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

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 shape s of a polyethylene pin were used: flat wear faces of 3.0 and 8.9 mm in dia meter. 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 poly ethylene acetabular cups. With 8.9-mm-in-diameter wear faces, the wear fact ors and wear mechanisms were consistent with clinical ones. The mean wear f actor against stainless steel in serum was 1.46 times higher than that agai nst alumina, and the difference was statistically significant. The mean wea r factors in albumin and gamma globulin were close to that in serum; the di fferences were not statistically significant. The results indicate that alb umin and gamma globulin are the fractions of synovia that influence the wea r of polyethylene. A practical test parameter combination for the CTPOD dev ice has new been established for future studies of modified and new materia ls and of lubricants. (C) 2000 John Wiley & Sons, Inc.