Zanetti Elisabetta M, Salaorno Massimiliano, Grasso Giovanni, Audenino Alberto L
Department of Industrial and Mechanical Engineering (DIIM), University of Catania, V.le Andrea Doria 6, 95125 Catania, Italy.
Open Med Inform J. 2009 Apr 21;3:19-26. doi: 10.2174/1874431100903010019.
A global study of geometry and material properties of orthopedic screws was performed, considering not only the effect of each single factor (screw pitch, number of threads, fillet angle, etc.) but also their interactions with respect to bone density.The stress patterns resulting from different screw geometries and bone densities were analyzed using finite element techniques, taking into account different levels of osseointegration between the screw and the bone. These numerical models where validated through experimental pull-out tests, where a pull out force of 120 N produced localized failure of the last thread (stresses above 0.42 MPa). The results of the numerical simulations were then summarised using a multi-factorial parametric analysis. This demonstrated the great relevance of the interaction between bone density and screw pitch, showing that the optimal screw pitch can vary by more than 25% for different densities (0.35 g/cm(3) and 0.47 g/cm(3), respectively).The parameters calculated by means of the multi-factorial analysis allow the pull out force to be estimated for different osseointegration levels, different screw geometries and material properties, and for different bone densities. The final objective is to determine the best choice of implant for each individual patient.
开展了一项关于骨科螺钉几何形状和材料特性的全球研究，不仅考虑了每个单一因素（螺距、螺纹数量、圆角角度等）的影响，还考虑了它们与骨密度的相互作用。使用有限元技术分析了不同螺钉几何形状和骨密度产生的应力模式，同时考虑了螺钉与骨之间不同程度的骨整合。这些数值模型通过实验拔出试验进行了验证，在该试验中，120 N的拔出力导致最后一个螺纹出现局部失效（应力高于0.42 MPa）。然后使用多因素参数分析总结了数值模拟结果。这证明了骨密度与螺距之间相互作用的重大相关性，表明对于不同密度（分别为0.35 g/cm³和0.47 g/cm³），最佳螺距可变化超过25%。通过多因素分析计算得出的参数可用于估计不同骨整合水平、不同螺钉几何形状和材料特性以及不同骨密度下的拔出力。最终目标是为每个患者确定最佳的植入物选择。
