Dammak M, Shirazi-Adl A, Zukor D J
Department of Mechanical Engineering, Ecole Polytechnique, Montreal, Quebec, Canada.
J Biomech. 1997 Feb;30(2):121-9. doi: 10.1016/s0021-9290(96)00110-8.
Measured interface nonlinear friction properties are used to develop models to study the short-term fixation response of smooth- and porous-surfaced posts, bone screws, and plates fixed with and without posts/screws. Experimental studies are carried out to validate the model predictions and identify the relative role of posts and screws in fixation of a plate on a polyurethane block under symmetric/eccentric axial compression loads. The idealized Coulomb's friction is also used for the sake of comparison. The incorporation of measured nonlinear, rather than the idealized Coulomb, friction is essential to compute realistic results. For plate fixation, the experimental and finite element results show that the screw fixation yields the stiffest response followed by the smooth- and then porous-coated post fixation. For example, under 1000 N eccentric axial compression, the edge of the plate opposite the loaded edge is measured to lift by 1147 +/- 72, 244 +/- 38, or 112 +/- 28 microns, respectively, for the cases with no fixation, with smooth-surfaced posts, or with screws. The corresponding models predict, respectively, values of 1538, 347, or 259 microns and also 556 microns for the plate fixed with porous coated posts. The satisfactory agreement between numerical and experimental results confirms the importance of proper interface modelling for the analysis of posts, screws, and complex fixation systems. This becomes further evident when considering cementless implants in which the bone-implant interface exhibits relatively large displacements as the maximum resistance force is reached. The developed models can be used to investigate the post-operative short-term stability of various cementless implant designs.
测量得到的界面非线性摩擦特性被用于建立模型，以研究光滑表面和多孔表面的桩柱、骨螺钉以及带或不带桩柱/螺钉固定的钢板的短期固定响应。开展实验研究以验证模型预测结果，并确定在对称/偏心轴向压缩载荷下，桩柱和螺钉在聚氨酯块上固定钢板时的相对作用。为了进行比较，还采用了理想化的库仑摩擦。纳入测量得到的非线性摩擦而非理想化的库仑摩擦对于计算实际结果至关重要。对于钢板固定，实验和有限元结果表明，螺钉固定产生的响应最刚硬，其次是光滑涂层桩柱固定，然后是多孔涂层桩柱固定。例如，在1000 N偏心轴向压缩下，对于无固定、有光滑表面桩柱或有螺钉的情况，钢板与加载边缘相对的边缘分别被测量到抬起1147±72、244±38或112±28微米。相应的模型分别预测值为1538、347或259微米，对于有多孔涂层桩柱固定的钢板预测值为556微米。数值结果与实验结果之间令人满意的一致性证实了正确的界面建模对于分析桩柱、螺钉和复杂固定系统的重要性。当考虑无骨水泥植入物时，这一点变得更加明显，在无骨水泥植入物中，当达到最大阻力时，骨-植入物界面会出现相对较大的位移。所建立的模型可用于研究各种无骨水泥植入物设计的术后短期稳定性。
