Degradation and Wear of Ultra-High-Molecular-Weight Polyethylene

Abstract

A ten-station joint simulator was used to examine the wear properties of 18 total hip prostheses. The wear rates of polyethylene acetabular cups bearing against titanium alloy femoral components were compared to those with either Type 316 stainless steel or cobalt-chrome alloy controls. Three titanium alloy prostheses and three controls were tested from three different manufacturers. Wear was determined by weighing the acetabular cups, using soak-controls to correct for fluid absorption. One million cycles were run under physiological loading, with bovine serum lubrication. For two of the three sets of prostheses, the titanium alloy generated higher mean polyethylene wear rates than the controls. However, the difference was not statistically significant (p > 0.05). The titanium alloy components showed more extensive surface abrasion than either the stainless steel or cobalt-chrome components. This appeared to be an artifact of joint simulator testing, since such extensive surface abrasion was not observed on numerous prostheses removed from patients after several years of use. The third set of titanium alloy prostheses, which had been subjected to a special surface hardening process, showed virtually no surface abrasion, and the mean polyethylene wear rate was identical to that with the cobaltchrome controls. All of the polyethylene wear rates were in the range generally reported for total hip prostheses in clinical use.

A multidirectional motion pin-on-disk wear test method for prosthetic joint materials

“…Realistic wear rates and wear mechanisms have been obtained in serum-lubricated tests with the USC hip wear simulator 21,22 in which the motion is very different from the typical motion of the hip joint in walking. In the USC device, a typical wear rate for a stainless steel on polyethylene prosthesis was about 26 mg per one million cycles.…”

Wear of the polyethylene acetabular cup: Metallic and ceramic heads compared in a hip simulator

“…The use of protein-containing lubricants in laboratory wear tests has been emphasized by McKellop and Clarke (1985). in order to prevent the formation of a polyethylene transfer layer on the counterface, since a transfer layer was not observed on retrieved femoral components, but a heavy transfer occurred in water or saline lubricated, statically loaded, pin-on-disk tests.…”

“…The tests should naturally be performed at body temperature. Only 1 design, Link's 32-mm Co-Cr-Mo on UHMWPE, was included both in the present study and in the study based on the USC simulator (McKellop and Clarke 1985). In the latter report the components were not specified by catalogue numbers, though, and the duration of a test was only 1 million cycles and the peak value of the load curve was only 2 kN.…”

A Hip Wear Simulator with 100 Test Stations

“…All this is true despite the fact that the CTPOD test employs a flat-onflat contact instead of a ball-in-socket contact of the actual prosthetic hip. Interestingly, the CTPOD motion is analogous to that of the most widely used hip joint simulator, the biaxial rocking motion design, originally introduced by McKellop and Clarke [6]. The type of loading was found to be clearly less important than the type of motion [7].…”