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Medical Patent Abstract
A medical implant, having a proximal and a distal end, that is preformed
to assume a superimposed structure at an implantation site but can
be made to take on a volume-reduced form making it possible to introduce
it with a micro-catheter and a guide wire arranged at the proximal
end, with the implant in its superimposed structure assuming the
form of a longitudinally open tube and having a mesh structure of
interconnected strings or filaments. The implant has a tapering
structure at its proximal end where the strings or filaments converge
at a connection point.
Medical Patent Claims
What is claimed is:
1. An expandable medical implant for implantation in a vessel,
comprising: a mesh structure comprising a first plurality of mesh
cells, the mesh structure having a proximal end and a distal end;
a tapering portion comprising a second plurality of mesh cells,
the tapering portion disposed toward the proximal end of the mesh
structure; and a connection point, at which the tapering portion
converges, located at a proximal end of the tapering portion, a
first guide wire detachably coupled and proximally extending from
the connection point; wherein the implant is performed by curling
the mesh structure such that a seam extends along the longitudinal
axis of the implant; wherein the implant is delivered in a volume-reduced
form having overlapping edges; and wherein the mesh structure partially
uncurls such that the implant assumes a volume-enlarged form to
provide wall opposition to the vessel, and wherein the volume-enlarged
implant takes the form of a tube tapering toward the connection
point and the tube further comprises substantially open ends.
2. The implant according to claim 1, comprising an alloy having
shape-memory properties.
3. The implant according to claim 1, wherein: the connection point
is centrally arranged in the tapering portion.
4. The implant according to claim 3, further comprising: a platinum
spiral coupled to the connection point.
5. The implant according to claim 1, wherein: at least one of the
tapering portion and the mesh structure is made from one of: a cut
foil curled to form the longitudinally open tube; and an expanded
metal foil curled to form the longitudinally open tube.
6. The implant according to claim 1, wherein: at least one of the
tapering portion and the mesh structure comprises one of: a plurality
of filaments interconnected to one another by welding; and a mesh
braiding of individual filaments.
7. The implant according to claim 6 wherein each filament comprises
individual strands worked into a rope-like structure.
8. The implant according to claim 1, further comprising at least
one marker disposed at the distal end of the mesh structure.
9. The implant according to claim 6, further comprising at least
one marker disposed at the distal end of the mesh structure, wherein
the at least one marker is arranged at a junction point of at least
two filaments.
10. The implant according to claim 6, wherein the mesh braiding
comprises a knitted structure that imparts curled up edges to at
least one of the tapering portion and the mesh structure.
11. The implant according to claim 10, wherein the knitted structure
comprises a fluse-like structure.
12. The implant according to claim 1, wherein the mesh cells of
the first plurality are smaller than the mesh cells of the second
plurality.
13. System for the treatment of aneurysms or other vascular malformations,
comprising a micro-catheter; and a second guide wire for the placement
of the micro-catheter; wherein the implant of claim 1 is detachably
coupled to the first guide wire through the micro-catheter.
14. The system according to claim 13, wherein the implant is detachably
coupled to the first guide wire via an electrolytically corrodible
element.
15. The implant of claim 1, further comprising a substantially
continuous mesh along the longitudinal axis.
16. The implant of claim 1, wherein the implant comprises a longitudinally
open tube in the volume-enlarged form.
Medical Patent Description
FIELD OF THE INVENTION
The present invention relates to a medical implant that is preformed
in order to assume, at the site of implantation, a superimposed
structure and while being implanted is presented in a volume-reduced
form. Furthermore, the present invention relates to the application
of such an implant as a neuro-stent, its combination with a guide
wire as well as a system for the application of such implants when
treating aneurysms or other vascular malformations.
BACKGROUND OF THE INVENTION
It is known to treat vascoconstriction (stenoses) with stents (vascular
endoprostheses, vessel props) that are inserted into the stenotic
area to keep the vessel lumen open. It is further known to use such
stents for closing off vessel wall ballooning (aneurysms) or fistulae.
For the foregoing purposes, balloon-dilatable stents are traditionally
used. For placement, these stents are crimped over a non-expanded
balloon in a non-dilated state, moved to the treatment location
by means of a catheter system and then, by expanding the balloon,
dilated and thus anchored within the vessel. As there is no need
for sophisticated supporting and guiding sheaths when placing balloon-dilatable
stents in position, these stents can also be inserted into very
fine vessels. It is, however, problematic that on account of their
plastic deformability these stents can easily be compressed when
external pressure is exerted on them. Another disadvantage is encountered
when anchoring such a stent, by applying high pressure, the stent
has to be expanded initially beyond the circumferential size it
will finally have. Such an expansion beyond the required circumferential
size may involve the risk of a vessel injury that may entail the
formation of a thrombus.
Further, these traditional balloon-dilatable stents, due to their
structure, cannot simply be introduced through an already laid micro-catheter
and advanced to the implantation site but have to be arranged in
the distal area of a specially designed micro-catheter in order
to be moved to the implantation location by means of a so-called
pusher. This process calls for a rather sophisticated catheter technology
that is difficult to handle. Additionally, a stent, once placed
in position, can only be relocated or retrieved with great difficulty,
if at all. After a wrongly placed stent has been dilated it can
neither be relocated nor removed as a rule.
It is further known to apply self-expanding stents that are made
of shape-memory materials. These stents possess a braid-like structure
and are initially introduced and moved in a collapsed state through
a catheter to the destination site where they expand either due
to temperature changes (thermo-memory effect) or because the mechanical
force exerted by the catheter (super-elasticity) is no longer effective.
Such stents, as well, require mechanisms for their introduction
that are relatively expensive and space-consuming. The known super-elastic
expandable stent requires the use of a supporting and guiding sheath
that results in a relatively large catheter size and, what is more,
also makes it difficult to introduce such stents through an already
laid catheter.
For the introduction into small-lumen intra-cranial vessels, it
is furthermore known to use stents made of shape-memory materials
that initially are present in the form of an elongated filament.
Not until the stent exits the catheter will it assume its tubular
structure due to the change in temperature or because of the compression
force no longer being exerted by the catheter.
It is known to treat aneurysms and similar diseases by using a
stent consisting of two stretched out filaments that due to the
mechanical constraint of a strand, are kept, by tension, in the
stretched out form until when pushed out of the catheter, said constraint
is removed and the strands assume the actual form of a stent. This
structure enables the use of stents having shape-memory properties
in vessels of very small lumen such as the intra-cranial and cerebral
vessel branches.
SUMMARY OF THE INVENTION
The present invention is directed to implants that can be introduced
through traditional micro-catheters into small-lumen intra-cranial
vessels, that are well placeable and relocatable, that can be moved
back into the micro-catheter in case of need, and that are suited
to bridge vessel ballooning and fistulae in such a manner that these
can be filled with occlusion agents. Furthermore, it is desirable
to provide implants capable of adapting to the vessel caliber relatively
freely, i.e., not tailored to a specific vessel caliber.
According to the present invention, a medical implant that has
the form of a longitudinally open tube with interconnected strings
or filaments forming a mesh structure culminating, on one side,
in a tapering structure at a connection point is provided.
An implant according to the present invention consists of a flat
object that, as a result of its impressed and superimposed structure,
assumes the form of a slotted tube or hose with the free edges preferably
overlapping. In its volume-reduced form it continues to be present
in a curled-up condition, i.e., the diameter of the implant, in
a volume-reduced state, is significantly reduced in comparison to
that of the superimposed structure. After the implant has been released,
it assumes the structure impressed on it and expands to such an
extent that the vessel surrounding the implant allows. Such an expansion
in the form of an expanding spiral spring shape leads to the implant
automatically adapting to the vessel caliber or lumen in such a
manner that it can be applied in vessels having different calibers.
In the case of narrow vessels, this results in a relatively wide
overlap of the two free edges, with wider vessels this overlap is
smaller or even a free gap forms which, in the event of vessel branches,
is a desirable trait.
In one aspect of the present invention, the implant is a flat or
two-dimensional structure that is rolled up to form a longitudinally
open object capable of establishing close contact with the wall
of the vessel into which it is introduced.
The strings or filaments taper on one side and culminate in a connection
point that permits the implant to be connected to a guide wire to
be easily retracted into a catheter in an event of an incorrect
placement or inadequate adaptation to the implantation site so that
it may be replaced by another implant or reimplanted after the catheter
has been repositioned. As a result of its tapering structure, the
implant entering the micro-catheter curls up more closely and again
assumes its volume-reduced form with the pull force applied to the
guide wire and the forces exerted via the catheter rim interacting.
In the catheter itself, the implant is present in its volume-reduced
form, resembling rolled-up wire netting. Through the action of the
guide wire and when thrust forces are applied, an axial compression
will be caused, and when released, the superimposed structure assumes
a minor longitudinal contraction. Advantageously, the stent according
to the present invention exhibits an insignificant longitudinal
contraction when released in comparison to dilatable stents.
A connection point of the medical implant situated at the end of
the tapered structure serves, at the same time, as a fastening point
for the guide wire, either directly or via a connecting element.
In the event of a cut or expanded metal foil, this connection point
represents the point where the strings of the implant converge.
In the case of a mesh-like structure consisting of individual filaments,
at least two filaments converge at this connection point and are
connected with each other by welding or crimping.
The connection point serves also as a connecting element or part
thereof that remains attached to the implant after the guide wire
has been detached from the implant. In one embodiment, this connection
point is arranged within a platinum spiral or attached to it via
a platinum spiral to a connecting element. The spiral may also serve
as an X-ray reflecting marker for positioning purposes. In one embodiment,
the connecting elements are electrolytically corrodible. Such connecting
elements enable the implant, after it has been correctly positioned,
to be detached from the guide wire by applying electrical energy
for brief periods of time, 10 to 60 seconds, for example.
Advantageously, the medical implant according to one embodiment
of the invention does not incur a longitudinal contraction when
adapting to the vessel. The longitudinally open structure, having
a predetermined winding property, has no effect on the longitudinal
expansion of the stent. The foil structures have been found to be
remarkably true to size under the influence of thrust and tensile
forces. The same applies to the warp-knitted structure and the mesh-like
structure consisting of individual filaments interconnected by welding.
In an embodiment where the superimposed structure cannot be impressed
onto the implants with the help of the warp or weft knitting method
or by braiding, material may be put to use that possesses shape-memory
properties. For example, such materials consist of alloys containing
titanium and nickel which are known by the name of Nitinol, as well
as iron and copper based alloys. Shape-memory properties may be
based on a stress-induced martensitic transformation or a temperature-induced
martensitic transformation or may be the result of a combination
of the two.
The implants according to one embodiment of the present invention
are also provided with X-ray reflecting markers that enable the
positioning and implantation to be monitored. Such markers may have
the form of spirals that are arranged proximally, for example, at
the connection point of the strings or filaments. The X-ray reflecting
markers can also be arranged at the distal end of the implant, in
the form of platinum or platinum/iridium elements incorporated in
or attached to the mesh structure. The meshes of the implant, according
to one embodiment the invention, may, at the distal end, be provided
with a lug or end in a lug that accommodates the marker element
arranged levelly.
Furthermore, the present invention operates in a combination of
the implant with a guide wire that is linked to the distal end of
the implant in a manner so as to be detachable. Such detachability
is brought about by an element that, under the influence of electrical
energy, is capable of corroding. The guide wire can be a known and
applied guiding wire of suitable kind for pushing the implant through
a catheter to the site of implantation and, should it have been
improperly positioned, retract it into the catheter. It is clearly
understood that the corrosion point may also be in the area of the
guide wire or may be based on an otherwise known mechanical or thermal
detachment technique.
The invention also relates to a system to be used for the treatment
of aneurysms or other vascular malformations. The system comprises
a first micro-catheter, a first guide wire to bring the first micro-catheter
into position, a second guide wire to move the implant through the
first micro-catheter and place it in position and the implant arranged
at the distal end of the second guide wire in a way so as to be
detachable. Due to the curled up structure of the implant, and as
a result of making use of the combination with the guide wire, it
is possible, after having placed the first micro-catheter, to remove
the first guide wire and introduce and handle the second guide wire
which is provided with the implant.
As per one embodiment, the system has additionally been provided
with a second micro-catheter to accommodate the second guide wire
with the implant in such a way that it is slidable within the second
micro-catheter and can be moved through the first micro-catheter
to the target site. Coatings of the second micro-catheter that enhance
its slidability may facilitate handling.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and further advantages of the invention may be better
understood by referring to the following description in conjunction
with the accompanying drawings in which:
FIG. 1 is an implant according to one embodiment of the present
invention having a honeycomb structure;
FIG. 2 is another embodiment of a stent according to the present
invention having a honeycomb structure;
FIG. 3 is a third embodiment of a stent according to the present
invention having a honeycomb structure;
FIG. 4 is a warp-knitted structure as can be used for an implant
according to the invention;
FIG. 5 is a stent according to the present invention together with
a guide wire and a catheter;
FIGS. 6a and 6b are is a schematic representation of an implant
according to an embodiment of the present invention shown in its
superimposed and in its volume-reduced shape;
FIGS. 7a and 7b show is a marker element as can be used in the
system according to the present invention; and
FIGS. 8a and 8b are is a schematic representation of two detachment
locations by which the implant, according to the present invention,
can be detachably linked to a guide wire.
DETAILED DESCRIPTION
An implant, according to FIG. 1, consists of a mesh or honeycomb
structure that, in one embodiment, comprises a multitude of filaments
interconnected by a laser welding technique. The implant can be
subdivided into a functional structure A and a tapering proximal
structure B, the two structures being distinguishable, inter alia,
by a different mesh size. To enable the functional structure A to
perform its retaining function, its mesh cells 3 are held relatively
narrow so that they lend themselves to the retention of occlusion
spirals arranged in an aneurysm. In general, the mesh width is in
the range of 0.5 to 4 mm and may vary within an implant.
In one aspect of the present invention, the implant is a flat or
two-dimensional structure that is rolled up to form a longitudinally
open object capable of establishing close contact with the wall
of the vessel into which it is introduced.
In the tapering proximal structure B of the implant, there is provided
a wider mesh cell 4 structure which has been optimized towards having
a minimum occlusion effect. In the area of the tapering structure
2, the filaments have a greater thickness and/or width to be able
to better transfer to the functional structure A the thrust and
tensile forces of the guide wire exerted at a connection point 5
when the implant 1 is introduced and placed in position. In the
area of the tapering structure it is normally not necessary to provide
support for, and coverage of, the vessel wall, but on the other
hand requirements as to tensile and thrust strength increase. The
filament thickness in the functional structure A generally ranges
between 0.02 and 0.076 mm, and in proximal structure part B, the
filament thickness is greater than 0.076 mm.
The proximal structure forms an angle from 45.degree. to 120.degree.
at the connection point 5, in particular an angle of about 90.degree..
The filament thickness (or string width) is the same as the mesh
size and its shape may vary over a great range to suit varying requirements
as to stability, flexibility and the like. It is understood that
the proximal structure B, as well, contacts the vessel wall and
thus does not interfere with the flow of blood within the vessel.
At a distal end, the filaments 2 end in a series of tails 6 that
are of suitable kind to carry platinum markers that facilitate the
positioning of the implant.
The implant 1 is curled up in such a way that edges 7 and 8 are
at least closely positioned to each other and may overlap in the
area of the edges. In this volume-reduced form, the implant 1, similar
to a wire mesh roll, has curled up to such an extent that the roll
so formed can be introduced into a micro-catheter and moved within
the catheter. Having been released from the micro-catheter, the
curled-up structure springs open and attempts to assume the superimposed
structure previously impressed on it and in doing so closely leans
to the inner wall of the vessel to be treated, thus superficially
covering a fistula, vessel branch or aneurysm that exists in that
location. In this case the extent of the "curl up" is
governed by the vessel volume. In narrower vessels a greater overlap
of the edges 7 and 8 of the implant 1 will occur whereas in wider
vessels the overlap will be smaller or even "underlap,"
will be encountered, and due care must be exercised to make sure
the implant still exhibits a residual tension.
Suitable materials that can be employed in the device include alloys
having shape-memory properties. The finished product is subjected
to a tempering treatment at temperatures customarily applied to
the material so that the impressed structure is permanently established.
The implant has a mesh-like structure consisting of strings or
filaments connected with each other. Strings occur if the implant
comprises cut structures as, for example, are frequently put to
use in coronary stents, a mesh-like structure consisting of filaments
is found if the implants are present in the form of mats having
knitted or braided structures or in the form of individual filaments
that are welded to one another.
FIG. 2 shows another embodiment of a stent 1 according to the invention
having the above described honeycomb structure where the tapering
proximal structure B is connected with the functional structure
part A by additional filaments 9 in a peripheral area 10 as well
as in the central area. The additional filaments 9 and 10 bring
about a more uniform transmission of the tensile and thrust forces
from the proximal structure B to the functional structure A. As
a result, the tensile forces can be better transmitted, especially
if the stent might have to be repositioned by having to be retracted
into the micro-catheter. The additional filaments 9, 10 facilitate
the renewed curling up of the stent. Similarly, the transmission
of thrust forces occurring when the stent is moved out and placed
in position is facilitated so that the stent can be gently applied.
FIG. 3 shows another embodiment of a stent 1 according to the invention
having a honeycomb structure with the edges 7 and 8 being formed
of straight filaments 9. According to this embodiment, the thrust
or pressure exerted by the guide wire at the connection point 5
is directly transmitted to the edges 7 and 8 of the functional structure
part A which further increases the effect described with reference
to FIG. 2.
The embodiment as per FIG. 3, similar to those depicted in FIGS.
1 and 2, may be based on a cut foil, i.e., the individual filaments
2, 9 and 10 are substituted by individual strings being the remaining
elements of a foil processed with the help of a cutting technique.
Laser cutting techniques for the production of stents having a tubular
structure are known. The processing of a foil for the production
of a pattern suitable for a stent is performed analogously. The
impression of the superimposed structure is carried out in the same
way as is used for the filament design
In one embodiment, expanded metal foil may be used with the respective
string widths being of the same magnitude. In one embodiment, it
is envisioned to subsequently smooth the foil to make sure all strings
are arranged on the same plane. The thickness of the foil usually
ranges between 0.02 and 0.2 mm. Foils of greater thickness also
permit the stent to be used in other fields of application, for
example, as coronary stents or in other regions of the body including,
for instance, the bile duct or ureter.
Foils worked with the help of a cutting technique are finished
by electrochemical means to eliminate burrs and other irregularities
to achieve a smooth surface and round edges. One of ordinary skill
in the art will understand these electrochemical processes as these
processes already are in use in medical technology. In this context,
it is to be noted that the stents according to the invention that
are based on a two-dimensional geometry and on which a three-dimensional
structure is impressed subsequently can be manufactured and processed
more easily than the conventional "tubular" stents that
already, during manufacture, have a three-dimensional structure
and necessitate sophisticated and costly working processes and equipment.
As pointed out above, the mesh structure of the implant according
to the invention may consist of a braiding of individual filaments.
Such a knitted structure is shown in FIG. 4 where the individual
filaments 2 are interwoven in the form of a "single jersey
fabric" having individual loops 3 forming a mesh-like structure
11. Single jersey goods of this type are produced in a known manner
from a row of needles. The single jersey goods have two fabric sides
of different appearance, i.e., the right and left side of the stitches.
A single jersey fabric material features minor flexibility in a
transverse direction and is very light.
Filaments consisting of a braid of individual strands and formed
into a rope can also be employed. Braids comprising twelve to fourteen
strands having a total thickness of 0.02 mm can be used. Platinum,
platinum alloys, gold and stainless steel can be used as materials
for the filaments. Generally speaking, all permanent implant materials
known in medical technology can be employed that satisfy the relevant
requirements.
In one embodiment, It is advantageous to have the fabric rims of
such a knitted structure curling up as is known, for example, from
the so-called "Fluse" fabric, a German term, which is
of benefit with respect to the superimposed structure and application
dealt with here. In this case, the superimposed structure can be
impressed by means of the knitting process. However, the use of
shape-memory alloys in this case as well is feasible and useful.
For the production of such knitted structures, known knitting processes
and techniques can be employed. However, since the implants according
to the invention are of extremely small size--for example, a size
of 2 by 1 cm--it has turned out to be beneficial to produce the
implants in the framework of a conventional warp or weft knitting
fabric of textile, non-metallic filaments, for example, in the form
of a rim consisting of the respective metallic filaments from which
the weft or warp knitting fabric either starts out or that extends
from such a fabric. The arrangement of the metallic part of the
weft or warp knitting fabric at the rim achieves the aforementioned
curling effect. The non-metallic portions of the knitted fabric
are finally removed by incineration, chemical destruction or dissolution
using suitable solvents.
FIG. 5 shows a combination of a guide wire 21 with the implant
1 attached to it that consists of filaments 2 connected to each
other by welding. The distal ends 6 and the connection point 5 where
the filaments of the implant converge in a tapering structure and
that simultaneously represents the joining location with guide wire
21 are shown. The guide wire 21 is introduced into a micro-catheter
22 which is of customary make.
Shifting the guide wire 21 within the catheter 22 will cause the
implant 1 to be pushed out of or drawn into the catheter. Upon the
stent being pushed out of the micro-catheter the mesh-like structure
attempts to assume the superimposed shape impressed on it, and when
being drawn in, the mesh structure folds back into the micro-catheter
adapting to the space available inside.
As a result of the stiffness of its mesh structure, the implant
can be moved to and fro virtually without restriction via the guide
wire 21 until it has been optimally positioned within the vessel
system.
As mentioned earlier, customary micro-catheters can be used. One
advantage of the implant according to the invention and of the combination
of implant and guide wire according to the invention is, however,
that after having placed the micro-catheter in position with a customary
guide wire/marker system, the combination of guide wire 21 and implant
1 according to the invention can be introduced into the micro-catheter,
moved through it towards the implantation site and then moved out
and applied in that position. Alternatively, it will be possible
to have a second micro-catheter of smaller caliber accommodate guide
wire 21 and implant 1 and with this second micro-catheter within
the firstly positioned micro-catheter shift them to the implantation
site. In any case, the implant can be easily guided in both directions.
FIG. 6 shows a schematic representation of an implant according
to the invention in its superimposed or volume-expanded shape and
in its volume-reduced shape. In its expanded shape, as illustrated
in FIG. 6a, the implant 1 forms a ring-shaped structure with slightly
overlapping edges 7 and 8. In FIG. 6a the implant 1 is viewed from
its proximal end as a top view with the connection point 5 being
approximately positioned opposite to the edges 7 and 8. In the combination
according to the invention, the guide wire 21 is affixed at the
connection point 5.
FIG. 6b shows the same implant in its volume-reduced form as it
is arranged, for example, in a micro-catheter in a curled up condition.
In the case illustrated there is a total of two windings of the
curled-up implant 1 with the connection point 5 being located at
the proximal side and the two lateral edges 7 and 8 being the starting
and final points of the roll or spiral. The structure is held in
its volume-reduced form by the micro-catheter 22 and when the implant
1 is pushed out of the micro-catheter 22 it springs into its expanded
shape, as illustrated by FIG. 6a, similar to a spiral spring.
FIG. 7a shows a marker element 12 suitable for the implant according
to the invention with the marker element 12 being capable of being
arranged at the distal end of the implant 1. The marker element
12 consists of a lug 13 provided with a small marker plate 15 levelly
arranged inside it, i.e., flush with the plane of the implant without
any projecting elements. The plate 15 is made of an X-ray reflecting
material, for example, platinum or platinum-iridium. The marker
plate 15 may be connected to the surrounding implant structure by
known laser welding techniques. As shown in FIG. 7b, the marker
elements 12 are arranged at the distal end of the implant 1.
FIGS. 8a and 8b are representations, respectively, of two variations
of a separating arrangement by which the implant 1 according to
the invention is detachably connected to a guide wire 21. In each
case, a separating arrangement consists of a dumb-bell shaped element
23 that dissolves under the influence of electrical energy when
in contact with an electrolyte. At the proximal (guide-wire side)
end of the dumb-bell shaped separating element 23, as per FIG. 8a,
a spiral structure 25 is located that interacts with a strengthening
spiral 26 of the guide wire 21. At the distal end, a ball-shaped
element 27 is arranged that, with the help of a laser welding technique,
is connected to a platinum spiral 28 which, in turn, is linked with
the connection point 5 situated at the proximal end of the implant
1. The platinum spiral 28 also serves as an X-ray reflecting proximal
marker of the implant 1.
To strengthen the joint between the ball-shaped element 27 and
the connection point 5, a reinforcement wire 29 may be provided.
Alternatively, the platinum spiral 28 may also be designed in such
a manner that it withstands the tensile and thrust forces imposed
on it.
The separating element 23 can include a steel material that is
susceptible to corrosion in an electrolyte under the influence of
electrical energy. To accelerate corrosion and shorten the separating
time span, a structural or chemical weakening of the dumb-bell shaped
element 23 may be beneficial, for example, by applying grinding
methods or thermal treatment.
Generally, the portion of the dumb-bell 23 accessible to the electrolyte
has a length of 0.1 to 0.5 mm, particularly 0.3 mm.
The spiral structure 25 is secured via welding both to the dumb-bell
shaped element 23 and the reinforcement spiral 26 of the guide wire
21. The guide wire 21 itself is slidably accommodated within the
micro-catheter 22.
FIG. 8b shows a second embodiment that differs from the one described
with respect to FIG. 8a, in that the dumb-bell shaped element 23
has a ball-shaped element 27 at each end. The ball shaped elements
27 are connected distally to the connection point 5 of the implant
1 and proximally to the guide wire 21 via spirals 28, 26, respectively.
It is of course also provided that other separating principles
may be applied, for example, those that are based on mechanical
principles or melting off plastic connecting elements.
Although various exemplary embodiments of the present invention
have been disclosed, it will be apparent to those skilled in the
art that changes and modifications can be made which will achieve
some of the advantages of the invention without departing from the
spirit and scope of the invention. It will be apparent to those
reasonably skilled in the art that other components performing the
same functions may be suitably substituted. |