Patent Publication Number: US-10327934-B2

Title: Prosthesis delivery device

Description:
RELATED APPLICATIONS 
     The present patent document is a continuation of application Ser. No. 13/844,237, filed Mar. 15, 2013, which is hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     This invention relates to medical device delivery systems for the introduction of a medical device into a patient, in particular to an introducer/delivery device, systems and methods for delivering a prosthesis to an implantation site in a patient. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to delivery devices for prostheses, such as stents, grafts and stent grafts (collectively prostheses) in the vascular system of a patient. In particular, the invention relates to a prosthesis delivery system, device and method that provides the controlled release and implantation of a prosthesis in a controlled manner. In particular, the invention relates to an introducer/delivery device delivery handle that permits controlled release of a prosthesis from the introducer/delivery device. 
     BRIEF SUMMARY OF THE INVENTION 
     A prosthesis delivery device comprises a proximal end and a distal end, a prosthesis retention section at the proximal end, and a prosthesis retained on the prosthesis retention section. The prosthesis has a proximal end releasably attached at the prosthesis retention section and a distal end releasably attached at the prosthesis retention section. A sheath is slidably disposed over the prosthesis. A delivery handle near the distal end the delivery device comprises a rotatable inner cannula having a cannula lumen and cannula handle. The cannula handle is rotatable with the inner cannula, the inner cannula having a proximal end releasably engaged to the proximal end of the prosthesis. 
     Further, a positioner handle is releasably engaged with the cannula handle. Rotation of the inner cannula releases the proximal end of the prosthesis from the delivery device and withdrawal of the sheath from over the prosthesis releases the distal end of the prosthesis from the delivery device. 
     Other systems, methods, features and advantages of the invention will be, or will become, apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be within the scope of the invention, and be encompassed by the following claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the claims, are incorporated in, and constitute a part of this specification. The detailed description and illustrated examples described serve to explain the principles defined by the claims. 
         FIG. 1  is a partial side view of a prosthesis delivery device, in particular the handle portion of the device at the distal end of the delivery device. 
         FIG. 2  is a further view of the prosthesis delivery device of  FIG. 1  at a stage of deployment of a prosthesis. 
         FIG. 3  is a further side view of the prosthesis delivery device of the  FIG. 1  at another stage of deployment of the prosthesis. 
         FIG. 4  is a further side view of the prosthesis delivery device of the  FIG. 1  at another stage of deployment of the prosthesis 
         FIG. 5  is a further side view of the prosthesis delivery device of the  FIG. 1  at another stage of deployment stage of deployment of the prosthesis 
         FIG. 6  is a partial side view of a proximal end of a delivery device with an exemplary prosthesis end attachment and release mechanism. 
         FIG. 7  is a close up partial side view of the proximal end attachment and release mechanism 
         FIG. 8  shows a partial side view of the delivery device of  FIG. 6  having a prosthesis on the delivery device with the proximal end stent attached to the proximal end attachment and release mechanism. 
         FIG. 9  shows the device of  FIG. 8  with the end stent released from the proximal end attachment and release mechanism. 
         FIGS. 10-14  show further partial side views of the device of  FIGS. 8 and 9  and the procedure for releasing the distal end of the prosthesis from the distal end attachment and release mechanism and releasing the proximal end of the prosthesis from the proximal end attachment and release mechanism. 
         FIGS. 15A-D  are perspective views of the prosthesis distal end with exemplary distal end attachment and release mechanisms. 
         FIGS. 16A-B  are perspective views of the prosthesis distal end with another exemplary distal end attachment and release mechanism. 
         FIGS. 17A-B  are perspective views of the prosthesis distal end with another exemplary distal end attachment and release mechanism. 
         FIGS. 18A-B  are perspective views of the prosthesis distal end with another exemplary distal end attachment and release mechanism. 
         FIGS. 19A-D  are perspective views of the prosthesis distal end with another exemplary distal end attachment and release mechanism. 
         FIG. 20  is a cross-sectional view of the cannula/cannula handle connection element. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The embodiments described in this disclosure will be discussed generally in relation to deployment of prostheses, such as stents, grafts and stent grafts into the aorta, but the disclosure is not so limited and may be applied to other vasculature or other body vessels or lumens. 
     In the present application, the term “proximal” refers to a direction that is generally closest to the heart during a medical procedure, while the term “distal” refers to a direction that is furthest from the heart during a medical procedure. 
     The term “stent graft” refers to a device that has a tubular body of biocompatible graft material and at least one stent fastened to the tubular body to define a lumen through the stent graft. The stent graft may be bifurcated and/or may include fenestrations, side arms, or the like. Other arrangements of stent grafts also are within the scope of this disclosure. 
     The present delivery device operates to release a prosthesis from a delivery device at an implantation site within a body vessel. In particular, the delivery device may release the proximal end of a prosthesis from retention at and/or within the delivery system. For example, the delivery device may release the proximal end, such as an end stent of a prosthesis from within a top cap holding the proximal end, such as an end stent of the prosthesis by twisting the cannula. 
     The delivery device may further release the distal end of the stent graft through sheath pull back. The distal end of the prosthesis may be held to the delivery device prior to release by holding the distal end to a part of the delivery device. In one example, a distal capture feature on the delivery device holds the distal end of the prosthesis. While the sheath is in place over the prosthesis the distal end remains held or captured on the delivery device. With the withdrawal of the sheath in a distal direction and past the distal capture feature, the distal end of the prosthesis is released from the delivery device. In this example, a trigger wire is not needed to retain the distal end of prosthesis or to release the distal end. 
     The delivery handle of the present delivery device includes one or more interlocks to prevent the physician from performing deployment steps out of sequence and from failing to perform or complete the delivery steps, which may be critical to the proper delivery of the prosthesis. The present device also provides a handle design that eliminates or reduces the need for the physician to remove his/her hands from the handle to complete delivery of the prosthesis, hence providing increased control over the device and the delivery process, which can mean the difference between a successful and a less than successful or unsuccessful procedure. 
     As described more fully below with regard to  FIG. 1-5 , the delivery device  100  has a deployment handle  102  which accomplishes the above functions. The handle has three primary grip points—a sheath handle  104 , a positioner handle  106 , and a cannula handle  108 . The sheath handle  104  also may provide a valve housing for one or more valves for maintaining hemostasis. The sheath handle also may allow for flushing of the sheath. Exemplary valve structures that may be used as the one or more valves in the valve housing are shown in U.S. Patent/Publication Nos. 2012/0310178; 2005/0171479; 2007/0078395; 2008/0157017; 2011/0054585; and 2012/0238958 in which the descriptions and operations of the valves disclosed are incorporated by reference in their entirety herein. In operation, the sheath handle  104  is gripped by the physician to withdraw the sheath from over the prosthesis. 
     The second handle, the positioner handle  106 , maintains the position of the prosthesis during all stages of deployment. The positioner handle  106  provides a consistent point of reference of the prosthesis during the procedure. The third handle, the cannula handle  108 , provides control over the cannula and the proximal end of the delivery device. Specifically, the cannula handle  108  provides rotational control of the cannula and hence controls release of the proximal part or stent of the prosthesis from the delivery device. 
       FIGS. 1-5  illustrate prosthesis delivery device  100  with deployment handle  102  as it is operated by a user to release the proximal and distal ends of a prosthesis, such as a stent, graft or stent graft.  FIGS. 6-10  illustrate an embodiment of the release of proximal end of the prosthesis with the deployment handle  102  of  FIGS. 1-5  is operated as described below. 
       FIGS. 1 and 2  show a partial side view of a prosthesis delivery device  100  having a distal end  101  a proximal end (not shown in  FIGS. 1 and 2 , but  103  in later figures) and a deployment handle  102  near the distal end  101  of the delivery device  100 . The deployment handle  102  is intended to remain outside of the patient. As set forth above, the deployment handle  102  preferably has three primary grip points, the sheath handle  104 , the positioner handle  106  and the cannula handle  108 . Any or all of the handles may be provided with gripping features that provide secure and/or ergonomic gripping of the handles by the physician. Any or all of the handles may further be provided with a mechanism or ability to provide the physician with tactile feedback while gripping and/or operating the handle. 
     As shown in  FIGS. 1-4 , the deployment handle  102  includes a sheath  110 , a sheath handle  104 , a positioner  112  having a positioner shaft  114 , a positioner handle  106 , a cannula  116  having an inner lumen  118 , a cannula handle  108 , a cannula handle stop  120 , a cannula safety  122 , and a safety collar  124 . 
     The sheath handle  104  is connected to the sheath  110 . As set forth above, sheath handle  104  provides a gripping point for the physician to withdrawn the sheath from over the prosthesis for deployment. The sheath  110  extends proximally of the sheath handle  104  and is disposed over the prosthesis prior to delivery of the prosthesis to the target treatment site. 
     The positioner shaft  114  is operatively connected to the positioner handle  106 , and extends proximally of the positioner handle  106 . In a preferred embodiment, the proximal end  126  (shown in  FIGS. 10-16 ) of the positioner handle  106  is located at or near the distal end  128  of a prosthesis  130  that is disposed on the delivery device  100 . As described more fully below with reference to  FIGS. 10-16 , the positioner proximal end  126  may engage the distal end  128  of the prosthesis  130  by way of a releasable distal attachment and release mechanism  132 . Positioner  112  further may include a positioner handle attachment region  134 , for attaching to the cannula handle  108 . The positioner handle attachment region  134  may be a keyed region with threading. A mechanism to limit full sheath pullback, such as safety collar  124 , may be disposed on the positioner  112  and is located adjacent to the proximal end  126  of the positioner handle  106 . Although safety collar  124  is shown as disposed about the shaft of the positioner, other mechanisms, such as a protrusion or other feature that at least temporarily prevents full pullback of the sheath, may be used. 
     The cannula  116  has a distal end  136  and a proximal end (not shown) and extends from the distal end  101  of the delivery device  100  to the proximal end  103  of the delivery device  100 . The cannula  116  may have an inner lumen  118  that runs from the distal end  136  of the cannula  116  to the proximal end of the cannula and/or the delivery device  100 . The cannula inner lumen  118  may accommodate a guide wire (not shown), one or more prosthesis release mechanisms (not shown), such as one or more trigger wires, and further may provide a passageway for the injection of a contrast medium through the lumen for viewing the delivery device and/or the prosthesis during a procedure. 
     Positioner  112  has an inner lumen  138 . Cannula  116  is at least partially disposed within the inner lumen  138  of positioner  112  and, in operation, may be axially slideable and rotatable relative to the positioner  112 . Sheath has sheath inner lumen  140 , which lumen inner diameter may closely approximate the outer diameter of the positioner  112 . Positioner  112  is at least partially disposed over the cannula  116  and may be at least partially disposed within the sheath  110  and/or the prosthesis  130 . 
     The cannula  116  includes at least one cannula marker  142 , which may be one or more marker bands, a notch, a color marker or other physical marker device that is physically viewable to the physician at least one point during the delivery procedure to indicate the completion of one or more delivery steps. Cannula  116  includes a cannula handle  108 , and a cannula handle stop  120 . Cannula handle  108  further may include a cannula/cannula handle connection element  144 , which be keyed, and connection element  146 . For example, cannula handle  108  may be keyed through the cannula/cannula handle connection element  144  to the cannula  116 . The cannula/cannula handle connection element  144  permits the cannula handle  108  to slide on the cannula  116 , even as the cannula handle  108  rotates the cannula  116 , to the cannula handle stop  120 . The cannula/cannula handle connection element  144  is more fully described with reference to  FIG. 20  below. The cannula/cannula handle connection element  144  may be keyed and may include a ratchet mechanism, as known to those of skill in the art, to allow uni-directional turning. Cannula handle connection element  146 , which engages the positioner handle attachment region  134 , also may be keyed and is temporarily connected to the positioner handle attachment region  134 . As shown in  FIGS. 1 and 2 , the positioner handle  106  is engaged with the cannula handle  108  through the positioner handle attachment region  134  and the cannula handle connection element  146 . Although the connection between the cannula handle  116  and the positioner handle  106  is described here as a keyed connection, other connections may be contemplated or used. The cannula safety  122 , which may be located on the cannula handle  108 , locks the connection between the cannula handle  108  and positioner handle  106 , until their disengagement is required. 
     As shown in the figures, cannula safety  122 , which may be located on the cannula handle  108 , locks the connection between the cannula handle  108  and positioner handle  106 , until their disengagement is required. Cannula safety  122  prevents rotational and axial movement of the cannula handle  108  relative to the positioner handle  106  until their disengagement. The cannula safety  122  may engage the positioner handle  106  through a latching or other engagement, such as a pin, clip and others known to one of skill in the art. Further, rather than be provided on the cannula handle, the safety may be provided on the positioner handle  106 . 
     In  FIG. 2  the graft deployment handle  102  is shown with the sheath  110  partially withdrawn along the positioner  112  in the distal direction as indicated by the arrow. In operation, the physician places one hand on the sheath handle  104  (valve housing) and the second hand on the positioner handle  106 , which is initially combined with the cannula handle  108 . The physician slowly pulls the sheath handle in the direction of the arrow shown in  FIG. 2  toward the positioner handle to unsheath the prosthesis. The positioner shaft  114  is constructed of a material or in such a manner to have sufficient rigidity/stiffness to resist buckling of the positioner shaft  114  as sheath  110  is withdrawn over it. The safety collar  124  on the positioner shaft  114  prevents the sheath handle  104  from moving too far distally and prematurely releasing the distal attachment of the prosthesis. 
       FIG. 3  shows the deployment handle  102  with the cannula safety  122  disengaged from the positioner handle  106 . The cannula safety  122  may be disengaged from the positioner handle  106  by moving the cannula safety  122  distally, as shown by the arrow in  FIG. 3 . The cannula handle  108  and cannula  116  are rotated as shown by the arrow in  FIG. 3  to disengage the cannula handle  108  from the positioner handle  106 . As set forth above, the cannula handle  108  is connected to the cannula  116  through the cannula/cannula handle connection element  144  which causes the cannula  116  to turn as the cannula handle  108  is disengaged from the positioner handle  106 . 
     As the cannula handle  108  rotates the cannula  116 , the cannula handle  108  is removed from engagement with the positioner handle  116  by, for example, unthreading the cannula handle  108  from the positioner handle  106 . As the unthreading or disconnection occurs, the cannula handle  108  separates from the positioner handle  106  and slides axially along the cannula  116  in a distal direction until it reaches the cannula handle stop  120  as shown in  FIG. 3 . As set forth above, the cannula handle  108  includes a mechanism, such as a ratchet mechanism, to permit rotation in a single direction. 
     The number of turns required to separate the two handles is preferably equal to the minimum number of cannula turns required to release the proximal end of the prosthesis from its holding mechanism. Once the cannula handle  108  and the positioner handle  106  are separated, the cannula handle  108  may be further withdrawn to pull the delivery device tip out of the proximal region of the prosthesis, such as the area where one or more stents are located at the proximal end, and into the main body of the prosthesis. When the cannula handle  108  makes contact with cannula handle stop  120 , further withdrawal of the handle causes pullback of the cannula  116  as shown by the arrow in  FIG. 4  to a desired point. Marker(s)  142  on the cannula gives the physician the visual indication that the cannula  116  is pulled back to the desired point. In lieu of a marker, a further stop may be provided to limit the pullback of the cannula to the desired point. 
       FIG. 5  further shows the completion of the retraction of the sheath  110 . Up to this point, further retraction of the sheath  110  has been prevented by a mechanism  124  to prevent sheath pullback, such as a removable safety collar  124 . As shown, the safety collar  124  is removed from the positioner shaft  114  and the sheath  110  is further withdrawn in a distal direction until the sheath  110  is adjacent to the proximal end of the positioner handle  106 . The safety collar  124  may be a hinge ring that may be opened and removed from the positioner. The further withdrawal of the sheath  110  exposes the proximal end (shown in  FIGS. 10-16  as element  126 ) of the positioner  112  and releases the distal end  128  of prosthesis  130  from the positioner  112 , as discussed in further detail below. 
     As set forth above, the various features described provide for sequential operation of the delivery device with various interlocks to prevent performing of the deployment steps in the wrong order and require completion or to prevent completion of the steps. In summary, the sheath  110  is pulled back to partially release the prosthesis from the sheath. The sheath is prevented from complete pullback due to a safety mechanism, such as a collar, that prevents further movement ( FIG. 2  showing sheath handle moves in the direction of the arrow). A safety connecting the positioner handle and the cannula handle is released and the cannula handle is unthreaded from the positioner handle by rotating the cannula handle ( FIG. 3 ). This unthreading also causes the cannula handle to move distally dues to its keyed relationship with the cannula ( FIG. 3 ). The cannula handle moves distally until it meets the cannula stop, at which point the cannula and the cannula handle move distally together to fully disengage the cannula handle from the positioner handle ( FIG. 3 ). The unthreading of the cannula handle from the positioner handle by rotating the cannula handle serves to rotate the proximal end of the cannula to release the proximal end of the prosthesis from the delivery device as will be explained in detail below. When the cannula handle  108  makes contact with cannula handle stop  120 , further withdrawal of the handle causes pullback of the cannula  116  as shown by the arrow in  FIG. 4 . Marker(s)  142  on the cannula gives the physician the visual indication that the cannula  116  is pulled back to the desired point. ( FIG. 4 ). The safety collar  124  is then removed permitting further withdrawal of the sheath over and off the prosthesis. This further withdrawal of the sheath operates to release the distal end of the prosthesis from the delivery device as further explained below. 
       FIGS. 6 and 7  show partial views of a proximal end and proximal portion of the delivery device  100 , and illustrate an embodiment of a prosthesis proximal attachment and release mechanism for the release of the proximal end of the prosthesis using the delivery handle described above.  FIG. 6  shows the cannula  116 , a tapered nose cone/dilator  148  having a proximal tip  150 . As shown, nose cone  148  has a reverse distal taper  152  at its distal end  154 . The nose cone surface  162  presents a smooth tapered surface to facilitate entry into and movement through a body vessel. An exemplary prosthesis proximal end attachment and release mechanism  156  is disposed at or near the distal end  154  of the nose cone  148  and on the cannula  116 .  FIG. 7  shows the proximal end attachment and release mechanism  156  in greater detail. The proximal end attachment and release mechanism  156  comprises coiled member  164  which comprises a proximal end  166 , a distal end  168 , and a plurality of turns  170  disposed therebetween, as shown in  FIG. 7 . In this non-limiting example, the proximal end  166  of the coiled member  164  is secured to the outer surface  172  of the cannula  116  using a suitable mechanism, such as a solder, weld, mechanical attachment, friction fit, crimp, or combination of these or other techniques and mechanisms. Accordingly, the proximal end  166  of the coiled member  164  cannot move relative to the outer surface  172  of the cannula  116 . The proximal end  166  of the coiled member  164  comprises a first diameter d 1 , which may be approximately the same diameter, or slightly greater than, an outer diameter of the cannula  116 . 
     The distal end  168  of the coiled member  164  is unsecured relative to the outer surface  172  of the cannula  30 , as shown. The distal end  168  of the coiled member  164  may comprise a second diameter d 2 , which is greater than the first diameter d 1  of the proximal end  166  of the coiled member  164 . There is a separation or gap  174  between the distal end  168  of the coiled member  164  and the outer surface  172  of the cannula  116 , as best seen in  FIG. 7 . 
     The plurality of turns  170  are divided into a proximal series of turns  170   a , which have the first diameter d 1 , and a distal series of turns  170   b , which have the second diameter d 2 . The proximal series of turns  170   a  may be disposed in close proximity or abutting one another, as depicted in  FIG. 7 . By contrast, the distal series of turns  170   b  may be spaced apart from one another a greater distance than the proximal series of turns  170   a . In  FIG. 7 , the distal series of turns  170   b  are spaced apart a predetermined distance denoted by spacing  176 . 
     As shown in  FIGS. 8 and 9 , stent graft  200  is disposed on the device and has a proximal end  202  and distal end  204 . Stent graft  200  includes, in this example, a graft material  206 , a bare proximal top stent  208  (though the disclosure is not so limited), and one or more stents  210  attached to the graft material  206 . The stents  210  may be on either or both surfaces of the tube of graft material  206  and may have the characteristics of self expanding stents, balloon expanding stents, or both, depending on the desired stent characteristics. 
     At or adjacent the distal end  154  of the nose cone  148 , a proximal prosthesis retention mechanism  156  (shown in the dotted box, which is not part of the device) may be disposed. For example, the release mechanism may include the coiled member  164  discussed with regard to  FIGS. 6 and 7 , and further include at least one suture loop  212 . 
     In  FIGS. 8 and 9 , an exemplary coupling of the stent graft  200  to the delivery device  100  of  FIG. 1-5  is shown and described. The stent graft  200  has an uncoupled state in which the stent graft  200  is positioned coaxially over the cannula  116  with the proximal end  202  of the stent graft  200  in longitudinal proximity relative to the distal end  216  of the coiled member  164 , as shown in  FIG. 9 . During assembly, one or more suture loops  212  that are coupled to the proximal apices  214  of the stent  208  are threaded around the distal end  160  of the coiled member  164  one at a time, preferably until all of the suture loops  212  are coupled to the coiled member  164 . Such coupling may be achieved by rotating the cannula  116  in a clockwise direction until the proximal end  202  of the stent  208  is sufficiently compressed in a radially inward direction, as depicted in  FIG. 8 . As gap between the distal end  160  of the coiled member  164  and the outer surface of the cannula  116  permits positioning of the suture loops  212  in the series of turns at the distal end  160  of the coiled member  164 . This type of attachment system of the proximal stent to the delivery system is more fully described with reference to FIGS. 4 and 5 of U.S. application Ser. No. 13/796,395 (filed Mar. 12, 2013) which description and Figures, and in particular FIGS. 1, 2, 4 and 5 and the corresponding description are hereby incorporated by reference in their entirety. 
     The suture loops  212  are further accommodated within a spacing between the distal series of turns. The suture loops  212  preferably are coupled to the coiled member  164  in a manner in which at least one suture loop  212  is positioned around at least one full turn of the distal series of turns, and preferably around at least 1.5 turns at the distal end  168  of the coiled member  164 , thereby reducing the likelihood of inadvertent uncoupling of the suture loops  212  from the coiled member  164 . 
     The coupling shown in  FIG. 9  secures the stent  208  to the cannula  116  via the coiled member  164  in a manner that may subsequently facilitate insertion of the subassembly comprising the cannula  116  and the stent graft  200  into an outer sheath. As will be apparent, the outer sheath is configured to radially restrain other regions of the stent graft  200  for delivery to a target site within a patient&#39;s anatomy. 
     The suture loops  212  may be coupled to every other proximal apex  214  as shown in  FIG. 8  to restrain the stent  208  during delivery. The suture loops  212  are not coupled to the second proximal apices  214   b , which may comprise barbs. By restraining the alternating proximal apices  214  using the suture loops  212  coupled to the coiled member  164 , the adjacent second proximal apices  214   b  also may be indirectly pulled in a radially inward direction during delivery. The configuration of the stent  208  facilitates the indirect compression of the adjacent second proximal apices  214   b . Since only selected ones of the proximal apices are restrained during delivery, the number of suture loops  212  may be reduced. This type of attachment system of the proximal stent to the delivery system is more fully described with reference to FIGS. 4 and 5 of U.S. application Ser. No. 13/796,395 (filed Mar. 12, 2013) which description and Figures, and in particular FIGS. 1, 2, 4 and 5 and the corresponding description are hereby incorporated by reference in their entirety. 
       FIGS. 10-14  illustrate the release of the distal end of the stent graft, with further reference to  FIGS. 15 and 16  for particular embodiments of the distal end attachment and release mechanism.  FIG. 10  shows the stent graft  200  loaded on the device and compressed by the sheath  110 . In operation, the operator withdraws the sheath  110  in the direction indicated by the arrow shown in  FIG. 11 . When the stent  208  is at least partially exposed, and it is desirable to deploy the restrained proximal end of the stent  208 , the cannula  116  may be rotated in a counter-clockwise direction (as shown by the arrow in  FIG. 12 ) until the suture loops  212  are uncoupled from the coiled member  164 , i.e., in a reverse manner from which the suture loops  212  were coupled to the coiled member  164 . The stent  208  then may be deployed as shown in  FIGS. 8 and 9 , and the remainder of the stent graft  200  may be deployed by further retraction of the sheath  110  (as shown by the arrows in  FIGS. 13 and 14 ) or actuation of any other devices that are constraining the remainder of the stent graft  200 . 
     Advantageously, the proximal end of the stent  208  is radially restrained without the use of conventional trigger wires that span a full longitudinal length of the delivery system. Accordingly, the radial profile of the delivery system may be reduced without the provision of multiple trigger wires and one or more associated sleeves to house the trigger wires, thereby reducing packing density of the system. Moreover, deployment may be simplified as reduced deployment forces are expected to be needed relative to the use of conventional trigger wires. 
     As a further advantage, deployment of a stent using the described device comprising at least one coiled member may allow for more precise positioning of the stent. In particular, deployment using the coiled member may provide a more controlled unwinding of the associated portion of the stent, whereas the release of conventional trigger wires may require higher deployment forces that can cause a portion of the stent to jump longitudinally, thereby potentially deploying the stent offset from the intended target site. 
       FIGS. 12-14  demonstrate the continued operation of the device to release the distal end  204  of the stent graft  200 . As shown in  FIGS. 10-12 , the distal end  204  of the stent graft is attached to the device by way of at least one distal end capture mechanism  132  on the positioner  112  which engages a corresponding element at the distal end of the stent graft  204 , such as a looped portion  306 . As shown in  FIG. 13 , the sheath is fully withdrawn in the direction of the arrow and removed from the stent graft  200 . The full withdrawal of the sheath  110  exposes the distal end  204  of the stent graft  200  and the distal end  204  of the stent graft  200  is released by releasing the loop  216  from the releasable distal attachment and release mechanism  132 . 
       FIGS. 15A-D  are perspective views of a prosthesis distal end with an exemplary distal attachment and release mechanism. In  FIGS. 15A-D , the sheath  110  is shown as transparent to allow objects covered by the sheath  110  to be visible. The sheath  110  may actually be opaque or transparent. As shown, positioner  112  has releasable distal attachment and release mechanism  132  at the proximal end  126  of positioner  112 . In this example, capture mechanism comprises a capture wire  302  on the positioner  112  which is bent to engage a loop  306  or other configuration at the distal end  204  of the stent graft  200 . Prior to release of the distal end, the sheath  110  is over the capture wire  302 . The space shown between the sheath  110 , the positioner  112 , and capture wire  302  in  FIGS. 15A-D  may be exaggerated to show the components device more clearly. 
     While the sheath  110  is disposed over the capture wire  302 , as shown in  FIGS. 15A-D , the sheath  110  prevents the bent capture wire  302  from straightening. A close fit of the sheath  110  over the positioner  112  and capture wire  302 , as shown in  FIG. 15B  prevents the looped portion  306  from releasing or becoming detached from the capture wire  302  while the sheath is positioned over it. As shown, at least a portion of the capture wire  302  is affixed to the positioner  112 . As shown, another portion  309  of the capture wire  302  may be free and not attached to positioner. 
     The unattached section  309  of the capture wire  302  may include an atraumatic section  304 . The atraumatic section  304  may prevent damage to a vessel wall or body cavity if the unattached section  309  of the capture wire  302  contacts vessel wall or body cavity. The atraumatic section  304  may take any shape that prevents or minimizes damage to a vessel wall or body cavity that comes in contact with the atraumatic section  304 , including, for example, a rounded ball, curved segment, curved end, or cushioned area. 
     As shown, the capture wire  302  may include one or more bends in the unattached section of the capture wire  302  when the sheath  110  covers the capture wire  302 . In the case of a single bend, the bend may be approximately 180 degrees. The unattached section of the capture wire  302  is held in the bent position by the presence of the sheath  110  where the unattached section  309  is prevented from straightening out and removing the bend  308 . 
     The capture wire  302  may be composed of any material capable of deforming and later returning to its un-deformed shape, such as bending and later straightening. The capture wire  302  may consist of, for example, nitinol or polypropylene filament. The length, thickness, and flexibility of the capture wire  302  may be varied depending on the application. For example, a thicker or less flexible capture wire  302  may be used if the looped portion  306  applies a relatively large force to the capture wire  302 . A longer capture wire  302  may be used if the diameter of the looped portion  306  is relatively large or if the space between the proximal end  126  of the positioner  112  is relatively large. The capture wire  302  may return to its un-deformed or unbent shape automatically upon removal of the sheath  110  from over it. The material properties of capture wire  302  may cause it to return to an unbent or substantially straight shape without any external force applied. 
       FIG. 15D  shows the sheath withdrawn from the capture wire  302 . Removal from the sheath from over the capture wire  302  permits the capture wire  302  to be relieved from its bent shape and release loop  306  and consequently releasing the distal end  204  of the prosthesis. After the distal end is released, the device may be removed from the prosthesis and the body vessel. 
       FIGS. 16-18  are further embodiments of a releasable distal attachment and release mechanism  132 . The sheath  110  is shown as transparent to allow objects covered by the sheath to be visible. The sheath  110  may actually be opaque or transparent. The space shown between the sheath  110  and the positioner may be exaggerated to show the components of the exemplary medical device delivery systems more clearly, and the inner diameter of the sheath  110  may more approximate the outer diameter of the positioner  112 . 
     As previously described with regard to  FIG. 15 , the capture wire  302  may include a bend  308  and an atraumatic portion  304  with the bend maintained by the presence of the sheath over the positioner  112  and the capture wire  302 . In the examples of  FIGS. 15 and 16 , the positioner has a recessed area  310  in the surface of the positioner for receiving the capture wire  302 . The recessed area  310  may contain part or all of the unattached section of capture wire  302 , as shown in  FIG. 16A , and may have a similar configuration to the unattached section  309 , or any other shape that is capable of substantially containing the unattached section  309  of capture wire  302 . Containing the unattached section  309  of capture wire  302  within the recessed area  310  may reduce the overall diameter of the delivery device, because space between the sheath and the positioner does not have to be maintained to accommodate the capture wire  302 . The attached end of the capture wire  302  may attached to the positioner proximal end within the recess  310  as shown in  FIG. 16  or it may be attached at another area of the surface of the positioner as shown in  FIG. 17 . When the capture wire  302  is bent, the free or unattached end of the capture wire  302  may be held almost entirely within the recess when the sheath is disposed over the recess as shown in  FIGS. 16A and 17A . As with the capture wire  302  of  FIG. 15 , once the sheath  110  is withdrawn, the capture wire  302  resumes its unbent or previous shape and releases the distal end of the prosthesis. 
     The capture wire  302  fixed section may be attached at any location around the perimeter of the positioner proximal end, including away from the recessed area as shown in  FIG. 17A . Attaching the fixed section of capture wire  302  at a location outside of the recessed area may allow the bend  308  to have a larger radius of curvature. A large radius of curvature may reduce the strain on capture wire  302  and improve is durability. 
       FIG. 18  shows another embodiment of the releasable distal attachment and release mechanism  132 . In this embodiment the releasable distal attachment and release mechanism  132  forms a closed loop. The closed loop has two attached or fixed ends that are attached to the positioner at the proximal end. When the sheath is in place over releasable distal attachment and release mechanism  132 , the loop lies against the positioner and is held there by the sheath. Although not shown, the loop engages a corresponding loop or hook at the distal end of the prosthesis. When the sheath is removed, the loop is permitted to spring away from the positioner in a proximal direction and release the distal end of the prosthesis by releasing the corresponding loop or hook. Further details regarding the embodiments of  FIGS. 16-18  are set forth in the concurrently filed application entitled “Automatic Wireless Medical Device Release System,” Inventors Blayne Roeder and Zach Wagner) which disclosure is incorporated in its entirety by reference herein and, in particular the disclosure regarding the capture wire. 
     A further embodiment of the capture mechanism is shown at  FIGS. 19A-D . This embodiment and further details of its construction and use are set forth in the concurrently filed application entitled “Wireless Medical Device Release Mechanism,” (Inventors William Havel, Matt Huser and Richard Hadley). As shown there, and in present  FIGS. 19A-D , the proximal end of the positioner itself has a configuration that engages a portion of the distal end of the prosthesis, such as a loop as described above. As described, the engagement element  306  at the distal end of the prosthesis may be a separate loop such as a suture loop, a hook, a part of the stent, or the like. 
     As shown in  FIGS. 19A  and B, the engagement element  306  of the prosthesis engages a recessed region  310  of the proximal end of the positioner  112  such that the engagement element  306  is held in the recessed region  310 . For example, the engagement element  306  is held within the recess against an inclined surface  312  which may be inclined away from the prosthesis distal end, thus capturing the engagement element  306  in the recess. The recess  310  may take the form of that sent forth in  FIGS. 1-16  of the concurrently filed application to Havel et al., entitled “Wireless Medical Device Release Mechanism,” incorporated by reference herein, for example that shown as element  506  in  FIGS. 5 and 7 , and the accompanying text, of the above incorporated reference or that shown in  FIGS. 8 and 9  of the incorporated reference above which includes a looped capture mechanism releasably embedded in a recess in the surface of the positioner. In the case of  FIGS. 1-5 and 7 , and the accompanying text, of the incorporated reference, upon removal of the sheath, a slight proximal axial movement of the positioner will release the loop from the recess and release the distal end of the prosthesis from the delivery device. 
     Although not so limited,  FIG. 20  show an exemplary cannula/cannula connection element  144  (though not shown in this figure, cannula  116  includes a lumen as set forth above).  FIG. 20  is cross-section of cannula  116  and cannula handle  108 . Connection element  114  comprises one or more radially projections  400  from the inner surface  402  of the cannula handle  108  cooperating with one or more slots, channels, indents, recesses or the like  404  in cannula outer surface  172 . Hence, the cannula/cannula connection element provides for rotation of the cannula with rotation of the cannula handle while also permitting longitudinal movement of the cannula handle along the cannula. 
     While particular elements, embodiments, and applications of the present invention have been shown and described, it is understood that the invention is not limited thereto because modifications may be made by those skilled in the art, particularly in light of the foregoing teaching. It is therefore contemplated by the appended claims to cover such modifications and incorporate those features which come within the spirit and scope of the invention.