Wear simulation of UHMWPE for total hip replacement with a multidirectional motion pin-on-disk device: Effects of counterface material, contact area, and lubricant

Abstract

The wear of nonirradiated ultra-high molecular weight polyethylene (UHMWPE) was studied with a circularly translating pin-on-disk (CTPOD) device. With this simple device, the wear of the acetabular cup is simulated. Two shapes of a polyethylene pin were used: flat wear faces of 3.0 and 8.9 mm in diameter. The load was always 70.7 N. Tests were done against stainless steel plates in serum, albumin, and gamma-globulin lubricants and against alumina plates in serum. With 3.0-mm-in-diameter wear faces, the wear factors were an order of magnitude lower than the average clinical wear factors of polyethylene acetabular cups. With 8.9-mm-in-diameter wear faces, the wear factors and wear mechanisms were consistent with clinical ones. The mean wear factor against stainless steel in serum was 1.46 times higher than that against alumina, and the difference was statistically significant. The mean wear factors in albumin and gamma globulin were close to that in serum; the differences were not statistically significant. The results indicate that albumin and gamma globulin are the fractions of synovia that influence the wear of polyethylene. A practical test parameter combination for the CTPOD device has now been established for future studies of modified and new materials and of lubricants.

Effect of contact pressure on wear and friction of ultra-high molecular weight polyethylene in multidirectional sliding

“…As the degradation effects in the present tests were minimal compared with long duration tests, the measured μ values were much higher than those measured in longer tests. For example, the coefficient of friction in the present tests was 0.26-0.34 with 1.1 MPa, while it was as low as 0.05 after several days of running in the earlier wear tests [12,14]. At low p values, mixed lubrication mechanism probably prevailed, as μ increased with increasing p. On the other hand, above 1.1 MPa, the decrease of μ with increasing p suggested dry sliding.…”

“…From the signal of the calibrated transducer-amplifier system, the coefficient of friction could be calculated. Since the slide track radius was 5 mm and the load limit of the transducer was 30 N, the maximum friction force that could be measured was shown that if several days are run with the same serum, friction may decrease for days due to serum degradation [12,14].…”

A Hip Wear Simulator with 100 Test Stations

“…If miniature specimens were used, it would not be too difficult to pack even a much higher number of test stations than 100 into one CTPOD device, but it has been shown that the wear behaviour of a miniaturized contact surface is quite different from that of actual bearing surfaces in vivo [18]. Note that the Super-CTPOD specimens are not miniaturized.…”

“…Excessive pressure is likely to lead to abnormal thermal phenomena [18]. Overheating of the tribocontact is a pitfall to be avoided in wear testing.…”

The effects of lubricant composition on in vitro wear testing of polymeric acetabular components

“…32,33 Antibiotics and fungicides are often used to retard bacterial and fungal growth in lubricants but there is no evidence indicating that this is effective in reducing the overall degradation of serum. On the contrary, Liao and co-workers 34,35 and Lu and McKellop 36 have shown that serum degradation is caused predominantly by frictional heating.…”