this invention involves a device and procedure for solving the problem of stabilizing the structure and placement of vaso - occlusive devices when they are placed in an aneurysm . these retaining devices prevent the migration of one or more occlusion devices such as coils from a target occlusion site , by forming a barrier at the entrance zone to the target site from a feeding vessel . the remainder of the retainer device which is remote from the mouth generally provides stability to the portion of the device which is in the mouth of the aneurysm . fig1 a and 1b show typical but simple variation of the device in which the retainer assembly ( 100 ) has a shape which approximates that of the aneurysm into which it is placed . specifically , the retainer device ( 100 ) has a plurality of array elements ( 102 ) or “ interior ” array elements ( 102 ) which extend from an electrolytic joint ( 104 ) and form a loop which comes around to join itself back in the vicinity of electrolytic joint ( 104 ). it is , of course , permissible to use joints other than electrolytic joints in place of ( 104 ), e . g ., joints which rely upon mechanical joining for structural certainty . however , joint ( 104 ) is desirably electrolytically severable because such joints are very functionally flexible in their deployment . that is to say , that should the aneurysm retainer somehow be malplaced , the fact that core wire ( 106 ) can be used to withdraw this device back into its delivery catheter or other suitable delivery tubular member , is a very big benefit . fig1 a , a side view of the inventive retainer ( 100 ), shows another aspect of this invention which is significant . in this variation , array member ( 102 ) has a proximal end ( 108 ) and a distal end ( 110 ). similarly , as a convention here , core wire ( 106 ) has a distal end ( 112 ) which is just proximal of the electrolytic joint ( 104 ). now as may be seen from fig1 a , joint ( 104 ) and core wire distal end ( 112 ) are both distally placed from the proximal end of the retainer assembly ( 108 ). this configuration has at least two benefits . first of all , the joint itself is not placed in the feed artery and should not cause the creation of an embolus in that vessel with the danger of subsequent blockage . furthermore , the plurality of array wires ( as may be shown from the top view in fig1 b ) form what might be characterized as a skeletal funnel a the top of the retainer device ( 100 ) and consequently in the aneurysm itself , placement or re - placement of the catheter in the retainer device so to permit introduction of the vaso - occlusive member ( not shown ) into the interior volume of the aneurysm retainer device is simplified . this variation of the invention as well as the others discussed below , are delivered through a tubular member such as a catheter . the shape of the device shown in fig1 a is the so - called secondary shape found after the retainer device ( 100 ) has been pushed from the distal end of the delivery . the retainer device ( 100 ) generally has a relatively linear shape as is pushed through catheter . this primary or delivery shape is essentially the shape of the interior of the catheter during the delivery step . after deployment , the device assumes its secondary shape as is seen in fig1 a . to undergo such massive changes in shape , it is usually preferable that the interior array elements ( 102 ) be produced of material such as a superelastic alloy . superelastic or pseudoelastic shape recovery alloys are well known in this art . for instance , u . s . pat . nos . 3 , 174 , 851 ; 3 , 351 , 463 ; and 3 , 753 , 700 each describe one of the more well known superelastic alloys , also known as nitinol . these alloys are characterized by their ability to be transformed from an austenitic crystal structure to a stress - induced martensitic ( sim ) structure at certain temperatures and then return elastically to the austenitic shape when the stress is removed . these alternating crystal structures provide the alloy with its superelastic properties . the alloy mentioned in the three patents just above , is a nickel - titanium alloy . it is readily commercially available and undergoes the austenitic - sim - austenitic transformation in a variety of temperatures between − 20 ° c . and + 30 ° c . these alloys are especially suitable because of their capacity to recover elastically — almost completely — to the initial configuration once the stress is removed . typically , in these services , there is little plastic deformation even at relatively high strains . this allows the retainer device ( 100 ) to undertake substantial bends both as it is collapsed to enter the tubular delivery device and as it undertakes further bending in passing through turns in the vasculature . in spite of this bending , it returns to its original shape once the bend has been traversed without retaining a kink or a bend . of the superelastic alloys currently available , we consider a preferred material to be nominally 50 . 6 ± 2 % nickel and most of the remainder , titanium . up to about 5 % of the alloy may be another member of the iron group of metals , particularly chromium and iron . the alloy shouldn &# 39 ; t contain more than about 500 parts per million of oxygen , carbon , or nitrogen . the transition temperature of this material is not particularly important , but it should be reasonably below the typical temperature of the human body so to allow it to be in its austinitic phase during use . the diameter of the wires or ribbons making up the array elements preferably are smaller than about 0 . 010 inches in diameter . as will be discussed below in conjunction with fig1 , the typical superelastic alloy is not always completely visible under fluoroscopy . consequently , it is often desirable to add some type of a covering to improve the radio - opacity of the device . radio - opaque metals such as gold and platinum are well known . although we have discussed the concept that these devices are desirably made from superelastic alloys , other metals may in certain circumstances be appropriate . such metals include a number of the stainless steels and other highly elastic , if not superelastic alloys . furthermore , it is within the scope of this invention that the array elements ( 102 ) be of polymeric material . polymeric materials are somewhat easier to work with in forming the device and may also suitable for maintaining the vaso - occlusive devices at an appropriate site within the aneurysm . such materials as polyethylene , polypropylene , polytetrafluoroethylene , various of the nylons , and the like would be easily chosen by one having ordinary skill in this art for the purposes shown herein . the electrolytic severable joint ( 104 ) may also be called a sacrificial link . core wire ( 106 ) is typically coated with an electrical insulator which is not susceptible to dissolution via electrolysis in blood or other ionic media . suitable coatings for core wire ( 106 ) include such insulating materials as the polyfluorocarbons ( e . g ., teflon ), polyurethane , polyethylene , polypropylene , polyimides or other suitable polymeric materials . sacrificial joint ( 104 ) is not coated with such an insulator and is of a material which is susceptible to electrolytic dissolution in blood . joint ( 104 ) may be a simple un - insulated continuation of , e . g ., stainless steel core wire ( 106 ), which has been insulated proximally of the joint . it should also be apparent that the sacrificial joint ( 106 ) is more susceptible to electrolysis than are the array elements ( 102 ). further discussion of construction of , placement of , and other physical details of such a joint may be found in u . s . pat . nos . 5 , 122 , 136 to guglielmi et al . ; u . s . pat . no . 5 , 354 , 295 to guglielmi et al . ; u . s . pat . no . 5 , 624 , 449 , to pham et al ., and others . although the array elements ( 104 ) are generally shown to be regular and of the approximate same shape on each of the axis through the retainer device ( 100 ), such obviously need not be the case . it is within the scope of this invention that the retainer assembly be irregular in shape so to fit the shape of an irregular aneurysm . placement of such devices must be done with some care , but it is within the purview of one having ordinary skill in the art with some instruction . fig2 a shows another variation of the inventive retainer assembly ( 120 ) in which the array elements are of two different types . array element ( 122 ) is of the same general shape as those shown in fig1 a and fig1 b . array element ( 122 ) extends directly into the aneurysm . array elements ( 124 ) are paired to extend axially from the region of the joint ( 104 ). these axially extending loops ( 124 ) are also intended to fit within the aneurysm and provide directional stability to the placement of the retainer device ( 120 ). only a single axial array element ( 122 ) is shown in fig2 a and 2b . the invention is , obviously , not so limited . the generally perpendicular array elements ( 124 ) may have larger loops than those shown as well . again , this device is situated in its secondary form so that the remainder ( 126 ) of any element attached formerly joint ( 104 ) after dissolution by electrolysis of joint ( 104 ), will not extend into the feeder vessel for this aneurysm . this retainer assembly ( 120 ) may be used to help close an aneurysm which is of substantial length but nominal width . fig3 a and 3b show still another variation of the inventive device ( 140 ). this variation shows one internal array member ( 142 ), although multiple array members may be used . in addition , fig3 a and 3b show a number of external array members ( 144 ) which are intended to remain outside of the aneurysm when the aneurysm is deployed . these exterior or outer array members ( 144 ) are of the same general makeup and material as those shown in the earlier discussed figures . although the overall configuration of this device ( 140 ) as shown in fig3 a and 3b may be indented at the top in the same manner as the variations shown in fig1 a , 1 b , 2 a , and 2 b , this neck configuration is shown for purposes of completing the variations of this invention . the exterior array members ( 144 ) and the interior array member ( 142 ) may be attached to core wire ( 150 ) via a ferrule ( 146 ) perhaps by crimping or perhaps by welding the devices components together . an electrolytic joint ( 148 ) on core wire ( 150 ) is also shown . this variation of the invention is less desirable because of the possibility that the ferrule member ( 146 ) can be present in the flowing artery . fig4 a and 4b show another variation of the inventive device ( 160 ) having another number of exterior array members ( 162 ). it should be noted out that in some instances where the back wall of the aneurysm is determined to be especially weak and the neck of the aneurysm is considered to be the strongest retention point , that device such as is shown in fig3 a , 3 b , 4 a , and 4 b is quite useful . the presence of a single loop array element ( 164 ) within the aneurysm may be of benefit . fig5 a and 5b show a very simple variation ( 170 ) of the inventive device . this variation is a simple pair of array members ( 172 ) to be placed within the aneurysm . it too has a joining element ( 174 ) which may be the site from which interior elements ( 174 ) extend . the core wire ( 176 ) extends inward from the joining element ( 174 ) much as in the other arrangements discussed above . fig6 a and 6b show an very simple variation ( 180 ) of the inventive device . in this variation ( 180 ), the array elements ( 182 ) extend away from the region of the joint ( 184 ) and perhaps the joining element ( 186 ) and do not form a loop extending to the bottom of the aneurysm . this device is shown as having a small surface coil ( discussed in more detail with regard to fig1 below ). in this variation , it may be typical that the ends of the array arms ( 182 ) farthest away from joint ( 184 ) form the contact regions with the aneurysm wall and therefore provide stability to this retainer device ( 180 ). that is to say that unlike the retainers discussed above , wherein the retainer is kept from movement by contact with multiple sites inside the aneurysm , this device may merely contact the farther - most walls of that aneurysm . fig7 a and 7b show another variation of , generally , both features of the fig6 a and 6b device as well as those shown in fig1 a , 1 b , 2 a , and 2 b . that is to say that the inventive device ( 190 ) utilizes loops as array members ( 192 ) which may extend to the bottom of the aneurysm . the joint for electrolytic dissolution ( 194 ) is recessed into the proximal end of the device ( 190 ). the upper portions of the array wires ( 192 ) are covered with a radio - opaque wrap ( 196 ). it should be understood that the secondary shapes of the devices shown in fig1 a through 7b are secondary shapes which occur when the retainer device is placed in the open air — that is to say not within aneurysm . any placement of these devices in a human body will likely cause the secondary shape to distort . the shape which these devices actually take within an aneurysm , although preferably those shown in the drawings noted above , may not be as depicted . fig8 shows a close - up partial sectional view of desirable electrolytic joint configuration . in fig8 , the core wire ( 200 ) has over it , a plastic sleeve ( 202 ) which is cut at a bias or angle ( 204 ). the electrolytic joint ( 206 ) is small , discrete area which concentrates the flow of current into that area so to accelerate the dissolution of that joint . preferably the region just proximal of the joint ( 208 ) is also covered with an insulator . electrolytic joint ( 206 ) is placed as far distal as is reasonably possible during assembly so to prevent jagged edges and points after dissolution . in this variation , the joining block ( 210 ) is a plastic joint into which both the element ( 212 )— distal to joint ( 206 )— is embedded . array members ( 214 ) are also shown and they are , as well , embedded in plastic junction member ( 210 ). this arrangement may provide some benefit , in that when an electric current is applied to core wire ( 200 ), there is no tendency for the current to flow into the array elements ( 214 ) because they are insulated by junction block ( 210 ). this is believed to accelerate the dissolution of joint ( 206 ). fig9 shows another close - up partial sectional view of the distal end of core wire ( 200 ) with joint ( 206 ) and proximal covering ( 208 ). the major difference between the variation shown in fig8 and that shown in fig9 is that the array members ( 214 ) are crimped onto distal member ( 212 ), using a ferrule ( 220 ). such a ferrule ( 220 ) may simply mechanically attach array members ( 214 ) to core wire ( 200 ) or additional joining arrangements , e . g ., welding or the like may be employed . although soldering is not typically desirable because of the potential creation of a ragged joint on the proximal end of distal element ( 212 ), in some circumstances it may be permissible to solder it as well . fig1 shows a partial cut - away of an array arm ( 220 ) having an interior wire ( 222 ) and a radio - opaque coil ( 224 ) wrapped about its exterior . exterior wire ( 224 ) may also be an exterior ribbon or the like , if such is a more pleasing variation to the designer using the teachings of this invention . coil ( 224 ) is merely a radio - opacifier for the overall device ( 220 ). this device may be deployed in the following manner . fig1 a shows a berry aneurysm ( 200 ) emanating from the wall of an artery ( 202 ). a catheter ( 204 ) is shown having radio - opaque band ( 206 ) at its distal end . the distal end of catheter ( 204 ) extends into the mouth ( 208 ) of the aneurysm ( 200 ). fig1 b shows a retainer device ( 212 ) having a shape similar to those discussed above . this variation of the inventive retainer ( 212 ) has interior array members ( 214 ) and exterior array members ( 216 ). it should be also noted that the exterior array members ( 216 ) are exterior to the aneurysm ( 200 ) and the remaining array members ( 214 ) are interior to aneurysm ( 200 ). it should probably be apparent that the various array members should not pinch the aneurysm in any very meaningful or deleterious way , lest some type of rupture occur . in fig1 c , it can be seen that the voltage has been applied to core wire ( 218 ), and the electrolytic joint has been dissolved . the core wire ( 218 ) is then withdrawn from catheter ( 204 ) and discarded . it may be also seen in fig1 c that the region of the joint adjacent the retainer device ( 212 ) is recessed out of the flow of artery ( 202 ). in fig1 d , catheter ( 204 ) has been re - introduced into the neck of aneurysm ( 200 ) and a number of vaso - occlusive devices — in this case , coils ( 220 )— have been introduced into the volume formed by retainer assembly ( 212 ). fig1 e show the withdrawal of catheter ( 204 ) from the feed vessel with the implantation of vaso - occlusive coils ( 220 ) and their stabilizing retainer ( 212 ) complete . many alterations and modifications may be made by those of ordinary skill in this art , without departing from the spirit and scope of this invention . the illustrated embodiments have been shown on for purposes of clarity and the example should not be taken as limiting the invention as defined in the following claims , which are intended to include all equivalents , whether now or later devised .
this is a device for bridging the neck of either a wide - necked or narrow - necked aneurysm in the vasculature . in general , it is a device used to stabilize the presence of vaso - occlusive devices in the aneurysm . the device preferably is delivered by a core wire which terminates in an electrolytically severable joint . the core wire will often be insulated . the retainer assembly itself is also attached to the electrolytic joint and typically has a number of array elements which are intended to be resident within the aneurysm after the device is deployed from the distal end of a catheter . after deployment of this retainer , the aneurysm is at least partially filled with a vaso - occlusive device such as helically wound coils .