骨质疏松程度对骶骨椎弓根螺钉固定的生物力学影响  

Biomechanical effect of osteoporosis on sacral pedicle screws instrumentation

作　　者：于滨生[1] 郑召民[1] 庄新明[1] 张加芳[1] 李泽民[1] 

机构地区：[1]中山大学附属第一医院脊柱外科骨科研究所,广州市510700

出　　处：《中国脊柱脊髓杂志》2009年第10期740-744,共5页Chinese Journal of Spine and Spinal Cord

基　　金：广东省科技计划项目(2008B050100012)

摘　　要：目的:评价骨质疏松程度对骶骨椎弓根螺钉固定强度的影响。方法:25具骨质疏松成人新鲜尸体骶骨标本,按尸体腰椎骨密度(BMD)值分为A组(n=9,BMD0.70～0.79g/cm2)、B组(n=8,BMD0.60～0.69g/cm2)和C组(n=8,BMD<0.60g/cm2)。在同一标本的S1左侧置入双皮质椎弓根螺钉,右侧置入单皮质椎弓根螺钉时用聚甲基丙烯酸甲酯(PMMA)骨水泥强化,4h后使用MTS实验机对螺钉尾部进行30～250N的头尾方向循环加载2000次后,测定椎弓根螺钉的下沉位移和轴向拔出力。2000次载荷中螺钉下沉超过2mm定义为锚定失败。结果:A组和B组螺钉均未出现锚定失败;C组双皮质椎弓根螺钉锚定失败6例(75%),PMMA强化单皮质椎弓根螺钉锚定失败5例(63%)。A组双皮质螺钉固定的下沉位移和轴向最大拔出力与PMMA强化螺钉固定比较无显著性差异(P>0.05);B组PMMA强化螺钉固定的下沉位移显著低于双皮质螺钉固定,轴向最大拔出力显著高于双皮质固定(P<0.05)。A组双皮质螺钉固定和PMMA强化螺钉固定的下沉位移均显著低于B组(P<0.05),A组双皮质螺钉固定的轴向最大拔出力显著高于B组(P<0.05),A组PMMA强化螺钉固定的轴向最大拔出力与B组比较无显著性差异(P>0.05)。C组内固定失败病例中,PMMA强化螺钉固定的承载次数显著高于双皮质螺钉固定(P<0.05)。结论:BMD≥0.70g/cm2时双皮质骶骨椎弓根螺钉固定和PMMA强化单皮质骶骨椎弓根螺钉固定可获得同等的锚定强度,BMD值为0.60～0.69g/cm2时PMMA强化单皮质骶骨椎弓根螺钉固定的锚定强度显著高于双皮质螺钉固定,BMD值<0.60g/cm2时两种锚定方式均容易导致早期松动。术前行腰椎BMD检查可指导选择骶骨螺钉固定方式。Objective：To investigate the biomechanical effect of osteoporosis on sacral pedicle screws instrumentation.Method：25 fresh adult human sacra specimen featuring osteoporosis were used in this study.According to the value of lumbar bone mineral density （BMD） assessed by a dual energy X-ray absorptiometry, specimens were assigned into three groups as follows,group A（n=9）,BMD 0.70-0.79g/cm^2,group B（n=8）,BMD 0.60-0.69g/cm^2,group C （n=8）,BMD〈0.60g/cm^2.For each specimen,S1 pedicle screw was inserted bicortically on the left side,and S1 pedicle screw augmented by polymethylmethacrylate（PMMA） was inserted unicortically on the contralateral side of sacrum.Following a dynamic cyclic loading from 30N to 250N on the screw head for 2000 cycles ,the subsidence displacement and axial pull-out strength of each screw were measured,and we defined subsidence displacement over 2mm after 2000 cyclic loading as anchoring failure.Result：No anchoring failure was noted in both group A and B.However,in group C,6 cases（75%） in bicortical fixation and 5 cases（63%） in PMMA augmented fixation had evidence of failure during cyclic loading.In group A,no significant difference between bicortical and PMMA augmented fixation was detected in terms of the subsidence displacement and maximal screw pull-out strength （P〉0.05）.In group B,significantly less subsidence and higher maximal screw pull-out strength were documented in the PMMA augmentation than that in bicortical fixation （P〈 0.05）. Both techniques in group A exhibited lower subsidence of the screw than that in group B（P〈0.05）.Bicortical technique in group A exhibited higher maximum pull-out strength than that in group B（P〈0.05）.However,statistical difference in terms of PMMA augmentation was not detected between group A and B（P〉0.05）. Among the cases with anchoring failure in group C,significantly more loading cycles（before failure） were observed in PMMA augmented unicortical fixation than that in bieortical fixation.Conc

关 键 词：腰骶融合 椎弓根螺钉 内固定 骨质疏松 聚甲基丙烯酸甲酯 生物力学 

分 类 号：R687.3[医药卫生—骨科学] R318.01[医药卫生—外科学]