Tetteh Emmanuel, McCullough Matthew B A
Industrial and Manufacturing Systems Engineering, Iowa State University, Ames, IA, USA.
Chemical, Biological and Bioengineering, College of Engineering, North Carolina Agricultural and Technical State University, Ames, IA, USA.
Comput Methods Biomech Biomed Engin. 2020 Jul;23(9):518-523. doi: 10.1080/10255842.2020.1743980. Epub 2020 Mar 26.
Gradual screw loosening is a well-known failure mechanism in internal fixation. Loosening is primarily due to progressive bone loss caused by stress shielding, a phenomenon in which a medical device absorbs a disproportionate amount of load within the screw-bone construct. The proximity of elastic moduli of magnesium and bone presents the potential for alleviating screw loosening by allowing optimum stress to be transferred between screw and bone, and in turn, supporting bone remodeling around the screw. In this study, the effect of thread profile on stress transfer in a magnesium fixation was simulated using a 2-D finite element model. Modified stress parameters from a previous study were used to estimate stress transfer across three thread profiles. Results showed highest stress transfer in trapezoidal-shaped magnesium screw thread. In accordance, this study corroborates the potential for magnesium as an ultimate screw material to eliminate progressive screw loosening.
螺钉逐渐松动是内固定中一种广为人知的失效机制。松动主要是由于应力遮挡导致的渐进性骨质流失，应力遮挡是指医疗器械在螺钉-骨结构中吸收了不成比例的大量负荷的一种现象。镁与骨的弹性模量相近，这使得在螺钉和骨之间实现最佳应力传递成为可能，进而支持螺钉周围的骨重塑，从而减轻螺钉松动。在本研究中，使用二维有限元模型模拟了螺纹形状对镁固定中应力传递的影响。采用先前研究中修正的应力参数来估计三种螺纹形状的应力传递。结果表明，梯形镁螺钉螺纹的应力传递最高。据此，本研究证实了镁作为最终螺钉材料消除螺钉渐进性松动的潜力。
