Residual stress due to curing can initiate damage in porous bone cement: experimental and theoretical evidence
Residual stress due to curing can initiate damage in porous bone cement: experimental and theoretical evidence
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DOI：
10.1016/s0021-9290(01)00216-0
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发表时间：
2002-03-01
影响因子：
2.4
通讯作者：
Prendergast, PJ
中科院分区：
文献类型：
--
作者：
Lennon, AB;Prendergast, PJ
聚甲基丙烯酸甲酯骨水泥聚合后收缩产生的残余应力可能是导致骨水泥型髋关节置换术外套膜开裂的一个因素。尚未证明残余应力与观察到的水泥开裂之间存在任何关系。为了研究是否存在任何关系，已经开发了一个物理模型，可以直接观察全髋关节置换术股骨侧骨水泥层的损伤。该模型在骨表面和金属股骨柄之间包含内侧和外侧骨水泥层;骨水泥鞘的管状性质被忽略。制备了五个试样，并使用着色裂纹的手动跟踪检查裂纹，通过透射显微镜观察：使用图像分析定位和测量裂纹。开发了一种用于预测由于收缩引起的残余应力的数学方法，该方法使用材料的热历史来预测何时发生应力锁定，并估计随后的热应力。采用有限元法计算了物理模型中水泥层的残余应力分布。结果表明，最大拉伸应力垂直于所观察到的裂纹方向，这表明残余应力和预载荷开裂之间的联系。预测的残余应力强烈依赖于应力锁定的参考温度的定义。预测最高残余应力（4-7 MPa）用于从最高温度收缩，在这种情况下，当考虑应力集中器（如骨/骨水泥界面处的孔隙或交错）的影响时，其量值足够高以引发裂纹（当根据Harrigan和Harris的方法计算孔隙周围的应力时高达24 MPa（J. Biomech. 24（11）（1991）1047-1058））。我们的结论是，损伤累积失效的情况下开始之前，由于孔隙或应力集中器周围的残余应力引起的开裂承重。(C)2002爱思唯尔科技有限公司。保留所有权利。
Residual stress due to shrinkage of polymethylmethacrylate bone cement after polymerisation is possibly one factor capable of initiating cracks in the mantle of cemented hip replacements. No relationship between residual stress and observed cracking of cement has yet been demonstrated. To investigate if any relationship exists, a physical model has been developed which allows direct observation of damage in the cement layer on the femoral side of total hip replacement. The model contains medial and lateral cement layers between a bony surface and a metal stem; the tubular nature of the cement mantle is ignored. Five specimens were prepared and examined for cracking using manual tracing of stained cracks, observed by transmission microscopy: cracks were located and measured using image analysis. A mathematical approach for the prediction of residual stress due to shrinkage was developed which uses the thermal history of the material to predict when stress-locking occurs, and estimates subsequent thermal stress. The residual stress distribution of the cement layer in the physical model was then calculated using finite element analysis. Results show maximum tensile stresses normal to the observed crack directions, suggesting a link between residual stress and preload cracking. The residual stress predicted depends strongly on the definition of the reference temperature for stress-locking. The highest residual stresses (4-7 MPa) are predicted for shrinkage from maximum temperature, in this case, magnitudes are sufficiently high to initiate cracks when the influence of stress raisers such as pores or interdigitation at the bone/cement interface are taken into account (up to 24 MPa when calculating stress around a pore according to the method of Harrigan and Harris (J. Biomech. 24(11) (1991) 1047-1058)). We conclude that the damage accumulation failure scenario begins before weight-bearing due to cracking induced by residual stress around pores or stress raisers. (C) 2002 Elsevier Science Ltd. All rights reserved.