Pettersen Sune H, Wik Tina S, Skallerud Bjørn
Department of Structural Engineering, Norwegian University of Science and Technology, 7491 Trondheim, Norway.
Clin Biomech (Bristol). 2009 Jul;24(6):480-7. doi: 10.1016/j.clinbiomech.2009.03.009. Epub 2009 Apr 14.
The primary stability of a cementless implant is crucial to ensure long term stability through osseointegration. In the present study we have examined how subject specific finite element models can be used to evaluate the stability of a cementless femoral stem.
Micromotion on the bone-implant interface of a cementless stem was measured experimentally in six human cadaver femurs. Subject specific finite element models were built from computed tomography of the same femurs, and used to simulate the same load scenario used experimentally.
Both experimental measurements and numerical analyses showed a tendency of increased rotational stability for bigger implants. Good correlation was found between measurements and calculated values of axial rotation (R(2)=0.74, P<0.001). The finite element models produced interface micromotion of the same magnitude as measured experimentally, with micromotion generally below 40 microm. Bigger femoral stems were found to decrease the micromotion in the experimental measurements. This tendency could not be recognised in the interface micromotion from the finite element models.
The finite element models showed limited success in predicting interfacial micromotion, but reproduced a similar pattern of rotational stability for the implants as seen experimentally. Since rotation in retroversion is often the main concern when studying implant stability, subject specific finite element models could be employed for pre-clinical evaluation of implants.
非骨水泥型植入物的初始稳定性对于通过骨整合确保长期稳定性至关重要。在本研究中，我们研究了如何使用个体化有限元模型来评估非骨水泥型股骨柄的稳定性。
在六具人类尸体股骨上通过实验测量了非骨水泥型股骨柄骨-植入物界面的微动。从相同股骨的计算机断层扫描构建个体化有限元模型，并用于模拟实验中使用的相同载荷情况。
实验测量和数值分析均显示较大植入物的旋转稳定性有增加的趋势。在轴向旋转的测量值与计算值之间发现了良好的相关性（R² = 0.74，P < 0.001）。有限元模型产生的界面微动与实验测量值大小相同，微动一般低于40微米。在实验测量中发现较大的股骨柄可减少微动。这种趋势在有限元模型的界面微动中未被识别。
有限元模型在预测界面微动方面取得的成功有限，但再现了与实验中所见植入物相似的旋转稳定性模式。由于在研究植入物稳定性时，后倾旋转通常是主要关注点，因此个体化有限元模型可用于植入物的临床前评估。
