IN VIVO EVALUATION OF A REDUCED MODULUS BONE CEMENT

骨水泥型全关节术后最常见的并发症 更换程序是一个或两个组件松动。 的 松动过程始于骨水泥处的骨吸收 接口. 局部应力过大和存在亚微米碎片 每一个都能触发骨的再吸收并开始松散级联。 一种模量较低、韧性较好的骨水泥， 聚甲基丙烯酸甲酯（PMMA）将降低局部接触应力， 产生更少的颗粒碎片。 任何不规则界面，例如 骨-骨水泥界面在几何位置处的接触应力将达到峰值 和材料不连续性。 根据定量模型， 材料接触，分析和数值，应力将是 如果水泥的弹性模量降低，则水泥的弹性模量降低。 低模量 丙烯酸骨水泥，在PMMA中加入聚甲基丙烯酸丁酯珠粒 矩阵，已开发和其静态和粘弹性材料 特性已被表征。 其在体温下的模量为 它的韧性明显低于PMMA，并且它的韧性大得多。 正在进行的体外实验正在验证局部接触应力 假说. 水泥的模量具有预期的效果， 相邻骨的剪切应变;降低骨水泥模量可降低 骨应变，从而减少触发松动的微损伤 级联。 初步的体内研究支持以下结论： 通过减少界面接触可以降低松动率 压力 通过影像学和力学评估， 使用低模量丙烯酸骨进行绵羊全髋关节置换术 骨水泥显著低于绵羊， 使用了水泥。 合乎逻辑的下一步是对松动率进行更大规模的体内研究 从统计学上验证试点研究的结果。 松动 使用标准PMMA和降低模量植入组件的比率 将在绵羊全髋关节模型中比较丙烯酸骨水泥。

The most frequent postoperative complication of cemented total joint replacement procedures is loosening of one or both components. The loosening process begins with resorption of bone at the bone-cement interface. Excessive local stresses and the presence of submicron debris can each trigger the resorption of bone and start the loosening cascade. A bone cement with a lower modulus and greater toughness than polymethylmethacrylate (PMMA) will decrease local contact stresses and produce less particulate debris. Any irregular interface, such as the bone-cement interface, will have peaks in contact stress at geometrical and material discontinuities. According to quantitative models for materials contact, both analytical and numerical, the stresses will be reduced if the elastic moduli of the cement are reduced. A low-modulus acrylic bone cement, formulated with polybutylmethacrylate beads in a PMMA matrix, has been developed and its static and viscoelastic material properties have been characterized. Its modulus at body temperature is significantly lower than that of PMMA and its toughness is much greater. Ongoing in vitro experimentation is verifying the local contact stress hypothesis. The modulus of the cement has the expected effect of the shear strain of the adjacent bone; reducing the cement modulus reduces the bone strain and will thus reduce microdamage which triggers the loosening cascade. Preliminary in vivo investigations support the conclusion that loosening rates can be decreased by diminution of the interface contact stresses. The loosening rate, assessed radiographically and mechanically, in sheep total hip arthroplasties using a reduced-modulus acrylic bone cement was significantly lower than that in sheep where standard PMMA bone cement was used. The logical next step is a larger in vivo investigation of loosening rates to statistically validate the findings of the pilot study. The loosening rates of components implanted using standard PMMA and reduced-modulus acrylic bone cements will be compared in a sheep total hip model.