Friction and wear characteristics of PVA/PVP hydrogels as synthetic articular cartilage

Many hydrogels have been tested as articular cartilage replacements and other tissue replacements. In the present study, the effect of load and lubricant on the tribological characteristics of poly(vinyl alcohol)/poly(vinyl pyrrolidone) (PVA/PVT) hydrogels have been investigated in a pin-on-disk setup under physiologic loading conditions. Cobalt-chromium pins were articulated against PVA/PVT hydrogels under three different load levels 100 N, 125 N, 150 N in bovine serum and synovial fluid lubrication. Each test lasted 100,000 cycles. The average coefficient of friction for the tests conducted in bovine serum was 0.1 ± 0.023, while it was 0.04 ± 0.023 in the case of synovial fluid lubrication. Wear was quantified by comparing the dry polymer mass of the hydrogel samples before and after the wear tests. Wear was observed on the non-articulating surface of the PVA/PVP hydrogels with an average of 6.1% dry polymer loss for all the tests. The results also suggest a transition in the lubricating mechanism at the pin-hydrogel interface at the critical 125 N load.