Lifetime of alkyl macroradicals in irradiated ultra-high molecular weight polyethylene

Brunella, Valentina Giovanna; Bracco, Pierangiola; Carpentieri, I.; Paganini, Maria Cristina; Zanetti, Marco; Costa, Luigi

doi:10.1016/j.polymdegradstab.2007.05.005

Cited by 30 publications

(33 citation statements)

References 14 publications

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“…Due to radiolytic bond scission, free radicals are produced in irradiated UHMWPE [15,18,20,30,38], which react with oxygen and trigger the oxidation cascade [2, 16, 17, 20, 22, 25-27, 54, 69] ( Fig. 2A, Reactions 1-4).…”

Section: Discussionmentioning

confidence: 99%

Vitamin E-stabilized UHMWPE for Total Joint Implants: A Review

Bracco

Oral

2011

Clinical Orthopaedics &Amp; Related Research

256

162

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Background Osteolysis due to wear of UHMWPE limits the longevity of joint arthroplasty. Oxidative degradation of UHMWPE gamma-sterilized in air increases its wear while decreasing mechanical strength. Vitamin E stabilization of UHMWPE was proposed to improve oxidation resistance while maintaining wear resistance and fatigue strength. Questions/purposes We reviewed the preclinical research on the development and testing of vitamin E-stabilized UHMWPE with the following questions in mind: (1) What is the rationale behind protecting irradiated UHMWPE against oxidation by vitamin E? (2) What are the effects of vitamin E on the microstructure, tribologic, and mechanical properties of irradiated UHMWPE? (3) Is vitamin E expected to affect the periprosthetic tissue negatively? Methods We performed searches in PubMed, Scopus, and Science Citation Index to review the development of vitamin E-stabilized UHMWPEs and their feasibility as clinical implants.Results The rationale for using vitamin E in UHMWPE was twofold: improving oxidation resistance of irradiated UHMWPEs and fatigue strength of irradiated UHMWPEs with an alternative to postirradiation melting. Vitamin E-stabilized UHMWPE showed oxidation resistance superior to that of irradiated UHMWPEs with detectable residual free radicals. It showed equivalent wear and improved mechanical strength compared to irradiated and melted UHMWPE. The biocompatibility was confirmed by simulating elution, if any, of the antioxidant from implants.Conclusions Vitamin E-stabilized UHMWPE offers a joint arthroplasty technology with good mechanical, wear, and oxidation properties. Clinical Relevance Vitamin E-stabilized, irradiated UHMWPEs were recently introduced clinically. The rationale behind using vitamin E and in vitro tests comparing its performance to older materials are of great interest for improving longevity of joint arthroplasties.

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Section: Discussionmentioning

confidence: 99%

Vitamin E-stabilized UHMWPE for Total Joint Implants: A Review

Bracco

Oral

2011

Clinical Orthopaedics &Amp; Related Research

256

162

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“…has been used as resin powder. This material has 75% of crystallinity (as evaluated with DSC analysis) and an amount of total double bonds (vinyl groups + vinylidene) equal to about 4 mmol/L (as evaluated with FTIR Spectroscopy [10] ). The studied material, in accordance with standards for implant material ASTM F 648-84, was completely free from any additives.…”

Section: Methodsmentioning

confidence: 99%

“…After irradiation the powder has been transferred into the EPR tube side of the container for EPR measurements, as reported elsewhere. [10] A spectrum of the empty irradiated cell has been run for comparison. During electron beam irradiation a temperature increase of about 12.5…”

Section: Methodsmentioning

confidence: 99%

Electron beam radiation effects on UHMWPE: an EPR study

Brunella¹,

Paganini²

2011

Magnetic Reson in Chemistry

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Electron paramagnetic resonance (EPR) technique has been employed to detect and characterise a series of different radical species generated in ultra-high molecular weight polyethylene (UHMWPE) via electron beam irradiation. Three different radical species have been found and assigned on the basis of their EPR spectra and of the related computer simulations. A secondary alkyl species, the prevalent one, is present immediately after irradiation, an allyl species appears only 24 h after irradiation when the alkyl species disappears.The third species, clearly visible at high microwave power only, has been observed for the first time and assigned to a tertiary alkyl carbon radical, whose formation is strictly connected with a Y-shape crosslink and a migration of the unpaired electron on a carbon atom localised in an adjacent position.

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“…The concentration of surviving macroradicals decreases with time after irradiation [13]. Their living time is on the order of 24 hours in the amorphous phase, but macro alkyl radicals can be found in the polymer bulk even after years, probably trapped in the crystalline phase [14].…”

Section: Reaction Of Isolated Radicalsmentioning

confidence: 99%

“…Moreover, experimental evidence shows that the level of crosslinking increases with the radiation dose, but it reaches a plateau for doses higher than 100 kGy, when the majority of the vinyl double bonds have been consumed [13]. A different behavior can take place in the molten state, where the mobility of radicals is higher.…”

Section: H-crosslinking Mechanismmentioning

confidence: 99%