CA2079944A1 - Apparatus for widening a stenosis in a body cavity - Google Patents

Abstract

ABSTRACT

An apparatus for widening a stenosis in a body cavity, such as an artery, in the bile duct, in the ureter, etc. is proposed, which in view of a problem-free, reliable and permanent widening of a stenosis is chara-cterized by a memory alloy part having a cylindrical jacket-shaped outer contour, said part radially widening at a transition temperature, which is above ambient temperature, but below body temperature, whilst maintaining a cylindrical outer contour and at a temperature below the transition temperature the diameter is smaller than that of the vessel.

Description

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Apparatus for widenin~ a stenosis in a body cavity.

The invention relates to an apparatus for widening or expanding a stenosis in a body caYity 9 such as in an artery, in the bile duct, in the ureter, etc.
/an elonqated bçdy cavi~y such as L~
An occlusion in a vesseI,especlally in an artery, lS generally initially widened, in that deposition material, such as plaque is removed by cutting and sucking out or the like. However, this cannot take place up to the tissue material, because at that point an injury risk esists.
If merely a narrowing and not a complete occlusion has formed, i.e.
a stenosis or a certain ~hrough-flow area has been created in the aforementioned manner in the previous complete occlusion, a radial widening of the stenosis is desired. This is carried out not only in blood vessels, but also in other body passages or tubes, such as in the ureter, bile duct, etc.

For this purpose hitherto use has been made of a balloon catheter with a double internal diameter, which brings about an instantaneous radial widening, which is to remain after the catheter has been remo-ved. Permanent widening of such a stenosis is also known. Thus, it has been proposed to axially fi~ a widening part to such a balloon catheter, insert it with the latter and by widening the balloon cathe-ter to plastically deform the ~same in such a way that the radial dimen-sions of the widening part are increased, it is forced into the wall of the stenosis and after the removal of air from the catheter the latter can be removed, whereas the widening part remains in situ in the plastically deformed state. As such a part, e.g. a sleeve in the form of a "helical" envelope has been provided.

A significant disadvantage of the last-mentioned process is that the sleeve can be introduced into the stenosis located on the outer circum-ference of a catheter. Firstly the axi.al fixing is complicated and can either not be reliably achieved, so that a part can be left behind 2 ~

on advancing the catheter, or a subsequent release of the part from the catheter is difficult. In addition, damage can result from a widening part e~ternally mounted on a catheter. Finally a widening by the balloon catheter in the case of such a part must lead to a radial extension, which significantly exceeds the ultimately desired radial extension, because such parts, like conventional biocompatible materials, to the e~tent that they have an adequate strength to keep open a stenosis, have a considerable elastic deformation range, before a permanent plastic deformation occurs to the desired radius. This more particularly applies to a "helically" shaped part of the afore-mentioned type.

The problem of the invention is therefore to provide an apparatus for widening a stenosis, which allows a simple, problem-free, reliable widening of a stenosis in a short time, whilst avoiding the aforement-ioned disadvantages.

According to the inven~ion this problem is solved by an apparatus for widening a stenosis in a body cavity, such as in an artery~ the bile duct, the ureter, etc., which is characterized by a shape memory alloy with a cylindrical jacket-like outer contour, said part radially widening, whilst maintaining a cylindrical contour, at a transition temperature, which is above the ambient temperature, but below the body temperature, and at a temperature below the transition temperature the diameter is smaller than that of the vessel.

The invention proposes a widening part made from a memory alloy, which assumes a shape above a certain transition temperature, which is below the body temperature, which corresponds to the desired widenng of the body cavity~ccording to a preferred development the memory alloy is a nickel-titanium alloy. However, it is also possible to use Cu-Zn-Al or Cu-Al-Ni alloys. Such alloys are known under the names Niti-nol, Biometal (Toki, Japan), Memotal.

The martensitic reaction or transformation bringing about the shape 2~9~

change takes place by modifying the temperature. Whereas the tran-sition temperature can be within wide limits, provided that it is below the body temperature, according to a preferred deYelopment the transition temperature is 20C. This temperature is sufficiently below the temperature brin8ing about a reliable widening of the memory alloy part in its high temperature state. However, simultaneously the temperature is sufficiently high that a part taken by the surgeon at ambient temperature, which is therefore in its low temperature state wlth small radial dimensions, only radially widens after a cer-tain time, which is adequate for inserting the part into the body up to the stenosis.

Yarious developments and constructions of such apparatuses are poss-ible. Thus, the memory alloy part can comprise a bent, flat sheet metal part or can be a wire part.

In the first case, according to a preferred development the sheet metal part has a spiral shape at a temperature below the transition temperature and widens to a cylinder jacket on passing above the trans-ition temperature This construction has the adYantage that there is no a~ial shortening of the widening part. The latter occurs in a preferred development, which is characterized in that the memory alloy metal is a cylinder jacket provided with elongated ~lots and web regions left be~ween them, in which the parallel directed, adjacent elongated slots are reciproca~ely displaced in their e~ten~cion dire-ction and, accompanied by the formation of diamond-shaped gapY between the web~, the part ic radially made erect on increa~ing the temperature to above the transition temperature. This construction can be relat-ively simply obtained, in that a metal cheet with the desired dimen-sions is punched as erpanded metal, then cylindrically bent and welded together at the longitudinal ed8es parallel to the slots. The shorten-ing of the par~ in the ca~e of a radial widening can be taken into account from the outset by having a greater length.

The latter also applies for another prePerred development, in which 2~7~

the part is made from a metal braid or gauze and is constructed as a cylinder jacket, or the memory alloy part is made from a multiply helically guided wire.

A particularly preferred development of the inventive apparatus is characterized in that the metallic material is constructed in meander-like manner in the a~ial direction and the indi~idual meanders are bent in an almost circular manner. If the meanders have axial outward bends, then according to a preferred further development the outward bends of a meander arm are connected to an adjacent meander arm.
Joining can in particular take place by soldering. I all ~he outward bends are not firmly joined to the adjacent meander arms in the typical manner and instead only part of them are joined, then according to another preferred development, the joining forces of the joints are greater than the "weighing" forces of the meander bends. Thus, the inventiYe apparatus, which can also be referred to as an endoprosthe-sis or sten~, in the areas in which the meanders are not a~ially firmly joined together by joints, such as soldered joints, can be expanded or compressed and therefore position-adapted, without the joints (sold-ered joints) at other points fracturing or breaking.

The joining points must also be constructed as clearly defined breakingpoint~ if a stent constructed in the abo~e-described manner is to be subsequently remoYed, so that on pulling at one end of the wire forming the stent the joining points break open, the wire stretches and therefore in easy manner the ~tent can be removed. The remo~l of a stent in ~he above-described construction, but also in a clrcular knitted construction or with a helically shaped stent, is facilitated if at least one end of the wire forming ~he apparatus a ball is prov-ided. It is then possible to apply hollow forceps to the ball and consequently the stent can be stretched. According to another prefe-rred construction it has a substantially a~ially parallel e~tending connecting web from which e~tend laterally circularly bent ribs, which e~tend on ei~her side of the connecting web and are in the axial dire-ction in each case alternately offset to one another. It i9 2~7~J~

alternatively possible to provide in the case of such stents that the ribs e~tend under an angle of 90 to the connecting web or the ribs extend under an angle no~ equal to 90, preferably an angle of 50 to 70 to the connecting web.

Whilst the outer contour of the stents is generally cylindrical jacket-shaped, in certain individual cases conical or biconical outer contours are preferred.

According to another preferred development the metal of the thus far described catheter is embedded in tissue-compatible plastics or prefer-ably silicone, so that despite the gaps between areas of the memory metal a closed jacket area is created. Thus7 in the case of malignant tumours, it is ensured that cells do not grow into the interior of the stent.

The stent according to the invention can be used in numerous different fields and for numerous different purposes, e.B~ in the urethra, ure-ter, neck of the bladder, deducti bilipheri, in blood vessels, such as arteries and veins, in the esophagus and trachea, as well as in the intestinal region, particularly in the intestinum rectum.

The invention offers stiff and highly fle~ible, particularly a~ially bendable stents, the latter more particularl~ applying for those ha~ing a wire guided in ~eandering manner.

The inrention is described in greater detail hereinafter relative to non-limitative embodiments and with reference to the attached draw-ings, wherein show:
ig. 1 a first embodiment of an inventire apparatus for widening a stenosis in a body cavity with the ~tarting position in spiral form.

2 ~ 7 ~

Fig. 2 another embodiment of the inventive apparatus with axially parallel slots in the form of an e~panded metal.

Fig. 3 a further preferred embodiment based on a wire gau~e.

Fig. 4 a development with a helically wound wire.

Fig. 5 the mesh pattern of a circular knitted stent according to the invention.

Fig. 6 a diagrammatic representation of a stent with a m~andering wire, the individual meanders being bent in partial ring shape and having a cylindrical outer contour.

~ig. 7 a stent similar to fig. 6 with a biconical outer contour, once again diagrammatically.

Fi8. 8 another development of an inventive stent.

Fig. 9 a modification of the stent of fig. 8 in the wound-on star-ting position.

Fig. 10 the prepunched starting plate for another development of - an inventive stent.

Fig. 1 shows a first embodiment of an inrentive apparatus for widening a stenosis in ~n elongated bcdy cavities,such as in an artery,the bile duct,the ureter, etc. and which is hereinafter referred to as a stent. In its low temperature state the stent of fig. 1 has a spiral shape and which on passing above a transition temperature in its high temperature state widens to an almost cylindrical jacket-shape. The stents accor-ding to the invention are made from a shape memory metal, particularly from nickel-titanium alloys, but also Cu-Zn-AJ. or Cu-Al~Ni alloys.
Memory alloys are know~ under the names Nitinol, Bimetal or Memotal.
The manufacture of the stent according to fig. 1 takes place in that . .

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in its high temperature form, i.e. the cylindrical jacket-shape of fig. 1, the stent is bent and then undergoes a heat treatment. After cooling to below the transition temperature the stent is permanently brought into lts spiral low temperature form. If it is again heated to above the transition temperature, which is in the range 30 to 35C
and pref~rably at 35C, then it "remembers" its cylindrical jacket-shaped high temperature form and reassume~ ~he latter.

Fig. 2 shows another stent in the form of an expanded metal. In the case of the latter into a sheet metal part are punched in successively aligned and ju~taposed manner a plurality of slots and adjacent, ju~ta-posed slots are in each case so reciprocately longitudinally displaced, that the two upper and lower regions of a 310t oYerlap with the near end region of adjacent slots. If the sheet metal is e~panded trans-~ersely to the estension direction of the slots, then it can be stret-ched, the slots widening to diamonds. Such a sheet metal piece is given a cylindrical jacket shape and is intercornected, such as by welding or soldering by its longitudinal sicles parallel to the slots.
It is brought into its widened form showing the diamonds and as is represented to the right in fig. 2 and is then correspondingly subject to the high temperature treatment and subsequently at low temperature is again permanen~ly deformed in the stretched form (to the left of fi8. 2). On heating ~o above the transition temperature this ~tent also remembers its widened high ~emperature form. In the case of radial widening the stent of fig. 2 and al~o those of figs. 3 and 4 ~horten, unlike in the case of the stent of fig. 1. However, thi3 shortening can be taken into account by choo~ing a corresponding len~
gth. The width of the web3 i~ e~tr~mely ~mall and i~ preferably appro-~imately 0.2 mm.

Fig. 3 show~ a metal braid or gauze stentl which also ha~ a cylindricaljacket-~haped outer contour. The tempera~ure and shape treatment once again take~ place in the above-described manner, qo that on incre-asing the temperature to above the tran~ition temperature the stent widens from its ~mall diameter, ~tretched sta~e into a radially widened 2Q17~

high temperature state. The same applies with respect to the further helical design of a metal wire stent with shape memory and here again the corresponding heat treatment is carried out.

Fig. 5 shows the mesh pattern of an inventive, circular knitted stent.
It has conventional knitted meshes formed from a weft thread 11, the meshes having a leg 12, a head 13 at the upper binding point and a base 14 at the lower binding point around which the head is placed.

According to a preferred development a ball 16 is fi~ed to the end of the wire filament 11. If an inserted stent is to be removed for some reason, then action can take place on the ball 16 by means of hollow forceps so as to pull the same and the mesh pattern of the stent is loosened and the latter can be removed from the body cavity in which it was positioned.

Such a removal by s~retching the wire filamen~ forming the stent is also possible in the case of the constructions according to figs.
6 and 7. These stents comprise a meandering, longitudinally wound wire (i.e. the meanders e~tend transversely to the longitudinal direc-tion). The meanders are bent in circular manner, so that the remote webs of adjacent meanders are bent towards one another. Such a stent ha~ the important advantage that its length can be changed without significantly influencing the cross~section. Compared with itq normal longitudinal e~tension the stent can be compressed or stretched and is held in the resulting position by the frictional forces between it and the qurrounding ~essel walls.

According to a preferred development arms 19 of the meanders 20 haYè
outward bends 21, which extend up to the adjacent meander arm, e.g.
19'. At least part of the outward bend 21 can be connected to the in esch case adjacent meander arm 19' by a qoldered joint 22. As a function of the intended use all the outward bends can be connected to adjacent meander arms. In this case the length of the stent is limited. Only part of the outward bends may be connected, no soldered 7 ~

_ 9 _ joints being provided on certain of them and as a result the length can be changed ~o a limited e~tent. Finally, stents can be constructed in such a way that no outward bends are firmly connected to adjacent meander arms. The outward bends cause a certain resilience in the radial or angular direction of the stent.

The stents according to figs. 6 and 7 once again have the balls 16 at the filament ends, so as to be able to remove ~he stent by stret-ching the filamen~ forming the same. If there are soldered joints 22, then their fastening force i~ much less than the tensile strength of the filament. However, it must e~ceed the bending force of the wire in the vicinity of the webs 17,18 of the meanders.
':
As in the ca~e of other stent con~tructions according to the inqention, the construction described above can have a cylindrical outer contour in accordance with fig. 6. However, like other of the stents shown, it can be conical or biconical, as shown in fig. 7 and in this case the larger diameter is on the end faces of the stent.

The inventive stent according to figs. 6 and 7 has very considerable fle~ibility, which is 8reater than that in the case of fig. 5. The stent according to figs. 6 and 7 is almost completely bendable. The inventive metal stent~ can be embedded in compatible pla~tics or pref-erably silicone, which assumes the same contour as the actual stent.
This makes it possible to ensure that in the vicinity of a thus desig-ned ~tent a malignant tumour cannot migrate throu8h the same.
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The above-described stent formed by a meandering configuration can be used in many different ways and for manq different purposes. With particular advaneage such a stent can be used as a urethral stent in the vicinity of the prostate for widening the urethràl area there when the pro~taee is enlarged. As a result of it~ flexibility, it adapts particularly well to the configuration of the male ure~hra.
As a result of its longitudinal variability its length can be modified 207~

in such a way that its rear or outer end does not come to rest in the ~iCillity of the external sphincter, so that the stent does not impair this function. Particularly in the case of such a use the above-described stent e~traction possibility by stretching the wire filament forming it and pulling out proves particularly advantageous.

Another preferred construction of an inventive stent is shown in fig.
8 and fig. 9 shows a modification in the wound-up state. Such a stent could be referred to as a "skeleton stent". It substantially has an a~iall~ parallel e~tending ridge, or a connecting web 31 and from it e~tend on either side ribs 32,33 at a right angle (fig. 8) or under an angle differing from a right angle (fig. 9), preferably in the range 50 to 70. The ribs 32,33 e~tending to either side are in each case alternately displaced in the longitudinal direction of the ridge 31, so that the circularly bent ribs 33, which e2tend to one side in each case engage in the gap between two ribs, which e~tend to the other side and vice versa.

The length of ~he ribs 32,33 and the diameter of the stent in the low and high tempera~ure position can be chosen in such a way that in the low temperature position there is an overlap of the material walls of the stent, aq would otherwise be the case under identical conditions, if the ribq 32,33 estending on either side of the ridge 31 were arranged at the same height of the latter. The ~tent shown in fig~. 8 and 9 al~o has a very conqiderable fle~ibillty and longi-tudinal bendability. In addition, the ribs 32,33 can be so clo3ely ju~taposed, that from the surrounding tissue of a cavity held by the stent liquid can enter and be removed from the interior of the stent.
However, tiqsue cannot penetrate the interior and lead to a narrowing.
In the construction according to fig. 9 a so~ewhat greater rigidity i9 obtained than in the ca~e of fig. 8.

Fig. 10 shows a blank for a further stent~ From a sheet metal part are punched elongated holes and ju~taposed elongated holes are alter nately reciprocately displaced and can consequently give in the end - 2~7~

regions elongated holes with a shorter length than th~ other elongated holes.

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Claims (21)

1. Apparatus for widening a stenosis in a body cavity, such as in an artery, the bile duct, the ureter or the like, with a wire part having a substantially cylindrical jacket-shaped outer contour made from shape memory alloy, said part widening radially whilst maintaining a cylindrical outer contour at a transition temperature which is above the ambient temperature, but below the body temperature, the diameter at a temperature below the transition temperature being smaller than the diameter of the vessel, characterized in that the part with a substantially cylindrical jacket-shaped outer contour is made from wire and that at at least one end of the wire is formed a ball.

2. Apparatus according to claim 1, characterized in that the part is made from metal braid or gauze and is constructed as a cylind-er jacket.

3. Apparatus according to claim 2, characterized in that the knitted structure is a circular knitted structure.

4. Apparatus according to claim 19 characterized in that the memory alloy part is formed from a multiply helically guided wire.

5. Apparatus for widening a stenosis in a body cavity, such as in an artery, the bile duct, the ureter or the like, with a wire part having a substantially cylindrical jacket-shaped outer contour made from shape memory alloy, said part widening radially whilst maintaining a cylindrical outer contour at a transition temperature which is above the ambient temperature, but below the body temperature, the diameter at a temperature below the transition temperature being smaller than the diameter of the vessel and optionally the characterizing part of claim 1, chara-cterized in that strip-like metal material, is so guided as a round or flat wire in meander form, that in each case adjacent arms of a meander pass in a substantially circumferential direc-tion, whilst the webs joining the arms are directed in a substa-ntially axially parallel manner.

6. Apparatus according to claim 5, characterized in that the part with a substantially cylindrical jacket-shaped outer contour is made from wire and that at at least one end of the wire is formed a ball.

7. Apparatus according to claims 5 or 6, characterized in that axially the meanders (20) have outward bends (21).

8. Apparatus according to claim 7, characterized in that the outward bends (21) of a meander arm (19) are connected to an adjacent meander arm (19) at (22).

9. Apparatus according to claim 8, characterized in that the joining forces of the joints (22) are greater than the bending forces of the meander bends (17,18).

10. Apparatus according to claim 7, characterized in that the joining forces of the joints (22) are smaller than the tensile strength of the wire.

11. Apparatus for widening a stenosis in a body cavity, such as in an artery, the bile duct, the ureter or the like, with a wire part having a substantially cylindrical jacket-shaped outer contour made from shape memory alloy, said part widening radially whilst maintaining a cylindrical outer contour at a transition temperature which is above the ambient temperature, but below the body temperature, the diameter at a temperature below the transition temperature being smaller than the diameter of the vessel, characterized by a substantially axially parallel exten-ding joining web (ridge 31) and from which on either side extend circularly bent ribs (32,33), which axially are in each case alternately reciprocately displaced.

12. Apparatus according to claim 11, characterized in that the ribs (32,33) extend under an angle of 90° to the connecting web (31).

13. Apparatus according to claim 11, characterized in that the ribs (32,33) extend under an angle not equal to 90°, preferably an angle of 50 to 70° to the connecting web (31).

14. Apparatus according to one of the preceding claims, characterized by a cylindrical outer contour.

15. Apparatus according to one of the claims 1,2,5,6,11,12, chara-cterized by a conical outer contour.

16. Apparatus according to one of the claims 1,2,5,6,11,12, chara-cterized by a biconical outer contour.

17. Apparatus for widening a stenosis in a body cavity, such as in an artery, the bile duct, the ureter or the like, with a wire part having a substantially cylindrical jacket-shaped outer contour made from shape memory alloy, said part widening radially whilst maintaining a cylindrical outer contour at a transition temperature which is above the ambient temperature, but below the body temperature, the diameter at a temperature below the transition temperature being smaller than the diameter of the vessel, characterized in that the memory alloy part comprises a cylindrically jacket-bent, flat sheet metal part and that the memory alloy part is provided with elongated slots and web regions left between them and parallel directed, adjacent elong-ated slots are reciprocately displaced in their extension direc-tion and the part is made radially erect accompanied by the formation of diamond-shaped gaps between the webs on increasing the temperature to above the transition temperature.

18. Apparatus according to one of the preceding claims, characterized in that the metal elements of the apparatus are embedded in a closed jacket of tissue-compatible basic materials, particul-arly silicone.

19. Apparatus according to one of the claims 1,2,6,7,11,12,17,18, characterized in that the memory alloy is a nickel-titanium alloy.

20. Apparatus according to one of the claims 1,2,6,7,11,12,17,18, characterized in that the transition temperature is between 30 and 35°C.

21. Apparatus according to claim 20, characterized in that the trans-ition temperature is 35°C.