Tubular Wall Structure And Fatigue Performance Of Endovascular Prosthesis

With the medical pattern changing,the trends of surgery began directing to mini-traumatic. For the dilative arterous diseases,a novel mini-invasive endovascular therapy emerged.The stent-graft is delivered intraluminaly to exclude the lesions out of the normal circulation.So the technique is named endovascular exclusion(EVE).Comparing with the traditional open surgery, the advantages of EVE are mini-traumatic,short operation time,less blood transfusion and rapid resumption.Though the EVE has so many advantages,the long-term implantation effect is not as good as traditional open surgery.The main reason is the fatigue failure such as fabric holes,suture rupture,metal stent deformation and fracture,which failed the whole therapy.Therefore,the long-term implantation effect in vivo is difficult to meet the expectation.At present,SG damage phenomenon was described on the clinic side,but the evaluation study of SG fatigue performance in vitro is little.Therefore,it's essential to establish an in vitro fatigue testing system of simulating the SG implantation condition in vivo to predict the fatigue property of SG.The fatigue resistance of SG in vitro was studied in this paper.Fatigue resistance,also known as durability,is an ability of the devices to maintain the original structure after they were implanted into human's body.The research on the fatigue performance of SG is seldom reported and the existed fatigue testing device need to be improved,for example,the existed device could not simulate real human conditions completely and the SG have not been studied as a whole for its fatigue property,as well as people have not understand the fatigue mechanism yet.According to the current problems above,an in vitro fatigue resistant testing system which was designed by former student of our research group for SG was improved.Except accelerating conditions and pulsatile flow,this improved device also provides a certain tension at both ends of SG and similar blood environment which is close to the physiological conditions of arteries in vivo. In addition,the testing method and evaluation indexes were determined after the improved fatigue testing device was examined.In a short-term fatigue testing,the changes of fabric count and the integral water permeability were selected as the evaluation indexes.In the light of the SG fatigue behaviour,the testing time points are chose.Tubular wall of SG is made up of fabric graft,mental stent and suture.The influences of metal stent and fabric graft on the SG fatigue performance were studied in this paper.First of all, the influence of metal stent on SG fatigue behaviour was researched.As a result,the fabric counts of SG fabric graft became uneven.That was due to the stress concentration on the stitched places of metal stent and fabric graft,which resulted in the uneven stress distribution in different parts of SG fabric graft.After fatigue testing a few times,the fabric count maintained the original values, but the value of integral water permeability decreased.In addition,the abrasion property of SG fabric graft was studied,based on a special abrasion instrument.It showed that the abrasion resistant of SG fabric graft influenced little on the SG fatigue property. Further study was to research the relationship between the textile parameter of fabric graft and SG fatigue behaviour.According to the result,the fatigue performance of SG with multifilament was better than the one with monofilament.And the textile structure of fabric graft worked on the fatigue durability of SG.The SG with even structure fabric graft had good fatigue property,because of the weaken points of the fabric graft.Finally,the long-term fatigue property of SG was preliminary explored,the results were as the same as short-term fatigue testing:the fabric count maintained the values of the original fabric count and the integral water permeability decreased owing to the sewing holes enlarging.Therefore,the fabric count could be only used in short-term fatigue testing as the evaluation index.However,the integral water permeability could be considered as the evaluation index during the whole fatigue testing.Additionally,the long-term fatigue performance could be appraised exactly from micro-level.The improvement of a in vitro fatigue resistance testing device for endovascular prostheses has been made,as well as the testing method and evaluation indexes were determined.Besides, the influences of metal stent and the textile parameters of fabric graft on SG fatigue property were studied in the short-term fatigue testing.Finally,the long-term fatigue performance was primarily explored.Above all,this paper provided the testing method to predict the short-term fatigue performance of SG and is meaningful for the further design and optimization of textile structure of SG fabric graft,which could lay a certain foundation for further relevant studies.