前路经枕-寰-枢关节螺钉内固定力学的三维有限元分析

Three-dimensional finite element biomechanical analysis of the anterior occiput-to-axis screw fixation

[目的]建立前路经枕-寰-枢关节螺钉内固定的三维有限元模型,并对其进行生物力学分析。[方法]采集1名健康成年男性CT图像,建立枕骨髁(C0)-C2的三维有限元模型,并验证其有效性。在此模型上通过单元结构的删减建立枕颈部不稳定模型,植入前路经枕-寰-枢关节螺钉行枕颈固定。对术后模型进行自由度约束,在其表面分别施加前屈、后伸、侧屈、旋转方向上的生理载荷。计算并分析螺钉各部的应力、应变情况。[结果]前路经枕-寰-枢关节螺钉在前屈、后伸方向载荷下的位移峰值、应力峰值,明显高于侧屈、旋转。在不同方向载荷下前路经枕-寰-枢关节螺钉的应力峰值均出现于螺钉通过寰枢关节区域。[结论]前路经枕-寰-枢关节螺钉内固定在抗侧屈、旋转上具有良好的力学性能,但在抗前屈、后伸方面力学性能较差,螺钉在通过寰枢关节处为应力集中最明显的区域,易产生固定疲劳。

[Objective]To establish a 3-D finite element model of anterior occiput-to-axis screw fixation and analyze its biomechanical properties. [Methods]A finite element model of the occipital condyle（C0）-C2 was developed from CT images of a healthy Chinese adult man,and its validity had been tested.The unstable model was established by deleting unit structure based on the validated normal model.Anterior occiput-to-axis screws were performed on this model.The inferior surface of the postoperative model was fully constrained,and the physiological load was exerted on the upper surface of the model in flexion,extension,lateral bending and axial rotation,respectively.The VionMisees stress and displacement of the screws were evaluated and analyzed.[Results]The peak values of displacement and largest stress force in screws under load in flexion and extension were significantly higher than those in bending and axial rotation.The peak stress occurred at the screws through the atlantoaxial joint zone under load of different directions.[Conclusion]The anterior occiput-to-axis screw fixation technique has excellent mechanical properties in terms of anti-lateral bending and anti-rotation but no stability in terms of flexion and extension.The zone of the screws passing through atlantoaxial joint is apt to cause stress fatigue.