Abstract:
An implantable prosthesis for placement in hollow tubular organs is described alongwith an instrument for deploying the said prosthesis. On radial compaction, the prosthesis has a low profile, allowing introduction into the body with a deployment instrument of low calibre. The prosthesis has a longitudinal strut to provide longitudinal support. One or more, outwardly biased, flexible curvilinear members with good shape-memory, symmetrically attached to the leading end of the prosthesis help unroll the prosthesis during deployment. Magnetized wires or powder may be attached to the prosthesis to facilitate this process and provide in addition radial elasticity to the prosthesis. The prosthesis may have tubular extensions to allow the treating lesions that involve the parent tubular organ and its branches. Alternatively, the prosthesis may be provided with apertures which can be widened in vivo. For implantation in branches, the prosthesis may be provided with a flange at its trailing end.

Description:
RELATED APPLICATION 
   This patent application claims priority from U.S. Provisional Patent Application Ser. No. 60/159,920, filed on Oct. 16, 1999, the entire disclosure of the application being expressly incorporated herein by reference. 

   TECHNICAL FIELD 
   This invention under consideration concerns a prosthetic device and related instrument for non-surgically treating diseases of tubular organs of the human body, and methods for using the using the said prosthesis for the said purpose. 
   BACKGROUND ART 
   Over the past two decades, treatment of diseases by the transluminal placement of a prosthesis has garnered increasing attention. In the field of vascular disease, this therapeutic modality now represents the intervention of choice for most occlusive lesions. The satisfactory results obtained with this treatment strategy has encouraged its application for the management of lesions such as aneurysms which are characterized by partial or complete loss of structural integrity rather than hindrance to blood flow. Beginning with U.S. Pat. No. 4,140,126, multiple prostheses have been described for the purpose, some of which the stage of clinical trial. Experience with these prostheses has demonstrated that while they do have therapeutic value, all suffer from a common drawback. They are too bulky to be implanted without creating a surgical vascular access, thereby negating one of the major advantages of the transluminal approach. This characteristic also make them difficult to implant in patients with tortuous blood vessels. Another limitation associated with the use of these prostheses is the inability to treat lesions involving the craniocerebral or visceral branches of the aorta. That the prostheses in use have the same disadvantage is not a coincidence because all are based on the same underlying design: a flexible non-porous tube braced by an expandable metallic skeleton. Reducing the metallic skeleton to a single, sturdy metallic collar has been proposed as one way to reduce the bulk of a prostheses during introduction (PCT International Application WO 97/48350). While this modification certainly makes for a more streamlined device, it does not eliminate the need for surgically creating a vascular access because the introducer catheter required has an outer diameter of is approximately 5 mm (15 Fr). Furthermore, clinical experience indicates that the absence of support along the longitudinal axis of the device is likely to increase the risk of complications associated with its use such as migration (Resch T. et. al. J Vasc Interv Radiol 1999; 10:257–64). 
   Deployment of the tubular component of the prosthesis and its metallic skeleton in sequence suggests itself as a possible solution to the problem. A retrievable prosthesis comprising a flexible polymer tube provided with two encircling resilient loops for temporary fixation attached independently to two metals leads during implantation is the subject of U.S. Pat. No. 5,776,186. The inherent resistance of a resilient loop to deformation limits the degree to which the prosthesis can be compacted during delivery into the arterial system. Besides, the presence of two manipulation leads running along the length of the prosthesis and the relatively complex and bulky mechanism for attaching them to the prosthesis, and the presence of the mechanism radially adjacent to the prosthesis further increases the profile of the device making it necessary for the introducer catheter to be at least 12 Fr in size (OD≈3.8 mm). This requirement mandates the surgical opening of a blood vessel for placement of the prosthesis. The prosthesis also lacks any intrinsic longitudinal support once the manipulation leads are withdrawn following implantation, detracting from its potential safety profile (Resch T. et. al. J Vasc Interv Radiol 1999; 10:257–64). Furthermore, in common with currently available prostheses, it cannot be used for treating aortic disease involving the craniocerebral, visceral, or renal branches. Perhaps for these reasons no reports about the use even in animal models has been published thus far in medical literature. Kerr described a conceptually similar prosthesis comprising a polymer tube supported by two bent guidewires each of which is bent to define a loop (U.S. Pat. No. 6,015,422). After the tube is deployed in the blood vessel and a stent coaxially implanted to anchor it, an expandable device such as an angioplasty catheter is used to break the loops allowing the guidewires to be withdrawn. As the prosthesis is not physically attached to the guidewires, the possibility exists of inadvertent separation of the prosthesis from the latter from the latter during delivery. Further in common with the invention covered U.S. Pat. No. 5,776,186, and cited above, the resilient loops limit the degree to which the prosthesis can be compacted during delivery into the target organ. In an alternative embodiment two guidewires are provided which are bent to form two outwardly-biased tines that are attached to the prosthesis with threads. Expanding the prosthesis with a device such as an angioplasty catheter tears the threads allowing the withdrawal of the guidewires. On the basis of published data, neither does this embodiment promise a materially more streamlined profile during delivery, as the introducer catheter 12.9 Fr (O.D.≈4.1 mm) in calibre is required for deployment (Kerr A. J Vasc Interv Radiol 1999; 10:281–4). The mechanism used for detaching the prosthesis carries the risk of damaging the prosthesis. Furthermore the prosthesis is not suitable for treating aortic disease involving the craniocerebral, visceral, or renal branches. 
   Thus there exists a need for a prosthesis for transluminal implantation that has a low enough profile to be introduced into the body by the non-surgical, percutaneous, approach and yet has sufficient longitudinal rigidity to minimise the risk of complications. In addition the prosthesis should be suitable for treating vascular lesions involving the aorta and its craniocerebral, visceral, or renal branches. These requirements are fulfilled by the invention under consideration. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     To facilitate understanding, throughout the description, the adjective “leading” identifies the end or edge of an object, such as a prosthesis or device, that precedes the rest of said object, when said object is being introduced into another object such as the human body. 
       FIG. 1A  is a perspective view of the preferred embodiment of the implantable prosthesis 
       FIG. 1B  is a perspective view of an alternative embodiment of the implantable prosthesis incorporating magnetised struts 
       FIG. 2  is a perspective view of an alternative embodiment of the implantable prosthesis, characterized by curvilinear members attached to the leading edge and the trailing edge of the prosthesis 
       FIG. 3  is a perspective view of an alternative embodiment of the implantable prosthesis with additional curvilinear members attached to the proximal free edge of the prosthesis via a linear member 
       FIG. 4  is a perspective view of a branched embodiment of the implantable prosthesis for deployment in a organ at its bifurcation 
       FIG. 5  is a perspective view of an branched embodiment of the implantable prosthesis for deployment in a organ and its branches 
       FIG. 6A  is a perspective view of an alternative branched embodiment of the implantable prosthesis for deployment in an organ and its branch, characterized by curvilinear members attached to the leading edge and the trailing edge of the prosthesis 
       FIG. 6B  is a perspective view of an alternative branched embodiment of the implantable prosthesis for deployment in a organ and its branch, characterized by curvilinear members being attached to the edges of the prosthesis along the entire circumference of the prosthesis 
       FIG. 7A  is a perspective view of an alternative embodiment of the implantable prosthesis, characterized by one aperture 
       FIG. 7B  is a perspective view of an alternative embodiment of the implantable prosthesis, characterized by multiple apertures 
       FIG. 8A  is a end-on view of an aperture of an implantable prosthesis 
       FIGS. 8B &amp; 8C  are transverse sectional views through alternative embodiments of an aperture of an implantable prosthesis 
       FIG. 9A  is a perspective view of an alternative embodiment of the implantable prosthesis with multiple apertures 
       FIG. 9B  is a perspective view of an alternative embodiment of the implantable prosthesis with multiple apertures, characterized by curvilinear members attached to the leading free edge of the prosthesis along the entire circumference 
       FIG. 10A  is a perspective view of an alternative embodiment of the implantable prosthesis with a single aperture 
       FIG. 10B  is a perspective view of an alternative embodiment of the implantable prosthesis with a single aperture, characterized by curvilinear members attached to both free edges of the prosthesis along the entire circumference 
       FIG. 11  is a perspective view of an alternative embodiment of the implantable prosthesis characterized by a supporting strut limited to the length of the prosthesis 
       FIG. 12  is a perspective view of an alternative embodiment of the implantable prosthesis, characterized by a flanged trailing end 
       FIG. 13  is a longitudinal sectional view of the delivery tool 
       FIGS. 14A and 14B  are respectively longitudinal sectional views of the leading end of the delivery tool before and after detachment of the implantable prosthesis 
       FIG. 15A  is a longitudinal sectional view of the leading end of an alternative embodiment of the delivery tool 
       FIGS. 15B and 15C  are respectively longitudinal sectional views of the leading end of the alternative embodiment of the delivery tool before and after detachment of the implantable prosthesis 
       FIG. 16  is a longitudinal sectional view of the introducer catheter with its inner stiffening catheter in situ and locked to the introducer catheter 
       FIG. 17  is a surface view of the introducer catheter without the inner stiffening catheter in situ 
       FIG. 18  is a surface view of the inner stiffening catheter 
       FIG. 19  is a longitudinal sectional view partly in section of the leading end of the introducer catheter with the inner stiffening catheter in situ and locked to the introducer catheter 
       FIG. 20  is a longitudinal sectional view of the leading end of the introducer catheter after partial withdrawal of the inner stiffening catheter 
       FIG. 21  is a longitudinal sectional view partly in section of the leading end of the introducer catheter with the inner stiffening catheter in situ and locked to the introducer catheter illustrating the engagement of the leading free edge of the introducer catheter in the sulcus at the base of the conical tip 
       FIG. 22  is a transverse section through the sulcus of the leading end of a stiffening catheter 
       FIG. 23  is a perspective view of the implantable prosthesis being prepared for insertion in its loading cartridge 
       FIG. 24  is a perspective view of trailing end of a loading cartridge 
       FIG. 25A  is a perspective view of a loading cartridge containing an implantable prosthesis 
       FIG. 25B  is a perspective view partly in section of a loading cartridge containing an implantable prosthesis 
       FIG. 26  is a perspective view partly in section of a loading cartridge containing an implantable prosthesis with multiple branches 
       FIG. 27  is a surface view of the leading end of a loading cartridge for an implantable prosthesis with multiple apertures 
       FIG. 28  is a perspective view of a loading cartridge containing an implantable prosthesis with one aperture 
       FIG. 29  is a perspective view partly in section of a loading cartridge containing an implantable prosthesis with one aperture 
       FIG. 30  is a perspective view partly in section of an implantable prosthesis within its loading cartridge attached to its delivery tool 
       FIG. 31  is a perspective view partly in section of a implantable prosthesis being introduced into the abdominal aorta with an aneurysm 
       FIGS. 32 to 35  are longitudinal sectional views illustrating the implantation of a prosthesis in an abdominal aorta with an aneurysm according to the invention 
       FIGS. 36 to 45  are longitudinal sectional views illustrating the implantation of prostheses in a thoracoabdominal aorta with an aneurysm involving the craniocerebral branches according to the invention 
       FIGS. 46 to 53  are longitudinal sectional views illustrating an alternative procedure for implanting prostheses in a thoracoabdominal aorta with an aneurysm involving the craniocerebral branches according to the invention 
   

   DISCLOSURE OF THE INVENTION 
   DETAILED DESCRIPTION 
   For the purpose of simplicity, the nomenclature selected for labelling some of the embodiments of the implantable prosthesis is of relevance to the arterial system. However as will be clear to anyone skilled in the art, the scope for the use of the prosthesis is not limited to the arterial system alone. 
   The invention is made from biocompatible materials. The materials used to make the components for permanent implantation are in addition characterised by long-term dimensional, structural, and configurational stability under cyclic loading. 
   The primary component of the invention is a uni- or multilamellar tube (tubular prosthesis)  1  with circular or elliptical cross-section, made from a flexible polymer ( FIG. 1A ). Multiple magnetised linear strips or wires (magnetic struts)  1   a  may be bonded to the prosthesis  1 , parallel to the longitudinal axis of the prosthesis  1  ( FIG. 1B ). The strips  1   a  may be bonded to the inner or outer surface of the prosthesis  1 , or sandwiched between two adjacent lamellae. The magnetic struts  1   a  are aligned and spatially arranged to ensure that radial centrifugal forces are exerted along the entire length of the prosthesis  1 . The magnetised linear strips or wires may be substituted with symmetrical deposits of biocompatible magnetised particles. The particles may either be bonded to the tubular prosthesis  1  or impregnated in a resorbable biocompatible matrix that is bonded to the tubular prosthesis  1 . The leading edge  2  and the trailing edge  3  of the prosthesis may or may not be parallel to each other, or perpendicular to the longitudinal axis of the tube. To the leading free edge  2  of the tube is symmetrically attached a pair of outwardly biased, flexible curvilinear members  4  made from a material with good shape memory; in one embodiment of the invention, curvilinear members are made from a thermodynamic material with a transitional temperature range below the normal human body temperature. To at least one of the curvilinear members  4  is attached a narrow strip or wire (supporting strut)  5  of a material stiffer than the prosthesis material. The support strut  5  is longer than the tubular prosthesis  1 , and is bonded to the latter along its entire length, parallel to its long axis. The supporting strut is bonded to the inner or outer surface of the prosthesis  1 , or sandwiched between two adjacent lamellae. The angle the curvilinear members  4  make with the supporting strut  5  is congruent to the angle the leading free edge  2  makes with the longitudinal axis of the tubular prosthesis  1 . The angle between the curvilinear members  4  and the supporting strut  5  can be reversibly altered by the application of force perpendicular to the plane defined by the curvilinear members  4 . On removal of the force, the curvilinear members  4  return to their original position. To the tip of the supporting strut may be attached a short, narrow, cylindrical peg (locking peg)  6  (FIGS.  1 A, 1 B). The locking peg  6  has a larger cross-section than the supporting strut  5 . 
   In an alternative embodiment of the prosthesis, one or more curvilinear members  4   a , are also symmetrically attached to the trailing edge  3  of the tubular prosthesis  1  ( FIG. 2 ). Curvilinear members  4   b  may also be attached to a prolongation  5 ″ of the supporting strut beyond the leading edge of the prosthesis ( FIG. 3 ). The modifications to the tubular prosthesis  1 , described in this and the preceding paragraph may also be incorporated singly or in various combinations in the remaining embodiments of the prosthesis. 
   An alternative embodiment of the prosthesis (aorto-bifemoral prosthesis)  7  has a branched configuration as illustrated in  FIG. 4 . The crotch  8  and the two limbs  7   a , 7   b  of the prosthesis  7  are supported by a “V” shaped wire or strip (bifurcation supporting strut)  9  of a flexible material with good shape memory. 
   An alternative embodiment of the branched prosthesis (aortic arch-descending aorta prosthesis)  10  has the configuration as illustrated in  FIG. 5 , and is provided with two branches: left carotid limb  11 , and left subclavian limb  12 . Each branch  11 , 12  is provided with a longitudinal supporting strut  5   a , and one or more outwardly biased, flexible curvilinear members with good shape memory  4   a  at its leading edge, at least one of which is attached to the supporting strut  5   a.    
   An alternative embodiment of the branched prosthesis (ascending aorta-aortic arch prosthesis)  13  has the configuration illustrated in  FIG. 6A  and  FIG. 6B , and is provided with one branch: the brachiocephalic limb  14 . One or more outwardly biased, flexible curvilinear members with good shape memory  4 , 4   b  are symmetrically attached to the leading edge and the trailing edge of the prosthesis  13 . At least one of the curvilinear members attached to each free edge is attached to or continuous with the supporting strut  5 . The curvilinear members may be attached to the free edges along the entire circumference ( FIG. 6B ). 
   In an alternative embodiment of the prosthesis (descending aorta module)  15 , the prosthesis is provided with one or more apertures  16 , 17  in its wall as illustrated in  FIG. 7A  and  FIG. 7B  Each aperture is reinforced along its entire circumference with a flat doughnut-shaped patch  18  of a non-elastic, polymer with low resistance to plastic deformation ( FIGS. 8A ,  8 B,  8 C). The patch  18  may incorporate a radio-opaque or ferromagnetic substance to facilitate detection with radiography and magnetic resonance imaging respectively. 
   Alternative embodiments of the prosthesis with aperture have the configurations illustrated in  FIGS. 9A and 9B  (aortic arch-descending aorta module)  19  and  FIGS. 10A and 10B  (ascending aorta-aortic arch module)  20  respectively. The aortic arch-descending aorta module  19  has two apertures,  19   a , 19   b . The ascending aorta-aortic arch module  20  has one aperture  20   a . The ascending aorta-aortic arch module  20  is characterized by both free edges having one or more symmetricallly attached outwardly biased, flexible curvilinear members with good shape memory  4 , 4   b  symmetrically attached to the trailing edge of the prosthesis  20 . At least one of the curvilinear members attached to each free edge is attached to or continuous with the supporting strut  5  ( FIGS. 10A ,  10 B). The curvilinear members may be attached to the free edges along the entire circumference (FIGS.  9 B, 10 B). 
   In an alternative embodiment of the prosthesis (ilio-femoral module)  21   FIG. 11 , the supporting strut  5  does not extend beyond the trailing edge of the prosthesis. 
   In an alternative embodiment of the prosthesis (branch artery module)  22  the trailing free end  23  of the prosthesis  22  has a larger diameter than the rest of the prosthesis thereby giving a flanged configuration ( FIG. 12 ). To the trailing edge of the prosthesis  22  is symmetrically attached one or more outwardly biased, flexible curvilinear members with good shape memory  4   b , at least one of which is attached to or continuous with the supporting strut  5 . The curvilinear members  4   b  may be attached to the trailing free edge along the entire circumference. 
   The delivery tool  24  to implant the invention is represented by  FIG. 13 . It consists of a thin-wall catheter (locking catheter)  25 , and an axially movable, luminal coaxial wire (detachment wire)  26  (FIGS.  14 A, 14 B). The hub of the locking catheter  25  incorporates a Tuohy-Borst valve  27 . The leading end  28  of detachment wire  26  may be recessed as illustrated in  FIG. 15A . The length of the recess (locking recess)  29  exceeds by a small margin the length of the locking peg  6  ( FIG. 15B ). To the trailing end  30  of the detachment wire is attached a plug (detachment wire handle)  31 . The trailing end of the supporting strut  5  is a tight fit within the lumen of the locking catheter  25  (FIGS.  14 A, 14 B), so that frictional forces secure the supporting strut  5  to the locking catheter  25 . In an alternative embodiment, the locking catheter  25  snugly accommodates the detachment wire  26  and supporting strut  5 , once the locking peg engages the locking recess  29  on the detachment wire  26 , such that radial movement of the supporting strut with respect to the detachment wire  26  is substantially restricted, while axial movement of the locking catheter  25  over the detachment wire  26  is unhindered ( FIG. 15B ). 
   A commercially available introducer sheath fitted with a haemostatic valve and a female Luer hub is used to implant all embodiments of the prosthesis that do not have an aperture  1 , 7 , 10 , 13 , 21 . Prostheses with apertures  15 , 19 , 20 , are implanted with the dployment tool  32  represented by  FIG. 16 . It consists of a introducer catheter  33  ( FIG. 17 ), and an inner, axially movable, coaxial stiffening catheter  34  with a central lumen  35  ( FIG. 18 ). The leading end  36  of the introducer catheter  33  is concentrically flared. To the trailing end of the catheter is fitted a Tuohy-Borst valve  37  carrying a female Luer hub  38 . The lumen of the introducer catheter  33  communicates with the lumen of the female Luer hub  38  via the Tuohy-Borst valve  37 . Along the shaft  39  of the introducer catheter  33  are single or multiple side-ports  40 , 41  that spatially correspond to the apertures on the respective prosthesis, when the prosthesis is radially compacted. The side-ports  40 , 41  extend linearly to the leading end  36  of the introducer catheter  33  in the form of narrow slits  42 , 43  (FIGS.  17 , 19 , 20 , 21 ). The stiffening catheter  34  has one or multiple side-ports ( FIG. 18 ), that spatially correspond to the sideports  34   a ,  34   b  of the introducer catheter  33  (FIGS.  19 , 20 , 21 ). The leading segment  44  of the stiffening catheter  34  tapers to a cone-shaped expansion  45  at the tip. At the base of the cone-shaped expansion  45 , is a circumferential sulcus  46  surrounding the leading segment  44  of the stiffening catheter  34  at its junction with the cone-shaped expansion  45  ( FIG. 22 ). Prior to use, the stiffening catheter  34  is coaxially placed in the introducer catheter. The leading end  36  of the introducer catheter  33  is engaged in the circumferential sulcus at the base of the cone-shaped expansion  45  on the tip of the stiffening catheter  34 , and the Tuohy-Borst valve  37  tightened around the stiffening catheter  34  (FIGS.  19 , 21 ). With the leading end  36  of introducer catheter  33  engaged in the circumferential sulcus  46 , the introducer catheter  32  presents a streamlined profile. 
   Use of the Invention 
   The procedure for using the invention will be explained with reference to implantation in the aorta for the purpose of simplicity alone. As will be clear to anyone skilled in the art, the use of the invention and the method for implantation is not limited to this organ alone. 
   I. Preparation for Implantation: 
   A. Loading on to Delivery Cartridge: 
   It is anticipated that this step will be performed at the site of manufacture before the device is sterilised. 
   To facilitate introduction into the body, the prosthesis is flattened ( FIG. 23 ) and tightly rolled such that it presents the lowest possible profile. 
   In the case of embodiments of the prosthesis without branches or aperture  1 , 21 , 22  a short thin-wall cannula  47  is placed adjacent and parallel to the supporting strut  5 , and the prosthesis rolled around them so that the cannula is coaxial to the prosthesis. A thin-wall polymer tube serves as the loading cartridge  48 . The trailing end  49  of the cartridge  48  is flared and its free edge has two symmetrically placed slits  50 , 51  extending a short distance along the length of the loading cartridge  48 , creating two flaps  52 , 53  ( FIG. 24 ). By applying traction on the flaps  52 , 53  perpendicular to the longitudinal axis of the loading cartridge  48 , the latter can be split into two separate parts. The loading cartridge  48  is drawn over the prosthesis to prevent it from unravelling ( FIGS. 25A ,  25 B). 
   In the case of the aorto-bifemoral prosthesis  7 , the coaxial cannula  47  is placed through the limb ipsilateral to the side of the detachment wire  26 . 
   In the case of branched prostheses  10 , 13 , a thin-wall cannula  47   a , 47   b  is introduced though each of the branches before the prosthesis is rolled up ( FIG. 26 ). 
   In the case of prostheses with apertures  15 , 19 , 20 , a flexible, thin-wall cannula  54  is placed through each aperture in the prosthesis (FIGS.  28 , 29 ). A third cannula may be placed coaxial to the lumen of the prosthesis. The prosthesis is rolled around the supporting strut  5 . The loading cartridge  56  is a thin-wall tube with slits  57 , 58  spatially corresponding to the position of the cannulae ( FIG. 27 ). The loading cartridge  56  is drawn over the rolled-up prosthesis such that cannula  54  engages the respective slit  57  (FIGS.  28 , 29 ). 
   B. Mating the Prosthesis to the Delivery Tool: 
   The trailing end of the supporting strut  5  is forcibly inserted into the lumen of the leading end of the locking catheter  25  ( FIG. 14A ). In an alternative embodiment of the prosthesis, the locking peg  6  of the prosthesis is engaged in the locking recess  29  of the detachment wire  26 , and the locking catheter  25  advanced until tip of the detachment wire  26  is within its lumen ( FIG. 15B ). The Tuohy-Borst valve  27  of the locking catheter  25  is tightened, securing the detachment wire  26  to the locking catheter  25 , and thereby the prosthesis to the delivery system  24  ( FIG. 30 ). 
   II. Implantation of Prosthesis: 
   A separate procedure is described for implanting each of the different embodiments in the vascular system are described. These represent only examples to illustrate some of the envisaged uses of the invention and do not limit in any way the scope of its application as set forth in this patent application. Furthermore the deployment of a single prosthesis per site is described. Multiple prostheses may be coaxially deployed using the same or similar procedure if warranted by the anticipated circumferential stresses at the site of the lesion, by using two access sites alternately. 
   A. Implantation in the Infrarenal Aorta: 
   After the anatomy of the lesion has been satisfactorily determined, a guidewire is placed traversing the lesion. An introducer sheath  59  of appropriate calibre and length, with a hub of female Luer configuration attached to the haemostatic valve, is introduced coaxially over the guidewire and advanced until it spans the lesion. The guidewire and the introducer&#39;s dilator are removed. The loading cartridge  48  is introduced into the hub of the introducer sheath. Axial force is applied to the delivery tool  24  to backload the prosthesis  1  into the introducer sheath  59 . Once the entire prosthesis  1  has passed beyond the haemostatic valve, the loading cartridge  48  is split as described above and removed. The prosthesis is advanced to the desired site under imaging guidance ( FIG. 31 ). Holding the delivery tool  24  in place, the introducer sheath  59  is withdrawn exposing the leading edge  2  of the prosthesis  1 . The curvilinear members  4  attached to the leading edge  2  regain their original shape, unrolling the prosthesis  1 . The introducer sheath  59  is withdrawn further until the entire prosthesis is deployed ( FIG. 32 ). Via another arterial access site, a guidewire is advanced coaxially through the prosthesis. A stent  60  is deployed across the leading edge of the prosthesis  1  using procedures well known to those skilled in the art, securing the prosthesis  1  to the vessel ( FIG. 33 ). The Tuohy-Borst valve  27  of the delivery tool  24  is opened. The locking catheter  25  is withdrawn detaching the prosthesis from the detachment wire  26 . The delivery tool  24  is withdrawn. Another stent  61  is placed across the trailing edge of the prosthesis ( FIG. 34 ). More stents  63  are place along the length of the prosthesis if deemed desirable ( FIG. 35 ). 
   B. Implantation at the Aortic Bifurcation: 
   Deployment of the bifurcated prosthesis  7  is performed as explained above, ensuring that the entire device lies in the descending aorta. The prosthesis  7  is withdrawn, if desired, using the delivery tool  24 , so that the prosthesis limb  7   b  contralateral to the detachment wire  26  enters its corresponding common iliac artery. Via the ipsilateral femoral artery, a guidewire is advanced coaxially through the prosthesis. A stent is deployed across the leading edge  2  of the prosthesis  7  securing it to the vessel. Another stent is placed overlapping the free edge of the ipsilateral limb  7   b  of the prosthesis. This step may be preceded by the placement of an iliofemoral module  21 . In that case, another stent is placed overlapping the trailing edge of the latter. The bifurcated prosthesis  7  is detached from delivery tool  24 . A stent is placed across the trailing edge of the prosthesis limb  7   a  on the same side. This step may be preceded by the placement of an iliofemoral module  21 . In that case, another stent is placed overlapping the trailing edge of the latter. More stents are place to bridge the gaps between the previously placed stents if deemed desirable. 
   Aorto-biiliac lesions may be alternatively treated by placing two tubular prostheses  1  in parallel, with one prosthesis extending into each iliac artery (Sakaguchi S, et. al. Twin-tube endografts for aortic aneurysms: an experimental feasibility study. J Vasc Intervent Radiol 1999; 10:1092–98.) 
   C. Implantation in the Aortic Arch and its Craniocerebral Branches: 
   (a) Implantation of Modular Prostheses: 
   One or multiple stents  64  are placed across the lesion ( FIG. 36 ). A guidewire is advanced into the left subclavian artery  65 . An angioplasty catheter  66  is advanced over the guidewire into the left subclavian artery  65 . The position of the catheter  66  is adjusted so that the balloon straddles the wall of stent  64 . The balloon is inflated to displace any stent strut crossing the ostium of the left subclavian artery  65  ( FIG. 37 ). The balloon catheter  66  is withdrawn. Using techniques well known to those skilled in the art, a branch artery module  22  of appropriate size is implanted in the left subclavian artery  65 , such that its flanged trailing edge  23  lies within the stent. A stent is placed in the prosthesis  22  to secure it in place. A branch artery module  22  is similarly placed in the left carotid  67  and in the brachiocephalic artery  68  via the same and contralateral access sites respectively. Stents are placed in the prostheses. The guidewires  69 , 70 , 71  are not removed ( FIG. 38 ). 
   Another guidewire is placed in the descending aorta via the access used to place the branch artery module in the brachiocephalic artery  68 . The stiffening catheter is placed in the introducer catheter and their hubs locked together. The trailing end of the guidewire is fed through the lumen of the stiffening catheter  34  until it exits from the hub of the stiffening catheter. Likewise, the trailing end of the guidewire  69  in the brachiocephalic artery  68  is fed through the sideports of the introducer catheter  33  and stiffening catheter  35 . The introducer catheter is advanced over the guidewires until the sideport of the introducer catheter is at the level of the ostium of the brachiocephalic artery  68 . The Tuohy-Borst valve  37  in the hub of the introducer catheter  33  is partially opened. The stiffening catheter  34  is advanced slightly to disengage the tip  36  of the introducer catheter  37 . The stiffening catheter  35  is then withdrawn with its coaxial guidewire. 
   The trailing end of the guidewire  69  in the brachiocephalic artery  68  is fed through the cannula  54  lying in the slit  57  of a cartridge containing an ascending aorta-aortic arch module  20 . The cannula is removed and the prosthesis  20  is introduced in the hub  38  of the introducer catheter  34 . The Tuohy-Borst valve  37  is opened, and the prosthesis  20  backloaded into the introducer catheter  34 , and the loading cartridge  56  removed. The prosthesis  20  is advanced until the aperture on the prosthesis is at the level of the ostium of the brachiocephalic artery  68 . The introducer catheter  34  is withdrawn, deploying the prosthesis  20  ( FIG. 39 ). Via the contralateral femoral artery, a stent  72  is placed overlapping the leading free edge  73  of the prosthesis  20 , and securing it in place ( FIG. 40 ). The prosthesis  20  is detached from the delivery tool  24 , and the latter withdrawn. An angioplasty catheter  66  is advanced into ostium of the prosthesis  20  in the brachiocephalic artery  68  over the guidewire in situ. The balloon is inflated to dilate the aperture of the prosthesis  20  ( FIG. 41 ). The angioplasty catheter is withdrawn ( FIG. 42 ). 
   The trailing end of the guidewire lying with its tip in the aorta is fed through the lumen of the stiffening catheter  34  of an introducer catheter  32 , with two side-ports until it exits from the hub of the stiffening catheter. Likewise, the trailing end of each of the guidewires  70 , 71  in the left carotid artery  67  and left subclavian artery  65  is fed through the appropriate sideport of the introducer catheter  33  and its coaxial stiffening catheter  34 . The introducer catheter-stiffening catheter ensemble is advanced over the guidewires until the sideports of the introducer catheter and stiffening catheter are at the level of the corresponding branch vessel ostium. The Tuohy-Borst valve  37  in the hub of the introducer catheter  33  is partially opened. The stiffening catheter  34  is advanced slightly to disengage the tip  36  of the introducer catheter  33 , and then withdrawn with its coaxial guidewire. 
   The trailing end of each of the guidewires  70 , 71  in the left carotid  67  and subclavian arteries  65  is fed through the appropriate cannula  54 , 55  in the slits  50 / 51  of a cartridge containing an aortic arch-descending aorta module  19 . The cannulae are removed. The prosthesis  19  is backloaded into the introducer catheter  33  as described for a prosthesis without apertures. The prosthesis  19  is advanced until the each sideport  40 , 41  is at the level of the corresponding branch ostium. The introducer catheter  33  is partially withdrawn, deploying the prosthesis with its leading edge  74  overlapping the trailing edge  75  of the prosthesis  20  already in situ ( FIG. 43 ). An angioplasty catheter is introduced into the aorta over the guidewire  70  and placed straddling the ostium of the left carotid artery  67 . The balloon is inflated dilating the corresponding aperture of the implanted prosthesis  19 . The same procedure is repeated for the left subclavian artery  65 . Via the femoral artery contralateral to that used to place the prosthesis  19 , a stent  76  is placed overlapping the leading free edge  74  of the aortic arch-descending aorta module  19  securing it in place ( FIG. 44 ). The delivery tool is detached from the prosthesis  19  and withdrawn. Another stent  77  is placed overlapping the trailing edge  78  of the prosthesis  19  ( FIG. 44 ). More stents  79  are placed if deemed necessary ( FIG. 45 ). Repeat dilatation of the ostium of the craniocerebral branches may be performed using, procedures familiar to those skilled in the art, if deemed necessary. 
   (b) Implantation of Branched Prostheses: 
   One or multiple stents  64  are placed spanning the lesion ( FIG. 46 ). Via the left carotid artery  67 , and via the left subclavian artery  65 , two microsnares  80 , 81  are placed in the aorta using procedures familiar to those skilled in the art ( FIG. 47 ). Via an introducer sheath placed in one common femoral artery, a loop snare is placed in the aorta. Using this loop snare, the two microsnares  80 , 81  are exteriorised. The introducer sheath  82  is advanced until its tip was immediately peripheral to the ostium of the left subclavian artery  65 . Each microsnare is placed around the corresponding limb  11 , 12  of an aortic arch-descending aorta branched prosthesis  10 , loaded in its cartridge  48 . The snares are tightened and branched prosthesis  10  is backloaded into the introducer sheath  83  ( FIG. 48 ). In synchrony, the microsnares  80 , 81  are withdrawn and the aortic arch-descending aorta branched prosthesis  10  advanced until each prosthesis limb  11 , 12  has entered its respective branch artery ( FIG. 49 ). The introducer sheath  82  is withdrawn. The microsnares  80 , 81  are withdrawn further and the delivery tool  24  advanced in tact until a satisfactory orientation of the aortic arch-descending aorta branched prosthesis  10  is achieved ( FIG. 50 ). The prosthesis limbs  10 , 11 , are released allowing them to open ( FIG. 51 ). Via the femoral artery contralateral to that used to place the branched prosthesis  10 , a stent is placed in each prosthesis limb  11 , 12 , securing it in place. The aortic arch-descending aorta branched prosthesis  10  is detached from the delivery tool  24 , and the latter withdrawn. Via the brachiocephalic artery  68 , a microsnare  83  is introduced into the aorta ( FIG. 52 ). Using the procedure described for aortic arch-descending aorta branched prostheses  10 , an ascending aorta-aortic arch branched prosthesis  13  is implanted ensuring That its trailing edge  84  overlaps the leading edge  85  of the previously implanted aortic arch-descending aorta branched prosthesis  10 . A stent  86  is placed overlapping the leading edge  87  of the ascending aorta-aortic arch branched prosthesis  13 . The prosthesis  13  is detached from the delivery tool  24 , and the latter withdrawn. Another stent  88  is placed across the trailing edge  89  of the aortic arch-descending aorta prosthesis  10  ( FIG. 53 ). More stents are placed along the length of the prosthesis if deemed necessary.