Multidirectional Wear and Impact-to-wear Tests of Phospholipid-polymer-grafted and Vitamin E-blended Crosslinked Polyethylene: A Pilot Study

Abstract

Background Modifying the surface and substrate of a crosslinked polyethylene (CLPE) liner may be beneficial for high wear resistance as well as high oxidative stability and excellent mechanical properties, which would be useful in contributing to the long-term performance of orthopaedic bearings. A grafted poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) layer on a vitamin E-blended crosslinked PE (HD-CLPE[VE]) surface may provide hydrophilicity and lubricity without compromising the oxidative stability or mechanical properties. Questions/purposes (1) Will the modifications (PMPC grafting and vitamin E blending) affect the lubrication characteristics of the CLPE surface? (2) Will the modifications affect wear resistance? (3) Will the modifications affect fatigue resistance? Methods We investigated the effects of surface and substrate modifications (PMPC grafting and vitamin E blending) on the wear and fatigue fracture of thin CLPE samples. For each of the untreated and PMPC-grafted CLPE surfaces with and without vitamin E blended (four groups), wettability and lubricity surface analyses were conducted as well as multidirectional wear and impact-towear tests using a pin-on-disk testing machine. Results The water wettability and lubricity (CLPE [mean ± 95% confidence interval]: 23.2°± 1.8°, 0.005 ± 0.001; HD-CLPE[VE]: 26.0°± 2.3°, 0.009 ± 0.003) of the PMPCgrafted surfaces were greater (p \ 0.001) than that (CLPE: 90.3°± 1.2°, 0.067 ± 0.015; HD-CLPE[VE]: 90.8°± 2.0°, 0.063 ± 0.008) of the untreated surface regardless of vitamin E additives. It was observed that the PMPC grafting (CLPE: 0.23 ± 0.06 mg; HD-CLPE[VE]: 0.05 ± 0.10 mg) was associated with reduced gravimetric wear (CLPE: 0.53 ± 0.08 mg, p = 0.004 HD-CLPE[VE]: 0.23 ± 0.07 mg, p = 0.038) in the multidirectional wear test. The PMPC-grafted surface characteristics did not appear to affect the impact fatigue resistance regardless of vitamin E blending. Conclusions PMPC grafting improved the surface hydrophilicity and lubricity, and it reduced the gravimetric wear in terms of multidirectional sliding. It did not result in differences in terms of the impact-to-unidirectional sliding regardless of vitamin E blending. Further research is needed to evaluate the wear resistance of PMPC-grafted HD-CLPE(VE) in long-term hip simulator tests under normal

Prevention of bacterial adhesion and biofilm formation on a vitamin E-blended, cross-linked polyethylene surface with a poly(2-methacryloyloxyethyl phosphorylcholine) layer

“…In contrast, the surface roughness of the PMPC-grafted HD-CLPE(VE) sample decreased markedly (p < 0.01) to 0.71 nm. These results indicated that PMPC was successfully grafted on the HD-CLPE(VE) surface and that PMPC grafting resulted in a smoother surface [32,33].…”

An Overview on the Tribological Performance of Titanium Alloys with Surface Modifications for Biomedical Applications

“…No adverse effects and no revision surgery and no osteolysis were informed and observed. However, cobalt-chromium-molybdenum (Co-Cr-Mo) and cobalt-chromium (Co-Cr) alloys were used in recent studies as the head material against PMPC-grafted CLPE liner [67][68][69][70][71].…”

Highly lubricated polymer interfaces for advanced artificial hip joints through biomimetic design

“…For example, a study is currently underway for the fabrication of a highly lubricious nanoscale modified surface using poly(MPC) grafting onto the surface of an antioxidative X-UHMWPE substrate involving vitamin E blending. 97,98 In 2009, Kyomoto and Ishihara discovered a special photochemical reaction with the super-engineering plastic poly(ether ether ketone) (PEEK). 99 Recently, PEEK has been the focus of major attention as new type of polymeric biomaterial, where the potential has been recognized for the substitution of metal and ceramic biomaterials.…”