DE20306823U1 - Stent compression unit for vein implants has motor driven roller rows with decreasing spherical grooves defining compression cavity - Google Patents

Abstract

A stent compression unit has two rows of radial compression rollers (12) with spherical compression faces (16) of decreasing diameter and separation driven by a motor (36) through worm (26) and gears (30) creating a cavity (2) through which the stent is fed into a catheter. Includes an INDEPENDENT CLAIM for compression surfaces of constant cross section.

Description

· J

95 314 r4/t3/cvi

Angioraed GmbH & Co.

Medical Technology KG

Wachhausstrasse 6

76227 Karlsruhe Germany

Device for radially compressing an elastic

Workpiece

Technical area

The invention relates to a device for radially compressing an elastic workpiece, and in particular to a device for introducing a stent into an outer catheter of a stent introducer.

Stents serve as support implants to support and/or bridge narrowed or diseased vessels in the human and animal body. Stents are known from the state of the art and are used in the area of the coronary arteries, the urethra, the ureter and the esophagus, to name just a few examples. Stents are used primarily when the flow through the respective vessel is significantly restricted or blocked due to deposits on the vessel wall, or when there is a risk of the vessel wall breaking through due to other vascular diseases. In such cases, a radially expandable stent is inserted into the vessel lumen and placed in the diseased or narrowed area of the vessel. The stent is then radially expanded, or expands on its own, and the radial expansion of the stent exerts a sufficiently large force on the vessel wall in order to enlarge the cross-section of the vessel lumen at the narrowed area, or to support the vessel wall.

Stents can essentially be divided into two categories: self-expandable stents and balloon-expandable stents.

The stents belonging to the first category are either stents made of stainless steel, the deformation of which due to radial expansion takes place within the Hooke limits of the material, or, as described below, stents made of a shape memory alloy. Such stents are released by proximally withdrawing an outer catheter in the vessel to be treated. When the outer catheter is withdrawn proximally, it must be ensured that the stent does not move with the outer catheter in the proximal direction. This is achieved by a counter bearing, such as a stop element, which rests on the proximal end of the stent.

In contrast, stents belonging to the second category are expanded radially within the diseased vessel using an inflatable balloon. The radial expansion of the stent using a balloon located in the lumen of the stent causes a plastic deformation of the stent material.

An example of a self-expandable stent made of stainless steel is known from US-A-4,580568 to Gianturco, and an example of an expandable stent which is radially expanded by means of a balloon is known from EP-A-221 570 to Palmaz.

In addition, as mentioned above, there are self-expanding stents made of a shape memory alloy, such as a biocompatible nickel-titanium shape memory alloy. Such stents are also inserted into the stent by an external catheter.

a radially compressed configuration and released by proximal retraction of the outer catheter into the area to be treated within the vessel.

Due to the property of the shape memory alloy, the stent can assume different equilibrium states at two different temperatures, for example the radially compressed configuration at the low temperature and the radially expanded configuration at the higher temperature. Most of the known shape memory alloys require a temperature below 0 ⁰ C at which the stent is in equilibrium in its radially compressed configuration. After the stent has been inserted into the outer catheter at the low temperature, the outer catheter can be inserted endoscopically into a vessel to be treated. By retracting the outer catheter proximally, the stent is deposited in the vessel lumen, and due to the higher temperature in the vessel, the stent now expands radially and assumes its second radially expanded equilibrium configuration.

Depending on the size of the body vessel to be treated and the extent of the vascular constriction, stents of different sizes are used. To place these stents in the vessel, external catheters of different sizes are used, into which the stent must first be inserted. In addition, the stent must be inserted into the external catheter under sterile conditions, or the entire package consisting of catheter and stent is sterilized after the stent has been inserted into the catheter. If stents coated with ePTFE are used, this type of sterilization can certainly lead to problems.

The wide variety of different stents requires a versatile device for inserting the stent into a corresponding external catheter. The high resistance

The resistance of large diameter stents to radial compression during insertion of the stent into the outer catheter requires a stable stent loading device whose compression mechanism can withstand such resistance of the stent until its complete insertion into the catheter.

The present invention provides an alternative to conventional stent loading devices by which both self-expandable and balloon-expandable stents can be introduced into an external catheter. Although the invention is described in the context of stents, it is not limited to such, but may also be useful for radially compressing elastic workpieces.

A number of differently designed stent loading devices are known from the prior art.

An example of such a stent loading device is described in WO 01/21103. This loading device comprises at least three movable plates which are operatively connected to one another and which are arranged along the circumference of a reference circle, thus forming a clearing into which the stent can be inserted. The cross-sectional size of the clearing can be varied by appropriately displacing the plates. When the plates are displaced, one plate moves on the surface of its adjacent plate, with the overall movement of all plates resembling the closing of a shutter. One end of the plates has a pin-shaped extension which is accommodated in a linear sliding bearing. The entirety of the linear sliding bearings is coupled to a drive plate, the rotation of which causes a linear displacement of the extension pins in the sliding bearings, thus causing a displacement of the plates.

·

·

• t

· ♦·

A coolant can also be passed through the opening of this stent loading device. This means that stents made from a shape memory alloy can also be brought into a radially compressed configuration using this loading device.

Another example of a stent loading device is commercially available from Machine Solutions, Inc. In this device, a plurality of triangular compression elements are arranged in a circle so that a clearance is created between the compression elements, the cross-sectional size of which can be varied by moving the compression elements.

Another stent loading device is known from WO 01/35861. In this device, the stent is pulled through a funnel-shaped compression element and thereby compressed radially.

Summary of the invention

It is an object of the invention to provide a loading device with which an elastic workpiece can be compressed in the radial direction and which has such a compact and stable design that the backlash between force-transmitting components of the device is minimized.

It is also an object of the invention to provide a device which is so versatile that elastic workpieces with different lengths and diameters can be compressed in the radial direction.

These objects are achieved by a device having the features of claim 1.

• t · ·

■■■·■■·■...· &ogr;.:■■

Preferred embodiments of the invention are described in the subclaims.

The device according to the invention is used for radial compression of elastic workpieces. In particular, it is suitable for bringing stents into a radially compressed configuration so that they can then be introduced into an external catheter. It is obvious to the person skilled in the art that not only stents can be compressed in the radial direction with the device according to the invention, but also grafts, stent grafts and vena cava filters. Furthermore, the loading device is suitable for crimping a sleeve, such as an X-ray-opaque marking sleeve, onto the outer surface of a catheter.

The device according to the invention comprises a plurality of compression elements which can be moved relative to one another and which each have a compression surface, the compression surfaces of the compression elements being arranged in such a way that they form a clearing or a lumen with a longitudinal axis, a first end and a second end for receiving the stent. The distance between adjacent compression surfaces substantially perpendicular to the longitudinal direction of the clearing is greater at the first end of the clearing than at the opposite second end of the clearing.

With the aid of the device according to the invention, an elastic workpiece introduced into the first end of the clearing can be moved through the device or along the longitudinal axis of the clearing, the radial dimension of the workpiece being increasingly reduced as the movement through the device progresses. The compression elements advantageously cause both the compression of the workpiece in the radial direction and the movement of the workpiece along the longitudinal axis of the device.

•#

·

Preferably, the distance between adjacent compression surfaces decreases at regular intervals, essentially perpendicular to the longitudinal direction of the clearing, from the first end to the second end of the clearing. This achieves a uniform radial compression of the workpiece. If the length of the workpiece extends over several compression surfaces along the clearing, this minimizes stresses in the workpiece in the direction of its longitudinal extension. This also prevents the radially elastic workpiece from "piling up" between two compression elements that are adjacent in the longitudinal direction of the clearing.

In a further preferred embodiment, the compression surfaces are designed as concave recesses on the surfaces of the compression elements. The concave recesses are preferably spherical, the radius of which decreases at regular intervals from the first end to the second end of the clearing. The radius of the spherically concave compression surfaces perpendicular to the longitudinal direction of the clearing of adjacent compression elements is preferably essentially the same. According to the invention, this achieves an optimal adaptation of the compression surfaces to the outer surface of a circular cylindrical workpiece, whereby radial compression of the workpiece takes place uniformly from all radial directions.

In a further preferred embodiment, the compression elements are rotatably mounted and are advantageously set in rotation via a drive means, preferably synchronously with one another, so that when the workpiece, in particular a stent, is inserted, a movement of the stent along the longitudinal axis of the clearing is achieved by rotating the compression elements, and at the same time as the stent moves forward along the longitudinal axis of the clearing, a compression of the stent in the radial direction takes place. Because the compression elements for radially compressing the stent

At the same time, the stent is moved along the longitudinal direction of the lumen, so compressive and tensile stresses in the stent are reduced to a minimum.

Short description of the drawings

An embodiment of the invention will now be described by way of example with reference to the following drawings, in which:

Fig. 1 is a perspective view of the inventive

device is;
Fig. 2 is a side view of the inventive

device is;
Fig. 3 is a cross-sectional view along the line AA of the

Fig. 2 is; and
Fig. 4 is a cross-sectional view taken along line BB of Fig. 2.

Description of a preferred embodiment

Fig. 1 shows a perspective view of the stent loading device 1 according to the invention. The stent loading device shown in Fig. 1 has a base plate 10 on which a plurality of rollers 12 are rotatably mounted. The end 14 of the rollers 12 facing the base plate has a smaller diameter than the area 13 of the circular cylindrical rollers 12. The rotatable mounting of the rollers is achieved by inserting the end 14 into a correspondingly designed recess in the base plate (see Fig. 4). It is obvious to the person skilled in the art that other rotary connections between the base plate and the rollers are conceivable, such as a rotary pin coupling, ball or roller bearing arrangements, etc.

·

The upper end of the rollers shown in Fig. 1, which also has a smaller diameter than the area 13 of the rollers, is passed through a bore 21 provided in an upper plate 20 (see Fig. 4) and is rigidly connected to a gear 30. For a more detailed illustration of the connection to the gear 30, reference is made to Fig. 4.

The circular-cylindrical rollers are arranged in two linear rows along the longitudinal axis 2 of the device 1. Each of the rollers has a spherically concave recess 16 in the middle along the entire circumference of the circular-cylindrical cross-section of the roller. The spherically concave recess 16 is rotationally symmetrical with respect to the cylinder axis of the rollers. If only one row of rollers is considered, the radius of the spherically concave recess 16 decreases at regular intervals along the longitudinal axis 2 of the device 1. As can be seen in Fig. 1, the radius of the spherically concave recess 16 of two adjacent rollers 12 perpendicular to the longitudinal direction 2 of the device 1 is identical. As will be seen later from Fig. 3, the first row of rollers corresponds to the second row of rollers with regard to the geometric design and arrangement of its rollers, so that the radius of the spherically concave recesses 16 of the second row of rollers decreases at the same interval along the longitudinal direction of the device as the spherically concave recesses 16 of the first row of rollers.

Furthermore, it can be seen in Fig. 1 that, identical to the number of rollers and their arrangement, a gear 30 is provided for each roller above the upper plate 20. The upper end of the rollers shown in Fig. 1 is rigidly connected to one of the gears 30. The gears 30 of a row are in engagement with a worm 26, whereby each gear 3 0 of a row meshes with the associated worm 2 6. The gears 3 0 of a row are

&Lgr;..

the worm 26 associated with the gear row is driven. In Fig. 1, two worms 26 can be seen which are in engagement with the gears associated with them. The ends of the worms are rotatably held in corresponding flange sections 22 and 23 provided on the upper plate 20. One end of each worm has a further gear 28 which is in engagement with a further gear 32 which is arranged centrally between the two gears 28. This centrally arranged gear is rigidly connected to a drive shaft 34 which in turn is connected in a conventional manner to a drive means 36, such as an electric motor. The drive means is attached to the upper plate 20 by means of a flange 24.

Alternative arrangements to the row-wise arrangement of gears 30 shown in Fig. 1, which are each in engagement with corresponding worms 26 and further gears 28, are known to the person skilled in the art. A further detailed description of such arrangements is therefore omitted.

Fig. 2 shows a side view of the stent loading device 1 shown in Fig. 1. From Fig. 2 it can be clearly seen how the compression surfaces 16 of compression elements or rollers adjacent in the longitudinal direction of the device 1 describe a circle 18A to 18Q in a plane through the cylinder axes of the rollers. The radius of these circles decreases from the left side to the right side in Fig. 2 in the longitudinal direction of the device at regular intervals. However, the circles described by compression surfaces 16 adjacent in the longitudinal direction of the device have a step, since the radius of the compression surface determined by a spherically concave recess of a roller differs from the radius of the compression surface determined by the spherically concave recess of a roller adjacent in the longitudinal direction of the device. The difference between the two radii is

can be recognized by the steps on the respective circumference of the circles. The other components shown in Fig. 2 correspond to those that have already been described in detail with reference to Fig. 1.

Fig. 3 shows a cross-sectional view along the line AA of Fig. 2. The hatched circle 16B in Fig. 3 corresponds to the area of the spherically concave recess 16 which has the smallest diameter. The outer circle 16A in Fig. 3 indicates the diameter of the circular cylindrical area 13 of each roller 12. It can also be seen that the maximum diameter of each roller 12 is the same for each roller, while the area of the spherically concave recess with the smallest diameter increases at regular intervals from the left end in Fig. 3 to the right end. Furthermore, Fig. 3 shows how a clearing is formed by the two linear rows of rollers, into which the stent or an elastic workpiece is to be inserted. It should also be noted that the centers of the concentrically arranged circles 16A and 16B of a row of rollers lie on a line parallel to the longitudinal axis 2 of the clearing.

Referring now to Fig. 4, a cross-sectional view is shown along the line B-B of Fig. 2. In Fig. 4, a pair of rollers is shown perpendicular to the longitudinal direction 2 of the device 1. Both rollers 12 are rotatably mounted on the base plate 10. It can be clearly seen how the spherically concave recesses 16, which represent the compression surfaces 16, of both rollers describe a circle. Since the radii of the two spherically concave recesses 16 of both rollers 12 are identical in this cross-sectional view, the circle has no steps on its circumference. The upper, tapered end of the two rollers shown in Fig. 4 is in engagement with the gears 30. Such connections are known to those skilled in the art and are therefore not described in detail here.

The mode of operation of the stent loading device shown in the drawings is described below. To this end, the drive device 36, which is only shown schematically in Figs. 1 and 2, drives the gear 32 via the drive shaft 34, which in turn is in engagement with the gears 28 provided at the end of the two worms 26. This causes the worms 26 to rotate, and the engagement of the worms with the two rows of gears 30 causes the rollers 12 to rotate in a synchronous manner.

If an elastic workpiece, such as a stent, a stent graft, a graft or an elastic vena cava filter, is now introduced into the front end of the clearing formed by the rollers 12 shown in Fig. 1, the stent moves along the longitudinal direction 2 of the device or through the clearing to the rear end of the device due to the rotation of the rollers. Because the radii of the spherically concave recesses 16 of the rollers 12 decrease at regular intervals in the longitudinal direction of the device, the stent is compressed in the radial direction during the movement from the front end to the rear end. The friction that exists between the stent and the rollers is minimized by the drive of the rollers or the rotation of the rollers, whereby possible compressive or tensile stresses in the stent structure are also reduced to a minimum.

It should be noted here that a stent cut from a wire mesh or sheet metal using modern laser technology is a very sensitive construct to compressive or tensile stresses in the axial direction of the stent, and such compressive or tensile stresses directed in the axial direction should be avoided when compressing the stent in the radial direction in order to avoid possible plastic deformation of the stent structure. By having the means for radially compressing the stent simultaneously compress the stent along the longitudinal direction of the clearing

move, compressive and tensile stresses in the stent are reduced to a minimum.

If an outer catheter, which has an inner radius that corresponds at least to the radius of the spherical concave recess 16 at the rear end of the roller shown in Fig. 1, is positioned precisely at the rear end of the device 1, the stent, which is in its radially compressed configuration when it emerges from the rear end, can be inserted directly into the outer catheter. The outer catheter loaded with the compressed stent therefore only needs to be attached to an insertion device so that the stent can be inserted into a vessel during an endoscopic procedure.

The stent loading device according to the invention can be operated under sterile conditions, which eliminates the need for subsequent sterilization of the outer catheter loaded with the stent.

Furthermore, the device can be placed in a previously evacuated chamber filled with nitrogen gas or another suitable gas, and the device can be cooled to a temperature whereby the gas contained in the chamber prevents possible condensation, so that in this way a stent made of a shape-memory alloy can be introduced into an external catheter. It is also conceivable that the rollers themselves are flowed through with cooling liquid or are filled with such a liquid in order to cool the stent with the aid of the rollers.

Furthermore, it is possible to replace the drive device 3 6 for rotating the rollers 12 by another suitable means. It is also possible to drive each of the rollers 12 individually, whereby the rotational speed of the rollers can be varied along the longitudinal direction of the device in order to

to compensate for a possible change in the length of the stent during its radial compression.

In addition, it is obvious to the person skilled in the art that the diameter of the region 13 of the roller 12 does not have to be the same for all rollers. It has been considered that the diameter of the region 13 of adjacent rollers 12 perpendicular to the longitudinal direction 2 of the device 1, which constitute a pair of rollers, can be the same, and that the diameter of the region 13 of successive pairs of rollers in the longitudinal direction of the device can decrease. As a result, the distance in the longitudinal direction of the device between adjacent pairs of rollers becomes increasingly smaller towards one end of the device, thereby minimizing the risk of the stent escaping from the spherically concave recess, which increases with increasing compression of the stent.

Furthermore, in a device in which the diameter of the region 13 of the roller pairs changes along the longitudinal direction of the device, the axes of the rollers of a row can also be arranged at a certain angle to the longitudinal axis 2 and are no longer arranged on a line parallel to the longitudinal axis 2 of the clearing.

Claims (16)

1. Device ( 1 ) for radially compressing an elastic workpiece, in particular a stent, comprising a plurality of compression elements ( 12 ) which are movable relative to one another and each have a compression surface ( 16 ), wherein the compression surfaces ( 16 ) of the compression elements ( 12 ) are arranged such that they form a clearing with a longitudinal axis ( 2 ), a first end and a second end for receiving the stent, and wherein the distance between adjacent compression surfaces substantially perpendicular to the longitudinal axis ( 2 ) of the clearing is greater at the first end of the clearing than at the opposite second end of the clearing. 2. Device according to claim 1, wherein the distance between adjacent compression surfaces ( 16 ) decreases substantially perpendicular to the longitudinal axis ( 2 ) of the clearing from the first end to the second end of the clearing at uniform intervals. 3. Device according to claim 1 or 2, wherein the compression surfaces are formed as concave surfaces ( 16 ) on the surfaces of the compression elements ( 12 ). 4. Device according to one of the preceding claims, wherein the compression surfaces ( 16 ) are spherically concave on the surfaces of the compression elements ( 12 ), and wherein the radius of the spherically concave compression surfaces ( 16 ) decreases from the first end to the second end of the clearance at regular intervals. 5. Device according to claim 4, wherein the radius of the spherically concave compression surfaces ( 16 ) perpendicular to the longitudinal axis ( 2 ) of the clearance of adjacent compression elements ( 12 ) is substantially equal. 6. Device according to one of the preceding claims, wherein the compression elements ( 12 ) are designed as right circular cylinders, and wherein the compression surfaces ( 16 ) are rotationally symmetrical with respect to the cylinder axes of the compression elements ( 12 ). 7. Device according to claim 6, wherein all compression elements ( 12 ) have the same cylinder radius. 8. Device according to claim 6 or 7, wherein the compression surfaces ( 16 ) extend along the entire circumference of the compression elements ( 12 ). 9. Device according to one of claims 6 to 8, wherein the compression surfaces ( 16 ) of adjacent compression elements ( 12 ) describe a circle in a plane through the cylinder axes of the compression elements ( 12 ), and wherein the circle radii decrease at regular intervals along the longitudinal axis ( 2 ) of the clearing. 10. Device according to claim 9, wherein the centers of the circles described by the compression surfaces ( 16 ) of compression elements ( 12 ) arranged adjacent to one another perpendicular to the longitudinal axis ( 2 ) of the clearing lie on the longitudinal axis ( 2 ) of the clearing. 11. Device according to one of the preceding claims, wherein the compression elements ( 12 ) are arranged in two linear rows extending parallel to the longitudinal axis ( 2 ) of the clearing. 12. Device according to one of the preceding claims, wherein the compression elements ( 12 ) are rotatably mounted, and the device further comprises a means ( 36 , 34 , 32 , 30 , 28 , 26 ) for driving the compression elements ( 12 ), so that an elastic workpiece introduced at the first end of the clearing is moved to the second end of the clearing by driving the compression elements ( 12 ) and is thereby compressed in the radial direction. 13. Device according to claim 12, wherein all compression elements ( 12 ) can be driven synchronously by the means. 14. Device according to claim 12 or 13, wherein the means ( 36 , 34 , 32 , 30 , 28 , 26 ) comprises gears ( 30 ) rigidly connected to the compression elements ( 12 ) which are in engagement with a worm ( 26 ), and wherein the worm ( 26 ) is in engagement with a drive shaft ( 34 ) which is operatively connected to an electric motor ( 36 ). 15. Device according to one of the preceding claims, wherein the elastic workpiece is a medical stent, a graft, a stent-graft or a vena cava filter. 16. The device of claim 15, wherein the stent is made of stainless steel or a shape memory alloy.