Department of Mechanical Engineering, Rice University, Houston, Texas, USA.
Department of Orthopedic Surgery, The University of Texas Health Science Center at Houston, Houston, Texas, USA.
Med Eng Phys. 2023 Jan;111:103930. doi: 10.1016/j.medengphy.2022.103930. Epub 2022 Nov 23.
Despite showing promising functional outcomes for pelvic reconstruction after sarcoma resection, custom-made pelvic implants continue to exhibit high complication rates due to fixation failures. Patient-specific finite element models have been utilized by researchers to evaluate implant durability. However, the effect of assumed boundary and loading conditions on failure analysis results of fixation screws remains unknown. In this study, the postoperative stress distributions in the fixation screws of a state-of-the-art custom-made pelvic implant were simulated, and the risk of failure was estimated under various combinations of two bone-implant interaction models (tied vs. frictional contact) and four load cases from level-ground walking and stair activities. The study found that the average weighted peak von Mises stress could increase by 22-fold when the bone-implant interactions were modeled with a frictional contact model instead of a tied model, and the likelihood of fatigue and pullout failure for each screw could change dramatically when different combinations of boundary and loading conditions were used. The inclusion of additional boundary and loading conditions led to a more reliable analysis of fixation durability. These findings demonstrated the importance of simulating multiple boundary conditions and load cases for comprehensive implant design evaluation using finite element analysis.
尽管在肉瘤切除后的骨盆重建中显示出有前景的功能结果，但由于固定失败，定制的骨盆植入物仍然表现出高并发症率。研究人员已经利用患者特异性有限元模型来评估植入物的耐久性。然而，固定螺钉失效分析结果中假设的边界和加载条件的影响仍然未知。在这项研究中，模拟了最先进的定制骨盆植入物中固定螺钉的术后应力分布，并在平地行走和楼梯活动的四个载荷情况下，评估了两种骨-植入物相互作用模型（绑定与摩擦接触）和四种载荷情况下固定螺钉失效的风险。研究发现，当骨-植入物相互作用采用摩擦接触模型而不是绑定模型建模时，平均加权峰值 von Mises 应力可能增加 22 倍，并且当使用不同的边界和加载条件组合时，每个螺钉的疲劳和拔出失效的可能性会发生显著变化。包含更多的边界和加载条件可以更可靠地分析固定耐久性。这些发现表明，在使用有限元分析进行全面的植入物设计评估时，模拟多个边界条件和载荷情况非常重要。
