脊柱外科中的椎弓根螺钉设计：是否存在差异？初次和翻修拔出强度的生物力学研究。
Pedicle Screw Designs in Spinal Surgery: Is There a Difference? A Biomechanical Study on Primary and Revision Pull-Out Strength.
机构信息
Department of Orthopaedic Surgery, Tan Tock Seng Hospital, National Health Group, Nanyang, Singapore.
School of Mechanical and Aerospace Engineering, College of Engineering, Nanyang Technological University, Nanyang, Singapore.
出版信息
Spine (Phila Pa 1976). 2019 Feb 1;44(3):E144-E149. doi: 10.1097/BRS.0000000000002789.
STUDY DESIGN
An experimental laboratory-based biomechanical study.
OBJECTIVE
The objective of this study was to evaluate, in a synthetic bone model, the difference in primary and revision pull-out strength using pedicle screws of different thread designs.
SUMMARY OF BACKGROUND DATA
Over the past few decades, there has been a growing interest in optimizing the screw pull-out strength using various screw designs (single-thread, mixed-thread, dual-thread). Although primary pull-out strength has been studied previously, little is known about revision pull-out strength of different pedicle screws.
METHODS
The pull-out strengths of three different pedicle screw designs (single-thread, mixed-thread, dual-thread) were tested in standardized polyurethane foam in three sequences. Sequence 1: A 6.5 mm screw was inserted into the foam block and the primary pull-out strength measured. Sequence 2: A 6.5 mm screw was inserted, removed, and then reinserted into the same foam block. The revision pull-out strength was then measured. Sequence 3: A 6.5 mm screw was inserted, removed and a 7.5-mm screw of the same thread design was reinserted. The revision pull-out strength was then measured.
RESULTS
The primary pull-out strength was similar across screw designs, although dual-thread screws showed higher primary pull-out strength (2628.8 N) compared to single-thread screws (2184.4 N, P < 0.05). For revision pull-out strength, the mixed-thread screws had significant reduction in revision pull-out strength of 18.6% (1890.2 N, P = 0.0173). Revision with a larger diameter screw improved the pull-out strength back to baseline. Single and dual-thread screws showed no significant reduction in revision pull-out strength.
CONCLUSION
The dual-threaded screws provided the strongest primary pull-out strength for spinal fixation. The mixed-thread screws, however, had the poorest revision pull-out strength, decreasing by 18.6% compared to other screw designs. In cases in which mixed-threaded screws have to be revised (at the index or revision surgery), surgeons should consider the use of larger diameter screws to improve the pull-out strength.
LEVEL OF EVIDENCE
研究设计
一项基于实验实验室的生物力学研究。
目的
本研究的目的是在合成骨模型中评估不同螺纹设计的椎弓根螺钉的初次和翻修拔出强度差异。
背景资料概要
在过去的几十年中，人们越来越关注通过各种螺钉设计（单螺纹、混合螺纹、双螺纹）来优化螺钉拔出强度。虽然已经研究了初次拔出强度，但对于不同椎弓根螺钉的翻修拔出强度知之甚少。
方法
在三个不同的序列中，在标准化的聚氨酯泡沫中测试了三种不同的椎弓根螺钉设计（单螺纹、混合螺纹、双螺纹）的拔出强度。序列 1：将 6.5mm 螺钉插入泡沫块中，测量初次拔出强度。序列 2：将 6.5mm 螺钉插入、取出，然后重新插入相同的泡沫块。然后测量翻修拔出强度。序列 3：将 6.5mm 螺钉插入、取出，并用相同螺纹设计的 7.5mm 螺钉重新插入。然后测量翻修拔出强度。
结果
尽管双螺纹螺钉的初次拔出强度（2628.8N）高于单螺纹螺钉（2184.4N，P<0.05），但螺钉设计的初次拔出强度相似。对于翻修拔出强度，混合螺纹螺钉的翻修拔出强度显著降低了 18.6%（1890.2N，P=0.0173）。使用更大直径的螺钉进行翻修可将拔出强度恢复到基线水平。单螺纹和双螺纹螺钉的翻修拔出强度没有显著降低。
结论
双螺纹螺钉为脊柱固定提供了最强的初次拔出强度。然而，混合螺纹螺钉的翻修拔出强度最差，与其他螺钉设计相比降低了 18.6%。在需要翻修混合螺纹螺钉的情况下（在指数或翻修手术中），外科医生应考虑使用更大直径的螺钉来提高拔出强度。
证据等级
5。
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