Papers by Author: Michel Fiset

Abstract: In the last years a new clinical method to carry out surgical operations has been introduced. It consists in minimally invasive vascular surgery (also called laparoscopy). In one hand, during laparoscopy procedures, sutures cannot be handled with fingers, and the use of stainless-steel needle holders is required. In the other hand, companies that fabricate sutures clearly mention that metal-made devices should be avoided when manipulating the monofilaments. Therefore, the manipulation of the suture monofilaments (made of polymers) by laparoscopic needle holders (made of metals) is controversial. Literature in this field is limited and incomplete. Therefore, the aim of this study was to investigate the mechanical and microstructural effects of the manipulations with laparoscopic needle holder on polymeric suture monofilament. Surgipro© (polypropylene), Teflene© (polyvinylidene fluoride) and Gore-Tex© (polytetrafluoroethylene) monofilament suture were pinched with a standard clinical protocol by a surgeon. Scanning electron microscopy, micro-mechanical testing, differential scanning calorimetry, x-ray diffraction, small angle x-ray scattering and Fourier transform infrared spectroscopy were then performed. Results showed that the ultimate tensile strength of Teflene and Gore-Tex sutures does not change after pinching whereas it decreases significantly for Surgipro sutures. This is attributed to stress concentration and to the compressive strength applied on the monofilament, which are closely related to the permanent deformation of the suture after pinching. Teflene and Gore-Tex monofilament sutures showed to be not affected even after severe pinching with laparoscopic needle holders. Therefore, our results clearly showed that the use of Surgipro II sutures in laparoscopic interventions should be avoided.

Abstract: The short-term need of scaffolding function of stent and the prevention of potential longterm complication of permanently implanted stent have directed to the original idea of biodegradable stent. Selecting and developing materials showing appropriate mechanical and degradation properties are key steps for the development of this new class of medical devices. Therefore, the study of their in vitro degradation behaviour is mandatory for the selection of potential candidate materials suited in vivo. In this work, the degradation behaviour of current studied biodegradable metals including three magnesium alloys (Mg, AM60B and AZ91D), pure iron and Fe-35Mn was investigated. The tests were performed in a simulated blood plasma solution at 37±0.1 oC, using three different methods; potentiodynamic polarization, static immersion, and dynamic test in a test-bench which mimics the flow condition in human coronary artery. Degradation rate was determined as ion release rate measured by using atomic adsorption spectroscopy (AAS) and also estimated from weight loss and corrosion current. Surface morphology and chemical composition of corroded specimens were analyzed by using SEM/EDS. The three degradation methods provide consistent results in corrosion tendency, where Mg showed the highest corrosion rate followed by AZ91D, AM60B, Fe-35Mn and iron. Potentiodynamic polarization gives a rapid estimation of corrosion behaviour and rate. Static immersion test shows the effect of time on the degradation rate and behaviour. Dynamic test provides the closest approach to the environment after stent implantation and its results show the effect of the flow on the materials degradation. In conclusion, the three investigated methods can be applied for screening, selecting and validating materials for degradable stent application before going further to in vivo assessments.