Effect of lubricant composition on the fatigue properties of ultra-high molecular weight polyethylene for total knee replacement.

Ultrahigh molecular weight polyethylene (UHMWPE) fatigue is a critical factor affecting the longevity of total knee replacement (TKR) bearings. With the increased need for laboratory studies to mimic near in vivo conditions for accurate characterization of material performance, the present study investigated the role of hyaluronic acid (HA) in testing lubricant on the crack growth response of UHMWPE. It was hypothesized that the change in lubricant viscosity as a result of HA would affect the fatigue life of the polymer. A fracture mechanics approach as per ASTM E 647 was adopted for this study. Surface micrograph and surface chemistry analyses were employed to study the micromechanisms of fatigue failure and protein adsorption of the specimen surfaces. Rheological analysis indicated that the addition of HA to diluted bovine serum increased testing lubricant viscosity. HA concentrations of 2.22, 0.55, and 1.5 g/l closely matched the viscosity ranges reported for osteoarthritis, rheumatoid arthritic diseased joint fluid, and periprosthetic fluids respectively. Results showed that the addition of HA to standard diluted bovine serum lubricants, in concentrations similar to that of periprosthetic fluid, delayed crack initiation and crack growth during fatigue testing.