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Characterizing the free volume of ultrahigh molecular weight polyethylene to predict diffusion coefficients in orthopedic liners
Author(s) -
Ludwig Kyle B.,
Chandrasekar Vaishnavi,
Saylor David M.,
Van Citters Douglas W.,
Reinitz Steven D.,
Forrey Christopher,
McDermott Martin K.,
Wickramasekara Samanthi,
Janes Dustin W.
Publication year - 2018
Publication title -
journal of biomedical materials research part b: applied biomaterials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.665
H-Index - 108
eISSN - 1552-4981
pISSN - 1552-4973
DOI - 10.1002/jbm.b.34045
Subject(s) - polyethylene , volume (thermodynamics) , materials science , oxidizing agent , composite material , diffusion , ultra high molecular weight polyethylene , chemistry , thermodynamics , organic chemistry , physics
Liners used in orthopedic devices are often made from ultrahigh molecular weight polyethylene (UHMWPE). A general predictive capability for transport coefficients of small molecules in UHMWPE does not exist, making it difficult to assess properties associated with leaching or uptake of small molecules. To address this gap, we describe here how a form of the Vrentas–Duda free volume model can be used to predict upper‐bound diffusion coefficients ( D ) of arbitrary molecules within UHMWPE on the basis of their size and shape. Within this framework, the free‐volume microstructure of UHMWPE is defined by analysis of a curated set of model diffusants. We determined an upper limit on D for vitamin E, a common antioxidant added to UHMWPE, to be 7.1 × 10 −12 cm 2 s −1 . This means that a liner that contains 0.1 wt % or less Vitamin E and has <120 cm 2 patient contacting surface area would elute <100 µg/day of vitamin E. Additionally, the model predicts that squalene and cholesterol—two pro‐oxidizing biological compounds—do not penetrate over 820 µm into UHMWPE liners over the course of 5 years because their D is ≤7.1 × 10 −12 cm 2 s −1 . © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2393–2402, 2018.