单髁膝关节置换胫骨元件不同固定柱形状的有限元分析

目的针对单髁膝关节置换后胫骨前内侧疼痛、胫骨元件松动以及对侧关节炎恶化的问题,通过有限元方法比较分析胫骨元件固定柱的不同几何形状对胫骨应力分布的影响。方法建立有效的单髁膝关节置换有限元模型,对胫骨元件固定柱的形状进行设计。在相同的加载条件下,分别对双柱形、单脊形、双脊形和十字星形胫骨元件进行有限元分析,并与完整膝关节模型进行对比,评估胫骨元件固定柱不同形状设计对胫骨前内侧皮质骨应力、胫骨截骨面松质骨应力、胫骨对侧软骨应力的影响。结果单髁置换后胫骨前内侧皮质骨应力峰值均增大。与完整膝关节相比,在双柱形、单脊形、双脊形和十字星形胫骨元件固定柱的模型中,胫骨前内侧皮质骨应力峰值分别增加56.1%、55.9%、54.5%和68.4%。单脊形和双脊形胫骨元件松质骨截骨面应力峰值比完整胫骨分别减小8.1%和15.6%,而双柱形和十字星形则分别增大67.9%和121.5%,超过松质骨的疲劳屈服应力。双柱形、单脊形、双脊形和十字星形胫骨固定柱对应的胫骨对侧软骨应力峰值相比于完整胫骨分别减小42.1%、26.6%、24.2%和28.5%。结论单髁膝关节置换改变了胫骨内外侧的载荷分布,使置换侧承受更大的载荷。单脊形和双脊形胫骨元件在降低胫骨前内侧皮质骨和截骨面松质骨应力方面效果更好,其中单脊形胫骨元件更接近完整膝关节胫骨的应力分布。研究结果可为设计更符合膝关节力学性能的单髁膝关节假体提供理论依据。

人工髋关节内衬的材料及磨损测试

人工髋关节由髋臼杯、内衬、球头和股骨柄四部分组成。无菌性松动是人工髋关节失效最常见的原因之一,占比为10%~50%[1⁃2]。研究表明,人工髋关节内衬因运动而产生的磨损颗粒(粒径小于100μm)被巨噬细胞吞噬而释放大量的细胞因子,激活破骨细胞造成骨溶解,最终引发人工髋关节无菌性松动。如何控制人工髋关节内衬的磨损从而提高假体的存活寿命是临床面临的严峻问题,也是重要的研究热点之一。

Biomechanical comparison of interspinous distraction device and facet screw fixation system on the motion of lumbar spine： a finite element analysis

Background A large amount of biomechanical and clinical evidence from previous studies suggest the efficiency of the two different posterior lumber non-fusion methods,interspinous distraction device （ISDD） and facet screw fixation system （FSS）,but the biomechanical comparison of ISDD and FSS has not been thoroughly clarified.Methods In the current study,finite element methods were used to investigate the biomechanical comparison of ISDD and FSS.The range of motion （ROM）,intradiscal pressure （IDP） and the protective effects gained by maintaining disc heights were evaluated.Results The ROM was similar between the two non-fusion methods under static standing,flexion and lateral bending.The FSS appeared to be more effective in resisting extension.At the implanted level L3/4,FSS displayed better results for maintaining and increasing posterior disc heights.At the L4/5 level in extension and lateral bending,FSS was better than ISDD,with comparable results observed in other motions.Comparing the posterior and lateral disc heights,FSS appeared to be more effective than ISDD.FSS also had a minor effect on the inferior adjacent segment than ISDD.FSS was more effective in reducing IDP than ISDD in extension.Conclusion Through the finite element analysis study,it can be seen that FSS demonstrates more beneficial biomechanical outcomes than does ISDD,such as being more effective in resisting extension,maintaining and increasing lumbar disc heights and reducing the inferior adjacent IDP in extension.