Effects of simulated oxidation on the<i>in vitro</i>wear and mechanical properties of irradiated and melted highly crosslinked UHMWPE

Oral, Ebru; Neils, Andrew L.; Doshi, Brinda N.; Fu, Jun; Muratoglu, Orhun K.

doi:10.1002/jbm.b.33368

Cited by 31 publications

(27 citation statements)

References 52 publications

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“…Historically, an oxidation level of one was associated with a physically meaningful reduction in the mechanical properties of conventional, gamma sterilized UHMWPE . It also has to be noted that the mechanical strength of irradiated and melted UHMWPEs is substantially lower than unoxidized conventional UHMWPE; therefore, the oxidation rates and thresholds for clinically relevant mechanical deterioration for these highly cross‐linked UHMWPEs may be different than those for conventional UHMWPE . An analysis of the oxidation‐depth profiles, oxidation products, and the effect of oxidation on the crosslink density of retrievals as well as the development and refinement of clinically relevant accelerated aging methods is necessary and useful.…”

Section: Discussionmentioning

confidence: 99%

“…of O 2 at 70°C for 14 days) . Although this standardized test is able to induce oxidation in UHMWPEs with free radicals and in UHMWPEs without free radicals in non‐standardized long durations, it is unable to simulate accurately the oxidation rate and oxidation‐depth profiles observed in vivo. It is possible that oxidation of UHMWPE is affected by lipid absorption in vivo, a factor which was previously not considered in the development of in vitro accelerated aging methods.…”

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confidence: 99%

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In‐vitro oxidation model for UHMWPE incorporating synovial fluid lipids

Oral

Fung

Rowell

et al. 2018

Journal Orthopaedic Research

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Post-irradiation melting of ultra-high molecular weight polyethylene (UHMWPE) reduced the oxidation potential of UHMWPE in vivo. After mid-term (5-10 years) use in vivo, there is detectable oxidation in irradiated and melted joint implant retrievals. The absorption of the synovial fluid lipid squalene was identified as a possible factor initiating oxidation. We investigated the role of lipids in UHMWPE oxidation by asking: (1) Do other synovial fluid lipids initiate oxidation in irradiated and melted UHMWPE?; (2) What is the effect of the absorption of multiple lipids on UHMWPE oxidation?; (3) How does lipid-initiated oxidation in vitro compare to what is observed in long-term retrievals? We diffused emulsified single and mixed lipids into irradiated and melted UHMWPE and accelerated aged them. We analyzed the oxidation in these samples and in four long-term highly crosslinked, irradiated, and melted Longevity™ UHMWPE liner retrievals (in vivo for up to 190 months) using Fourier Transform Infrared Spectroscopy (FTIR). We showed that lipids other than squalene could initiate oxidation in UHMWPE and that the types of absorbed lipids determined the amount of resultant oxidation. Although mixed lipids doping and accelerated aging reproduced the average and maximum oxidation values and oxidation products observed in vivo, the oxidation depth profile and its effect on cross-link density was different. One reason for this was the variability of oxidation in retrievals, suggesting additional factors contributing to oxidation. The understanding of oxidative processes in vivo and the development of clinically relevant in vitro protocols to evaluate implant materials is crucial for their long-term performance. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1833-1839, 2018.

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

In‐vitro oxidation model for UHMWPE incorporating synovial fluid lipids

Oral

Fung

Rowell

et al. 2018

Journal Orthopaedic Research

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“…After irradiation and annealing, numerous crosslinked networks were formed in X‐UHMWPE. These crosslinked networks had smaller COFs and wear rates compared with the pristine UHMWPE and hardened the composite . The COFs and wear rates of the crosslinked parts apparently decreased with absorbed dose, especially when the dose was not large .…”

Section: Resultsmentioning

confidence: 96%

“…This process increases the molecular weight and induces the formation of crosslinking networks. These characteristics sufficiently improve the mechanical properties of UHMWPE such as creep resistance, hardness, wear resistance, and yield strength . Some studies have reported that the wear rate decreased by 90% through radiation crosslinking at a dose of 100 kGy .…”

Section: Introdutionmentioning

confidence: 96%

“…Some studies have reported that the wear rate decreased by 90% through radiation crosslinking at a dose of 100 kGy . However, radiation crosslinking leads to reduced tensile strength, processability, ductility, and fatigue resistance, which are important for polymers used in engineering . UHMWPE devices are mostly used in the form of sheets or bars.…”

Section: Introdutionmentioning

confidence: 99%

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More wear‐resistant and ductile UHMWPE composite prepared by the addition of radiation crosslinked UHMWPE powder

Wang

Zhang

et al. 2016

J of Applied Polymer Sci

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Radiation crosslinked ultrahigh molecular weight polyethylene (X-UHMWPE) powder was prepared by g-ray irradiation under nitrogen atmosphere with a dose of 50-200 kGy at a dose rate of 7 kGy/h and further annealing in vacuum at 120 8C for 4 h. The crosslinked powder was characterized by FT-IR spectroscopy, gel content, and hot-press molding. Then, X-UHMWPE was added to pristine UHMWPE to prepare a composite with 0-25 wt % filler. The morphology, wear resistance, and tensile property of the composite were investigated. Using X-UHMWPE as a filler could sufficiently improve the wear resistance of the composite. Adding 25 wt % X-UHMWPE (dose: 150 kGy) improved wear resistance by 130% and retained approximately 90% tensile strength and 70% ductility. Wear-resistant and ductile UHMWPE composite may be potentially used for artificial joint replacement and engineering devices. The proposed route is useful in fabricating UHMWPE material with excellent comprehensive performance or functional polymer composite. INTRODUTIONUHMWPE is a polymer with numerous outstanding properties such as chemical inertness, excellent biocompatibility, good mechanical properties, and widely used in medical and engineering applications. Several unsatisfactory mechanical properties of this polymer are its poor creep-resistance and yield strength. Although UHMWPE exhibits better wear resistance than many other polymers, prolonged use of medical devices made from this polymer used as artificial joint produced debris in the human body. 1 This phenomenon shortens the lifetime of the device and induces pain to the patient. 2,3 Therefore, improving the wear resistance of UHMWPE is still urgent for its application as artificial organ and in engineering devices. Physical blending 4 and radiation crosslinking 5 are two useful methods for improving the wear resistance of UHMWPE. 6,7 Many fillers, such as carbon black, carbon fibers, 8,9 carbon nanotubes (CNTs), 7,10 and Al 2 O 3 , have been added to UHMWPE for physical blending to improve the wear resistance of this polymer. 11 However, dispersion compatibility remains a problem in most cases primarily because of the remarkable difference in chemical structure and surface energy. In addition, the chemical and physiological toxicity of the added material are important in vivo. For instance, 0.1 wt % CNTs in polyethylene can reduce the 80% wear of polyethylene, 12 but this supplementation can even induce cancer in vivo. 13 Therefore, these composites have not been used clinically. Polyethylene blends with other types of polyethylene exhibit better compatibility and lower physiological toxicity than blends with other materials. [14][15][16] This blending method can be used to improve the mechanical properties of UHMWPE. 15,17 Radiation crosslinking can obviously alter the chemical and crystal structures of UHMWPE. This process increases the molecular weight and induces the formation of crosslinking networks. These characteristics sufficiently improve the mechanical properties of UHMWPE such as creep resistanc...

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An antioxidant stabilized, chemically cross‐linked UHMWPE with superior toughness

et al. 2018

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Chemical cross-linking of ultrahigh molecular weight polyethylene (UHMWPE) using an organic peroxide followed by high temperature melting results in a large increase in toughness accompanied by a decrease in cross-link density, which, surprisingly does not compromise the wear resistance. We compared the mechanical properties and wear behavior of a vitamin E blended, chemically cross-linked and high temperature melted UHMWPE produced by ram extrusion (PRX HTM) to those measured with the clinically available 100-kGy irradiated and melted UHMWPE (CISM 100). We also assessed the local biocompatibility of PRX-HTM in rabbit subcutaneous pouch and osteochondral defect models. The ultimate tensile strength and pin-on-disc wear rate were similar to CISM 100; whereas the elongation-at-break and impact toughness were much higher with PRX-HTM. The stress intensity factor range at crack inception was also higher with PRX-HTM. Accelerated aging did not result in any measurable oxidation or changes in mechanical properties. Hip simulator wear rate of acetabular liners made with PRX-HTM was 0.3 AE 0.4 mg/million-cycle, similar to that reported for CISM 100 liners. The wear particles were largely spherical with a number-averaged particle size of 0.95 μm with~75% of particles below 1 μm. The subcutaneous and osteochondral rabbit implantations showed no histological differences between PRX-HTM and the control CISM 100. Preclinical wear, mechanical, and biocompatibility testing of PRX HTM showed feasibility for the use of this material as a total joint arthroplasty implant bearing surface. This process has the potential of eliminating the additional step of radiation cross-linking by combining consolidation and cross-linking while improving toughness.

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Effects of simulated oxidation on thein vitrowear and mechanical properties of irradiated and melted highly crosslinked UHMWPE

Cited by 31 publications

References 52 publications

In‐vitro oxidation model for UHMWPE incorporating synovial fluid lipids

In‐vitro oxidation model for UHMWPE incorporating synovial fluid lipids

More wear‐resistant and ductile UHMWPE composite prepared by the addition of radiation crosslinked UHMWPE powder

An antioxidant stabilized, chemically cross‐linked UHMWPE with superior toughness

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