Effect of counterface roughness on the wear of conventional and crosslinked ultrahigh molecular weight polyethylene studied with a multi-directional motion pin-on-disk device
V. Saikko et al., Effect of counterface roughness on the wear of conventional and crosslinked ultrahigh molecular weight polyethylene studied with a multi-directional motion pin-on-disk device, J BIOMED MR, 57(4), 2001, pp. 506-512
The effect of counterface roughness on the wear of conventional gamma -ster
ilized, and electron-beam-crosslinked ultrahigh molecular weight polyethyle
ne was studied with a circularly translating pin-on-disk device. The counte
rfaces, CoCr disks, were either polished, or roughened so that they represe
nted the type of roughening and the range of surface roughness values (R-a
= 0.014-0.24 mum) observed in explanted femoral heads of total hip prosthes
es. The lubricant was diluted calf serum, and the test length 3 million cyc
les. A total of 24 tests were done. With both types of polyethylene, there
was a strong correlation between R-a, and wear factor k. The power equation
s were k = 5.87 x 10(-5)(R-a)(0.91) for conventional polyethylene (R-2 = 0.
94), and k = 7.87 x 10(-5)(R-a)(2.49) for crosslinked polyethylene (R-2 = 0
.82). Crosslinking improved wear resistance significantly. The wear of cros
slinked polyethylene against the roughest counterfaces was lower than the w
ear of conventional polyethylene against the polished counterfaces. Against
rough counterfaces, the wear of crosslinked polyethylene was an order of m
agnitude lower than that of conventional polyethylene. On the crosslinked p
olyethylene pins that were tested against polished counterfaces, remains of
original machining marks were still visible after the test. The average si
ze of wear particles produced by both types of polyethylene against rough c
ounterfaces was similar, 0.4 mum, whereas that produced by conventional and
crosslinked polyethylene against polished counterfaces was significantly s
maller, 0.2 and 0.1 mum, respectively. (C) 2001 John Wiley & Sons, Inc.