BIOTRIBOLOGY OF DIARTHRODIAL JOINTS

描述（由申请人提供）：近年来，在我们对关节软骨润滑的基础工程科学的理解方面取得了很大进展，这是由本基金先前资助期间（1995 - 2008）取得的进展所推动的。虽然在过去的几十年中已经提出了许多相互竞争的假设，但从20世纪30年代开始，由关节软骨的间质液加压驱动的润滑的基本机制现在已经从理论和许多实验中被确定和验证。在加载时，接触关节层的间质液显著加压，支撑大部分接触力;因此，只有一小部分接触力由接触胶原蛋白-蛋白聚糖基质支撑，产生可忽略的摩擦力，因此摩擦系数较低。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，摩擦的主要降低是由这种间质液加压机制造成的。如果组织间液压力下降，如在某些负荷条件下可能发生的，摩擦系数急剧上升，并且来自我们的实验的证据表明软骨磨损伴随增加。由于可用的有效的理论框架解释润滑机制的间隙液加压，它是可能的，以预期这些负载条件下，间隙液加压可能消退。这一竞争性延续申请的具体目标是将这些基础科学发现转化为关节半关节成形术的重要临床相关见解。半关节置换术是一种外科手术，用光滑的不可渗透人工关节面置换半个关节，使对置关节层保持完整。临床经验表明，半关节置换术后，自体关节层的退化可能比骨关节炎的预期进展速度更快。本申请的总体目标是a）研究半关节成形术是否由于未能促进充分的软骨间质液加压而产生较高的摩擦系数而表现不佳;以及B）研究人工关节面为可变形多孔渗透材料的半关节成形术是否可以产生比传统不可渗透关节面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关节面奠定基础。 公共卫生相关性：美国每年进行超过120，000例髋关节半关节置换术。本申请的两个主要目的是（1）根据摩擦和磨损原理，为观察结果提供解释，即半关节成形术导致手术关节的原生关节面磨损比骨关节炎中预期的磨损更快;（2）提出一种工程解决方案，用于重新设计半关节成形术以减少摩擦和磨损。如果成功，这些研究可以导致半髋关节置换术的显著改善。

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. PUBLIC HEALTH RELEVANCE: There are more than 120,000 hip hemiarthroplasties performed each year in the US. The two principal aims of this application are to (1) provide an explanation for the observation that hemiarthroplasties lead to a faster wear of the native articular surface of an operated joint than otherwise expected in osteoarthritis, based on principles of friction and wear; and (2) propose an engineering solution for redesigning hemiarthroplasties to reduce friction and wear. If successful, these studies can lead to a significant improvement in hemiarthroplasty procedures.