US20140190587A1

US20140190587A1 - Device and Method for Crimping an Implant

Info

Publication number: US20140190587A1
Application number: US14/146,678
Authority: US
Inventors: Amir Fargahi
Original assignee: Biotronik AG
Current assignee: Biotronik AG
Priority date: 2013-01-09
Filing date: 2014-01-02
Publication date: 2014-07-10
Also published as: EP2754425A1

Abstract

A device (10, 10′) and method for crimping an implant (20), which can assume either a compressed state or an expanded state, at least over a portion of the length thereof. An crimping device is attained according to the invention in that a hollow-cylindrical and/or hollow-conical, preferably braided wire netting is provided, in the inner volume (14, 14′) of which the implant (20) in the expanded state can be placed, at least via a section thereof, wherein, upon application of a tensile force on at least one end in the longitudinal direction, and/or upon application of a compressive force in the radial direction, the wire netting simultaneous undergoes extension and a reduction of the inner diameter (d, d′) such that the implant (20) can be transformed, at least along a section thereof, from the expanded state into the compressed state.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. provisional patent application Ser. No. 61/750,361, filed Jan. 9, 2013.

TECHNICAL FIELD

The present invention relates to a device for crimping an implant, in particular an intraluminal endoprosthesis, and an associated method.

BACKGROUND

A wide variety of medical implants, in particular intraluminal endoprostheses, for highly diverse applications are known from the prior art. Implants according to the present invention are endovascular prostheses or other endoprostheses, such as stents (vascular stents (including stents for use in the region of the heart, and heart valve stents, e.g. mitral valve stent, pulmonary valve stent) and bile duct stents), endoprostheses for closing a patent foramen ovale (PFO), stent grafts for treating aneurysms, endoprostheses for closing an ASD (atrial septal defect), and prostheses in the region of hard and soft tissue. Such an implant is often introduced into the organ or vessel to be treated by way of a catheter.
In many cases, stents and other implants have a filigree, hollow-cylindrical (tubular) and/or hollow-conical main structure that is open at both longitudinal ends, wherein the main structure is often composed of a plurality of struts. Valve cusps, for example three valve cusps, can be disposed on the inner side of such a main structure, for example in the case of a heart valve stent, wherein the valve cusps can form the heart valve and comprise a plastic or a biological material, for example porcine pericardium. In this case, the stent carries the heart valve and anchors this in the heart.
Stents and other implants typically assume two states, namely a compressed state having a small diameter and an expanded state having a larger diameter. Using a catheter, the implant in the compressed state can be introduced through narrow vessels into the vessel or organ to be treated and can be positioned at the point to be treated. To this end, the implant is crimped and thereby transformed at least over a portion of the length thereof from the expanded state having a larger diameter into the compressed state having a smaller diameter. The implant is then dilated at the treatment site, for example using the balloon of the catheter, and returns to the expanded state, in which the implant remains in the vessel or organ, being fixed there, after the catheter has been removed from the body of the treated patient. Alternatively, in the case in which the main structure of the implant is made of a self-expanding metal (e.g. Nitinol), the implant assumes the compressed state via compression below the transition temperature and assumes the expanded state above the transition temperature.
Document U.S. Pat. No. 8,029,564 B2 discloses a heart valve prosthesis and a deflection device. The system also includes a line, which is guided through the free ends of the stent posts, which carry the heart valve. By way of this line, the stent posts can be deflected inwardly in order to attain a closed state. However, this system is not suitable for being transferred non-invasively using a catheter to the point to be treated since this system is too voluminous in the base region.
US 2011/0056064 A1 discloses a crimping tool that is very cost-intensive to manufacture since it has a complex design having a large number of precisely manufactured parts that must move in a synchronous manner. The crimping tool has a plurality of bars in particular, which are disposed next to one another around a circumference and can rotate about an axis extending transversely to the particular bar. The implant to be crimped can be placed into the opening formed between the ends of the bars. A lever is moved in order to displace guide pins—each guide pin being disposed at a front end of a bar—in a slot such that the radius of the opening formed between the bars is decreased or increased. In order to crimp a heart valve stent, the pins are displaced such that the radius of the opening is reduced. In this tool, the stent is completely covered by the tool during the crimping procedure since the bars and the pins are located between two plates, and the tool therefore has a large expansion in the longitudinal direction of the stent and has a relatively great weight. For this reason, the implant cannot be visually monitored during crimping. Furthermore, it cannot be ruled out that the bars will overlap when the opening radius is reduced, and therefore the risk of damage to the implant and the tissue parts disposed on the implant is high. Furthermore, due to the large mass of the tool, a great deal of effort is required to bring the tool below the transition temperature, which is necessary when the implant is made of a self-expanding material.
EP 2 229 921 A1 discloses a device for crimping that has a plurality of wires stretched between two interspaced rings along a cylinder jacket line. If one of these rings is rotated relative to the second ring about an axis parallel to these jacket lines, the wires are twisted to the common axis and thereby form an hourglass-type geometric surface similar to a hyperboloid of rotation. The opening defined by the section having the smallest diameter, which is formed between these wires, is made smaller or larger as the rings are twisted further. An implant can be disposed in this opening and can be crimped by reducing the size of the opening. This known device also has a relatively complex design and is therefore difficult to assemble. The implant is covered by the wires of the device during crimping, thereby preventing visual monitoring of this known device as well during the crimping process. A further disadvantage is that the tension in the wires is greater at the two ends, at which the wires are attached to the opposing rings, than in the central region thereof. This results in non-uniform distribution of the compressive force on the implant. Due to the large number of wires and the required large rings at the ends thereof, the known device is relatively large and heavy.

SUMMARY

The problem to be addressed is therefore that of creating a device for crimping such an implant that has a less complicated design and is smaller and easier to handle. A method for crimping that is reliable and easy to carry out shall also be provided.
The aforementioned problem is solved by a device as provided herein.
In particular, a device according to the invention has a hollow-cylindrical and/or hollow-conical, braided wire netting, into the inner volume of which the implant, in the expanded state, can be placed at least via a section thereof or in entirety, wherein, upon application of a tensile force on at least one end in the direction of the longitudinal axis, and/or upon application of a compressive force in the radial direction, the wire netting simultaneously undergoes extension and a reduction of the inner diameter such that the implant placed in the inner volume of the wire netting can be transformed from the expanded state into the compressed state, at least along a section (i.e. along a portion of the length thereof) or along the entire length thereof due to the reduction of the inner diameter of the wire netting. The wire netting is also referred to in the following as a braid. The device according to the invention makes it possible, for example, to reduce the inner diameter at most to 1/4 of the inner diameter in the expanded state, preferably at most to 1/5 of the inner diameter in the expanded state.
The aforementioned device has a relatively compact design. In the starting state, in which the implant in the expanded state can be placed into the inner volume, the inner diameter of the wire netting is only slightly larger than the outer diameter of the implant. The length of the wire netting in the longitudinal direction is also preferably slightly greater than the length of the implant or the length of the section of the implant to be crimped.
The design of the device according to the invention in the form of a wire netting (braid) results in a simple and lightweight design of the device according to the invention. For example, the wire netting comprises a polymer or a metal alloy, wherein the metal alloy preferably contains at least one of the elements of the group iron (Fe), cobalt (Co), chromium (Cr), nickel (Ni). Particularly preferably, the wire netting comprises stainless steel or a cobalt-based superalloy. The braid can be deformed elastically, homogeneously and uniformly, thereby enabling the braid to expand and bend in all directions. Particularly preferably, the braid has self-expanding properties, in particular the braid can comprise a Phynox (Elgiloy) alloy. Phynox (Elgiloy) is an austenitic, hardenable, superalloy based on cobalt (40% by weight Co, 20% by weight Cr, 16% by weight Ni and 7% by weight Mo). The mechanical strength thereof can exceed 2,600 N/mm2. The maximum tensile strength is highly dependent on the cold working carried out in advance. The alloy is non-magnetic, highly corrosion-resistant (more corrosion-resistant than any other stainless steel) and temperature-resistant. Furthermore, the alloy has a high modulus of elasticity (220 kN/mm2) combined with a yield strength of 1,800 N/mm2, and so the alloy is extremely well-suited for the braid according to the invention. The alloy is available from the company Lamineries MATTHEY SA (La Neuveville, Switzerland).
As mentioned above, pulling the braid longitudinally results in a reduction of the inner diameter. In the opposite case, expanding the wire netting such that the inner and outer diameter are increased shortens the wire netting. The metal alloys that can be used for the o braid are preferably not alloys having a memory effect, thereby ensuring that phase conversion does not occur in the temperature range of 0° C. to 40° C. in particular. It is therefore possible for continuous elongation of the wire netting with diameter reduction, or shortening with an increase in diameter to take place in a reversible manner in this temperature range without phase-conversion influences.
In a further exemplary embodiment, the wire netting comprises a first hollow-cylindrical section and a second hollow-conical section. In this exemplary embodiment, the implant is inserted in the hollow-cylindrical section and is advantageously crimped or compressed in the hollow-conical section. This shape is favorable for crimping.
In order to reduce diameter in a particularly simple manner, a ring is provided on at least one first end in the longitudinal direction (direction of the longitudinal axis) of the wire netting, the ring being displaceable relative to the second end of the wire netting in the direction of the longitudinal axis, preferably along a rail. The second end of the wire netting is held stationary. The displacement of the ring results in application of a tensile force onto the wire netting. To this end, the ring is fastened to the particular end of the wire netting. In a preferred exemplary embodiment, the braid comprises a ring on both ends in the longitudinal direction. The rail preferably extends parallel to the longitudinal axis of the hollow-cylindrical or hollow-conical wire netting.
Since the device is compact and lightweight, as described above, the device can be easily placed into a coolant, thereby enabling the implant and the wire netting to be cooled to a temperature below the transition temperature. Cold water at 0° C., for example, can be used as such a coolant.
The aforementioned problem is further solved by a simple method for crimping an implant
According thereto, the following steps in particular are carried out. In a first step, the implant, which is initially present in the expanded state, is placed at least via a section thereof or in entirety into the inner volume of a hollow-cylindrical or hollow-conical, preferably braided wire netting. Next, a tensile force is applied on at least one end of the wire netting in the direction of the longitudinal axis thereof, and/or a compressive force is applied to the wire netting in the radial direction, thereby reducing the inner diameter of the wire netting such that the inserted implant is transformed from the expanded state into the compressed state at least along a section. This method is very simple and can be carried out cost-effectively. It can be implemented manually or in an automated process.
In a further exemplary embodiment, the implant and, preferably, the device are cooled in a coolant to below the transition temperature before the implant is transformed into the compressed state.
In a simple manner, a tensile force can be applied to the wire netting in the longitudinal direction of the wire netting in that a ring mounted at a first end of the wire netting in the longitudinal direction is preferably displaced on a rail relative to the stationary, opposing second end of the wire netting, wherein the rail preferably extends parallel to the longitudinal direction. In the present description of the invention, the direction that extends parallel to the longitudinal axis of the wire netting or the implant is referred to as the longitudinal direction of the wire netting or the implant.
In a further exemplary embodiment, after the transition to the compressed state, the associated section of the implant can be inserted into a tubular outer shaft of a catheter in order to optionally also fix the compressed state above the transition temperature or to introduce the implant into the body to be treated.
In a development of the invention, a second section of the implant, which was initially not inserted into the outer shaft, is then also transformed into the compressed state, preferably by way of the above-described device according to the invention or the above-described method according to the invention, and is then also inserted into the outer shaft.
Further objectives, features, advantages, and possible applications of the invention will become apparent from the following description of exemplary embodiments of the invention, with reference to the figures. All the features that are described and/or graphically depicted are the subject of the present invention, either alone or in any combination, independently of their wording in the claims or their dependency reference.

DESCRIPTION OF THE DRAWINGS

The drawings show, schematically:

FIG. 1A a first exemplary embodiment of a device according to the invention in a view from the side in the starting state,

FIG. 1B an intersection point of a device according to the invention in a view from the side in the expanded state,

FIG. 1C a mesh of a device according to the invention in a view from the side,

FIG. 1D the mesh shown in FIG. 1C in a view from the side in the expanded state and in the compressed state,

FIG. 2 the implant to be crimped in a view from the side,

FIG. 3 a container containing coolant, in which the implant to be crimped is cooled, in a perspective view from the side,

FIG. 4 a section of the device according to the invention as shown in FIG. 1, in a view from the side, comprising an implant in the expanded state disposed therein,

FIG. 5 the section according to FIG. 4 in a first intermediate step of the crimping process in a view from the side,

FIG. 6 the section according to FIG. 4 in a second intermediate step of the crimping process in a view from the side,

FIG. 7 the implant after crimping, in the compressed state in a view from the side, wherein the wire netting was reshaped back into the starting state,

FIG. 8 the insertion of the crimped implant into an outer shaft of a catheter in a view from the side,

FIGS. 9 and 10 the implant, which has been partially inserted into the outer shaft of a catheter, disposed in the device according to the invention as shown in FIG. 1, wherein in FIG. 10 the implant after crimping is disposed entirely, i.e. along the entire length thereof, in the outer shaft, in a view from the side,

FIG. 11 the implant, which is disposed in entirety in the outer shaft of a catheter, after conclusion of the crimping process, in a view from the side,

FIG. 12 a second exemplary embodiment of a device according to the invention in a perspective view from the side in the starting state and

FIG. 13 the exemplary embodiment according to FIG. 12 in a perspective view from the side in the final state after conclusion of the crimping process.

DETAILED DESCRIPTION

The figures show two exemplary embodiments of a device according to the invention in a schematic and simplified manner and, in particular, show the details that are important in order to understand the invention. Some of the details that are insignificant for the invention were omitted. Furthermore, the expression “distal end” in the context of the present invention refers to the end of the implant that points away from the treating physician while the implant is being introduced into the body, and the “proximal end” points toward the person who is operating a catheter, for example.
The exemplary embodiment of a device 10 for crimping an implant 20 (e.g. a heart valve stent), which is shown in FIGS. 1 to 7 and 9 to 10, comprises a hollow-cylindrical, braided wire netting in a first section 11 and a hollow-conical braided wire netting in a second section 12.
The wire netting can be formed, for example, of wires 15 having a circular cross section made of a Phynox (Elgiloy) alloy (Co—Cr—Ni alloy, see above), which have a wire diameter of 0.2 mm. The angle between the wires at the intersection points is α=175°, for example, in the expanded state. The mesh length L of the mesh 15 a spanned by the wires 15 is 5 mm, and the mesh width b is 0.9 mm in the expanded state. There are fifteen intersection points 19 disposed around the entire circumference of the wire netting. One intersection point 19 of such a wire netting is shown in FIG. 1B. A mesh 15 a spanned by wires 15 is shown in the expanded state in FIGS. 1C and 1D. The wire netting is stretched in order to transform the mesh into the state 15 a′ shown in FIG. 1D. The forces acting on the mesh 15 a during compression are illustrated by the outer arrows in FIG. 1D. The exemplary embodiment of a device according to the invention, which is shown in FIGS. 1A to 1D, comprises round wire, as described above, although this can also comprise flat wire or a combination of the two wire types.
In the starting state before crimping, which is shown in FIG. 1A, the implant 20 can be inserted in the expanded state into the inner volume 14 of the wire netting, as shown in FIG. 4. The inner volume 14 is formed by the hollow space enclosed by the hollow cone or hollow cylinder. The direction indicated by the arrow 25 in FIG. 4 extends parallel to the longitudinal axis 13 of the wire netting in the sections 11 and 12. The implant 20 is preferably inserted from the side on which the wire grating forms the hollow cylinder 11.
In a preferred exemplary embodiment, the implant 20 was cooled in a coolant 40 to a temperature below the transition temperature, for example to 0° C., before being placed into the crimping device 10, as shown in FIG. 3. An ice block 41 floats in the water bath in order to hold the coolant 40, which is preferably water, at the temperature of 0° C. In a further exemplary embodiment, the entire crimping process can be carried out in the coolant 40.
After the implant 20 has been placed into the wire netting of the crimping device 10, the next step—after the implant was slid into the hollow-conical section 12 of the crimping device 10—is to stretch the crimping device in the longitudinal direction (see the arrow 25) or to apply pressure from the outside in the radial direction, which extends transversely to the longitudinal direction, as indicated by the arrow 26 in FIG. 5, thereby reducing the inner diameter d of the inner volume 14 and crimping the implant 20. For example, the inner diameter d is reduced by the external pressure to 1/5 of the value in the expanded state.
In Table 1 that follows, the aforementioned example is explained once more, using numbers.

TABLE 1

Material of the crimping device 10	e.g. Phynox (Elgiloy)
	(Co Cr Ni alloy)
Diameter d of the wire of the wire	0.2 mm
netting
Angle α between the wires in the inter-	175°
section point in the expanded state
Mesh length L (see FIG. 1C)	5 mm
Mesh width b (see FIG. 1C)	0.9 mm
Number of intersection points around	15
the circumference of the wire netting
Circumference of the wire netting in	15 × 0.9 mm = 13.5 mm
the compressed state
Circumference of the wire netting in	15 × 5 mm = 75 mm
the expanded state
Compression ratio: circumference	455%
(circumference in the expanded state	(75 mm => 13.5 mm)
to the circumference in the compressed
state)
Change in the inner diameter upon tran-	21.2 mm
sition from the expanded state to the	(23 mm − 0.8 mm) =>
compressed state	3.4 mm
	(4.2 mm − 0.8 mm)

FIG. 6 shows the implant 20 in the compressed state, wherein the crimping device 10 is shown in this illustration in the state thereof having the smallest inner diameter dmin. The crimping tool 10 can now be shortened once more in the longitudinal direction or stretched in the radial direction (arrow 26), whereupon the inner diameter d increases. This is illustrated in FIG. 7. In this state, the implant 20 can be removed from the crimping tool 10.
Next, the implant 20 is inserted by way of the crimped section thereof, into an outer shaft 30, which is formed by a polymer tube, for example (cf. FIG. 8).
In a next step, which is shown in FIG. 9, the implant 20 is now inserted together with the outer shaft 30 thereof into the crimping device 10 once more in order to crimp the section of the implant 20 that still protrudes from the outer shaft 30. In this step as well, in analogy to the crimping step explained by reference to FIGS. 5 and 6, the inner diameter of the crimping device 10 is reduced via the application of a tensile force along the longitudinal direction of the crimping device, and/or a compressive force in the radial direction. Next, as shown in FIG. 10, the outer shaft 20 is slid entirely over the implant until the outer shaft reaches the catheter tip 33 (cf. FIG. 11).
FIGS. 12 and 13 show how the inner diameter can be easily reduced, via reference to a further exemplary embodiment of a crimping device.
As shown in the first exemplary embodiment, which is depicted in FIG. 1, the second exemplary embodiment of a device 10′ according to the invention also comprises a wire netting, which is hollow-cylindrical in this case. A ring 16, 17 is provided at both ends of the wire netting in the longitudinal direction, wherein the ring (proximal ring) 16 disposed on the left side in the illustration is stationary, while the (distal) ring 17 disposed on the right side in the illustration is disposed such that it is displaceble on a rail 18. If the distal ring 17 is now displaced parallel to the longitudinal direction of the wire netting along the rail 18 (arrow 25), the inner diameter d′ of the inner volume 14′ is reduced, in particular in the center section of the wire netting, until a minimal inner diameter dmin′ is reached there when the distal ring 17 has the greatest distance from the proximal ring 16 in the direction of the rail 18. An implant (which is not shown in FIGS. 12 and 13) disposed in this region of the wire netting is reliably crimped by way of this diameter reduction.
It will be apparent to those skilled in the art that numerous modifications and variations of the described examples and embodiments are possible in light of the above teaching. The disclosed examples and embodiments are presented for purposes of illustration only. Other alternate embodiments may include some or all of the features disclosed herein. Therefore, it is the intent to cover all such modifications and alternate embodiments as may come within the true scope of this invention.

LIST OF REFERENCE SIGNS

10, 10′ crimping device
11 hollow-cylindrical section
12 hollow-conical section
13 longitudinal axis of the crimping device 10
14, 14′ inner volume
15 wire
15 a mesh spanned by wires 15 in the starting state
15 a ′ mesh 15 a after reduction of the inner diameter
16 proximal ring
17 distal ring
18 rail
19 intersection point
20 implant
25, 26 arrow
30 outer shaft
33 catheter tip
40 coolant
41 ice block
b mesh width
d wire diameter
d, d′ inner diameter
dmin, dmin′ smallest inner diameter of the wire netting of the implant 10, 10′
L mesh length
α angle at the intersection point of the wires 15

Claims

What is claimed is:

1. A device for crimping an implant, in particular an intraluminal endoprosthesis, which can assume either a compressed state or an expanded state at least over a portion of the length thereof, characterized by a hollow-cylindrical and/or hollow-conical, optionally braided wire netting, in an inner volume of which the implant in the expanded state can be placed, at least via a section thereof, wherein, upon application of a tensile force on at least one end in the longitudinal direction, and/or upon application of a compressive force in the radial direction, the wire netting simultaneously undergoes extension and a reduction of the inner diameter such that the implant can be transformed, at least along a section thereof, from the expanded state into the compressed state.

2. The device according to claim 1, characterized in that the wire netting comprises a polymer or a metal alloy, optionally a stainless steel or cobalt-based alloy, the metal alloy optionally containing at least one element selected from the group consisting of Fe, Co, Cr and Ni.

3. The device according to claim 1, characterized in that the wire netting comprises a ring on at least one end in the direction of the longitudinal axis, the ring being displaceable relative to the other end of the wire netting in the longitudinal direction, optionally along a rail.

4. The device according to claim 1, characterized in that the device can be placed into a coolant.

5. A method for crimping an implant, in particular an intraluminal endoprosthesis, which can assume either a compressed state or an expanded state at least over a portion of the length thereof, optionally via the use of a device for crimping according to claim 1, the method having the following steps:

inserting at least a section of the implant, which is initially in the expanded state, into the inner volume of a hollow-cylindrical and/or hollow-conical, optionally braided wire netting; and

reducing the inner diameter via application of a tensile force on at least one end of the wire netting in the longitudinal direction, and/or a compressive force onto the wire netting in the radial direction such that the inserted implant is transformed from the expanded state into the compressed state, at least along a section.

6. The method according to claim 5, characterized in that the implant and, optionally the device for crimping, are cooled in a coolant to below a transition temperature before the implant is transformed into the compressed state.

7. The method according to claim 5, characterized in that, in order to apply a tensile force, a ring mounted at a first end of the wire netting in the longitudinal direction is displaced optionally on a rail relative to the stationary, opposing second end of the wire netting.

8. The method according to claim 5, characterized in that, after the transformation into the compressed state, the compressed section of the implant is inserted into a tubular outer shaft of a catheter.

9. The method according to claim 8, characterized in that the implant is also transformed into the compressed state in a second section, which was initially not inserted into the outer shaft, and is then inserted into the outer shaft.