Apparatus for correcting the position of a stent

An apparatus for correcting a positioning of a stent for widening or keeping open a stenosis, in blood vessels, the urethra, the ureter, etc. The apparatus includes a guide part slidably housing an elongated wire part provided at a forward end thereof with radially expandable wire portions having structures for grasping the stent.

FIELD OF THE INVENTION 
The invention relates to an apparatus for correcting the position of a 
stent in a vessel or the like, such as a stent for widening a stenosis or 
the like, with at least one guide part. 
BACKGROUND OF THE INVENTION 
For keeping open stenoses or the like in blood vessels or similar hollow 
members in the human body, such as the ureter, urethra or the like, use is 
made of short stents, which are inserted in the vicinity of the stenosis 
and are intended to support the sane as a result of the intrinsic 
stability. Preferably wire stents are used, which are either widened by 
means of a balloon catheter in the radially expanded position or in the 
case of construction from a memory alloy material following insertion 
widened due to the body heat to an automatically radially prestamped, 
widened position. It can occur that such a stent is not positioned in the 
desired manner. It can also occur that the stent moves for same reason 
despite the widening. If e.g. a stent enters the urethra in the vicinity 
of the urethral sphincter, it can no longer fulfil its function and this 
can lead to incontinence. In such a case it is desirable to either reapply 
the stent if the original position is not desired, or subsequently correct 
the axial position of the stent in the body vessel. The seine applies with 
respect to stents in other organs, such as biliary or fenoral stents. 
SUMMARY OF THE INVENTION 
The aim underlying the invention is to provide an apparatus allowing the 
correction of the position of such a stent. 
According to the invention, in an apparatus of the aforementioned type by 
providing an elongated wire part provided at its front end with radially 
expandable wire portions. 
The elongated wire part provided with the radially expandable wire portions 
is inserted through a guide part, such as a cystoscope, which can 
optionally have a second working channel, a catheter, a tubular part, a 
hollow stylet or the like, in blood vessels, the urethra or the like, into 
the vicinity of the stent and namely to just in front of the stent if the 
latter is to be further advanced or behind the stent if the latter is to 
be retracted, or solely into the area covered by the stent. This is 
followed by the radial widening of the radially widenable wire portions, 
either in that they are prestamped in such a way that they automatically 
radially expand after passing out of the guide part when the latter has 
been retracted, or in that the radially widenable wire portions can be 
widened by a suitable device, such as a pull wire, until their furthest 
radially outwardly projecting areas can engage in front of or behind the 
stent or on the latter in the central region thereof. As a result of the 
advance or retraction of the wire part the stent position can be modified. 
According to a preferred development the wire portions are of a 
self-expanding nature on being relieved and in particular the wire 
portions are constructed in one piece with the elongated wire part. In 
such a case the wire portion preferably comprises individual interlinked 
wire strands, which divide in the vicinity of the expandable wire 
portions, but are recombined at the front free end thereof. The wire 
portions have a prestamping such that they can radially expand on freeing 
from externally acting forces. In an alternative construction the wire 
part has a pull wire guided through a hollow wire and which at the front 
of the wire portions engages thereon, whereas at the rear end connection 
takes place to the front end of the hollow wire, the wire portions also 
being constructed in one piece with the hollow wire. In such a 
construction the expansion of the expandable wire portions can be brought 
about by pulling on the pull wire. 
In order to allow a better action of the radially widenable wire portions 
on the stent, according to further preferred developments the radially 
expandable wire portions are provided in their furthest radially outwardly 
projecting area with corners and/or the radially expandable wire portions 
are provided on their furthest radially outwardly projecting areas with 
hooks. Alternatively the radially expandable wire portions are provided 
with thickened portions on their furthest outwardly projecting areas and 
in particular the thickened portions are small balls. 
Whilst the guide tube can basically be constructed as a metal tube, it can 
be provided at its front end with flat edges and can therefore be 
constructed as a hollow stylet. Optionally it is introduced percutaneously 
with the aid of an internal stylet. The guide part can also be flexible, 
e.g. in the form of a catheter. 
Whilst the radially expandable wire portions basically form a small basket, 
they can also have a helical construction and here again the helix can in 
cross-section or in projection not merely be given a circular, oval or 
elliptical cross-section, but can also be angular in projection. 
According to a highly preferred development of the invention, the radially 
expandable wire portions are fixed to the elongated wire portion (2) and 
in particular the expandable wire portions are soldered in the elongated 
wire portion. Whereas the radially expandable wire portions can be made 
from steel, such as spring steel and can be held in their reciprocally 
engaging insertion position by a guide tube or hose, whereby they radially 
expand from the guide tube or hose during advance as a result of their 
pretension, so that the radially expandable wire portions move into their 
radially expanded position in the relieved state, according to a preferred 
development the radially expandable wire portions are made from a 
nickel-titanium alloy (Nitinol). The use of such a material also permits 
what has been described hereinbefore. According to a preferred further 
development tile radially expandable wire portions are oriented in axially 
parallel manner in a low temperature position and extend radially further 
outwards in a high temperature position. 
Whilst the wire portions can fundamentally form a basket-like structure, 
being guided and interconnected by the front end thereof and radially 
expand in intermediate areas, according to a highly preferred development, 
in the radially outwardly directed position radially furthest outward 
projecting areas of the radially expandable wire portions are the free 
ends thereof and in particular in the expanded position of the radially 
expandable wire portions the furthest radially outwardly extending areas 
are approximately perpendicular to the axis of symmetry of the apparatus. 
To avoid any injury risk in this case, a preferred development is 
characterized in that the free ends are provided with blunted or rounded 
portions, e.g. in the form of spherical ends. To require a minimum amount 
of radial space particularly in the insertion position, in which the wire 
portions are very closely juxtaposed in a guide tube or hose and 
consequently permit the use of thin guide tubes or hoses, an extremely 
preferred development provides for the radially expandable wire portions 
to have different lengths. The ends, particularly if they are provided 
with small balls or the like, are then not located in a common radial 
plane in the insertion position, so that the balls are not close together 
and are instead axially displaced, so that the balls are also located in 
radially succeeding manner on the different radially expandable wire ends.

DETAILED DESCRIPTION 
The apparatus according to the invention for correcting the position of a 
stent fitted in a vessel or the like firstly has a guide part 1 in the 
form of a guide tube or hose or a styler (FIG. 2). The apparatus according 
to the invention also has an elongated wire part 2, which in the 
embodiment of FIG. 1 has a hollow wire element 3, e.g. formed from 
helically wound wire, whose individual turns engage on one another. To the 
front end 4 of the hollow wire 3 is either fixed a basket 6 on the hollow 
wire part or individual wires of the hollow wire 3 are not coiled and 
instead are guided in a longitudinal plane to the front end 7 of the 
complete wire part 2. At the latter they are connected to the front end of 
a pull wire 8, which is guided through the hollow wire part 3 up to its 
rear end and out of the latter (not shown). The wire portions 9 of the 
basket 6 can have prestamped corners or edges 11. Without loading the wire 
portions 9 engage closely on one another, so that the complete wire part 2 
can be moved through the guide part 1. If the basket 6 with the wire 
portions 9 is located in the vicinity of a fitted stent 12, it can be 
expanded into the radially expanded or widened position shown in FIG. 1 by 
pulling on the pull wire 8. The corners 11 then engage, as after axial 
positioning, either in front of or behind the stent 12 or in the interior 
thereon, e.g. its meshes or turns. As a result of the movement of the wire 
part 2 the stent 12 can be moved axially backwards and forwards and better 
positioned in an appropriate manner. 
The guide part 1 is constructed as a hollow stylet in FIG. 2. This e.g. 
makes it possible to percutaneously correct the position of a stent, such 
as e.g. in the case of a biliary or fenoral stent. The hollow stylet in 
FIG. 2 can also be inserted in an apparatus constructed according to FIG. 
1, whereas the guide part of FIG. 1, either in the form of a tube or a 
hose, can also be used in the construction according to FIG. 2, as will be 
described hereinafter. 
In the case of the construction according to FIG. 2 the elongated wire part 
can be a single wire or a helical or spiral wire, optionally formed from 
several individual strands, which then in turn form a small basket 6, 
which can be separately fitted to the wire part 2. In FIG. 2 the wire 
portions 9 of the basket 6 are pretensioned or prestamped in the radially 
expanded position shown, so that without the effect of external forces the 
basket 6 is expanded into said radially widened position. The individual 
wires 9 are interconnected at the front free ends 7 of the basket 6. If 
the basket 6 is drawn into the guide part 1, it is radially compressed by 
the latter. There is firstly an introduction of the guide part 1 into the 
vicinity of the stent whose position is to be corrected. The wire part 2 
with the radially compressed basket 6 located in the guide part 1 is then 
further advanced, so that the basket 6 is freed and can radially expand 
into the position shown in FIG. 2. Following axial position its edges 11 
once again engage upstream, downstream or in the vicinity of the stent 12, 
so that the position of the latter can be corrected by pushing or pulling 
on the wire part 2. 
Further elements of the apparatus according to the invention can be, in 
addition to the stent 12, a guide part 2', which can correspond to the 
guide part 2 and a slide 13, which can be slid through the guide part 2' 
and can slide the stent located therein out of the guide part 2'. If a 
correction of the axial position of the stent 12 is still necessary, then 
following the removal of the slide 13, a wire part 2 according to FIGS. 1 
or 2 can be inserted through the guide part 2', until it can act on the 
fitted stent 12 in order to position the latter. 
Whereas in FIGS. 1 and 2 the wire portions 9 of the basket 6 are only 
provided with corners or edges 11, in the vicinity thereof it is also 
possible to provide small hooks 12, as shown in FIG. 4a. The corners or 
edges 11 can also be shaped to hooks 12', as is the case in FIG. 4b. As 
means for acting on the stent 12 or engaging in its turns or meshes, in 
the vicinity of the corners it is also possible to provide widened 
portions on the wire parts 9, e.g. in the form of small balls 14 as shown 
in FIG. 4c. 
FIG. 5 shows another variant of the radially expandable wire portions 9' or 
9" in the form of spirals with a helical contour. Whereas the outer 
contour in the case of the wire portion 9 is cylinder envelope-like, i.e. 
it has a circular cross-section or a circular axial projection, which can 
also be e.g. elliptical or oval, the spiral wire portion 9" of FIG. 5b has 
several corners or edges 11 and e.g. as a result a rectangular or 
multiangular cross-section or corresponding axial projection. Such 
constructions are in particular provided if the wire portions 9' or 9" are 
to act in the vicinity of the stent 12, i.e. not upstream or downstream 
thereof. Here again the corners 11 engage in the meshes of the stent 12, 
so that the latter can be positioned in optimum manner by pushing or 
pulling. The edges 11 can be constructed in accordance with FIGS. 4a to 
4c. 
FIGS. 6a to 6c show another construction according to the invention, in 
which the radially expandable, distal wire portions 16a, 16b, 16c can be 
made from a nickel-titanium alloy such as Nitinol and have a shape memory. 
The elongated wire part 22 can also be made from a corresponding alloy, 
but no shape memory contour is impressed thereon. 
To avoid injury the expandable, distal wire portions 16a-16c are provided 
with small balls 18 at their free ends 17a-17c. The desired blunting or 
rounding of the free ends 17a-17c can also be obtained in same other way. 
In the low temperature position, such as at 0.degree. C., the free wire 
portions 16a-16c extend parallel to one another, as shown in FIG. 6c. As 
can be gathered from FIGS. 6a-6c, they have different lengths, so that the 
balls 18 of the individual wire portions 16a-16c are in different axial 
positions in the low temperature setting thereof and are not radially 
juxtaposed, so that the internal diameter of the insertion catheter or 
tube 19 can be smaller than would be the case if the three balls 18 were 
located in one radial plane. 
In the high temperature setting of tile nickel-titanium material of the 
expandable wire portions 16a-16c, which must be reached under 35.degree. 
C., the transition temperature generally being between 10.degree. and 
30.degree. C., the expandable, distal wire portions 16a-16c extend 
arcuately radially outwards, their free ends 17a-17c forming an angle of 
approximately 90.degree. to the axis of the elongated wire part 22, as can 
be clearly gathered from FIG. 6a. 
For correcting the stent the apparatus according to the invention is 
inserted with the guide tube 19 and the elongated wire part 22 located 
therein with expandable wire portions 16a-16c into the vicinity of the 
previously inserted stent or intraluminal tube. The elongated wire part 22 
is advanced until the expandable wire portions 16a-16c pass out of the 
insertion tube or hose 19 and radially expand in the position shown in 
FIGS. 6a and 6b, either under a pretension which has existed from the 
outset, or due to their high temperature setting in this form. The free 
ends 17a-17c with the balls 18 engage in gaps of the stent or the 
intraluminal tube, which can be formed from wire and can in particular be 
knitted, or can comprise flat material provided with openings, so that by 
advancing and retracting the elongated wire part 22, the axial position of 
the stent or intraluminal tube can be corrected. 
For advancing the elongated wire part 22 in the guide tube or hose 19 there 
is preferably an actuator, as shown in FIG. 7. The actuator 21 comprises 
two handle parts 23, 24, which are axially movable relative to one 
another. The handle part 24 has two gripping rings 25, 26, in which can be 
placed the index and middle finger, whilst the handle part 23 has a ring 
part 27 in which is placed the thumb. The guide catheter or tube 19 is 
fixed to the handle part 24. An axial shoulder 28 of the handle part 23 
projects into the handle part 24 and is axially movable to a limited 
extent therein through a slot guide 29 therein and a can 30 on the axial 
part 28. 
The elongated wire part 22 is fixed on the handle part 23, e.g. by means of 
a plugging part provided with spring legs 31, the latter embracing a ball 
33 fitted to the rear end 32 of the elongated wire pact 22 and which has a 
larger diameter than the elongated wire part 22. In this way the elongated 
wire part 22 and with it the expandable wire portions 16a-16c are securely 
held in the handle part 23. FIG. 7 shows the advanced operating position 
of the apparatus according to the invention, in which the expandable wire 
portions 16a-16c project out of the hose or tube 19 (FIGS. 6a and 6b). In 
the inserted position the handle part 24 and handle part 23 are axially 
drawn apart and namely until the can 30 strikes against the rear (left) 
end of the guide slot 29 of the handle part 24. In this insertion position 
the expandable wire portions 16a-16c are in the position shown in FIG. 6 
within the guide tube or hose 19. 
Whereas the construction of the actuator 21 according to FIG. 7 has been 
explained with reference to an apparatus constructed according to FIGS. 
6a-6c, the actuator can also be used in an apparatus according to the 
invention constructed in accordance with the earlier drawings, the guide 
part 1 being fixed to the handle part 24 and the wire part 22 to the 
handle part 23.