A new process to improve the mechanical performance of crosslinked UHMWPE injoint replacement prostheses

虽然全关节置换假体在80多年来在为患者提供活动性方面取得了巨大成功， 骨关节炎患者，术后并发症，如无菌性松动，脱位和感染仍然存在 这些问题通常导致昂贵且复杂的翻修手术。这项建议的目的是 解决全髋关节置换手术第二大常见并发症--植入物脱位。一 减少脱位发生率的解决方案是增加股骨头的直径， 降低超高分子量聚乙烯组分的厚度。的后果 这些设计变化是关节面面积越大，可能导致体积磨损越大， 较薄的聚乙烯部件经受较高的应力，具有较大的断裂可能性。的 在90年代后期引入的高耐磨性交联聚乙烯已经解决了磨损问题 但是这些交联材料也具有较低的机械韧性，限制了较薄聚乙烯的使用 件.为了解决这个问题，我们开发了一种受专利保护的快速加压工艺， 具有极大地增加交联聚乙烯的延展性而不损害其强度的潜力。 我们假设，含有交联聚乙烯的抗氧化剂的压力淬火将超过 韧性、强度和抗疲劳裂纹扩展性 损害耐磨性或抗氧化性。我们对压力淬火的初步数据和过去的研究 热淬火表明，一个伪流体静力学过程中，熔融，交联聚乙烯， 可以使用简单的液压机在大圆筒上进行快速加压和结晶， 可容易地转化为制造过程，提供本体交联聚乙烯， 可以对植入物进行机加工。该建议的具体目标是：目标1将优化压力淬火 含维生素E的交联聚乙烯的工艺，并使用 拉伸、断裂韧性和冲击试验。目标2将使用加速老化来证明 含维生素E的压力淬火交联聚乙烯具有抗氧化性。目标3将包括 长期磨损和疲劳裂纹扩展测试，以验证压力淬火，维生素E含有 交联聚乙烯保持耐磨性并具有更高的抗疲劳裂纹扩展性。 该建议有可能指导全髋关节置换组件的制造， 可能会脱位，但不会影响耐磨性或机械损坏的风险。此外，委员会认为， 承受更高应力的膝关节和肩关节部件可以更好地保护， 机械损伤长期计划是利用该材料配方研究来研究植入物 在较大项目中的设计，可以减少脱位的发生率，而不会影响磨损或 机械损伤更持久的关节置换将大大有利于患有骨关节炎的老年人， 需要这些植入物来移动。

While total joint replacement prostheses have been a great success for over 80 years in providing mobility to patients with osteoarthritis, post-surgery complications like aseptic loosening, dislocation and infections remain as problems, often leading to costly and complicated revision surgery. The objective of this proposal is to address implant dislocation, the second most common complication for total hip replacement surgeries. One solution to reduce the incidence of dislocation is to increase the diameter of the femoral head and accordingly decrease the thickness of the ultra-high molecular weight polyethylene component. The consequences of these design changes are that the larger articular surface area could lead to higher volumetric wear and the thinner polyethylene components are subjected to higher stresses with a greater likelihood for fracture. The highly wear resistant crosslinked polyethylenes introduced in the late 90’s have addressed the issue of wear but these crosslinked materials also have lower mechanical toughness, limiting the use of thinner polyethylene components. To solve this problem, we have developed a patent-protected rapid-pressurization process which has the potential to greatly increase the ductility of crosslinked polyethylene without compromising its strength. We hypothesize that pressure-quenching of antioxidant containing crosslinked polyethylene will exceed the toughness, strength and resistance to fatigue crack propagation over uncrosslinked polyethylene without compromising wear or oxidation resistance. Our preliminary data on pressure quenching and past research on thermal quenching show that a pseudo-hydrostatic process in which the melted, crosslinked polyethylene is rapidly pressurized and crystallized can be performed on large cylinders using a simple hydraulic press, which is easily translatable into a manufacturing process, providing bulk crosslinked polyethylene from which implants can be machined. The specific aims of the proposal are: Aim 1 will optimize the pressure-quenching process of Vitamin E containing crosslinked polyethylene and verify its superior mechanical properties using tensile, fracture toughness and impact tests. Aim 2 will use accelerating aging to demonstrate that the pressure-quenched Vitamin E containing crosslinked polyethylene is oxidation-resistant. Aim 3 will include long-term wear and fatigue crack propagation tests to verify that pressure-quenched, Vitamin E containing crosslinked polyethylene preserves wear resistance and has a higher resistance to fatigue crack propagation. This proposal has the potential to guide in the fabrication of total hip replacement components which are less likely to dislocate, without compromising either wear resistance or risk for mechanical damage. Furthermore, knee and shoulder joint components, which are subjected to higher stresses could be better protected from mechanical damage. The long-term plan is to leverage this materials-formulation study to investigate implant designs in a larger project that can reduce the incidence of dislocation without compromising either wear or mechanical damage. Longer lasting joint replacements would greatly benefit the elderly with osteoarthritis who require these implants for mobility.