Engineering functional partial joint replacement: a soft solution to a hard problem

关节炎是一个常见的问题，通常的治疗方法包括在关节两侧用硬金属替换关节表面，用介入的塑料或陶瓷替换关节表面。虽然成功了，但随着时间的推移，这些都失败了，进一步的手术是广泛的，结果是不可预测的。在很大一部分病例中，关节炎始于关节一侧的一个局部区域，在这种情况下，可以替换其中一个接触的关节软骨表面。这是一种侵入性较小的方法，可以让患者更快地恢复日常活动。目前，这些治疗方案(称为半关节置换术)包括用硬金属表面替换软关节软骨，并在治疗继发于创伤和/或关节炎的关节问题中很常见。目前存在用于髋关节、膝关节、脚踝和肩部的半关节置换术，但结果有些不可预测。体外研究表明，用坚硬的、金属的、轴对称的半关节置换术取代相对顺应性较好的软骨覆盖的天然表面，可以减少关节接触面积，比天然关节减少多达三分之二，并产生更高的峰值接触应力。异常的接触力学可能会促进天然软骨的退化和侵蚀，导致持续性疼痛、僵硬和功能丧失。毫无疑问，发生在装置-软骨界面的相互作用是植入成功的关键。在利兹大学，我们最近开发了一种新的两步法，用于理想化的金属和聚合物生物材料的表面引发功能化。它利用软物质材料的概念来产生一种在结构和化学上类似于磷脂双层的材料体系。这些凝胶层使我们能够产生相对较厚(~3微米)和柔软的润滑层(微米和0.01微米)，尽管具有单一的模数和有限的承载能力(有效接触压力高达~20兆帕)。然而，利用这种方法，这些层的性质可以很容易地通过合成参数来改变，并且很容易转化为低模数的生物材料(即PEEK)。这为未来的设备和应用提供了巨大的机会，在这些设备和应用中，种植界面的接触需要与软骨或软组织相适应。本研究的目标包括：1.开发一种坚固的多模软-水基界面，当滑动到关节软骨上时，能够承受在上述应用中观察到的常见关节反作用力。这将在2D表面(PEEK和CoCrMo)上完成，并使用一系列表面敏感性(FTIR、XPS、低温扫描电子显微镜)、机械(AFM、纳米压痕)和功能评估(摩擦学、腐蚀)进行表征。研究添加针对感染或局限性关节炎的靶向治疗药物(分别为硫酸庆大霉素或氨基葡萄糖)的可行性。翻译并演示建议的技术在临床相关组件上的功能。这些设备的耐用性将使用关节模拟器套件来确定。

Arthritis is a common problem and typically treatment includes replacing the articular surfaces with hard metal on both sides of the joint with intervening plastic or ceramic. Although successful, with time these fail and further surgery is extensive with unpredictable outcomes. In a significant proportion of cases, the arthritis starts as a focal area on one side of the joint and in such cases, the replacement of one of the contacting articular cartilage surfaces is possible. This is less invasive and allows the patient to return to day to day activities quicker. Currently, these treatment options (known as hemiarthroplasty) include replacing the soft articular cartilage with a hard metallic surface, and are common in the treatment of joint problems secondary to trauma and/or arthritis. Hemiarthroplasty devices for hip, knee, ankle and shoulder currently exist but with somewhat unpredictable results. In vitro studies have shown that replacing the relatively compliant cartilage-covered native surface with a stiff, metallic, axisymmetrical hemiarthroplasty implant can reduce joint contact area by up to two thirds compared with the native joint and cause higher peak contact stress. The abnormal contact mechanics may promote degeneration and erosion of the native cartilage leading to persistent pain, stiffness, and loss of function. Without a doubt, the interactions occurring at the device-cartilage interface are key to successful implantation.At Leeds, we have recently developed a novel two step method for the surface initiated functionalisation of idealised metallic and polymer biomaterials. This exploits soft matter materials concepts to produce a materials system similar in structure and chemistry to a phospholipid bilayer. These gel-type layers have enabled us to produce a relatively thick (~ 3 micrometers) and soft lubricious surface layer (micro < 0.01), although with a single moduli and limited load bearing capacity (effective up to contact pressures of ~ 20 MPa). However with this methods, the properties of these layers can be varied easily through synthesis parameters and are easily translatable to lower moduli biomaterials (ie PEEK). This presents tremendous opportunities for future devices and application where contact of implant interfaces need to be compliant with cartilage or soft tissues. Objectives of this studentship include:1. Develop a robust multi-moduli soft - aqueous based interface capable of withstanding common joint reaction forces observed in the aforementioned applications when slid against articular cartilage. This will be completed on 2D surfaces (PEEK & CoCrMo) and characterised using a range of surface sensitive (FTIR, XPS, cryo-SEM), mechanical (AFM, Nano-indentation) and functional assessments (Tribology, Corrosion).2. Investigate the feasibility of adding therapeutic agents for the targeted treatment of infection or localised arthritis (gentamicin sulphate or glucosamine sulphate, respectively).3. Translate and demonstrate the functionality of the proposed technology on clinically relevant components. The durability of these devices will be determined using the suite of joint simulators.