A Study upon Durability of the Artificial Knee Joint with PVA Hydrogel Cartilage

Abstract

An experimental investigation upon the durability of the artificial knee joints with PVA hydrogel articular cartilage is presented. PVA hydrogel is manufactured by the cyclic freezing/thawing and annealing methods; femoral component is a disc made in stainless steel. This work is original in the meaning that: a weighting method to differentiate the worn mass from the mass of exuded water for PVA hydrogel is suggested; an original wear test rig, which simulates the anterior-posterior displacement of the knee motion during walking is proposed; wear factor variation against the number of walking cycles (durability curve) for PVA hydrogel is reported. The lowest wear factor obtained is on order of 10^-6-10^-5mm³/Nm. PVA hydrogel with reduced water content (45-50%) produces the smallest wear factor, for the same polymerization degree. Reduction of the wear factor is on order of 10⁴ when the PVA polymerization degree increases from 1800 to 12300. PVA hydrogel manufactured on a hydrophobic substrate (PTFE) presents a 16-27% lower wear factor than that prepared on a hydrophilic substrate (glass). When layer thickness increases from 2 to 3.6mm, the wear factor reduction is 18%. Influence of the standing interval in start-up conditions on the wear factor is also investigated.