经骶1-2侧块螺钉固定的最大拔出力测定

The maximum pull-out force of the sacral 1-2 translateral mass screw, an in vitro experiment

中文关键词:  骶骨  侧块螺钉  内固定  生物力学

英文关键词:Sacrum  Lateral mass  Screw fixation  Biomechanics

中文摘要:

  【摘要】 目的：测量经骶1-2侧块螺钉固定的最大拔出力，初步探讨该内固定方法的有效性。方法：8具甲醛溶液固定湿润成人骶骨标本，采用双能X线吸收测定仪（dual-energy X-ray absorptiometry, DEXA）测定S1椎体骨密度。在同一骶骨标本上随机置入3种骶骨螺钉：经骶1-2侧块螺钉（A组）、S1椎弓根螺钉（B组）、S1前外骶骨翼螺钉（C组）。将标本固定于858型MTS材料试验机上，对螺钉施加轴向拔出力，根据3种骶骨螺钉轴向拔出实验的数据绘制力（N）-位移（mm）曲线，取曲线的顶点作为最大拔出力数值。应用SPSS 16.0统计软件对3组骶骨螺钉的最大拔出力数值行方差分析。结果：8具骶骨标本S1椎体骨密度为0.43～0.74g/cm3，平均0.641±0.275g/cm3。3种骶骨螺钉固定的螺钉即刻平均最大拔出力：A组为379.62±73.10N，B组为829.12±170.74N，C组为230.62±98.52N，3组之间两两比较差异有统计学意义（P＜0.05）。结论：经骶1-2侧块螺钉固定的最大拔出力低于S1椎弓根螺钉固定，但高于S1前外骶骨翼螺钉固定，当S1椎弓根螺钉固定不能施行时，骶1-2侧块螺钉固定可作为一种有效的选择。

英文摘要:

  【Abstract】 Objectives: To measure the maximum pull-out force of the sacral 1-2 translateral mass screw（STMS）, and to discuss the efficacy of this technique. Methods: Eight adult cadavers which were soaked and fixed in formalin liquid were used in this study. The bone mineral density(BMD) of S1 vertebra was measured by the dual-energy X-ray absorptiometry(DEXA). The average data of BMD were recorded. Three types of sacral screw were implanted into these specimens randomly. The experimental groups were divided as follows: group A(STMS fixation), group B(S1 pedicle screw fixation) and group C(S1 anterolateral screw fixation). Then the specimens were placed on a MTS 858 bionix testing machine, and a pull-out test was perfomed along the axis of the screw until the screw was completely pulled out of the sacrum. According to the experimental data, the curves of force(N)-displacement(mm) were drawed. The vertex of curves was taken as the maximum pull-out force. Then variance analysis was carried out by statistical software SPSS 16.0. Results: The BMD of 8 S1 vertebra was 0.43-0.74g/cm3(average 0.641±0.275g/cm3). The average maximum instant pull-out force for three fixations was 379.62±73.10N, 829.12±170.74N and 230.62±98.52N for group A, B and C respectively, with significant difference between each 2 groups(P＜0.05). Conclusions: The pull-out force of STMS is lower than that of S1 pedicle screw, but higher than that of the S1 anterolateral fixation. When S1 pedicle screw placement is unavailable, STMS instrumentation is an effective option.