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

Abstract

The effect of counterface roughness on the wear of conventional gamma-sterilized, and electron-beam-crosslinked ultrahigh molecular weight polyethylene was studied with a circularly translating pin-on-disk device. The counterfaces, CoCr disks, were either polished, or roughened so that they represented the type of roughening and the range of surface roughness values (R(a) = 0.014-0.24 microm) observed in explanted femoral heads of total hip prostheses. The lubricant was diluted calf serum, and the test length 3 million cycles. 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 equations 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 crosslinked polyethylene against the roughest counterfaces was lower than the wear of conventional polyethylene against the polished counterfaces. Against rough counterfaces, the wear of crosslinked polyethylene was an order of magnitude lower than that of conventional polyethylene. On the crosslinked polyethylene pins that were tested against polished counterfaces, remains of original machining marks were still visible after the test. The average size of wear particles produced by both types of polyethylene against rough counterfaces was similar, 0.4 microm, whereas that produced by conventional and crosslinked polyethylene against polished counterfaces was significantly smaller, 0.2 and 0.1 microm, respectively.

Effect of CoCr Counterface Roughness on the Wear of UHMWPE in the Noncyclic RandomPOD Simulation

“…This observation is in agreement with an earlier cyclic pinon-disk study that was restricted to hip wear [16]. The size and shape of the wear particles, which are important from the point of view of adverse clinical reactions [20], were also close to those analyzed earlier [4,16,19] and in agreement with clinical findings [21]. The wear factor of crosslinked UHMWPE was 80 to 86 per cent lower than that of conventional UHMWPE in the hip wear simulation, and 87 to 96 per cent lower in the knee wear simulation.…”

“…The wear factors of crosslinked UHMWPE against the roughest counterfaces were of the same order of magnitude as the wear factors of conventional UHMWPE against the polished counterfaces, or lower. This observation is in agreement with an earlier cyclic pinon-disk study that was restricted to hip wear [16]. The size and shape of the wear particles, which are important from the point of view of adverse clinical reactions [20], were also close to those analyzed earlier [4,16,19] and in agreement with clinical findings [21].…”

“…Used serum samples were digested, and UHMWPE wear particles were isolated on polycarbonate membrane filters of 0.05 µm pore size and analyzed with a field emission scanning electron microscope (JEOL 6335 F FE-SEM) as described elsewhere [4,16,19]. 7 …”

“…Crosslinking of UHMWPE by high-dose irradiation and elimination of concomitant free radicals by various methods, including thermal treatments, has been shown to increase the clinical wear resistance significantly [11,12]. However, not only conventional but also crosslinked UHMWPEs may show substantial wear against rough counterfaces [13][14][15][16][17][18]. The principal motivation for the present study was to learn how roughening affects the wear of conventional and highly crosslinked UHMWPEs in the non-cyclic hip and knee wear simulation in comparison with earlier cyclic wear studies.…”

Mechanical and tribological behavior of silicon nitride and silicon carbon nitride coatings for total joint replacements

“…When coatings were deposited on CoCr, the failure loads were only half of those on Si-wafers, which indicates that further optimization of the coating adhesion to CoCr is possible. , CrN-on-CrN and CrCN-on-CrCN, and performed better than TiNon-TiN and CoCr-on-CoCr (Williams et al, 2003), and were also superior to most CoCr-on-UHMWPE ( (Saikko et al, 2001), summary table p. 512). In relation to r.f.…”