WO2004002368A1

WO2004002368A1 - Stent

Info

Publication number: WO2004002368A1
Application number: PCT/EP2003/006775
Authority: WO
Inventors: Andreas Schuessler; Michael Ehrlinspiel
Original assignee: Admedes Schüssler Gmbh
Priority date: 2002-06-26
Filing date: 2003-06-26
Publication date: 2004-01-08
Also published as: DE10228529A1; AU2003250850A1

Abstract

The invention relates to a stent (28) for implanting in a living body and comprising a plurality of adjacent cells (26), whose walls (30) are composes of respective wall sections. The aim of the invention is to produce a cost-effective stent (28), which exhibits a high degree of flexibility when expanded. To achieve this, the wall of at least one cell (26), when viewed in cross-section (30) has an alternating configuration, in the peripheral direction, of a concave wall section (44, 46, 48) and an adjacent convex wall section (50, 52, 54).

Description

description

The invention relates to a stent for implantation in a living body with a plurality of adjoining cells, the walls of which are each formed from wall sections. In particular, the invention relates to an intraluminal stent that is suitable for implantation in lumens with different properties. Such different properties of lumens can be different curvatures, side branches, variable diameters or different flexible lumen walls.

Stents of this type are used to separate different channels of living bodies, e.g. Protect blood vessels, esophagus, urethra, kidney ducts by expanding a tubular stent structure in the interior of the channel against collapse or occlusion and / or to enable at least local therapy as a carrier of medication in body channels. The stent must be expandable radially in the channel to support the channel wall. In addition, the stent must be flexible or tube-like in the expanded state in order to enable the support function even in curved channel or vein areas. Furthermore, the stent must also be flexible in the compressed state in order to be able to pass through curved or curved channels and blood vessels.

To achieve this, known functional stents combine various functional geometric elements as wall sections to form a large number of cells which adjoin one another. The individual wall sections are designed in a certain manner, for example curved or straight, in order to give the stent the desired deformation properties. So that radial expansion of the stent is made possible, so-called zig-zag structures are formed, which are connected by bridges. The bridges can deform or flatten when the zig-zag structures are stretched and thus enable a tangent-like bending line of the stent. 1 and 2, a known stent 10 is illustrated, which is formed from a plurality of cells, of which a first cell is designated by 12 and a second cell by 12 '. Each individual cell 12, 12 'is designed with four straight wall sections 14, a concave wall section 16 in the form of a folded edge being located between each two straight wall sections 14. There are two curved wall sections 18 between the straight wall sections 14 opposite each other in this way.

A single wall section 18 forms a convex wall section in the first cell 12, which lies between two adjacent concave wall sections 20. At the same time, the wall section 18 in the second cell 12 ′ forms a concave wall section which is arranged between two convex wall sections 22.

In other words, a connection node 24 is formed with the wall sections 16, 20 and 22, to which two straight and one curved wall section 14 and 18 connect.

Viewed in cross section, the individual cell 12 of a known stent 10 is successively in the circumferential direction, that is, from a first straight wall section 14, a first concave wall section 16, a second straight wall section 14, a first concave wall section 20, a first convex wall section 18, and a second concave Wall section 20, a third straight wall section 14, a second concave wall section 16, a fourth straight wall section 14, a first convex wall section 22, a second concave wall section 18 and a second convex wall section 22, which finally adjoins the first straight wall section 14.

Stents 10 designed in this way have a so-called radial and a so-called axial component when deformed. This means that they expand or contract in the radial and axial direction of the channel or lumen into which they are inserted. In the radial direction, the stent expands while contracting in the axial direction. The radial component is generated by spreading the straight wall sections 14 on the concave wall section 16. The wall sections 18 serve as bridges or connectors between the straight wall sections 14. They have the task of ensuring the flexibility of the stent 10 in the expanded and non-expanded state.

In known stents, the walls of the cells are partially covered with medication, which should be distributed as evenly as possible on the vessel wall. It is therefore desirable that the walls of the cells are supported as evenly as possible on the vessel wall. Known stents, however, lead to a relatively uneven covering of a channel or vessel wall with the walls of the cells.

In addition, known stents often have insufficient flexibility in the compressed and also in the expanded state. In a known stent, the above-mentioned axial component leads to an axial shortening of the stent during expansion and to an uneven contact pressure against the vessel wall sections, which is undesirable.

The object of the invention is to overcome the disadvantages mentioned above and, in particular, to provide a stent which is inexpensive to manufacture and at the same time has a high degree of variability during expansion.

The task is inventively solved by a stent initially mentioned, in which at least one cell seen in cross section, the wall in the circumferential direction alternately from each ^• a concave wall portion and an adjacent convex wall portion is formed. Advantageous developments of the invention are described in the subclaims.

In the stent according to the invention, the wall is formed in succession in the circumferential direction from concave and convex wall sections. In this way, several areas are formed in the wall, on each of which a concave and initially folded each cell when expanding the stent adjacent convex wall section can be stretched or unfolded. The stretching of the folded concave and convex wall sections leads to a simultaneous enlargement of the cell in several areas of the wall.

The simultaneous stretching or unfolding of the wall in several areas means that the stent according to the invention has several directional components, in particular more than two directional components, in which it is stretched when expanded. The stent according to the invention, on the other hand, is not compressed in its expansion in one direction at the same time in another direction, as is the case with the axial component of the known stent described above.

When expanding in cross section, the stent according to the invention is expanded in several directions across the circumference of the individual cells. According to the invention, this expansion takes place on all cells almost simultaneously because the stretching or unfolding of concave and convex wall sections on one cell simultaneously leads to a stretching of an adjacent cell.

According to the invention, the stretching process thus propagates across the cells. The expansion of a stent according to the invention thus leads to a uniform deformation of a cell wall over its entire circumference, i.e. the stent deforms continuously. A stent according to the invention can therefore preferably be better lined with channels or vessels of different sizes with the same initial diameter of a stent. When the deformation load on a stent according to the invention is removed, its deformation stops almost suddenly, without the duct wall having to be overstretched. The stent according to the invention also remains sufficiently strong radially to support the channel wall.

In addition, the wall of a stent according to the invention is relatively uniformly folded or corrugated over the circumference. A coating on the wall, for example a drug-releasing coating, for example with cytostatics (cell poisons), a radioactive coating, a antithrombogenic and / or hemocompatible coating, an antibacterial coating, a coating with anti-tumor agent (s), an antithrombogenic coating and / or a coating with gene therapeutic or therapeutic agents is therefore easier to develop and moreover is more uniform to one Channel wall delivered. With a stent made from a radioactive material, the radioactivity is also released more evenly than with conventional stents.

Because of the uniformly corrugated shape of the wall, stress peaks and local deformation peaks in the stent are avoided according to the invention. Furthermore, narrow radii or preferably the formation of different radii are advantageously avoided. This avoids the risk of damage or chipping, in particular of a metallic or ceramic coating on the walls of the stent according to the invention. This also reduces the risk of material overload due to voltage peaks. According to the invention, the material properties of the material used in each case are better utilized.

With a stent, the strength of the material of the stent increases with increasing deformation under certain conditions. This so-called consolidation effect can be used particularly well according to the invention because the walls of the stent are deformed uniformly and at the same time to a relatively small extent. The deformation to solidify the material can therefore be controlled very precisely according to the invention and, moreover, is almost the same across the entire stent.

According to the invention, the known bridges described above in the form of wall sections 18 have preferably been dispensed with. In other words, the wall of a cell of a stent according to the invention is formed solely from curved or folded wall areas and nodes at which such wall areas abut one another. The flexibility of known stents is usually inversely proportional to the length and number of bridges in the axial direction. The stent according to the invention preferably has no bridges. This makes it particularly flexible in the axial direction. In addition, the stent according to the invention does not shorten in the axial direction when expanding. Rather, a stent according to the invention is characterized by a uniform expansion of the stent structure in several directions.

The stent according to the invention can be expanded and shrunk again in a particularly homogeneous manner. This advantage can be used if the stent is to be manufactured in the expanded or partially expanded state. This advantage can also be used in electropolishing and coating processes. The stent can be stretched before the procedure and subsequently compressed evenly again. The quality of the surfaces achieved by the method can be increased in this way.

The networking and formation of different deformation directions according to the invention is also advantageous when bending an expanded stent. The cells of a stent according to the invention deform depending on the position of the bending line, expanding or compressing uniformly, and thus enable homogeneous bending of the stent.

The invention can be particularly useful for balloon-expanded stents made of stainless steel, tantalum, niobium, cobalt alloys and other materials such as e.g. Polymers, self-degradable materials (e.g. lactic acid materials or derivatives), as well as with stents made of Nitinol (nickel-titanium alloys) and / or from other self-expandable materials or shape memory materials.

In an advantageous further development of the invention, viewed in cross section, at least one convex wall section is designed with a radius of curvature which is essentially the same as a radius of curvature of an adjacent concave wall section. Essentially the same Radii of curvature on the folded wall of the cells lead to a particularly uniform structure of the stent. Such a stent can therefore be electrochemically polished or coated particularly well. Furthermore, coating or coating processes are facilitated because shadowing effects are avoided or reduced in the so-called PVD or CVD process and / or drop effects in immersion processes (which are caused by the capillary action of narrow radii) are avoided.

The mentioned advantages of a stent according to the invention can furthermore advantageously be expressed in that, viewed in cross section, the wall sections are each of the same or almost the same design. A stent developed in this way is built up from the same geometry elements apart from nodes. In this way, a stent with particularly favorable flow properties is created. The geometric elements can have identical outside and inside diameters and identical structure widths. A basic element in the form of a cell is formed from such geometric elements by various types of nesting.

In addition, viewed in cross section, the wall sections can advantageously each be designed in the form of a circular arc or as a circular arc or circular structure. Stress peaks in the material of the stent can be avoided in this way and torsion of the stent is facilitated.

Furthermore, it is advantageous if, viewed in cross section, at least one cell is each made up of at least three convex wall sections, in each of which a concave wall section is formed between two convex wall sections. Such an individual cell of a stent according to the invention is stretched in three directions that are not parallel to one another when expanded. The directions are in particular offset by an angle of 120 °. The stent has a multi-axis deformation component and, in contrast to known stents which have only two directional components offset by an angle of 90 °, is uniformly expanded in a particularly simple manner, as has already been explained above. The stent according to the invention can be compressed to a particularly small size and at the same time be expanded easily and uniformly, when viewed in cross section, when the stent is compressed, the convex wall sections of at least one cell are designed to abut one another.

According to the invention, the developments of the invention described above as advantageous and set out in the subclaims can also be independently worthy of protection without the features mentioned in claim 1 as individual objects or in combination with one another.

It should also be noted that the individual concave and convex wall sections according to the invention can be formed by different types of shapes. These shapes can be circular in cross-section or in particular have short straight sections. The basic idea is that the wall of a cell of the stent is covered by a _. A series of concave and convex wall sections is formed, which - in particular - can be of the same design. The individual wall sections can advantageously be constructed from one and the same geometric basic element. These basic elements can be connected by nodes, the outer shape of which is particularly advantageously adapted to the outer shape of a basic element.

The stent designed in this way is particularly advantageous both in terms of its achievable surface quality and thus also its biocompatibility and also the required production technology. In order to achieve particularly good biocompatibility, the stent is usually subjected to a surface finish, such as an electrochemical polish, which preferably produces a thin, protective oxide film on the surface. Such a method is based on a targeted mass removal of the surface of the stent. The electropolished surface has very low roughness and a high level of purity. The polishing process is carried out in a current-assisted manner in an acid mixture, whereby for an even polish, due to the field, a component structure that is as homogeneous as possible must be present. As has been explained above, the stent according to the invention consists of such a particularly homogeneous structure. Particularly large or small radii on the structure are avoided according to the invention. Known stents, however, consist of different structural components that have only been optimized with regard to the mechanical properties of the stent.

As already mentioned, the stent according to the invention is advantageously made of stainless steel, tantalum, niobium, cobalt alloys, polymers, self-degradable materials and / or nitinol.

It is also advantageous if the cells of the stent according to the invention are arranged in rows, the individual rows all being helically shaped at an angle of approximately 10 ° to approximately 30 °, preferably approximately 20 °, to the circumferential direction or azimuthal direction of the stent , The cells then point within the individual rows in the axial direction of the stent. low offset, such that a helical structure is formed overall in the stent. This structure gives the stent a significantly improved set-up behavior. In particular, the stent expands more evenly in the radial direction. In the freely expanded state, such a stent has essentially the same extent along its axis.

Exemplary embodiments of a stent according to the invention are explained in more detail with reference to the attached schematic drawings. Show it:

1 shows a cross section of a stent according to the prior art in the compressed state,

Fig. 2 shows a cross section of the stent of FIG. 1 in the expanded

Status, 3a to 3d a sequence of graphics to illustrate the structure of a cell of a first embodiment of a stent according to the invention,

4a to 4c a sequence of graphics to illustrate the structure of a structure from cells of the first embodiment of a stent according to the invention,

5 shows a cross section of the first exemplary embodiment of a stent according to the invention in the compressed state,

Fig. 6 shows a cross section of the first embodiment of a stent according to the invention in the expanded state, and

Fig. 7 shows a cross section of a second embodiment of a stent according to the invention in the compressed state.

FIGS. 3a to 3d illustrate the basic structure of a cell 26 (see FIG. 3d) which, in combination with other cells, forms a stent 28 (see FIG. 4c). The cell 26 has a wall 30 which is composed of individual wall sections.

A circular ring 32, as illustrated in FIG. 3a, serves as the basic element for the individual wall sections.

Two such circular rings 34 and 36 are conceptually placed on such a circular ring 32. The walls of the applied circular rings 34 and 36 touch and each cover the wall of the first circular ring 32.

In turn, three circular rings 38, 40 and 42 are placed on the circular rings 34 and 36. The wall of the circular ring 38 covers the walls of the circular rings 34 and 40. The wall of the circular ring 40 covers the walls of the circular rings 38 and 42 and touches the walls of the circular rings 34 and 36. The wall of the circular ring 42 covers the walls of the circular rings 36 and 40.

In this way, a total of six circular rings are combined to form a triangle, the walls of the circular rings overlapping in the outer region of the triangle and touching each other in the central region of the triangle (see FIG. 3b).

FIG. 3 c shows how the wall sections of the wall 30 of an individual cell 26 are constructed from the circular rings 32 to 42 arranged in this way.

When viewed in cross section, the wall 30 is basically in the form of a serpentine line, each consisting of concave and convex wall sections which alternate in the circumferential direction of the wall 30 or are arranged alternately and are explained in more detail below.

According to the basic structure of the triangle of FIG. 3b, the wall 30 also has three "corner regions" which are each formed from a concave wall section 44, 46 and 48. The wall sections 44, 46 and 48 are preferably in the form of a circular arc and each represent part of the circular rings 32, 38 and 42 according to FIG. 3b.

Convex wall sections 50, 52 and 54 are formed between the concave wall sections 44, 46 and 48, which come from the circular rings 34, 36 and 40, respectively. The wall sections 50 and 52, 52 and 54 as well as 50 and 54 preferably touch each of these wall sections in the fully compressed state of a cell 30, as shown in FIG. 3c. In the compressed state of a cell 30, however, the wall sections 50, 52 and 54 do not necessarily have to touch. Conditions are also possible in which the cell 30 is only partially compressed and the wall sections 50, 52 and 54 are at least slightly spaced apart. Accordingly, the “folded” wall 30 of a cell 26, as illustrated in FIG. 3d, is composed overall of the concave or convex wall sections 44 to 54.

The stent 28 is constructed from a multiplicity of cells 26 which abut one another. The cell 26 illustrated in FIG. 3d is found in a stent 28 as shown in FIG. 4b.

Due to the combination of the cells 26 to form a stent structure, the individual wall sections 44 to 54 of a cell 26 also simultaneously belong to neighboring cells as wall sections. This fact is illustrated in FIGS. 4a to 4c.

The graph according to FIG. 4b shows that the walls 30 of a stent 28 can in principle also be viewed as a structured structure made up of many arcs 56 which are arranged between nodes or connecting elements 58. Three arcs 56 each protrude from a node 58.

The individual circular arc 56 extends over an angular range between 160 ° and 180 °, in particular over an angular range of approximately 170 °. It is circular in cross-section on its inside and outside, so that its surfaces represent parts of circular cylindrical surfaces. The wall of the individual circular arc 56 preferably has a constant thickness. The individual nodes 58 each connect three such arcs 56.

The nodes 58 each have three sides or end regions, each of which is joined by an arc 56. A concave curve 58 ′ is formed at the nodes 58 between the three end regions, the radius of which essentially corresponds to the inner radius of an arc 56. The curves of the arcs 56 thus merge smoothly into the adjacent curves 58 'of nodes 58, which in turn are followed by arcs 56. The curvature of the surface at the transition is constant. The curves 58 ′ of the nodes 58 and the inner surfaces of the arcs 56 belong to the concave wall regions 50, 52 and 54 described above. The convex wall sections 44, 46 or 48 are formed by the outer surfaces of the arcs 56. At the transitions between arcs 56 and nodes 58 there are turning points of curvature where a convex wall section 44, 46 or 48 borders on a node 58, ie where a concave wall section merges into an adjacent convex wall section.

5 and 6 illustrate how a stent 28 is transferred from its compressed position according to FIG. 4c to an expanded state. When expanding, the three individual regions of the wall 30, which are each formed from a convex and the two adjacent concave wall sections, unfold outward in three directions 60, 62 and 64. Between these directions 60, 62 and 64 there is an angle of 120 °.

As particularly illustrated in FIG. 6, the stent designed in this way expands uniformly in directions 60, 62 and 64, whereby the advantages mentioned above in connection with the invention are achieved.

7 illustrates a second exemplary embodiment of a stent 28, in which multiply folded wall areas 68 are formed between nodes or connecting elements 66. The multiply folded wall areas 68 are each individually formed from three substantially semicircular arches 70, 72 and 74, which successively form a convex, a concave and a further convex wall section in the designated cell 26. In an adjacent cell, these arches simultaneously form a concave, a convex and a further concave wall section.

The individual arches 70, 72 and 74 span an angle of approximately 150 ° to 250 °, preferably approximately 200 °. Their surfaces correspond essentially a section of a circular cylinder. The thickness of the wall of arches 70, 72 and 74 is essentially constant.

The nodes 66 have four sides or end regions, each of which is connected to a wall section 68. Between these end regions there are concave curves 66 ', the radius of which corresponds in each case to the inner radius of an arc 70, 72 or 74. A single node 66 is therefore essentially cruciform in cross-section. The transition between a knot 66 and an arch 70, 72 or 74 is smooth or without an edge. The curvature of the surface at the transition is again essentially constant. The individual concave curves 66 'at the nodes 66 each extend over an angle of approximately 70 ° to 110 °, preferably over an angle of approximately 90 °.

7, the wall 30 of a cell 26 of the stent 28 is accordingly all formed from alternately concave and convex wall sections which, viewed in cross section, individually follow the basic shape of an arc or a circular ring. Four such wall areas 68 each protrude from a node 66. The structure of the stent according to FIG. 7 leads to simultaneous expansion in four directions. However, stents with a "spider-like" shape are also conceivable, in which cells are at least partially provided, all of which are formed from alternately concave and convex wall sections and whose nodes protrude from five or more wall regions.

The production of the stent according to the invention or a preferred embodiment thereof can be carried out both from raw material and from flat material, in which case the stent is later rolled, welded and / or finished. Furthermore, the stent can be produced by means of laser cutting, laser ablation, photochemical etching and / or eroding. Furthermore, the stent can also be produced in such a way that the stent structure is manufactured in an at least partially expanded form and the stent is then compressed, for example, for insertion into the catheter Shape is reduced before it is subsequently at least partially expanded again in the body.

In one embodiment, not shown, the cells of the stent are arranged in rows, the individual rows all being helically inclined at an angle of approximately 10 ° to approximately 30 °, preferably approximately 20 °, to the circumferential direction of the stent. In this embodiment, the individual cells are not arranged exactly in a row in the circumferential direction, as illustrated in FIGS. 5 and 6, but a slight offset or a relative displacement is formed within the individual row between successive cells in the axial direction of the stent. Overall, a helix structure is created in the stent. In other words, successive cells of a row are not arranged in the axial direction with respect to one another, but the successive cells of a row are arranged along a row direction which is inclined to the axial direction of the stent, preferably from about 10 ° to about 30 °, particularly preferably around about 20 °. The inclined rows are not to be confused with the row of cells which, according to FIG. 6, has an angle of 60 ° to the circumferential direction of the stent.

LIST OF REFERENCE NUMBERS

Prior art stent first cell 'second cell straight wall section concave wall section

Wall section or bridge concave wall section convex wall section

junction

Cell according to the invention

Stent according to the invention

wall

annulus

Circular ring concave wall section concave wall section concave wall section convex wall section convex wall section convex wall section

arc

Rounding node first direction second direction third direction knot rounding folded wall area arch arch arch

Claims

Expectations

1. stent (28) for implantation in a living body, in particular intraluminal stent, with a plurality of adjoining cells (26), the walls (30) of which are each formed from wall sections, characterized in that at least one cell (26) viewed in cross section, the wall (30) is alternately formed in the circumferential direction from a concave wall section (44, 46, 48) and an adjacent convex wall section (50, 52, 54).

2. Stent according to claim 1, characterized in that viewed in cross section, at least one convex wall section (50, 52, 54) is formed with a radius of curvature which is substantially equal to a radius of curvature of an adjacent concave wall section (44, 46, 48) ,

3. Stent according to claim 1 or 2, characterized in that viewed in cross section, the wall sections (44, 46, 48, 50, 52, 54) are each of identical or almost identical design.

4. Stent according to one of claims 1 to 3, characterized in that viewed in cross section, the wall sections (44, 46, 48, 50, 52, 54) are each designed in the shape of a circular arc.

5. Stent according to one of claims 1 to 4, characterized in that, viewed in cross section, at least one cell (26) is each formed from at least three convex wall sections (50, 52, 54), in each of which between two convex wall sections (50, 52, 54) a concave wall section (44, 46, 48) is formed.

6. stent according to one of claims 1 to 5, characterized in that, when viewed in cross section, when the stent (28) is compressed, the convex wall sections (50, 52, 54) of at least one cell (26) are designed to abut one another.

7. Stent according to one of claims 1 to 6, characterized in that a drug-releasing and / or antibacterial coating, a coating with anti-tumor agent (s), an anti-trombogenic coating and / or a coating with gene therapeutics on the surface of the stent is arranged.

8. Stent according to one of claims 1 to 7, characterized in that a coating is formed from radioactive material and / or the material of the stent itself emits radioactive radiation.

9. Stent according to one of claims 1 to 8, characterized in that it is made of stainless steel, tantalum, niobium, cobalt alloys, polymers, self-degradable materials and / or nitinol.

10. Stent according to one of claims 1 to 9, characterized in that the cells (26) are arranged in rows, the individual rows all to the circumferential direction of the stent at an angle of about 10 ° to about 30 °, preferably of about 20 ° are helically inclined.