THE INFLUENCE OF LUBRICATION ON WEAR MECHANISM OF THE DIE DRAWN ULTRA HIGH MOLECULAR WEIGHT POLYETHYLENE IN KNEE REPLACEMENT APPLICATION

Abstract

Polymerized material such as Ultra High Molecular Weight Polyethylene (UHMWPE) is commonly used as a bearing cushion with titanium alloy, austenistic stainless steel, ceramic and cobalt chrome alloy to be used for the tibial and femoral components in knee replacement application. As a biomaterial product these substances must comprise a wear resistance capacity.

This study was conducted to observe the wear product and wear factor of the die drawn GUR 1120 UHMWPE that was rubbed against nitrogen based-ion implantation of cobalt chrome alloy (irradiated at 100 Kev for 90 min) and employment of bovine serum in various concentration as lubricant.

The wear mechanism was tested with the application of bovine calf serum pre-conditioned similar to synovial fluids in human knee. The experiment was tested with a Pin on Plate Unidirectional Reciprocating Movement with various lubricant protein concentrations applied. The ‘A’ lubricant is a serum with protein concentration of 19.3 g/L and the ‘B’ lubricant is a serum with protein concentration of 30 g/L; these lubricants were then compared after the reciprocating movement test with constant load of 180 N force, 116.5 mm/s constant friction velocity and 25 mm average gait length with total of 35 km distance covered.

This study showed that protein concentration augmentation would decrease the wear factor up to 300%. This value was derived after increasing the protein concentration of the lubricant (from 19.3 g/L to 30 g/L) which then altered the wear factor from 5.12×10-7 mm3/Nm to 1.71×10-7 m3/Nm respectively.