A study of the wear resistance of three types of clinically applied UHMWPEfor total replacement hip prostheses

Ultra high molecular weight polyethylene (UHMWPE) is routinely used as one half of a bearing couple in clinical orthopaedic applications. This materia l is generally one of two grades, compression moulded GUR 1120, with a mole cular weight of 4.4 x 10(6) g mol(-1), or ram extruded GUR 4150HP with a mo lecular weight of 7.3 x 10(6) g mol(-1) although other grades are used as w ell. This study examines the effect of molecular weight and processing meth od by comparing the wear resistance of these two materials together with a non-standard extruded form of GUR 1120. Wear studies have been conducted ag ainst counterface surfaces which represent new and scratch-damaged femoral heads with bovine serum lubricant in a uniaxial reciprocating test configur ation. No difference in the wear resistance was found between any material when tested against smooth cobalt chrome counterfaces. On rough cobalt chro me counterfaces, although no statistically significant difference (P > 0.05 ) was found between the extruded and compression moulded GUR 1120, the extr uded GUR 4150HP had a consistently better wear resistance. These results ar e discussed with reference to previous wear studies as well as the physical and mechanical properties of these materials. (C) 1999 Elsevier Science Lt d. All rights reserved.