09461 Pitting Resistance of Nitinol Stents Before and After Implantation

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Product Number: 51300-09461-SG

ISBN: 09461 2009 CP

Author: Robert Cannon and Lorrie A. Krebs

Publication Date: 2009

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This study explores the pitting susceptibility of Nitinol wires with blue oxide surfaces before processing into a vascular graft device, after processing, and explanted after in vivo exposure during a clinical trial. Only two explanted devices were made available for testing. The blue oxide surfaces of the control specimens tended to perform poorly in a commonly performed cyclic polarization test intended to screen implantable devices for pitting susceptibility, however the explanted devices performed far better under the same test conditions. Electrochemical polarization, x-ray photoelectron spectroscopy, optical and scanning electron microscopies were performed on adjacent wire samples cut from selected specimens. It must be noted that some of the details of handling and storage for the explants from the time of removal to the time that they were provided for analysis are unknown.

Many screening tests are intentionally aggressive, the goal being to provide an adequate safety margin for acceptability. Nonetheless, these results raise potential questions regarding the environmental parameters of the in vitro screening test and whether it is always a reliable indicator of in vivo performance.

Key Words: Medical Implant, In Vivo, Nitinol, Pitting, Potentiodynamic Polarization, Screening