Märdian Sven, Schmölz Werner, Schaser Klaus-Dieter, Duda Georg N, Heyland Mark
Centre for Musculoskeletal Surgery, Charité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany.
Department of Trauma Surgery, Medical University Innsbruck, Anichstraße 35, 6020 Innsbruck, Austria.
Clin Biomech (Bristol). 2019 Dec;70:89-96. doi: 10.1016/j.clinbiomech.2019.08.008. Epub 2019 Aug 16.
A mechanical characterisation of lag screw fixation plus locking plate - although clinically widely used as either "mixed fixation concept" or absolutely stable fixation - is so far missing. This study aimed to evaluate the influence of an interfragmentary lag screw on the resulting motion at the fracture site of locking plate constructs using a simple fracture at the distal femur.
Human cadaver femora were in vitro loaded in torsion and axial bending-compression with and without lag screw fixation next to a locking plate fixation. In addition, two plate working lengths were tested. Interfragmentary movement was measured optically.
Axial interfragmentary movement is reduced with lag screw (102 mm plate working length, 1000 N, mean): 0.28 mm versus 0.82 mm. With lag screw, the fracture gap stays closed with mean normal interfragmentary movement ≤0.03 mm. Fracture gap tends to open without lag screw: normal interfragmentary movement up to -0.29 mm. Reduction of shear interfragmentary movement was observed throughout all tested loads and groups. Mean true shear remains generally low with lag screw (≤0.42 mm) compared to without lag screw (≤1.46 mm). We also found that interfragmentary movement variance decreases with lag screw, especially for longer plate working length.
An interfragmentary lag screw next to locking bridge plating reduces fragment motion in vitro for a simple fracture pattern and provides a sufficient tool to decrease detrimental shear movements. Prospective clinical trials with interfragmentary lag screw fixation should prove these findings in wide clinical use to treat simple fracture patterns.
拉力螺钉固定加锁定钢板的力学特性——尽管在临床上广泛用作“混合固定概念”或绝对稳定固定——但目前尚缺乏相关研究。本研究旨在通过股骨远端简单骨折模型，评估拉力螺钉对锁定钢板固定结构骨折部位运动的影响。
对人体尸体股骨进行体外扭转和轴向弯曲-压缩加载，分别在有和没有拉力螺钉固定的情况下进行锁定钢板固定。此外，测试了两种钢板工作长度。采用光学方法测量骨折块间运动。
使用拉力螺钉时轴向骨折块间运动减少（钢板工作长度102mm，1000N，平均值）：0.28mm对0.82mm。使用拉力螺钉时，骨折间隙保持闭合，平均正常骨折块间运动≤0.03mm。不使用拉力螺钉时骨折间隙倾向于张开：正常骨折块间运动可达-0.29mm。在所有测试载荷和组中均观察到剪切骨折块间运动减少。与不使用拉力螺钉（≤1.46mm）相比，使用拉力螺钉时平均真实剪切力通常较低（≤0.42mm）。我们还发现，使用拉力螺钉时骨折块间运动方差减小，尤其是对于较长的钢板工作长度。
在锁定桥接钢板旁使用拉力螺钉可减少体外简单骨折模型中的骨折块运动，并提供一种有效的工具来减少有害的剪切运动。关于拉力螺钉固定的前瞻性临床试验应在广泛的临床应用中验证这些发现，以治疗简单骨折类型。
