Cordista Andrew, Conrad Bryan, Horodyski MaryBeth, Walters Sheri, Rechtine Glenn
Department of Orthopaedics and Rehabilitation, University of Florida, 1600 SW Archer Road, Gainesville, 32610, USA.
Spine J. 2006 Jul-Aug;6(4):444-9. doi: 10.1016/j.spinee.2005.08.015.
Pedicle screws have been shown to be superior to hooks in the lumbar spine, but few studies have addressed their use in the thoracic spine.
The objective of this study was to biomechanically evaluate the pullout strength of pedicle screws in the thoracic spine and compare them to laminar hooks. STUDY DESING/SETTING: Twelve vertebrae (T1-T12) were harvested from each of five embalmed human cadavers (n=60). The age of the donors averaged 83+8.5 years. After bone mineral density had been measured in the vertebrae (mean=0.47 g/cm(3)), spines were disarticulated. Some pedicles were damaged during disarticulation or preparation for testing, so that 100 out of a possible 120 pullout tests were performed.
Each vertebra was secured using a custom-made jig, and a posteriorly directed force was applied to either the screw or the claw. Constructs were ramped to failure at 3 mm/min using a Mini Bionix II materials testing machine (MTS, Eden Prairie, MN).
Pedicle claws had an average pullout strength of 577 N, whereas the pullout strength of pedicle screws averaged 309 N. Hooks installed using the claw method in the thoracic spine had an overwhelming advantage in pullout strength versus pedicle screws. Even in extremely osteoporotic bone, the claw withstood 88% greater pullout load.
The results of this study indicate that hooks should be considered when supplemental instrumentation is required in thoracic vertebrae, especially in osteoporotic bone.
已有研究表明，椎弓根螺钉在腰椎方面优于椎弓根钩，但针对其在胸椎的应用研究较少。
本研究旨在对胸椎椎弓根螺钉的拔出强度进行生物力学评估，并与椎板钩进行比较。
研究设计/地点：从五具防腐处理的人体尸体（n = 60）中各取出12个椎体（T1 - T12）。供体平均年龄为83 ± 8.5岁。在测量椎体骨密度（平均 = 0.47 g/cm³）后，将脊柱关节离断。在关节离断或准备测试过程中，部分椎弓根受损，因此在可能的120次拔出试验中进行了100次。
每个椎体使用定制夹具固定，对螺钉或爪施加向后的力。使用Mini Bionix II材料试验机（MTS，明尼苏达州伊甸草原）以3 mm/min的速度加载直至结构破坏。
椎弓根爪的平均拔出强度为577 N，而椎弓根螺钉的平均拔出强度为309 N。在胸椎中，采用爪法安装的钩在拔出强度方面相对于椎弓根螺钉具有压倒性优势。即使在极度骨质疏松的骨中，爪承受的拔出载荷也高出88%。
本研究结果表明，在胸椎需要辅助器械时，尤其是在骨质疏松的骨中，应考虑使用椎弓根钩。
