BIOTRIBOLOGY OF DIARTHRODIAL JOINTS

描述(由申请人提供)：近年来，我们对关节软骨润滑的基本工程科学的理解取得了很大进展，这主要是由于这笔赠款的前几个资助期(1995-2008年)所取得的进展。尽管在过去的几十年里提出了许多相互矛盾的假说，但从1930年的S开始，关节软骨间质流体加压驱动的基本润滑机制现在已经从理论和大量实验中得到确认和验证。加载时，接触关节层的间质流体显著加压，支持大部分接触力；因此，这种接触力只有一小部分由接触的胶原-蛋白多糖基质支撑，产生的摩擦力可以忽略不计，因此摩擦系数很低。虽然滑液中存在的边界润滑剂有助于进一步降低摩擦系数，但我们最近的研究表明，摩擦的主要减少是由间隙流体加压机制贡献的。如果间质流体压力下降，就像在某些加载条件下可能发生的那样，摩擦系数会急剧上升，我们的实验证据表明，软骨磨损也随之增加。由于有一个有效的理论框架解释了间质流体加压润滑的机理，因此有可能预测到间质流体加压作用减弱的加载条件。这一竞争性延续应用的具体目的是将这些基础科学发现转化为对关节半关节成形术具有重要临床意义的见解。半关节置换术是一种外科手术，将腹股沟关节的一半替换为光滑的不透水的人工关节表面，保留相对的关节层完整。临床经验表明，在半关节置换术后，骨关节炎自然关节层的退化速度可能比预期的要快。这项应用的总体目标是：a)调查半关节置换术是否因为未能促进足够的软骨间质流体加压而产生更高的摩擦系数而效果不佳；以及b)调查人工轴承表面是可变形的多孔渗透材料的半关节置换术是否能够产生比传统不渗透轴承材料更低的持续摩擦和磨损。其他目标旨在进一步加深我们对软骨润滑和磨损的基础科学理解，为设计改进的半关节成形术轴承表面奠定基础。

DESCRIPTION (provided by applicant): In recent years much progress has been made in our understanding of the basic engineering science of articular cartilage lubrication, driven significantly by the progress achieved in the prior funding periods (1995- 2008) of this grant. Though many competing hypotheses had been advanced over past decades, starting from the 1930's, a fundamental mechanism of lubrication driven by interstitial fluid pressurization of articular cartilage has now been identified and validated from theory and numerous experiments. Upon loading, the interstitial fluid of contacting articular layers pressurizes significantly, supporting most of the contact force; consequently, only a small fraction of this contact force is supported by the contacting collagen-proteoglycan matrixes, producing a negligible friction force, and thus a low friction coefficient. Though boundary lubricants present in synovial fluid help to further reduce the friction coefficient, our recent study has shown that the dominant reduction in friction is contributed by this interstitial fluid pressurization mechanism. If the interstitial fluid pressure subsides, as may occur under certain loading conditions, the friction coefficient rises dramatically, and evidence from our experiments indicates that cartilage wear increases concomitantly. Thanks to the availability of a validated theoretical framework explaining the mechanism of lubrication by interstitial fluid pressurization, it is possible to anticipate those loading conditions where interstitial fluid pressurization may subside. The specific aims of this competing continuation application are to translate these basic science findings into important, clinically relevant insights for joint hemiarthroplasties. Hemiarthroplasty is a surgical procedure that replaces one half of a diarthrodial joint with a smooth impermeable artificial bearing surface, leaving the apposing articular layer intact. Clinical experience suggests that, following hemiarthroplasty, degeneration of the native articular layer may progress at a faster rate than expected in osteoarthritis. The overall objective of this application is to a) investigate whether hemiarthroplasties fare poorly because they produce elevated friction coefficients by failing to promote sufficient cartilage interstitial fluid pressurization; and b) investigate whether hemiarthroplasties where the artificial bearing surface is a deformable porous-permeable material can produce lower sustained friction and wear than traditional impermeable bearing materials. Additional objectives aim to further deepen our basic science understanding of cartilage lubrication and wear, setting the stage for designing improved bearing surfaces for hemiarthroplasties.