Taddei Fulvia, Martelli Saulo, Gill Harinderjit Singh, Cristofolini Luca, Viceconti Marco
Laboratorio di Tecnologia Medica, Istituto Ortopedico Rizzoli, Via di Barbiano 1/10, 40136 Bologna, Italy.
J Biomech Eng. 2010 Feb;132(2):021002. doi: 10.1115/1.4000065.
Metal-on-metal hip resurfacing is becoming increasingly popular, and a number of new devices have been recently introduced that, in the short term, appear to have satisfactory outcome but many questions are still open on the biomechanics of the resurfaced femur. This could be investigated by means of finite element analysis, but, in order to be effective in discerning potential critical conditions, the accuracy of the models' predictions should be assessed. The major goal of this study was to validate, through a combined experimental-numerical study, a finite element modeling procedure for the simulation of resurfaced femurs. In addition, a preliminary biomechanical analysis of the changes induced in the femoral neck biomechanics by the presence of the device was performed, under a physiologic range of hip joint reaction directions. For this purpose, in vitro tests and a finite element model based on the same specimen were developed using a cadaver femur. The study focused on the Conserve Plus, one of the most common contemporary resurfacing designs. Five loading configurations were identified to correspond to the extremes of physiological directions for the hip joint. The agreement between experimental measurements and numerical predictions was good both in the prediction of the femoral strains (R(2)>0.9), and in the prosthesis micromotions (error<20 microm), giving confidence in the model predictions. The preliminary biomechanical analysis indicated that the strains in the femoral neck are moderately affected by the presence of the prosthesis, apart from localized strain increments that can be considerable, always predicted near the stem. Low micromotions and contact pressure were predicted, suggesting a good stability of the prosthesis. The model accuracy was good in the prediction of the femoral strains and moderately good in the prediction of the bone-prosthesis micromovements. Although the investigated loading conditions were not completely physiological, the preliminary biomechanical analysis showed relatively small changes for the proximal femur after implantation. This validated model can support realistic simulations to examine physiological load configurations and the effects of variations in prosthesis design and implantation technique.
金属对金属髋关节表面置换术正变得越来越流行，最近有许多新设备问世，短期内这些设备似乎有令人满意的效果，但关于表面置换股骨的生物力学仍有许多问题有待解决。这可以通过有限元分析来研究，但是，为了有效地识别潜在的关键情况，应该评估模型预测的准确性。本研究的主要目标是通过实验与数值相结合的研究，验证一种用于模拟表面置换股骨的有限元建模程序。此外，在髋关节反应方向的生理范围内，对该装置的存在引起的股骨颈生物力学变化进行了初步的生物力学分析。为此，使用一具尸体股骨进行了体外测试，并基于同一标本开发了有限元模型。该研究聚焦于Conserve Plus，这是当代最常见的表面置换设计之一。确定了五种加载配置，以对应髋关节生理方向的极端情况。实验测量与数值预测之间的一致性在股骨应变预测（R(2)>0.9）和假体微动（误差<20微米）方面都很好，这让人们对模型预测有信心。初步的生物力学分析表明，除了在假体柄附近总是预测到的相当大的局部应变增加外，股骨颈的应变受假体存在的影响适中。预测的微动和接触压力较低，表明假体稳定性良好。该模型在预测股骨应变方面准确性良好，在预测骨-假体微动方面中等良好。尽管所研究的加载条件并非完全生理，但初步的生物力学分析表明植入后近端股骨的变化相对较小。这个经过验证的模型可以支持实际模拟，以检查生理载荷配置以及假体设计和植入技术变化的影响。
