Radboud University Nijmegen Medical Centre, Orthopaedic Research Laboratory, Nijmegen, the Netherlands.
Acta Orthop. 2009 Jun;80(3):319-24. doi: 10.3109/17453670902947465.
Two contradictory cementing techniques (using an undersized stem versus a canal-filling stem) can both lead to excellent survival rates, a phenomenon known as the "French paradox". Furthermore, previous studies have indicated that the type of bone supporting the cement mantle may affect implant survival. To further evaluate the mechanical consequences of variations in cementing technique, we studied the effect of implant size and type of bone supporting the cement mantle on the mechanical performance of cemented total hip arthroplasty, using finite element analysis.
In a generic 2-dimensional plane-strain finite element model of a transverse section of a cemented total hip arthroplasty with a Charnley-Kerboull stem, we varied implant size and type of bone supporting the cement mantle. The models were subjected to 2 x 106 cycles of an alternating loading pattern of torque and a transverse load. During this loading history, we simulated cement fatigue crack formation and tracked rotational stability of the implant.
Canal-filling stems produced fewer cement cracks and less rotation than undersized stems. Cement mantles surrounded by trabecular bone produced more cement cracks and implant rotation than cement mantles surrounded by cortical bone.
Our investigation provides a possible explanation for the good clinical results obtained with canal-filling Charnley-Kerboull implants. Our findings also indicate that inferior mechanical properties are obtained with these implants if the cement is supported by trabecular bone, which may be minimized by an optimal cementing technique.
两种相互矛盾的固位技术（使用小直径柄 versus 髓腔填充柄）都可以获得出色的生存率，这一现象被称为“法国悖论”。此外，先前的研究表明，支撑骨水泥覆盖层的骨类型可能会影响种植体的存活率。为了进一步评估固位技术变化的力学后果，我们使用有限元分析研究了种植体大小和支撑骨水泥覆盖层的骨类型对骨水泥全髋关节置换术力学性能的影响。
在 Charnley-Kerboull 柄骨水泥全髋关节置换术的横截面上的通用二维平面应变有限元模型中，我们改变了种植体大小和支撑骨水泥覆盖层的骨类型。对模型进行了 2 x 106 次扭矩和横向载荷交替加载模式的循环加载。在这种加载历史下，我们模拟了骨水泥疲劳裂纹的形成，并跟踪了种植体的旋转稳定性。
髓腔填充柄产生的骨水泥裂纹和旋转比小直径柄少。由松质骨支撑的骨水泥覆盖层比由皮质骨支撑的骨水泥覆盖层产生更多的骨水泥裂纹和种植体旋转。
我们的研究为 Charnley-Kerboull 髓腔填充植入物获得良好的临床结果提供了可能的解释。我们的发现还表明，如果骨水泥由松质骨支撑，这些植入物的机械性能会降低，这可能通过优化的骨水泥技术最小化。
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