BACKGROUND In osteoporotic bone, the quality of the bone-to-implant interface is decreased, which may lead to early implant failure. Screw anchorage can be improved by augmentation. This effect is mainly investigated with a pull-out test. To our knowledge, the effect of cement augmentation in an in vivo physiological setup focusing on screw movement has not been investigated to date. The aim of this work was to investigate and compare augmented and native screw behavior in a physiologically related setup. METHODS Twelve fresh-frozen human lumbar vertebrae were divided into two groups. Each vertebra was bilaterally instrumented with either non-augmented or augmented pedicle screw systems and loaded in a recently developed test setup that provided cyclic conditions comparable to a physiological gait. The cyclic loading should test the primary implant stability, comparable to the postoperative period of two months in a worst-case scenario in the absence of osseous remodeling. Screws were tracked optically, and screw movement and failure patterns were observed. RESULTS Mutual influence between the left and right sides resulted in a successive, rather than simultaneous, failure. Augmentation of the screws in vertebrae with poor bone quality reduced screw subsidence and thus improved the rigidity of the screw-to-implant interface by up to six-fold. The non-augmented condition was significantly related to early screw failure. CONCLUSIONS Pedicle screw system failure involves a complex bilateral-coupled mechanism. The cyclic loading based on physiological conditions during walking has allowed the postoperative conditions and clinical failure mechanisms to be simulated in vitro and clarified. Future implant systems should be investigated with a physiologically related setup.

中文翻译：

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非增强型和椎弓根螺钉在人椎骨中的复杂生物力学特性，具有降低的骨密度。

背景技术在骨质疏松性骨中，骨-植入物界面的质量降低，这可能导致早期植入物失效。螺钉锚固可以通过增加来改善。主要通过拉出试验研究该效果。据我们所知，迄今为止，尚未研究骨水泥在体内专注于螺钉运动的生理设置中的作用。这项工作的目的是研究和比较生理相关设置中的增强和自然螺钉行为。方法将十二个新鲜冷冻的人腰椎分为两组。每个椎骨都使用非增强或增强椎弓根螺钉系统进行双向器械测试，并加载到最近开发的测试装置中，该装置可提供与生理步态相当的循环条件。在没有骨重塑的最坏情况下，周期性载荷应测试主要的植入物稳定性，相当于两个月的术后时期。对螺钉进行光学跟踪，并观察到螺钉的运动和破坏模式。结果左侧和右侧之间的相互影响导致了连续而不是同时的故障。骨骼质量较差的椎骨中螺钉的增加减少了螺钉的下沉，从而将螺钉与植入物的界面的刚度提高了六倍。非增强状态与早期螺钉失败显着相关。结论椎弓根螺钉系统故障涉及复杂的双侧耦合机制。基于步行过程中生理状况的周期性负荷，可以在体外模拟并阐明术后状况和临床衰竭机制。未来的植入物系统应以生理相关的设置进行研究。