DE10228529A1 - stent - Google Patents

Abstract

A stent (28) for implantation in a living body is provided with a multiplicity of adjoining cells (26), the walls (30) of which are each formed from wall sections. In order for the stent (28) to be manufactured particularly cost-effectively and at the same time has a high degree of flexibility in the expanded state, the wall (30) in at least one cell (26), viewed in cross section, alternates in the circumferential direction from a concave wall section (44, 46, 48) and an adjacent convex wall section (50, 52, 54).

Description

The invention relates to a stent for implanting in a living body with a variety of adjacent cells, the walls of which consist of wall sections are trained. In particular, the invention relates to an intraluminal Stent for implantation in lumens with different properties suitable is. Such different properties of lumens can have different curvatures, Side branches, variable diameters or different compliant Be lumen walls.

Stents of this type are used around different channels living body, such as. Blood vessels, esophagus, urethra, kidney ducts, through Expand a tubular stent structure to protect against collapse or sealing inside the channel and / or as a carrier of drugs in body channels a to enable at least local therapy. The stent must be radial be expandable in the channel to support the channel wall. Furthermore must the Stent in the expanded state be flexible or tubular, around the support function to enable also in curved duct or core areas. Furthermore, the Stent can also be flexible in the compressed state to be bent through or curvy channels and blood vessels enter to be able to.

In order to achieve this, known stents are used various functional geometric elements as wall sections combines a large number of cells that are adjacent to each other. The individual wall sections are in a certain way, for example bent or straight, designed to give the stent the desired deformation properties to lend. To enable the stent to expand radially, so-called Zig-Zag structures are formed, which are connected by bridges are. The bridges can deform or flatten when the zig-zag structures are stretched and enable such a tangent-like bend line of the stent.

In 1 and 2 is a well-known stent 10 illustrated, which is formed from a plurality of cells, of which a first cell is designated by 12 and a second cell by 12 '. Every single cell 12 . 12 ' is with four straight wall sections 14 designed, being between two straight wall sections 14 a concave wall section 16 is in the form of a folded edge. Between the straight wall sections opposite in this way 14 there are two curved wall sections 18 ,

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

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

The single cell is viewed in cross section 12 of a known stent 10 successively in the circumferential direction 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 , 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 formed, which eventually to the first straight wall section 14 borders.

Stents designed in this way 10 have a so-called radial and a so-called axial component during deformation. This means that they expand or contract in the radial and axial direction of the channel or lumen into which they are inserted. The stent is expanded in the radial direction while at the same time contracting in the axial direction. The radial component is created by spreading the straight wall sections 14 on the concave wall section 16 generated. The wall sections 1 $ serve as bridges or connectors between the straight wall sections 14 , They have the task of being in the expanded and unexpanded state of the stent 10 ensure its flexibility.

In known stents, the walls of the cells partially covered with medication that is as even as possible on the Vessel wall too are distributed. It is therefore desirable that the walls of the cells be on the Vessel wall if possible support evenly. Known Lead stents but to a relatively unequal Covering a canal or vessel wall with the walls of the cells.

They also have known ones Stents are often still insufficient flexibility in the compressed and also in the expanded state. The above leads axial component in a known stent during of expansion to an axial shortening of the stent and one unequal contact pressure to the vessel wall sections, which is undesirable is.

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

The task is according to the invention with one mentioned stent solved, in the case of at least one cell viewed in cross-section, the wall in the circumferential direction alternately from a concave wall section 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 consecutively concave in the circumferential direction and convex wall sections. That way are in The wall formed several areas where the stent expands first at each cell folded concave and adjacent convex wall stretched or be unfolded. Stretching the folded concave and leads to convex wall sections a simultaneous enlargement of the Cell on multiple areas of the wall.

The simultaneous stretching or unfolding of the Wall on several areas causes the stent of the invention when expanding several directional components, especially more as two directional components in which it is stretched. The stent according to the invention will not, however, expand in one direction at the same time compresses in another direction, as is the case with the axial component of the known stent described above is the case.

The stent according to the invention will expand viewed in cross section over the circumference of the individual cells expands in several directions. 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 at the same time as stretching an adjacent cell leads.

According to the invention, the stretching process is planted so about the cells away. The expansion of a stent according to the invention performs this way to an even deformation over a cell wall their entire scope, i.e. the stent deforms continuously. With a stent according to the invention can therefore preferred different sizes channels or vessels with the same Output diameter of a stent can be better lined. at Removal of the strain on a stent according to the invention stops its deformation almost suddenly, without overstretching the channel wall should be. The stent according to the invention remains sufficiently strong radially to support the channel wall.

In addition, the wall is one stent according to the invention over the Folded relatively evenly across the circumference or corrugated. A coating on the wall, for example a drug-releasing coating e.g. with cytostatics (cell toxins), a radioactive coating, an antitrombogenic and / or hemocompatible Coating, an antibacterial coating, a coating with anti-tumor agent (s), an anti-thrombogenic coating and / or one Coating with gene therapeutic or therapeutic agents is therefore easier educate and will about it more evenly delivered a channel wall. For a stent that consists of a radioactive Material is made, the radioactivity is also more uniform than delivered with conventional stents.

Because of the evenly wavy According to the invention, the shape of the wall is voltage peaks and local Deformation peaks avoided in the stent. Furthermore, tight radii or preferably the formation of different radii advantageously avoided. As a result, there is a particular risk of damage or chipping a metallic or ceramic coating on the walls of the stents according to the invention avoided. It also increases the risk of material overload reduced by voltage peaks. The material properties of the the materials used in each case become better according to the end exploited.

With a stent increases strength under certain conditions with increasing deformation the material of the stent. This so-called consolidation effect can be particularly inventive be exploited well because the walls of the stent are even and at the same time in a relatively small amount Deformed extent become. According to the invention, the deformation to solidify the material can be very great can be controlled precisely and is also almost across the entire stent equally pronounced.

According to the invention is on the known bridges described above in the form of wall sections 18 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 node points at which such wall areas abut one another.

The flexibility of known stents is in the Usually inversely proportional to the length and number of bridges in axial direction. The stent according to the invention preferably has no bridges. This makes it particularly flexible in the axial direction. Furthermore shortened the stent according to the invention expands not in the axial direction. A stent according to the invention stands out rather by even stretching 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 Be layering can be used. 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 training according to the invention different directions of deformation is also when bending one expanded stents are an advantage. Deform the cells of a stent according to the invention depending on the position of the bending line, expanding or compressing evenly and thus enable a homogeneous bend 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 polymers self-degradable materials (e.g. lactic acid materials or derivatives), and for stents made of nitinol (nickel-titanium alloys) and / or other self-expanding materials or shape memory materials used become.

With an advantageous further education The invention is viewed in cross section at least one convex Wall section with a radius of curvature formed which is substantially equal to a radius of curvature of an adjacent concave wall section is designed. Essentially the same radii of curvature on the folded wall of the cells lead to a particularly uniform structure of the Stents. Such a stent is therefore particularly good at electrochemical use be polished or coated. Furthermore, coating or coating processes are facilitated because shadowing effects in the so-called PVD or CVD process avoided or reduced and / or drop effects in immersion processes (which are caused by the capillary action of narrow radii) avoided become.

The stated advantages of a stent according to the invention can are further advantageously expressed, by looking at the wall sections in cross section in each case the same or are almost identical. A stent developed in this way is made up of the same geometric elements except for nodes built up. In this way, a stent is particularly special Great flow characteristics created. The geometric elements can be identical outside and Have inner diameters and identical structure widths. From such Geometric elements is characterized by different types of nesting Base element formed in the shape of a cell.

In addition, in Cross-section advantageously considers the wall sections in the form of an arc or be designed as a circular arc or circular structure. spikes in the material of the stent can be avoided in this way and torsion of the stent will be relieved.

It is also advantageous if in Cross-section considers at least one cell from at least three is designed convex wall sections, in each case between two convex wall sections formed a concave wall section is. Such a single cell of a stent according to the invention when expanding in three non-parallel directions stretched. In particular, the directions are each at an angle offset from 120 °. The stent has a multi-axis deformation component and will in contrast to known stents, which are only two at an angle of Offset 90 ° Have directional components, expanded uniformly in a particularly simple manner, as already explained above has been.

The stent according to the invention can be particularly small compressed and at the same time easily and evenly expanded by viewed in cross section when the stent is compressed, the convex Wall sections of at least one cell formed adjacent to each other are.

In addition, according to the invention those described above as advantageous and set out in the subclaims Developments of the invention without the features mentioned in claim 1 as individual objects or in combination with each other independently worthy of protection.

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. This Formations can in Cross-section in the shape of a circular arc be or in particular have short straight sections. basic idea is it that the Wall of a row of the stent through a concave array and convex wall sections is formed, in particular the same can be trained. The individual wall sections can advantageously constructed from one and the same basic geometric element his. These basic elements can be connected by nodes, the outer shape of which is particularly advantageous again to the outer shape of a Basic element adapted is.

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 an acid mixture with the aid of electricity, and a homogeneous component structure must be available for uniform polishing, depending on the field. 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. Be Known stents, however, consist of different structural components that have only been optimized with regard to the mechanical properties of the stent.

Exemplary embodiments of a stents according to the invention based on the attached schematic drawings closer explained. It demonstrate:

1 3 shows a cross section of a stent according to the prior art in the compressed state,

2 a cross section of the stent 1 in the expanded state,

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

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

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

In the 3a to 3d is the basic structure of a cell 26 (please refer 3d ) that combines a stent with other cells 28 (please refer 4c ) forms. The cell 26 has a wall 30 on, which is composed of individual wall sections.

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

Such a ring 32 are mentally two more circular rings 34 and 36 created. The walls of the created circular rings 34 and 36 touch and each cover the wall of the first annulus 32 ,

To the circular rings 34 and 36 are in turn three circular rings 38 . 40 and 42 created. The wall of the annulus 38 covers the walls of the circular rings 34 and 40 , The wall of the annulus 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 annulus 42 covers the walls of the circular rings 36 and 40 ,

In this way, a total of six circular rings are put together 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 3b ).

In 3c is shown as from the circular rings arranged in this way 32 to 42 the wall sections of the wall 30 a single cell 26 are set up.

The wall 30 is basically seen in cross-section in the shape of a serpentine, each consisting of concave and convex wall sections, which extend in the circumferential direction of the wall 30 alternate or alternate and are explained in more detail below.

According to the basic structure of the triangle of 3b also shows the wall 30 three "corner areas", each consisting of a concave wall section 44 . 46 and 48 are formed. The wall sections 44 . 46 and 48 are preferably circular arcs and each form part of the circular rings 32 . 38 or 42 according to 3b represents.

Between the concave wall sections 44 . 46 and 48 are each convex wall sections 50 . 52 and 54 trained by the circular rings 34 . 36 or 40. The wall sections preferably touch each of these wall sections 50 and 52 . 52 and 54 and 50 and 54 in the fully compressed state of a cell 30 as he is in 3c is shown. In the compressed state of a cell 30 need the wall sections 50 . 52 and 54 but do not necessarily touch. States 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.

Accordingly, the "folded" wall 30 a cell 26 as in 3d is illustrated, altogether from the concave or convex wall sections 44 to 54 composed.

The stent 28 is made up of a multitude of cells 26 built up that abut each other. In the 3d illustrated cell 26 is found in a stent 28 again as he is in 4b is shown.

Because of the combination of the cells 26 The individual wall sections belong to a stent structure 44 to 54 a cell 26 also as wall sections to neighboring cells. This fact is in the 4a to 4c illustrated.

The graphics according to 4b shows that the walls 30 of a stent 28 basically also as a structured structure from many arcs 56 can be considered between nodes or connecting elements 58 are arranged. From a knot 58 there are three arcs 56 from.

The single 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 single circular arc 56 preferably has a constant thickness. The single a knot 58 connect three such arcs 56 ,

The knots 58 each have three sides or end areas, each with a circular arc 56 followed. Between the three end areas is at the node 58 one concave curve each 58 ' formed, the radius of which is the inner radius of an arc 56 essentially matches. The curves of the arcs 56 so go smoothly into the adjacent curves 58 ' of knots 58 over, to which turn arcs 56 connect. The curvature of the surface at the transition is constant.

The curves 58 ' the knot 58 and the inner surfaces of the arcs 56 belong to the concave wall areas described above 50 . 52 and 54 , The convex wall sections 44 . 46 or 48 are from the outer surfaces of the arcs 56 educated. At the transitions between arcs 56 and knots 58 there are therefore inflection points of the curvature where there is a node 58 a convex wall section 44 . 46 or 48 borders, where a concave wall section merges into an adjacent convex wall section.

In 5 and 6 is illustrated as a stent 28 from its compressed position 4c is converted into an expanded state. When expanding, the three individual areas of the wall unfold 30 , which are each formed from a convex and the two adjacent concave wall sections, outwards in three directions 60 . 62 and 64 , Between these directions 60 . 62 and 64 there is an angle of 120 °.

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

In 7 is a second embodiment of a stent 28 illustrates, in the case of nodes or connecting elements 66 multiply folded wall areas 68 are trained. The multiple folded wall areas 68 are each made up of three essentially semicircular arches 70 . 72 and 74 designed in the designated cell 26 successively form a convex, a concave and a further convex wall section. 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 essentially correspond to a section of a circular cylinder. The thickness of the wall of the arches 70 . 72 and 74 is essentially constant.

The knots 66 have four sides or end regions, on each of which a wall section 68 followed. There are concave curves between these end regions 66 ' whose radius is the inner radius of an arc 70 . 72 or 74 equivalent. A single knot 66 viewed in cross section, it is thus essentially cruciform. The transition between a knot 66 and a bow 70 . 72 or 74 is flowing or smooth and without an edge. The curvature of the surface at the transition is again essentially constant. The individual concave curves 66 ' at the knot 66 each extend over an angle of approximately 70 ° to 110 °, preferably over an angle of approximately 90 °.

Also in the embodiment according to 7 is the wall 30 a cell 26 of the stent 28 accordingly all formed from alternately concave and convex wall sections, each of which, viewed in cross section, individually follows the basic shape of an arc or a circular ring. From a knot 66 there are four such wall areas 68 from. The structure of the stent according to 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 manufacture of the stent according to the invention or a preferred embodiment this can be done from both raw material and flat material the latter rolling the stent later, welded and / or finished. Furthermore, the manufacture of the Stents using laser cutting, laser ablation, photochemical etching and / or Eroding occur. Furthermore, the manufacture of the stent can also in such a way that the stent structure is manufactured in an at least partially expanded form and the stent then to Introduce e.g. is reduced to a compressed form in the catheter, before following in the body is at least partially expanded again.

10

stent according to the status of the technique

12

first cell

12 '

second cell

14

straight wall section

16

concave wall section

18

wall section or bridge

20

concave wall section

22

convex wall section

24

junction

26

cell according to the invention

28

stent according to the invention

30

wall

32

annulus

34

annulus

36

annulus

38

annulus

40

annulus

42

annulus

44

concave wall section

46

concave wall section

48

concave wall section

50

convex wall section

52

convex wall section

54

convex wall section

56

arc

58

node

58 '

curve

60

first direction

62

second direction

64

third direction

66

node

66 '

curve

68

folded wall area

70

arc

72

arc

74

arc

Claims (8)

Stent ( 28 ) for implantation in a living body, in particular intraluminal stent, with a large number of adjoining cells ( 26 ) whose walls ( 30 ) are each formed from wall sections, characterized in that at least one cell ( 26 ) viewed in cross section the wall ( 30 ) in the circumferential direction alternately from a concave wall section ( 44 . 46 . 48 ) and an adjacent convex wall section ( 50 . 52 . 54 ) is trained. 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 ) is designed. 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 the same or almost identical design. Stent according to one of claims 1 to 3, characterized in that viewed in cross section, the wall section ( 44 . 46 . 48 . 50 . 52 . 54 ) are each designed in a circular arc. Stent according to one of claims 1 to 4, characterized in that viewed in cross section, at least one cell ( 26 ) each from at least three convex wall sections ( 50 . 52 . 54 ) is designed, in each case between two convex wall sections ( 50 . 52 . 54 ) a concave wall section ( 44 . 46 . 48 ) is trained. Stent according to one of claims 1 to 5, characterized in that viewed in cross section when the stent is in a compressed state ( 28 ) the convex wall sections ( 50 . 52 . 54 ) at least one cell ( 26 ) are designed to fit together. Stent according to one of the claims 1 to 6, characterized in that a drug-releasing and / or antibacterial coating, a coating with anti-tumor agent (s), an anti-thrombogenic coating and / or a coating with Gene therapy on the surface of the stent is arranged. Stent according to one of the claims 1 to 7, characterized in that a coating of radioactive Material is formed and / or the material of the stent itself emits radioactive radiation.