CA1328391C - Radially expandable endoprosthesis and the like - Google Patents

Abstract

RADIALLY EXPANDABLE ENDOPROSTHESIS
Abstract of the Disclosure Radially expandable endoprostheses or stents are provided, as well as their method of manufacture.
These stents include a plurality of adjacent generally circumferential sections that are substantially axially positioned with respect to each other. At least one of the generally circumferential sections has a generally circumferentially disposed expandable segment that imparts circumferential and radial expandability to the stent.

Description

Case 88070 RADIALLY EXPANDABLE ENDOPROST~ESIS

DescriDtion -Backaround and DescriPtion of the Invention The present invention generally relateE to endoprosthesis device~, to a procedure for making same, and to the u~e thereof. More particularly, the invention relates to a gener~lly tubular endoprosthesis S that i8 radi~lly eYpandable between a generally unexpanded insertion circumference and an eYpanded implantation c~rcumference which is greater than the unexpanded insertion circumference. Included are a plurality of generally circumferential sections, one or - --more of which includes one or more espandable seg~ents that are bendable member~ which are generally coll~psed when the endoprosthesis is in its generally unexpanded insertion orientation and which are gener~lly opened when the endoprosthe~ls ~8 in its expanded implantation orientation.
~ ndoprosthe~e6 are known for treating stenoses, aneurysm conditions and the like. An endoprosthesis device of thig type, which is at times referred to a8 ~ stent, i8 typically placed or implanted by a mechanical tran~luminal procedure. Often a device of this type is percutaneously implanted within the vascular sy~em to reinforce coll~psing, partially occluded, weakened or abnormally dilated localized ~ections of a blood vesscl or the like. wnen endoprosthe~es or stents are used to treat a stenosis condition, typically such i8 done in a~sociation with a dilation element such as an angioplasty balloon. In thi~ in~tance, the dilation element or balloon device 132839~ ~

opens the con6triction, and ~ stent or the like i8 positioned thereat in order to prevent or at least substantially slow re-formation of the stenosi6.
One attribute of a stent i8 that it is radially compressible and espandable 80 that it will easily pass through a blood vessel or the like when collapsed and will espand to its implanted size after the stenosis, aneurysm or the like has been reached. It is also desirable that a stent be generally fleYible throughout its length so that it is easily maneuverable through bend~ and curves of the blood vessel or the like. It i8 typically de~irable that a stent or endoprosthe~is have A substanti~l amount of open space 80 ~8 to allow for endothelialization along its length and to minimize lnterference with collateral blood vessels and the like. ~hile it is important that a stent or endoproE~the6is lodge securely into place at the desired location, it can be ~dvantageous to have ~ stent that is removable through a transluminal percutaneous procedure, should remov~ be needed.
Various currently known ~tent products have structures that are esgenti~ly coiled springs. ~hen this type of spring stent is tightly coiled, its diameter i8 rel~tively gm~l for insertion through a blood vessel or the like. When the coil is sprung or coiled more loo~ely, the stent assumes its e~panded, implantation orientation. Maass et al U. S. Patent No. 4,553,5~5 is illustrati~e of this type of coiled spring stent or endoprosthe~sis. Multihelix or braided ~ -stents ~re ~80 kno~n, and they suffer from poor maneuverability. They are al80 difficult to remove once implanted, and they ~y eshibit numerous esposed, relatively sharp or ~gged ends. Palmaz U.S. Patent No. 4,733,665 is repre~entat~ve of an espandable stent of -~
this gener~ type. Gianturco U.S. Patent No. 4,580,568 illu~trates a percutaneous endovascular stent formed of tainless steel wire that i8 arranged in a closed - - .. : ; ,, , . . . .; , 132839~

zig-zag pattern ~omewhat in the nature of a bookbinder spring. Such a structure i8 somewhat unsymmetrical, and it may be subject to reocclusion due to the very large open ~pace that is typically pre~ent between the wire6 of this type of device. Another type of stent i8 known a6 a Statz stent, and it includes a hypodermic tube with longitudinal slot~ etched into its body. While such a device has a high ratio of une~panded to e~panded diameter, it is a comparatively rigid device which is difficult to maneuver through a tortuous path and is not easily removed in a transluminal manner.
With many of these currently known stent 6tructure~, the asial length of the stent decrease~ as the circumference of the stent increaaes, which i8 typiczlly a disadvantage. For esample, any such length reduction must be t~ken into consideration in selecting proper stent sizing for a particular implantation procedure. Also, this attribute of many prior stent~
requires the passage through the blood vessel or the like of a stent which is longer than the length actually needed for the implantation procedure being performed.
ThiB i8 a particularly difficult problem for procedure~
in which the stent must be passed through a pathway having twists or turns, espec~ally for a stent structure that is not easily bendable.
The present invention avoids the various deficiencies of these types of prior art structures and provides important and advantageoys features of endoprostheses or stents and the use thereof. In sum~ary, the endoprosthesis of this invention include~ a plurality of generally circumferential ~ection~ that are gener~lly ad;acent to one another along their re6pective opposing generally circumferential edges. At least one ;
of these generally circumferential section~ has an eYp~nd~ble 6egment that imparts radial espandability to the generally circumferential ~ection. The eYpandable segment i8 a bendable, elbow-like member that i8 bendable between a genera~ly collapsed or closed orientation and a generally opened orientation and i8 capable of assuming bending orientations between one S that is fully closed and one that is fully opened. By this structure, the endoprosthesis or stent has an unespanded insertion circumference and an expanded implantation circumference, which i8 greater than the insertion circumference. In addition, this variation in circumference is achieved witbout ~ubstantially changing the a~ial length of the endoprosthesis or stent. Tbe stent is made by a procedure that is relatively unco~plicated, and, gener~lly spea~ing, the stent can be tr~nsluminally e~planted if necessary.
It is a general object of the present invention to provi & an improved radially expandable, axially extending endoprosthes$~ of the type that c~n be tran lum~nally implanted.
Another object of the present invention is to provide an improved endoprosthesis or stent that can be constructed to h~ve very large radial e~pansion c~pabilities.
Another object of this invention is to provide an improved radi~lly expandable a~ially estending 2S endoprosthesi~ that is estremely maneuverable and c~p~ble of moving through a tortuous path. - ~
Another object of the preQent invention is to ~ -provide an improved radially e~pandable axially e~tending endoprosthesis th~t can, if desired, be transluminally explanted by means of, for example, a sn~re lead ol c~theter.
Another object of the present invention is to provide an improved radially expand~ble axially extending endoprosthe~is which include~ members that can be spaced apart in a manner that enhances lodging of the endoprosthesis at its implanted site.

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Another object of the present invention i8 to provide an improved asially extending endoprosthesis that can be conctructed in order to be radially espandable by an expanding member or balloon of a catheter device and/or can be radially espandable due to spring-like properties of the endoprosthe6is.
Another object of this invention is to provide an improved procedure for making an asially estending and/or generally tubular endoprosthesis that is radially espandable.
Another object of the pre~ent invention is to provide ~n improved procedure and syste~ for transluminally espl~nting an a~ially estending radially espandable endoprosthesis or stent.
Another object of the present invention is to pro~ide an improved radially e-pandable endoprosthesis th~t substantially avoids the presentation of any frayed edges and that generally maintains its aYi~l length ;
throughout various radial esp~nsion positions.
The~e and other objects, features and advantages of this invention will be clearly understood through a consideration of the following det~iled description.
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Brief Description of the Drawings In the course of this descript~on, reference will be made to the attached drawings, wherein:
Figure 1 is a perspective view illustrating an early step in the procedure of ~aking an endopro~the~is ~ccording to the present inventiont Fiqure 2 i~ an eleYation~l view illustrating ~ -step subsequent to that ~hown in Figure lt Figure 3 i8 an elevation~l view showing a manufacturing step subsequent to that of Pigure 2, while al80 illustr~ting a substantl~lly completed endoprostbesis in accordance with the present inventions Figure 4 i8 a cros~-sectional view ~long tbe line 4-~ of Figure 3;
Figure 5 is an enlarged detail view of a portion of one end of the endoprosthesis shown in Figure 3;
Figure 6 is a perspective view illustr~ting an early step in the procedure of making another embodiment of the endoprosthesis;
Figure 7 is an elevational view illustratinq a step subsequent to that shown in Figure 6 while also illustrating the configuration of a portion of this endoprosthesis prior to its circumferential orientation~
Figure 8 i~ a perspective view illustrating an early step in the procedure of making a further embodiment of the endoprostheæis;
Figure 9 is an elevational view illustrating a :~ -step subsequent to that shown in Figure 8 while also ~ :
illustrating the configuration of a portion of this ;~
endoprosthesis prior to its circumferential orientation~ ~-Figure 10 i8 an elevational view of an early step in the m~nufacturing procedure for still a further embodiment of the endoprosthesiss Figure 11 is an elevational view of a step subsequent to that shown in Figure 10~
Figure 12 i8 an elevational view of a manufacturing step subsequent to th~t illustrated in -Figure 11 and which shows a length of material suitable for winding on a mandrel in a generally helical manner -~
in order to form the endoprosthesis of this embodiment~
Pigure 13 is a g0nerally cross-sectional view .
illustrating an early step in a procedure for implanting an endoprosthesis according to the present invention this p~rticular procedure being especially suitable for an endoprosthesi~ having spring-like properties~
Figure 14 is a generally cross-sectional view illustrating an implantation step subsequent to that shown in Figure 13J
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Figure 15 is a generally cros~-sectional view illustrating an implantation step subseguent to that of Figure 14;
Figure 16 i~ a generally cross-sectional view S illu6trating an implantation step subsequent to that illustrated in Figure 15;
Figure 17 is a generally cross-sectional view of an implantation step subsequent to that illustrated in Figure 16; ;- ~
Figure 18 is a generally cro~s-sectional view ~ -of an implanted stent or endoprosthe~is in accordance with the present in~ention7 Figure 19 is an elevational view of an endoprosthesis and distal end of a balloon catheter for : -an implantation procedure that i 8 especi~lly ~uitable for ~n endoprosthesis according to the pre6ent invention that i8 constructed of a malleable-typa of material;
Figure 20 is a gener~lly cross-sectional illustration of the endoprosthesis and catheter of Figure 19 positioned within ~ blood vessels -Figure 21 i8 a generally cross-~ectional illustration of an implantation stage subsequent to that ~:
shown in Figure 20 Figure 22 i8 a generally cross-section~
illustrat$on of an implantation st~ge ~ubsequent to th~t shown in ~igure 217 Figure 23 is a generally cross-sectional llustr~tion of an implanted stent or endoprosthe~is ~ -according to the pre~ent invention;
P$gure 24 is a gener~lly cross-sectional illustration of ~ sn~re catheter shown e~planting a stent or endbprosthe~is in accord~nce with the present lnvention~ and Figure 25 i~ a generally cross-sectional lllustration showing a further stage of the espl~ntatlon procedurc illustrated in Figure 24.

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1~28391 DescriDtion of the Particular Embodiments A radially e~pandable asially estending endoprosthesis or stent is generally designated as 31 in Figure 3, as well as in Figure 4. The stent includes a plurality of generally circumferential sections 32. In this illustrated embodiment, each of the circumferential sections 32 are formed from the same continuous, helically wrapped length, such as the undulating length 33 shown in Figure 2.
At least one of the circumferential ~ections 32 include~ at least one expandable ~egment 34.
Esp~ndablo segment 34 i~ a bend~ U e member that typically includes one or more leg8 35. Eacb leg 35 i8 bendably ~ecured to the re~t of the circumferential section 32 by a so-c&lled living joint or hinge that is a unitary or integral component of the leg 35 and the adjacent portion of the circumferential section 32. For e~a~ple, in the embodiment illustrated in Figures 1 through 5, each leg 35 is bendably joined to another leg 35 through an integral or living hinge 36 which has a gener~lly arcuate shape. When the stent 31 espands, the integral hinge 36 perm~ts end portions 37 of the legs 35 to ove f~rther apart, thereby increa~ing the circumferènce and diameter of the stent 31. Of course, the circu~ference and diaoeter of the stent 31 can be reduced by forces which ~ove these end portions 37 closer to each other.
An understanding of the manner in which the endoprostheses according to this invention, such as the stent 31, can be made will be obtained from a consider~tion of Figures 1, 2 and 3. Figure 1 shows a mandre~l 38 that has a cross-sectional configuration th~t is somewhat oval in shape. ~andrel 38 can, for esample, be a circular tube that has been flattened on two opposing longitudinal portions in order to provide a cross-section that is generally rectangular in shape, . ~, . .. ~ . . ,. .. ~ , 9 132839~

with two oppo ing end portion~ thereof being arcuate or rounded. A strand 39 of wire or other material, as generally discussed elsewhere berein, i8 generally tightly wound over the mandrel to the estent that the 6trand 39 takes on a cros~-sectional shape along the lines of that of the mandrel 38. Preferably, this winding i6 done in a manner ~uch that there i8 a substantial spacing between each individual wind of the ~trand 39. Generally speaking, the tighter the wind and -~
the thinner the mandrel, the closer will be the ~pacing between the expandable segments 34 of the completed stent 31.
After this winding procedure has been co~pleted, the mandrel 38 i8 removed from the wound 6trand 39. m e wound strand 39 i8 then subjected to fl~ttening forces 80 that the three-dimensional wound ~trand 39 is transformed into a generally planar shape such as that of the undulating length 33 shown in ~igure 2. These forces may be applied by any suitable means.
For e~ample, the wound strand 39 can be compressed between two planar surfaces, during which procedure, portions of the wound strand 39 are twisted until the generally uni-pl~nar undulating length 33 is formed.
This length has a generally ~inu~oidal character.
In order to complete formation of the stent 31 illustrated in Figure 3, the undulating length 33 i8 then wound, in a generally helical manner, around a -substantially cylindrical mandrel 41, as i8 generally illu~trated in Figure 3. This generally helical wrapping procedure continues until the desired number of circumferential section~ are formed in order to provide --a ~tent 31 of a de~ired lengtb.
With reference to Figure S, this winding procedure that i8 generally illuatrated in Figure 3 includes proceedlng in a manner 80 ~8 to avoid the presentation of any loose ends in the completed stent : , ', , . ' ,' ' ' ' ~ '.

-lo- 1328391 31. This is readily acco~pli~hed by forming th- strand 39 and the undulating length 33 80 that each end circumferential 8ection 42 has a free end 43 that readily hooks onto an Adjacent portion of the ~tent 31, such as an integral hinge 36 of the circumferential section 32 that i~ adj~cent to and inwardly spaced from the end circumferential ~ection 42. The free end ~3 illustrated in Figure 5 i5 in the nature of a hook portion that readily loops or tucks into the integral hinge 36.
Regarding the enbodimen~ shown in Figure~ 6 and 7, the mandrel around which the ~trand 39 is wound is a substant~ally rectangular mandrel 4~. As a result, the generally planar structure th~t is subsequently lS for~ed is an undulating length 45 that includes a plurality of legs 46 joined by a unitary or integr~l hinge or livi~g hinge 47 th~t i~ typically less arcuate than the integral hinge 36. This undulating length 45 -~
is tben formed into an endoprosthe~is or stent by helically winding same on a ~tructure such a8 the cylindrical ~andrel 41.
Another embodi~ent of the endoprosthesis or stent i8 made in a manner gener~lly illustrated in Figures 8 and 9. Here, the mandrel is a generally lens-s~aped m~ndrel 51 w~ich has a transverse ~ ?
cross-sectio~ that can be described as defininq two conves surfaces positioned in back-to-back relation~hip with each other. Much in the ~ame manner a8 the other embodiments, the elongated strand 39 is wound around the l-ens-shaped mandrel Sl. The mandrel 51 is subseguently moved therefrom, and the ~ound ~trand 39 is rendered sub~tantially uni-planar in order to form undulating length 52 that i~ suitable for forming into a stent by wrapp$ng around the mandrel ~1.
Anotber embodi~ent illustrating the manufacture of an endopro~thesis or stent in accordance with this invention is generally illustrated in Figures 10, 11 and 12. A strand is wound around a small-diameter mandrel 53. In this case, the strand is formed into a tightly wound heli~ 54. Thereafter, the mandrel 53 is removed, and the strand is formed into a more loosely wound heli~ 55. For example, the helis 55 can be elongated ~uch that the pitch angle i8 les~ than approsimately 60. This heli~ 55 is then flattened generally in the manner previously discussed, for eYample to 15 tons in a pneumatic pre6s, in order to form a generally uni-planar undulating length 56. If desired, the length 56 c~n be asi~lly compre6sed in a contained mold to the desired pitch angle. Length 56 is 6uitable for winding around cylindrical mandrel 41 in order to thereby form an endoprosthesis or stent.
Stent~ illustrated herein are typically capable of moving through a tortuous path that may be encountered in vascular system implantation. Such stents can be ea6ily axially bent over a relatively 6mall radius without damage or high bending resistance.
It should be appreciated that in the lllustrated embodiments, each circumferential section 32 is generally identical. It is also possible within the spirit of the invention to provide circumferential section~ th~t are not this uniformly shaped. For example, the c$rcumference of adjacent sections can differ in order to form a stent that is not strictly sh~ped in the nature of ~ right cylinder. Por e~ample, tapered, truncated cone-6baped stent or stepped 6tents can be provided. In addition, in some applications, it can be suitable to include circumferenti~l sections that ~re not composed entirely of e~pandable segments, but instead could include non-e~p~ndable portions that are joined by e~pandable ~egments. It also may be possible to provide stents within the spirit of the pre~ent invention which include one or more circumferential .

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sections that form a stent devlce without proceeding with helical winding around cylindrical mandrel 41 or the like.
It is also possible to provide a stent that has a generally bifurcated structure for use in situations in which the stenosis, aneurysm or the like that is to be treated iB at a branching location within the vascular ~ystem or the like.
Such a bifurcated stent structure can be formed, for example, by ~oining portions of the opposing ends of two different unitary stents in order to provide a total structure that is bifurcated, Y-~haped or the like.
The materials out of which stents according to the present invention can be made, and especially the expandable segments thereof, fall into two general categories. The material can be either elastic or generally inelastic.
Examples of elastic materials include spring steels, stainles~ steel, Nitinol, Elgiloy, an alloy known as NP36N, and the like. Generally inela6tic materials can be characterized a~ being malleable. Included are tantalum, titanium, silver, gold, and annealed versions of the ela~tic materials described herein. Poly~ers may also be used, such a~ polyether sulfone, polyimide, polycarbonate, polypropylene, ultra high molecular weight polyethylene, carbon fiber, Kevlar (trademark), and the like. It i8 aloo possible to coat these materials with porous or textured surfaces for cellular ingrowth and the like or with non-thrombogenic agent~ such a~ pyrolytic carbon, heparin, hydrogels, Teflon (trademark) ~aterials, ~ilicones, polyurethanes and the like. The stents can be treated 80 that drug~ can be eluted therefrom. It is also possible that certain stent~ may be made of biodegradabl- material~.
In any event, the stent material, of course, is to be biocompatible.

Figures 13 through 18 illu~trate an ~ -implantation procedure and an insertion system that is r ~

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particularly ~uitable for stents that are constructed of an elastic material such as spring ~teel. A stenosis or lesion 61 i6 shown within a blood ve~sel 62. The ~tent 31 is positioned on a balloon catheter, generally S designated as 63. An introducer tube or plunger 64, or a similar stop-providing structure, is pos$tioned along the outside surface of the catheter tube 65. The stent 31 is located di~tally of the member 64, and a sheath 66 holds the stent 31 in a generally compre6sed state --during which the espandable segments of the stent 31 are ~ -generally collapsed or clo~ed. Figure 13 further shows ~-the balloon 67 of the c~theter in a mode in which it is eserting outwardly radially directed force~ on tbe lesion6 in order to dilate same to provide a wider lS opening as generally illustrated in Figure 14 in order to there~y generally reduce the overall extent of the lesion 61a. At this time, the balloon 67 i~ collapsed, and the catheter 63 i8 moved in a distal direction 60 that the coll~psed stent 31 is generally positioned within the lesion 61a. Next, a8 illustrated in Figure 15, the sheath 66 is withdrawn by moving same in a generally prosimal direction, and the stent 31 i8 released fro~ the sheath 66. This releage can be such that adjacènt circumferential section~ of the stent expand in a generally sequential manner, which i8 gener~lly illustrated in Figure lS.
After l:hi8 procedure i8 completed, the entire stent 31 has been sprung, and it springingly engages the dilated lesion 61a, which is generally illustrated in Figure 16. Tbereafter, 118 seen in Figure 17, the catheter 63 can be moved in a generally proximal direction until the balloon 67 i8 again generally aligned with the dilated lesion 61a, a8 des~red. Then, the balloon 67 can be pressurized in order to further implant the stent 31 and in order to further dilate the lesion as desired 80 as to form a treated lesion 61b 132839~

which remain6 after the catheter 63 i8 removed, as i8 generally shown in Figure 18.
Figures 19 through 23 show an arrangement that i8 e~pecially suitable for non-elastic stent~ in ~hich the expandable 6egments thereof are made of malleable material. With reference to Figure6 19 and 20, 6tenosis or le6ion 61 within blood vessel 62 is transluminally reached ~y a balloon catheter 71 baving a gtent 31 overlying the collapsed balloon 72 of the catheter 71. The balloon 72 i8 then expanded in a well-known manner, at which time the ~tent 31 is also e~panded bs opening the e~pandable seg~ent6 thereof. An intermediate dilation position i8 shown in Figure 21, and an initially dilated le6ion 61a i8 shown therein.
15 Figure 22 shows ~dditional dilation bs! the balloon 72, and tbe thus treated le ion 61b i8 also shown. After this E~tage is achieved, the balloon catheter 71 is remo~ed, as shown in Figure 23.
qhe stent 31 re lains in place as gener~ly 20 illustrated in Figurc 23 becau~e the malleable material ~or for that Dlatter an elastic material) e~erts a hoop stre~s when $t i~ e~panded to tbe 6ize illustrated in Figure 23 ~uch that it will not collapse l~y inwardly directed radial forces presented bs! the treated lesion 25 and ve~sel wall or the like. In other words, the hoop stres~ of the e~panded stent i6 greater than the hoop forces e~erted by the p~s~agewy within which the stent i8 i~planted. In add$tion, the force required to open the collapsed stent t~y the b~lloon is le~;~s than the hoop 30 force provided by the balloon. In other words, the hoop stress of the collapsed or une~tended stent is less than that of the hoop force provided bs! the pressurized balloon of the c~theter. One feature th~t can contribute to the advantaqeous hoop stress properties of 35 the malleable stents of the type illustrated in the drawing8 i8 the ab$1ity of the stent to e~pand well . . ~. ` i, `

1~28391 ~

beyond that needed to effect the dil~tion procedure.
For e~ample, a typical dilation procedure and stent extension is one in which the fully extended dilating dia~eter or circumference i~ appro~imately three times S the insertion or collapsed diameter or circumference.
With ~tent structures such as those illu6trated in the dravingc, the amount of pos~ible expansion can be on the order of twelve time~. This feature, together with the malleability of the particular material utilized, tends to reduce the hoop force that i8 needed to espand the stent to about tbree times its insertion or collapsed coni'lquration.
~$gures 24 and 25 illustrate a stent withdr~l procedure and a snare catheter system that can be used to remove or e~plant implanted stents according to the present invention. A n~re c~theter, generally designated as 74, is illustrated. An elongated member 75 is slidably po~itioned within a catheter body 76. Elongated member 75 includes a hook member 77 at its distal end. When estended into the fitent 31, the hook member 77 snare~ a portion of the stent 31. A suitable control structure, such a~ the puller ~ssembly 78 illustrated is manipulated in order that the hook member mo~es in a pro~imal direction, with the result that the ~tent begins to uncoil and is opened to such an e~tent that it can be passed through the blood vessel 62 or the like until it i8 totally remoYed fro~ the body by continued movement of the elongated member 75 in the pro~imal direction.
~or purpo~es of illustr~tion, the following details ~re gi~en regarding a typical stent 31. An e~e~plary m4ale~ble materi~l is tantalu~ wire having dia~eter of 0.005 inch wound on a mandrel having a nominal diameter of 0.020 inch. The length of eacb leg 46 i8 on the order of about 0.048 inch, and the center-to-center spacing between adjacent integral or ., ..... .., . ,, ,, . . . " . , . ., . , , ~ , , . ~ ., , . . . - .

13283~1 living hinge~ 36 is about 0.042 inch. A typical collapsed or insertion outer diameter for such a stent is about 0.085 inch, with the inner diameter thereof being about 0.070 inch. The overall length of the stent 31 is selected to be that generally needed to treat the lesion or the like inasmuch as the overall length of the stent will remain substantially the same whether it is collapsed or e~tended, e~cept to the degree that the legs 46 of the esterior circumferential sections 32 move somewhat inwardly as the hinge is fle~ed, thereby somewhat nominally decreasing the overall lenqth of the 6tent.
It will be understood that the embodiments of the present invention which have been described are illustrative of some of the applications of the principles of the present invention. Numerous modifications may be made by those skilled in the art without departing from the true spirit and ~cope of the invention.

Claims (20)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A radially expandable endoprosthesis, comprising:
a plurality of generally circumferential sections, including end and intermediate generally circumferential sections, said end and intermediate generally circumferential sections being substantially adjacent to one another and generally parallel to each other in order to thereby generally define an endoprosthesis having a longitudinal axis along which said generally circumferential sections are axially spaced;
each of said generally circumferential sections includes an expandable segment that imparts radial expandability to said generally circumferential section whereby said section has an unexpanded insertion circumference and an expanded implantation circumference which is greater than said unexpanded insertion circumference;
said expandable segment of each generally circumferential section is a generally foldable member that is bendable between a generally closed orientation and a generally opened orientation so as to impart radial expandability to the generally circumferential section;
said generally circumferential sections form a continuous helix that defines an axially extending endoprosthesis, wherein said end sections each include a free end; and the free end of each said and section engages an adjacent one of said intermediate generally circumferential sections, thereby avoiding the presentation of loose ends on the endoprosthesis.

2. The endoprosthesis according to claim 1, wherein said foldable member includes a generally elbow-like member.

3. The endoprosthesis according to claim 1, wherein said foldable member includes a pair of legs unitarily connected together at a bendable portion.

4. The endoprosthesis according to claim 1, wherein said generally circumferential sections form a substantially cylindrical endoprosthesis.

5. The endoprosthesis according to claim 1, wherein said expandable segment is a malleable member, and wherein the expanded implantation circumference is achieved by radially directed forces from an expandable element of a catheter.

6. The endoprosthesis according to claim 1, wherein each of said generally foldable members is substantially U-shaped, alternating ones of which are substantially oppositely oriented.

7. The endoprosthesis according to claim 1, wherein said generally foldable member is substantially V-shaped.

8. The endoprosthesis according to claim 1, wherein each of said generally foldable members is substantially V-shaped, alternating ones of which are substantially oppositely oriented.

9. The endoprosthesis according to claim 1, wherein said endoprosthesis is generally tubular, and respective circumferential edges of respective generally circumferential sections are generally adjacent to each other.

10. The endoprosthesis according to claim 1, wherein said expandable segment of the generally circumferential section had been formed by winding a strand on a shaped mandrel to form a wound strand which was subsequently flattened to a generally uni-planar configuration, and wherein said generally uni-planar wound strand was subsequently wrapped around a mandrel and removed therefrom to thereby provide said radially expandable endoprosthesis.

11. The endoprosthesis according to claim 1, wherein each of said generally foldable members has a pair of legs joined at substantially right angles at opposite ends of a substantially straight section in order to thereby define a generally right-angled zig-zag structure.

12. The endoprosthesis according to claim 1, wherein said free ends and said adjacent intermediate generally circumferential sections are engaged by hook means.

13. The endoprosthesis according to claim 1, wherein said generally foldable member is substantially U-shaped.

14. A radially expandable endoprosthesis assembly, comprising:
a plurality of generally circumferential sections, including end and intermediate generally circumferential sections, said end and intermediate generally circumferential sections being substantially adjacent to one another and generally parallel to each other in order to thereby generally define an endoprosthesis having a longitudinal axis along which said generally circumferential sections are axially spaced;
each of said generally circumferential sections includes an expandable segment that imparts radial expandability to said generally circumferential section whereby said section has an unexpanded insertion circumference and an expanded implantation circumference which is greater than said unexpanded insertion circumference;
said expandable segment of each generally circumferential section is a generally foldable elastic springlike member that is bendable between a generally closed orientation and a generally opened orientation so as to impart radial expandability to the generally circumferential section;
said generally circumferential sections form a continuous helix that defines an axially extending endoprosthesis, wherein said end sections each have a free end;

means for engaging the free end of each of said end sections with an adjacent one of said intermediate generally circumferential sections, thereby avoiding loose ends on the endoprosthesis; and further including overlying sheath means for maintaining the unexpanded insertion circumference of the endoprosthesis in opposition to outwardly directed generally radial forces imparted by said elastic spring-like member onto an inside surface of the sheath means until said spring-like member is removed from the sheath to obtain said expanded implantation circumference.

15. An implantable and explantable endoprosthesis system, comprising a radially expandable axially extending endoprosthesis and a device for transluminally explanting the endoprosthesis; said endoprosthesis includes:
a plurality of generally circumferential sections, including end and intermediate generally circumferential sections being substantially adjacent to one another and generally parallel to each other in order to thereby generally define an endoprosthesis having a longitudinal axis along which said generally circumferential sections are axially spaced;
each of said generally circumferential sections includes an expandable segment that imparts radial expandability to said generally circumferential section whereby said section has an unexpanded insertion circumference and an expanded implantation circumference which is greater than said unexpanded insertion circumference;
said expandable segment of each generally circumferential section is a generally foldable member that is bendable between a generally closed orientation and a generally opened orientation so as to impart expandability to the generally circumferential section;
said generally circumferential sections form a continuous helix that defines an axially extending endoprosthesis; wherein said end sections each have a free end;
means for engaging the free end of each of said end sections with an adjacent one of said intermediate generally circumferential sections, thereby avoiding loose ends on the endoprosthesis; and said device for transluminally explanting the endoprosthesis includes:
a catheter member that is percutaneously insertable into a blood vessel or the like within which said endoprosthesis has been radially expanded and implanted;
an elongated member slidably mounted within said catheter member, said elongated member having a proximal portion exterior of the body;
snaring means at a distal end of the elongated member, said snaring means having a size whereby it slidably passes through said catheter member;
means for manipulating a proximal portion of the elongated member from a location exterior of the body, said manipulating means facilitating engagement of said snaring means with one of said circumferential sections of the implanted endoprosthesis;
puller means for sliding the elongated member and the snaring means in a proximal direction within said catheter member by moving the body-exterior proximal portion of the elongated member in a direction away from the endoprosthesis; and said puller means further being for at least partially uncoiling said helix and for reducing the radial size of the endoprosthesis to less than said expanded implantation circumference and such that it will pass through the catheter member and from the body, whereby the endoprosthesis of reduced radial size has been fully explanted.

16. The system according to claim 15, wherein each of said generally foldable members has a pair of legs and a foldable portion, and alternating ones of said foldable portions are substantially oppositely oriented.

17. The system according to claim 1, wherein said foldable member of the endoprosthesis includes a generally elbow-like member.

18. The system according to claim 15, wherein said foldable member of the endoprosthesis includes a pair of legs unitarily connected together at a bendable portion.

19. The system according to claim 15, wherein said expandable segment of the generally circumferential section of the endoprosthesis had been formed by winding a strand on a shaped mandrel to form a wound strand, said wound strand having been subsequently flattened, and said circumferential section is defined by said flattened wound strand in that said flattened wound strand was subsequently wrapped around a mandrel and removed therefrom to thereby provide said radially expandable endoprosthesis.

20. An implantable and explantable endoprosthesis system, comprising a radially expandable axially extending endoprosthesis and a device for transluminally explanting the endoprosthesis; said endoprosthesis includes:
a plurality of generally circumferential sections, including end and intermediate generally circumferential sections, said end and intermediate generally circumferential sections being substantially adjacent to one another and generally parallel to each other in order to thereby generally define an endoprosthesis having a longitudinal axis along which said generally circumferential sections are axially spaced;
each of said generally circumferential sections includes an expandable segment that imparts radial expandability to said generally circumferential section whereby said section has an unexpanded insertion circumference and an expanded implantation circumference which is greater than said unexpanded insertion circumference, said expandable segment of each generally circumferential section is a generally foldable member that is bendable between a generally closed orientation and a generally opened orientation so as to impart radial expandability to the generally circumferential section;
said generally circumferential sections form a continuous helix that defines an axially extending endoprosthesis, wherein said end sections each have a free end;
means for engaging the free end of each of said end sections with an adjacent one of said intermediate generally circumferential sections, thereby avoiding the presentation of loose ends on the endoprosthesis; and said device for transluminally explanting the endoprosthesis includes:
an elongated member that is percutaneously insertable into a blood vessel or the like within which said endoprosthesis has been radially expanded and implanted, said elongated member having a proximal portion exterior of the body;
snaring means at a distal end of the elongated member;
means for manipulating a proximal portion of the elongated member from a location exterior of the body, said manipulating means facilitating engagement of said snaring means with one of said circumferential sections of the implanted endoprosthesis;
puller means for sliding the elongated member in a proximal direction by moving the body-exterior proximal portion of the elongated member in a direction away from the endoprosthesis;
said puller means further being for at least partially uncoiling said helix and for reducing the radial size of the endoprosthesis to less than said expanded implantation circumference and such that said endoprosthesis will pass through the blood vessel or the like; and means for completely removing the elongated member from the body until the endoprosthesis of reduced radial size has been fully explanted.