Wear performance of 1900 direct compression molded, 1020 direct compression molded, and 1020 sheet compression molded UHMWPE under knee simulator testing

Abstract

Ultra-high molecular weight polyethylene (UHMWPE) tibial inserts as used in total knee arthroplasy (TKA) are primarily manufactured in one of two ways: (1) machining the components from already consolidated resin or (2) directly consolidating the UHMWPE resin into the final product dimensions. Because these processes involve the introduction of heat and pressure, microscopic inconsistencies may arise and possibly influence wear behavior. To investigate how the two processes affect wear rate, direct, or net shape, molded and machined Ticona (NJ) GUR 1020 resin were compared in a wear test. Results indicate that there is no statistical difference in wear rates when comparing machined or molded inserts ( P = 0.41). Additional testing was then performed to investigate how resin selection influenced wear rate. GUR 1020 and Bassell (Brussels) 1900 were both direct molded into tibial inserts and subject to wear testing. At the conclusion of the wear test no statistical differences in wear rates were found between the molded GUR 1020 and Bassell 1900 resins ( P = 0.14) or between the machined GUR 1020 and molded Bassell 1900 ( P = 0.31) inserts. From this study, it is apparent that resin type and manufacturing method of tibial inserts do not significantly affect wear behavior. More influential parameters are likely post consolidation methods including crosslinking processes with varied irradiation dosage and thermal treatments, as well as sterilization methods which can substantially alter the final molecular structure and properties of the material.