Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.
Department of Mechanical Engineering, University of Alberta, Edmonton, Alberta, Canada.
J Mech Behav Biomed Mater. 2022 Jan;125:104936. doi: 10.1016/j.jmbbm.2021.104936. Epub 2021 Oct 28.
Talus implants can be utilized in cases of talus avascular necrosis and has been regarded as a promising treatment method. However, existing implants are made of stiff materials that directly oppose natural cartilage. The risk of long-term cartilage wear and bone fracture from the interaction between the cartilage and stiff implant surfaces has been documented in post-hemiarthroplasty of the hip, knee and ankle joints. The aim is to explore the effects of adding a layer of compliant material (polycarbonate-urethane; PCU) over a stiff material (cobalt chromium) in talus implants. To do so, we obtained initial ankle geometry from four cadaveric subjects in neutral standing to create the finite element models. We simulated seven models for each subject: three different types of talus implants, each coated with and without PCU, and a biological model. In total, we constructed 28 finite element models. By comparing the contact characteristics of the implant models with their respective biological model counterparts, our results showed that PCU coated implants have comparable contact area and contact pressure to the biological models, whereas stiff material implants without the PCU coating all have relatively higher contact pressure and smaller contact areas. These results confirmed that adding a layer of compliant material coating reduces the contact pressure and increases the contact area which in turn reduces the risk of cartilage wear and bone fracture. The results also suggest that there can be clinical benefits of adding a layer of compliant material coating on existing stiff material implants, and can provide valuable information towards the design of more biofidelic implants in the future.
距骨植入物可用于距骨缺血性坏死的病例，被认为是一种有前途的治疗方法。然而，现有的植入物由刚性材料制成，与天然软骨直接相对。髋关节、膝关节和踝关节半关节成形术后，已有文献记录了软骨与刚性植入物表面之间长期的软骨磨损和骨折风险。目的是探讨在距骨植入物中添加一层柔顺材料（聚碳酸酯-聚氨酯；PCU）对刚性材料（钴铬）的影响。为此，我们从四个中立位的尸体标本中获取初始踝关节几何形状，以创建有限元模型。我们为每个受试者模拟了七种模型：三种不同类型的距骨植入物，每种都涂有和不涂有 PCU，以及一种生物模型。总共构建了 28 个有限元模型。通过比较植入物模型的接触特性与其各自的生物模型对应物，我们的结果表明，涂有 PCU 的植入物的接触面积和接触压力与生物模型相当，而没有 PCU 涂层的刚性材料植入物的接触压力相对较高，接触面积较小。这些结果证实，添加一层柔顺材料涂层可以降低接触压力并增加接触面积，从而降低软骨磨损和骨折的风险。结果还表明，在现有的刚性材料植入物上添加一层柔顺材料涂层可能具有临床益处，并为未来更仿生植入物的设计提供有价值的信息。
