now , looking more closely at the drawings and in particular fig1 and 2 , a first embodiment of stent graft according to the present invention is described . in this embodiment , the stent graft leg extension 10 comprises a tubular body 12 of a biocompatible graft material with a number of zig - zag gianturco stents 14 on its outer surface between its ends and an inner zig - zag gianturco stent 16 at the proximal end 18 . on the outside of the proximal end , the biocompatible graft material provides a sealing surface 20 . at the distal end 22 of the tubular body is another sealing surface 24 and extending from the end 22 is a tubular self - expanding stent 26 . the tubular zig - zag stent 26 comprises circumferential zig - zag portions 26 a with flexible longitudinal links 26 b between the circumferential portions . as can be seen particularly in fig2 , which shows a longitudinal cross - section of the stent graft shown in fig1 , the tubular stent 26 extends within the tubular body 12 for at least a length equivalent to one diameter of the tubular body 12 and is suitably fastened , such as by stitching ( not shown ), inside the tubular body . the length of the tubular stent 26 beyond the distal end 22 of the tubular body 12 is equal to between a quarter to one times the length of the tubular body 12 . it will be noted that the tubular stent 26 can take a considerable degree of bending , as shown in fig1 , without kinking , whereas an extended tubular body 12 itself may well kink in the region 28 of bent to the same degree . it will be seen that by this arrangement a flexible transition is provided between the leg extension and the iliac artery . fig3 shows the use of the leg extension stent graft of fig1 in a vasculature of a patient . fig3 shows a schematic view of the vasculature of a patient , particularly showing the aorta and aortic bifurcation extending down towards the iliac arteries . the vasculature comprises aorta 30 in the region between the renal arteries 34 and the aortic bifurcation 36 . common iliac arteries 38 a and 38 b extend from the aortic bifurcation 36 . the common iliac artery 38 a has a considerable kink in it . the aorta 30 has an aneurysm 32 which extends between the renal arteries and the iliac bifurcation . to traverse the aneurysm , a bifurcated aortic stent graft 40 has been deployed into the aorta 30 . the proximal end 41 of the bifurcated stent graft 40 is engaged onto a non - aneurysed portion 43 of the aorta just distal of the renal arteries 34 . to ensure good fixation , the stent graft 40 includes a supra renal exposed stent 45 with barbs 47 engaging the wall of the aorta proximal the renal arteries 34 . the stent graft 40 has a short leg 42 and a long leg 44 extending from a bifurcation 49 at its distal end 51 . the long leg 44 has a sealing surface 46 at its distal end and this engages in a sealing manner into an non - aneurysed portion of the common iliac artery 38 b . a leg extension 10 of the type shown in fig1 and 2 has been deployed into the iliac artery 38 a with the sealing surface 20 within the shorter leg 42 of the bifurcated stent graft 40 and the leg extension extending down into the iliac artery 38 a . the tubular stent 26 allows for a degree of convolution in the iliac artery 38 a while still allowing the sealing surface 24 at the distal end 22 of the tubular body 12 of the leg extension 10 to seal conveniently within the iliac artery 38 a . fig4 shows another embodiment of leg extension . in this embodiment the leg extension 60 comprises a tubular body 62 of a graft material with a side arm 64 extending from the tubular body . a tubular self - expanding stent 66 extends from the distal end 68 of the tubular body 62 . this leg extension can be used where the internal iliac artery is very close to the aortic bifurcation and the placement of a leg extension without a side arm may cause occlusion of the internal iliac artery . a covered balloon expandable or self - expanding stent ( not shown ) can be used to extend between the side arm 64 and the internal iliac artery . fig5 and 6 shows another embodiment of leg extension in longitudinal cross section with a flexible transition according to the present invention . in this embodiment the leg extension 70 comprises a tubular body 72 of a graft material with a plurality of self - expanding stents 74 on the outside except at the proximal end 76 where the self - expanding stent 78 is on the inside to provide a sealing surface 80 on the outside of the tubular body . at the distal end 82 is a stent assembly 84 which comprises a plurality of self - expanding stents 86 connected together by flexible links 88 . in this embodiment the flexible links are formed from a suture tied to alternate apices 85 of adjacent zig - zag stents 86 to provide a degree of flexibility between adjacent stents . the proximal - most uncovered stent 90 of the stent assembly 84 is linked to the distal - most covered stent 92 by a flexible suture thread 94 . fig6 shows that a considerable degree of flexibility is provided by the stent assembly 84 so that a smooth transition is provided for the connection between the vasculature and the leg extension 70 . throughout this specification various indications have been given as to the scope of this invention but the invention is not limited to any one of these but may reside in two or more of these combined together . the examples are given for illustration only and not for limitation . throughout this specification and the claims that follow unless the context requires otherwise , the words ‘ comprise ’ and ‘ include ’ and variations such as ‘ comprising ’ and ‘ including ’ will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers .
a stent graft leg extension to extend from a bifurcated aortic stent graft into an iliac artery . the stent graft has a tubular body . of a biocompatible graft material and a plurality of self - expanding stents joined to and supporting the tubular body . an uncovered tubular self - expanding stent assembly extends from a first end of the tubular body and is fastened thereto . the uncovered tubular self - expanding stent assembly provides a smooth transition from the leg extension into the iliac artery to reduce the chance of kinks causing problems in the leg extension .