Factors and Interactions Affecting the Performance of Polyurethane Elastomers in Medical Devices

Coury, Arthur J.; Slaikeu, P. C.; Cahalan, Patrick T.; Stokes, Ken; Hobot, Christopher

doi:10.1177/088532828800300202

Cited by 94 publications

(47 citation statements)

References 21 publications

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“…Polyurethanes have been used in medical devices since the 1970s and the literature has reported on the biostability of polyurethanes [20][21][22][23][24][25]. Generally, the biostability of polyurethanes is strongly affected by multiple factors.…”

Section: Discussionmentioning

confidence: 99%

“…For example, polycarbonate soft segments are chemically more stable than either polyether or polyester counterparts and the biostability of a Shore 55D polyurethane is quite different from that of Shore 80A one [25]. The annealing process reduces environmental stress cracking (ESC) [20][21][22][23] while appropriate sterilization methods maintain the biostability of polyurethanes [20]. Bulky and dense polyurethanes are more stable than thin, porous or fibrous polyurethanes [22].…”

Section: Discussionmentioning

confidence: 99%

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In vivo biostability of polymeric spine implants: retrieval analyses from a United States investigational device exemption study

Shen¹,

Zhang²,

Koettig

et al. 2011

Eur Spine J

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The Dynesys System for stabilizing the lumbar spine was first surgically implanted in Europe in 1994. In 2003, a prospective, randomized, investigational device exemption clinical trial of the system for non-fusion dynamic stabilization began. Polycarbonate urethane (PCU) and polyethylene terephthalate (PET) components explanted from four patients who had participated in the study were analyzed for biostability. Components had been implanted 9-19 months. The explanted components were visually inspected and digitally photographed. Scanning electron microscopy was used to analyze the surface of the spacers. The chemical and molecular properties of the retrieved spacers and cords were quantitatively compared with lot-matched, shelf-aged, components that had not been implanted using attenuated total reflection Fourier transform infrared (FTIR) and gel permeation chromatography (GPC). FTIR analyses suggested that the explanted spacers exhibited slight surface chemical changes but were chemically unchanged below the surface and in the center. New peaks that could be attributed to biodegradation of PCU were not observed. The spectral analyses for the cords revealed that the PET cords were chemically unchanged at both the surface and the interior. Peaks associated with the PET biodegradation were not detected. GPC results did not identify changes to the distributions of molecular weights that might be attributed to biodegradation of either PCU spacers or PET cords. The explanted condition of the retrieved components demonstrated the biostability of both PCU spacers and PET cords that had been in vivo for up to 19 months.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

In vivo biostability of polymeric spine implants: retrieval analyses from a United States investigational device exemption study

Shen¹,

Zhang²,

Koettig

et al. 2011

Eur Spine J

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“…In order to make calculation more theoretical calculations of film thickness. Stribeck analysis has been used widely to detercompliant layer materials as they have a track record mine the lubrication regime in loaded contacts (a as long-term implants [32][33][34][35][36] and their mechanical plot of the friction factor, f, against the Sommerfeld properties (tensile strength and tensile modulus) number, z). In this study, the friction factor was compare well with articular cartilage (see Table 1).…”

Section: Introductionmentioning

confidence: 99%

Compliant Layer Acetabular Cups: Friction Testing of a Range of Materials and Designs for a New Generation of Prosthesis that Mimics the Natural Joint

Scholes

Burgess

Marsden

et al. 2006

Proc Inst Mech Eng H

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Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Abstract: Total joint replacements (TJRs) have a limited lifetime, but the introduction of components that exhibit good lubricating properties with low friction and low wear could extend the life of TJRs. A novel acetabular cup design using polyurethane (PU) as a compliant layer (to mimic the natural joint) has been developed. This study describes a series of friction tests that have been used to select the most appropriate material, optimize the design parameters, and fine-tune the manufacturing processes of these joints. To determine accurately the mode of lubrication under which these joints operate, a synthetic lubricant was used in all these tests. Friction tests were carried out to assess the lubrication of four PU bearing materials. Corethane 80A was the preferred material and was subjected to subsequent testing. Friction tests conducted on acetabular cups, manufactured using Corethane 80A articulating against standard, commercially available femoral heads, demonstrated friction factors approaching those for full-fluid-film lubrication with only approximately 1 per cent asperity contact. As the joint produces these low friction factors within less than half a walking cycle after prolonged periods of loading, start-up friction was not considered to be a critical factor. Cups performed well across the full range of femoral head sizes, but a number of samples manufactured with reduced radial clearances performed with higher than expected friction. This was caused by the femoral head being gripped around the equator by the low clearance cup. To avoid this, the cup design was modified by increasing the flare at the rim. In addition to this the radial clearance was increased. As the material is incompressible, a radial clearance of 0.08 mm was too small for a cup diameter of 32 mm. A clearance of between 0.10 and 0.25 mm produced a performance approaching full-fluid-film lubrication. This series of tests acted as a step towards the optimization of the design of these joints, which has now led to an in vivo ovine model.

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“…Abbreviations used in this paper: ATR/FTIR, attenuated total reflectance Fourier transform infrared spectroscopy; EPO, eosinophil peroxidase; ESCA, electron spectroscopic chemical analysis; HOCI, hy-5). However, questions have been raised regarding the biostability ofat least some forms of PEU (6)(7)(8)(9)(10). In one long-standing application, PEU has been used as insulation for cardiac pacemaker leads.…”

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confidence: 99%

Degradation of biomaterials by phagocyte-derived oxidants.

Sutherland¹,

Mahoney²,

Coury³

et al. 1993

J. Clin. Invest.

135

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Polymers used in implantable devices, although relatively unreactive, may degrade in vivo through unknown mechanisms. For example, polyetherurethane elastomers used as cardiac pacemaker lead insulation have developed surface defects after implantation. This phenomenon, termed "environmental stress cracking," requires intimate contact between polymer and host phagocytic cells, suggesting that phagocyte-generated oxidants might be involved. Indeed, brief exposure of polyetherurethane to activated human neutrophils, hypochlorous acid, or peroxynitrite produces modifications of the polymer similar to those found in vivo. Damage to the polymer appears to arise predominantly from oxidation of the urethane-aliphatic ester and aliphatic ether groups. There are substantial increases in the solid phase surface oxygen content of samples treated with hypochlorous acid, peroxynitrite or activated human neutrophils, resembling those observed in explanted polyetherurethane. Furthermore, both explanted and hypochlorous acid-treated polyetherurethane show marked reductions in polymer molecular weight. Interestingly, hypochlorous acid and peroxynitrite appear to attack polyetherurethane at different sites. Hypochlorous acid or activated neutrophils cause decreases in the urethane-aliphatic ester stretch peak relative to the aliphatic ether stretch peak (as determined by infrared spectroscopy) whereas peroxynitrite causes selective loss of the aliphatic ether. In vivo degradation may involve both hypohalous and nitric oxide-based oxidants because, after long-term implantation, both stretch peaks are diminished. These results suggest that in vivo destruction of implanted polyetherurethane involves attack by phagocyte-derived oxidants. (J. Clin. Invest. 1993Invest. . 92:2360Invest. -2367

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Factors and Interactions Affecting the Performance of Polyurethane Elastomers in Medical Devices

Cited by 94 publications

References 21 publications

In vivo biostability of polymeric spine implants: retrieval analyses from a United States investigational device exemption study

In vivo biostability of polymeric spine implants: retrieval analyses from a United States investigational device exemption study

Compliant Layer Acetabular Cups: Friction Testing of a Range of Materials and Designs for a New Generation of Prosthesis that Mimics the Natural Joint

Degradation of biomaterials by phagocyte-derived oxidants.

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