Observation of lubrication mechanisms in knee replacement: A pilot study

Abstract

The present study introduces a unique experimental approach for in situ observation of lubricant film formation in knee joint replacements. A knee joint simulator was designed and equipped with optical module based on fluorescent optical method for film thickness observation. The contact between the femoral knee metal implant and real-shaped polymer insert mimicking actual contact nature is observed. The shape of the polymer insert was fabricated with respect to the shape of original polyethylene insert to ensure corresponding contact conformity. Simple solutions of albumin and γ-globulin proteins as well as its mixture were used while the film thickness was studied as a function of time considering simplified flexion/extension motion with variable load over the cycle. Adequate fluorescent markers were employed enabling to observe one particular protein during each measurement. The results showed a clear importance of the interaction of proteins since the mixtures showed different results compared to simple solutions. Especially considering albumin protein, its behaviour was substantially affected by adding γ-globulin. Moreover, a satisfactory compliance with previous findings related to hip joint lubrication in terms of the behaviour of both proteins was found. Finally, the motivation for future experimental work is highlighted.