Bonnin Michel P, Archbold Pooler H A, Basiglini Luca, Selmi Tarik A, Beverland David E
Santy Orthopaedic Centre, 24 Av Paul Santy, Lyon, France.
Hip Int. 2011 Jul-Aug;21(4):428-35. doi: 10.5301/HIP.2011.8582.
During total hip arthroplasty (THA), medialisation of the cup decreases the lever arm of body weight and is considered to be beneficial. Theoretically it should be compensated by an equivalent increase of the femoral offset in order to maintain global offset.
We investigated via a numerical model the forces on each bundle of the abductor muscles and the loading forces at the head-cup interface. We compared THA with and without medialisation of the cup and with and without restoration of the global offset.
A digital finite element model of the hip joint with THA was constructed. Monopodal weightbearing was simulated with the cup positioned so that the hip centre of rotation was left unchanged. Forces in the abductors and pressure on the prosthetic head were measured and then compared with three other configurations: 1. Medialisation of the cup by 5 to 15 mm with reproduction of the native femoral offset or; 2. with an increased femoral offset compensating for the cup medialisation and; 3. no medialisation of the cup with a femoral offset increased.
Medialisation of the cup decreased stresses on the head-cup interface and on the abductor muscles, even when the global offset was not restored. Anatomical placement of the cup did not give the best results. The optimal outcome in terms of stress was observed when the cup was medialised but global offset restored. Any increase of global offset significantly increases the length and the tension in the anterior bundles of the abductor muscles.
在全髋关节置换术（THA）中，髋臼杯的内移可减小体重的力臂，被认为是有益的。理论上，这应由股骨偏心距的相应增加来补偿，以维持整体偏心距。
我们通过数值模型研究了外展肌各束上的力以及股骨头-髋臼界面处的加载力。我们比较了髋臼杯有无内移以及整体偏心距有无恢复的全髋关节置换术。
构建了一个带有全髋关节置换术的髋关节数字有限元模型。模拟单足负重，髋臼杯位置设定为使髋关节旋转中心保持不变。测量外展肌中的力和假体头部的压力，然后与其他三种配置进行比较：1. 髋臼杯内移5至15毫米，同时恢复天然股骨偏心距；或2. 增加股骨偏心距以补偿髋臼杯内移；以及3. 髋臼杯不内移，但增加股骨偏心距。
即使整体偏心距未恢复，髋臼杯内移也会降低股骨头-髋臼界面和外展肌上的应力。髋臼杯的解剖位置并未给出最佳结果。当髋臼杯内移但整体偏心距恢复时，观察到应力方面的最佳结果。整体偏心距的任何增加都会显著增加外展肌前束的长度和张力。
