Relationship between textile irregularities and pre-mature rupture of polyester vascular graft knitted fabric
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Polyethylene terephthalate (PET), commonly known as polyester, has been used as an artificial graft material since 1952 because of its bio-inertness and durability nature. However, over the years numerous deaths have been recorded due to the premature rupture of polyester grafts caused by graft tearing. In the current study, has been conducted to determine the role of material irregularities in the premature rupture of polyester graft. Thickness, diameter, breaking strength, and tearing strength of apparel grade polyester and Double Velour Polyester Vascular Graft Knitted Fabric (DVPVGKF) were measured to find irregularities. The irregularities in both apparel fabric and DVPVGKF were very high. For DVPVGKF, the breaking strength lies between 45.8 N to 55.5 N (SD: 4.09), however, probability analysis showed that this breaking strength variation alone cannot be responsible for the 25% graft failure as reported in the recent medical literature. Variation in tearing strength data and scanning electron microscopy (SEM) micrographs of virgin and hydrolysed DVPVGKF reveal that the manufacturing irregularities (cracks, holes) in the material are responsible for lower tearing strength. Further, these irregularities originated in the ‘weaker region’ of polyester and produced the angled transverse cracks. The study suggests that the regulatory body for Medical Devices (Health Canada) should specify a minimum standard specification of 4400 kPa for tearing strength of virgin polyester material which is twice the amount of post implantation pulsatile pressure (PIPP).