护作用,在与S1螺钉联合使用时,能有效分担S1螺钉所受应力,显著降低螺钉松动、拔出的风险。

Biomechanical Study of Spinal-pelvic Fixation System

Objective:To investigate the biomechanical stability as well as stress distribution on screws in spinal-pelvic fixation system with iliac screws.Methods:Six adult lumbar spine and pelvic specimens were taken. According to different fixation methods, 3 groups were divided: long segment lumbar fixation group(L2-L5 group), lumbar-sacral fixation group(L2-S1 group), lumbar-sacral-iliac fixation group(L2-S1-I group). The pure torque of 8 N·mwas applied in 6 directions: flexion, extension, left lateral bending, right lateral bending, left rotation and right rotation. The mobility of L2 and L5 levels as well as the stress of L5 pedical and S1 screws were investigated.Results:The mobility of L2-S1 group and L2-S1-I group were significantly reduced compared with L2-L5 group(P<0.05). The most reliable stability was showed in L2-S1-I group, especially in flextion and rotation test. The stress of L5 pedical screws in L2-S1-I group and L2-S1 group were significantly decreased compared with L2-L5 group (P<0.05). The stress of S1 screws in L2-S1-I group were significantly lower compared with L2-S1 group (P<0.05).Conclusion:The technique of iliac screws could attain reliable stability of lumbosacral portion. Stress concentration on fixation screws could be avoided, especially in S1 screws, which would play an important role in minimizing the risks of implants loosening and breaking.