Improving the Long-term Mechanical and Tribological Performances of Polymers for Total Joint Replacement Applications

项目总结 关节置换术是人体所有植入物应用中要求最高的之一。最多的 常用的人工关节有全髋关节置换(THR)和全膝关节置换(TKR)。 在美国，每年有28.5万例THR手术。各种聚合物，如超高分子 重量聚乙烯(UHMWPE)、聚醚醚酮(PEEK)和高密度聚乙烯(HDPE) 已用于THR和TKR假体。尽管有许多优点，但聚合物可以吸收液体， 这在关节的润滑环境中成为一个主要问题。聚合物表面的润湿 由于润滑最初可以减少磨损，但从长远来看，它可能会恶化机械性能 并显著提高了磨损率。磨损的碎屑会进入周围环境 组织，并可引起组织刺激和炎症，导致骨吸收，骨丢失，种植 松动，骨折。植入物的寿命短，需要进行翻修手术，这比 价格昂贵，成功率较低，可能会导致额外的组织损伤。因此，从长远来看， 聚合物在长时间接触润滑环境下的力学和摩擦学行为 TJR(全关节置换)假体的主要问题。这个项目的总体目标是增加 TJR假体的寿命，特别是THR和TKR，通过改善长期机械和 聚合物的摩擦学行为。假设增加聚合物的疏水性能 可改善其在润滑环境中的长期机械和摩擦学行为。为了改善 疏水性能、微观织构将应用于聚合物表面。表面粗糙度可形成为 微坑(凹坑或酒窝)或微柱(突起)。一系列的酒窝可以提高摩擦学性能 作为润滑剂储液器的性能；然而，它可能会恶化长期机械和 由于长时间接触表面而导致的聚合物的摩擦学性能。突出的 微观织构可以显著改善聚合物的疏水性能。然而，这样的 表面纹理非常容易磨损和磨损。拟议项目的具体目标是：1) 建立聚合物表面织构与疏水性能之间的关系；2)研究 疏水性对不同环境条件下长期力学行为的影响；3)研究 不同润滑条件下聚合物表面织构与摩擦学性能的关系 条件；4)用数值模拟分析纹理表面的接触机理；5)设计 聚合物的最佳表面纹理可改善疏水性，并具有长期机械和摩擦学性能 在各种润滑环境中的性能。拟议的项目将提高研究能力。 国际和平协会和他的机构，德克萨斯农工大学金斯维尔，这是一个西班牙裔服务机构。这个 该项目还将鼓励代表不足的学生在生物医学领域追求职业生涯。

PROJECT SUMMARY Joint replacement is one of the most demanding of all the implant applications in our body. The most commonly used artificial joints are total hip replacement (THR) and total knee replacement (TKR), with over 285,000 THR surgeries performed every year in the USA. A variety of polymers, such as ultra high molecular weight polyethylene (UHMWPE), polyetheretherketone (PEEK), and high density polyethylene (HDPE) have been used for THR and TKR prostheses. Although there are many advantages, polymers may absorb liquid, which becomes a major issue in the lubricated environment of the joints. The wetting of the polymer surface due to lubrication can reduce the wear initially; however, in the long run, it may deteriorate the mechanical properties and increase the wear rate significantly. The wear debris can incorporate into the surrounding tissues, and can cause tissue irritation and inflammation, leading to bone resorption, bone loss, implant loosening, and fracture of bone. The short lifespan of implants necessitates revision surgery, which is more expensive, has lower success rates, and may induce additional tissue damage. Therefore, the long-term mechanical and tribological behaviors of polymers under extended exposure to lubricated environment are major concerns in TJR (total joint replacement) prostheses. The overarching goal of this project is to increase the longevity of TJR prostheses, specifically THR and TKR, by improving the long-term mechanical and tribological behaviors of polymers. It is hypothesized that increasing the hydrophobic properties of a polymer can improve its long-term mechanical and tribological behaviors in a lubricated environment. To improve the hydrophobic properties, micro-texture will be applied on the polymer surface. Surface texture can be formed as micro-pit (cavity or dimple) or micro-pillar (protrusion). An array of dimples can improve the tribological performance by acting as lubricant reservoirs; however, it can deteriorate the long-term mechanical and tribological performances of a polymer due to wetting of the surface for an extended period of time. Protruding micro-texture has shown to improve the hydrophobic properties of polymers significantly. However, such surface textures are highly prone to wear and abrasion. The specific aims of the proposed project are to: 1) establish relationship between surface texture and hydrophobic properties of polymers; 2) study the effect of hydrophobicity on long-term mechanical behavior in various environmental conditions; 3) investigate the relationship between surface texture and tribological performance of polymers under various lubricated conditions; 4) analyze the contact mechanics of textured surfaces using numerical modeling; and 5) design optimum surface texture for polymers to improve hydrophobicity, and long-term mechanical and tribological performances in various lubricated environments. The proposed project will enhance the research capabilities of the PI and his institution, Texas A&M University-Kingsville, which is a Hispanic serving institution. The project will also encourage the underrepresented students to pursue career in the biomedical field.