Kluess Daniel, Martin Heiner, Mittelmeier Wolfram, Schmitz Klaus-Peter, Bader Rainer
Institute for Biomedical Engineering, University of Rostock, Germany.
Med Eng Phys. 2007 May;29(4):465-71. doi: 10.1016/j.medengphy.2006.07.001. Epub 2006 Aug 9.
Dislocation remains a serious complication of total hip replacement. An insufficient range of motion can lead to impingement of the prosthetic neck on the acetabular cup. Together with the initiation of subluxation and dislocation, recurrent impingement can cause material failure in the liner. The objective of this study was to generate a validated finite element (FE) model capable of predicting the dislocation stability of different femoral head sizes with regard to impingement in different implant positions as well as the corresponding stress distribution in the liner. In order to cover posterior and anterior dislocation, two total hip dislocation associated manoeuvres were simulated using a three-dimensional nonlinear finite element model. The dislocation stability of two head sizes was determined numerically and experimentally. After validation, the FE model was used to analyse the dislocation stability of four different head sizes in variable implant positions. Range of motion (ROM) until impingement, the resisting moment that was developed and ROM until dislocation were evaluated. Additionally, stress distribution within the polyethylene liner during impingement and subluxation was determined. For both dislocation modes, a cup position of 45 degrees lateral abduction and 15 degrees up to 30 degrees anteversion resulted in appropriate ROM and dislocation stability. In general, larger head diameters revealed an increase in ROM and higher resisting moments. Stress analysis showed decreased contact pressures at the egress site of the liners with the larger inner diameters during subluxation. The analysis shows that an optimal implant position and a larger head diameter can reduce the risk of dislocation induced by impingement. The finite element model that was developed enables simplification of design variations compared to experimental studies since prototyping and assembling are replaced by prompt numerical simulation.
脱位仍然是全髋关节置换术的一种严重并发症。活动范围不足会导致假体颈部撞击髋臼杯。反复撞击会引发半脱位和脱位，并导致内衬材料失效。本研究的目的是建立一个经过验证的有限元（FE）模型，该模型能够预测不同股骨头尺寸在不同植入位置时的脱位稳定性以及内衬中的相应应力分布。为了涵盖后脱位和前脱位，使用三维非线性有限元模型模拟了两种与全髋关节脱位相关的动作。通过数值和实验确定了两种股骨头尺寸的脱位稳定性。经过验证后，该有限元模型被用于分析四种不同股骨头尺寸在可变植入位置时的脱位稳定性。评估了撞击前的活动范围（ROM）、产生的抵抗力矩以及脱位前的ROM。此外，还确定了撞击和半脱位期间聚乙烯内衬内的应力分布。对于两种脱位模式，髋臼杯处于外展45度、前倾15度至30度的位置时，可获得合适的ROM和脱位稳定性。一般来说，较大的股骨头直径显示出ROM增加和抵抗力矩更高。应力分析表明，在半脱位期间，内径较大的内衬出口部位的接触压力降低。分析表明，最佳的植入位置和较大的股骨头直径可以降低撞击引起的脱位风险。与实验研究相比，所建立的有限元模型能够简化设计变化，因为原型制作和组装被快速的数值模拟所取代。
