Department of Biomedical Engineering, University Medical Center Groningen, University of Groningen, A. Deusinglaan 1, 9713 AV Groningen, The Netherlands.
J Biomech. 2012 Jul 26;45(11):1875-80. doi: 10.1016/j.jbiomech.2012.05.032. Epub 2012 Jun 6.
Currently available implants for direct attachment of prosthesis to the skeletal system after transfemoral amputation (OPRA system, Integrum AB, Sweden and ISP Endo/Exo prosthesis, ESKA Implants AG, Germany) show many advantages over the conventional socket fixation. However, restraining biomechanical issues such as considerable bone loss around the stem and peri-prosthetic bone fractures are present. To overcome these limiting issues a new concept of the direct intramedullary fixation was developed. We hypothesize that the new design will reduce the peri-prosthetic bone failure risk and adverse bone remodeling by restoring the natural load transfer in the femur. Generic CT-based finite element models of an intact femur and amputated bones implanted with 3 analyzed implants were created and loaded with a normal walking and a forward fall load. The strain adaptive bone remodeling theory was used to predict long-term bone changes around the implants and the periprosthetic bone failure risk was evaluated by the von Mises stress criterion. The results show that the new design provides close to physiological distribution of stresses in the bone and lower bone failure risk for the normal walking as compared to the OPRA and the ISP implants. The bone remodeling simulations did not reveal any overall bone loss around the new design, as opposed to the OPRA and the ISP implants, which induce considerable bone loss in the distal end of the femur. This positive outcome shows that the presented concept has a potential to considerably improve safety of the rehabilitation with the direct fixation implants.
目前，用于经股骨截肢后假体直接附着于骨骼系统的植入物（OPRA 系统，Integrum AB，瑞典和 ISP 内/外假体，ESKA 植入物 AG，德国）与传统的插座固定相比具有许多优势。然而，存在一些限制生物力学的问题，例如在干骺端周围存在大量骨丢失和假体周围骨折。为了克服这些限制问题，开发了一种直接髓内固定的新概念。我们假设，通过恢复股骨中的自然负荷传递，新设计将降低假体周围骨失效风险和不良的骨重塑。创建了完整股骨和植入 3 种分析植入物的截肢骨的基于通用 CT 的有限元模型，并对其进行了正常行走和前向跌倒负荷的加载。应变自适应骨重塑理论用于预测植入物周围的长期骨变化，并通过 von Mises 应力准则评估假体周围骨失效风险。结果表明，与 OPRA 和 ISP 植入物相比，新设计为正常行走提供了更接近生理的骨骼内应力分布和更低的骨失效风险。骨重塑模拟没有显示出任何新设计周围的整体骨丢失，而 OPRA 和 ISP 植入物则在股骨远端引起了相当大的骨丢失。这一积极结果表明，所提出的概念具有显著提高直接固定植入物康复安全性的潜力。
