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

项目摘要 关节置换是我们体内所有植入物应用中要求最高的一种。最 常用的人工关节是全髋关节置换术（THR）和全膝关节置换术（TKR）， 在美国每年进行285，000例THR手术。各种聚合物，如超高分子量聚合物， 重量聚乙烯（UHMWPE）、聚醚醚酮（PEEK）和高密度聚乙烯（HDPE）具有 用于THR和TKR假体。虽然有许多优点，但聚合物可以吸收液体， 这成为接头润滑环境中的主要问题。聚合物表面的润湿 由于润滑最初可以减少磨损;然而，从长远来看，它可能会恶化机械性能。 性能和磨损率显着增加。磨损碎片可以融入周围环境中， 组织，并可引起组织刺激和炎症，导致骨吸收、骨丢失、植入 松动和骨折。植入物的使用寿命短，需要进行翻修手术， 昂贵、成功率较低并且可能引起额外的组织损伤。因此，长期 聚合物在长期暴露于润滑环境下的机械和摩擦学行为， TJR（全关节置换）假体的主要问题。该项目的总体目标是增加 TJR假体的寿命，特别是THR和TKR， 聚合物的摩擦学行为据推测，增加聚合物的疏水性质 可以改善其在润滑环境中的长期机械和摩擦学性能。提高 疏水特性，微纹理将应用于聚合物表面。表面纹理可以形成为 微坑（空腔或凹坑）或微柱（突起）。凹坑阵列可以改善摩擦学性能， 作为润滑剂储存器的性能;然而，它可能会恶化长期的机械性能， 聚合物的摩擦学性能由于表面的润湿持续延长的时间段。突出 微结构已经显示出显著改善聚合物的疏水性能。但这种 表面纹理非常易于磨损和磨蚀。拟议项目的具体目标是：1） 建立了聚合物表面织构与疏水性能之间的关系; 2）研究了聚合物表面织构对聚合物疏水性能的影响， 疏水性对各种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）使用数值建模分析纹理表面的接触力学;和5）设计 聚合物的最佳表面纹理，以改善疏水性，以及长期的机械和摩擦学性能 在各种润滑环境中的性能。拟议的项目将提高研究能力 PI和他的机构，得克萨斯A&M大学金斯维尔，这是一个西班牙裔服务机构。的 该项目还将鼓励代表性不足的学生在生物医学领域从事职业。

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.