Frictional Behavior of Artificial Cartilage Materials Lubricated with Synovia Constituents

The frictional behavior of candidate materials for artificial cartilage lubricated with constituents of synovia was examined in the one-directional sliding test and the knee joint simulator test. Artificial cartilage materials were used to preserve the fluid film between articulating surfaces by soft elastohydrodynamic lubrication (EHL), and to overcome tribological problems, such as loosening and wear, in total knee prostheses. However, some of them exhibited unacceptable high friction in the mixed lubrication region. In this study, we tested polyvinylalcohol (PVA) hydrogels and polyurethanes (PU) as artificial cartilage, and compared their frictional behavior with an ultrahigh molecular weight polyethylene (UHMWPE). Solutions of the sodium hyaluronate (HA) were used as lubricants, and serum proteins were added to examine their effects on the frictional behavior. As a result, the PVA hydrogel, which has high water content, showed favorable frictional behavior under the thin film condition, and serum proteins functioned as boundary lubricants. The artificial knee joint model with a PVA hydrogel (high water content) as arificial cartilage exhibited excellent frictional behavior during walking when it was lubricated by the HA solution with serum proteins.