Structural characteristics of the pedicle and its role in screw stability
Structural characteristics of the pedicle and its role in screw stability
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DOI：
10.1097/00007632-199711010-00007
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发表时间：
1997-11-01
期刊：
影响因子：
3
通讯作者：
Ikeda, M
中科院分区：
文献类型：
--
作者：
Hirano, T;Hasegawa, K;Ikeda, M
研究设计.通过外周定量计算机断层扫描测量椎弓根的横截面区域骨密度。通过生物力学测试明确椎弓根在螺钉稳定性中的作用。明确椎弓根的结构特征，以支持椎弓根螺钉的稳定性，以及正常和退行性椎体在这些特征上的差异。椎弓根螺钉是许多用于对线脊柱的系统的基本组件。然而，椎弓根对螺钉稳定性的贡献尚未得到充分研究。通过外周定量计算机断层扫描测量骨小梁、皮质下和皮质骨密度以及椎弓根面积。骨矿物质密度也在四个圆周层中重新计算。这些参数之间进行了比较正常和肥胖的个人。通过在有或无椎体的椎体中进行头尾侧和拔出载荷来评价椎弓根对螺钉稳定性的相对贡献。椎弓根内骨小梁、中皮质下、外皮质骨密度及皮质骨面积均显著低于正常椎体。在椎弓根，骨密度增加接近外层。骨质疏松症患者的骨密度即使在外层也不厚。椎弓根螺钉大约80%的尾侧刚度和60%的拔出强度取决于椎弓根而不是椎体。螺钉稳定性取决于椎弓根的结构特征。与松质骨相比，皮质下骨的椎弓根更致密，螺钉螺纹与皮质下骨接合。在骨质疏松症中，即使在外层，骨矿物质密度也没有那么致密，皮质比正常人薄。较大的螺钉不会增强螺钉稳定性，可能会破坏骨质疏松椎体中的薄皮质。
Study Design. Cross-sectional regional bone mineral density of the pedicle was measured by peripheral quantitative computed tomography. Biomechanical tests were performed to clarify the role of the pedicle in screw stability.Objectives. to identify the structural characteristics of the pedicle that supports pedicle screw stability and the difference sin these characteristics between normal and osteoporotic vertebrae.Summary of Background Data. The pedicle screw is an essential component of many systems used to align the spine. The contribution of the pedicle to screw stability, however, has not been fully investigated.Methods. Trabecular, subcortical, and cortical bone mineral density and the area of the pedicle were measured by peripheral quantitative computed tomography. bone mineral density also was recalculated in four circumferential layers. These parameters were compared between normal and osteoporotic individuals. The relative contribution of the pedicle to screw stability was evaluated by caudocephalad and pull-out loading in a vertebra with or without its body.Results. Inner trabecular, middle subcortical, and outer cortical bone mineral density and cortical bone area in the pedicle were significantly lower in osteoporotic vertebrae than those in normal vertebrae. In the pedicle, bone mineral density increased close to the outer layer. Bone mineral density not as thick even in the outer layer in osteoporotic subjects. Approximately 80% of the caudocephalad stiffness and 60% of the pull-out strength of the pedicle screw depended on the pedicle rather than on the vertebral body.Conclusions. Screw stability depends on the structural characteristics of the pedicle. The pedicle was denser in the subcortical bone, in which the threads of the screw engage, than in trabecular bone. In osteoporosis, bone mineral density was not as dense even in the outer layer, and the cortex was thinner than normal. A larger screw would not enhance screw stability and may break the thin cortex in osteoporotic vertebrae.