尸体痉挛
医学
骨矿物
口腔正畸科
腰椎
射线照相术
生物力学
腰椎
固定(群体遗传学)
骨密度
极限荷载
扭矩
椎骨
外科
骨质疏松症
解剖
结构工程
有限元法
人口
物理
环境卫生
工程类
内分泌学
热力学
作者
Thomas A. Zdeblick,David N. Kunz,Mary E. Cooke,Ronald P. McCabe
出处
期刊:Spine
[Ovid Technologies (Wolters Kluwer)]
日期:1993-09-01
卷期号:18 (12): 1673-1676
被引量:257
标识
DOI:10.1097/00007632-199309000-00016
摘要
This study was designed to correlate several parameters regarding pedicle screw bone/metal interface strength. The insertional torque measured during tapping and placement of pedicle screws was correlated with the bone mineral density of the vertebral body, the dimensions of the pedicle, the method of preparation of the pedicle, and the amount of load and number of cycles to failure of the bone/metal interface. Thirty human cadaveric lumbar vertebrae were instrumented with 6.5-mm pedicle screws. The maximum torque achieved during insertion was digitally recorded. A cyclic pedicle screw pullout test was performed. A linear correlation existed between both the insertional torque when tapping or when inserting a screw and the number of cycles to ultimate pedicle screw pullout. An inverse linear relationship was found between the pedicle width and cycles to failure. There was no linear correlation found when comparing the number of cycles to failure to bone mineral density. These findings suggest that insertional torque is a good predictor of bone-metal interface failure. Bone mineral density of the vertebral body was less effective as a predictor of failure. Smaller pedicle width correlated with increased insertional torque and cycles to failure. This may explain why patients with osteoporosis on radiography may still obtain stable fixation with pedicle screws. Other factors, such as pedicle dimensions and shape, affect screw purchase as much as vertebral body bone density. Insertional torque less than 4.0 inch-pounds led to early pedicle screw pullout. This study forms the basis for the authors' clinical use of an instrumented torque screwdriver to measure insertional torque in the operating room.
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