Shirazi-Adl A, Patenaude O, Dammak M, Zukor D
Génie mécanique, Ecole Polytechnique, Montréal, Québec, Canada.
J Biomech Eng. 2001 Oct;123(5):391-5. doi: 10.1115/1.1395572.
The short- and long-term successes of tibial cementless implants depend on the initial fixation stability often provided by posts and screws. In this work, a metallic plate was fixed to a polyurethane block with either two bone screws, two smooth-surfaced posts, or two novel smooth-surfaced posts with adjustable inclinations. For this last case, inclinations of 0, 1.5, and 3 deg were considered following insertion. A load of 1031 N was eccentrically applied on the plate at an angle of approximately 14 deg, which resulted in a 1000 N axial compressive force and a 250 N shear force. The response was measured under static and repetitive loading up to 4000 cycles at 1 Hz. The measured results demonstrate subsidence under load, lift-off on the unloaded side, and horizontal translation of the plate specially at the loaded side. Fatigue loading increased the displacements, primarily during the first 100 cycles. Comparison of various fixation systems indicated that the plate with screw fixation was the stiffest with the least subsidence and liftoff. The increase in post inclination from 0 to 3 deg stiffened the plate by diminishing the liftoff. All fixation systems demonstrated deterioration under repetitive loads. In general, the finite element predictions of the experimental fixation systems were in agreement with measurements. The finite element analyses showed that porous coated posts (modeled with nonlinear interface friction with and without coupling) generated slightly less resistance to liftoff than smooth-surfaced posts. In the presence of porous coated posts, Coulomb friction greatly overestimated the rigidity by reducing the liftoff and subsidence to levels even smaller than those predicted for the design with screw fixation. The sequence of combined load application also influenced the predicted response. Finally, the finite element model incorporating measured interface friction and pull-out responses can be used for the analysis of cementless total joint replacement systems during the post-operation period.
胫骨非骨水泥型植入物的短期和长期成功取决于通常由桩柱和螺钉提供的初始固定稳定性。在这项研究中，一块金属板通过两根骨螺钉、两根表面光滑的桩柱或两根新型的可调节倾斜度的表面光滑的桩柱固定在一个聚氨酯块上。对于最后一种情况，插入后考虑了0°、1.5°和3°的倾斜度。在金属板上以大约14°的角度偏心施加1031 N的载荷，这导致了1000 N的轴向压缩力和250 N的剪切力。在1 Hz下进行静态和重复加载直至4000次循环，测量响应。测量结果表明，加载时会发生下沉，卸载侧会出现抬起，特别是在加载侧金属板会发生水平平移。疲劳加载增加了位移，主要发生在最初的100次循环中。各种固定系统的比较表明，螺钉固定的金属板最硬，下沉和抬起最少。桩柱倾斜度从0°增加到3°通过减少抬起使金属板变硬。所有固定系统在重复载荷下都表现出性能恶化。总体而言，实验固定系统的有限元预测与测量结果一致。有限元分析表明，多孔涂层桩柱（采用有无耦合的非线性界面摩擦建模）对抬起的阻力比表面光滑的桩柱略小。在有多孔涂层桩柱的情况下，库仑摩擦通过将抬起和下沉降低到甚至小于螺钉固定设计预测的水平，大大高估了刚度。组合载荷施加的顺序也影响了预测响应。最后，结合测量的界面摩擦和拔出响应的有限元模型可用于分析术后非骨水泥型全关节置换系统。
