MEDICAL DEVICE FOR INTRODUCING INTO A BODILY HOLLOW VISCUS, MEDICAL SET, AND PRODUCTION METHOD

Abstract

A medical device for inserting into a hollow organ of the body, said medical device having a compressible and expandable lattice structure made of webs, which are integrally connected to each other by web connectors and which bound closed cells of the lattice structure, wherein the web connectors each have a connector axis extending between two cells which, in a longitudinal direction of the lattice structure, are adjacent to each other. During the transition of the lattice structure from the production state to a compressed state, the web connectors rotate in such a way that an angle between the connector axis and a longitudinal axis of the lattice structure changes, in particular increases, during the transition of the lattice structure from a completely expanded production state to a partially expanded intermediate state.

Claims

1. A medical device for introduction into a hollow body organ, in particular a stent, with a compressible and expandable mesh structure formed from mesh elements and which has at least one closed cell ring which comprises at most 12, in particular at most 10, in particular at most 8, in particular at most 6 directly adjacent cells in a circumferential direction of the mesh structure, wherein the mesh structure is provided, at least in sections, with a covering formed from art electrospun fabric which has irregular pores, wherein the covering comprises at least 10 pores with a size of at least 15 μm.sup.2 over an area of 100,000 μm.sup.2.

2. The medical device as claimed in claim 1, wherein the covering comprises at least 10 pores with a size of at least 30 μm.sup.2 over an area of 100,000 μm.sup.2.

3. The medical device as claimed in claim 1, wherein the at least 10 pores have an inscribed circle diameter of at least 4 μm, in particular at least 5 μm, in particular at least 6 μm, in particular at least 7 μm, in particular at least 8 μm, in particular at least 9 μm, in particular at least 10 μm, in particular at least 12 μm, in particular at least 15 μm, in particular at least 20 μm.

4. The medical device as claimed in claim 1, wherein the mesh elements delimit closed cells of the mesh structure, wherein each closed cell is delimited by four respective mesh elements.

5. The medical device as claimed in claim 1, wherein the covering has at least 15 pores with a size of at least 30 m.sup.2, in particular at least 50 μm.sup.2, in particular at least 70 μm.sup.2, in particular at least 90 μm.sup.2 over an area of 100,000 μm.sup.2.

6. The medical device as claimed in claim 1, wherein the covering has at least 15, in particular at least 20, in particular at least 25 pores with a size of at least 30 μm.sup.2 over an area of 100,000 μm.sup.2.

7. The medical device as claimed in claim 1, wherein the size of the pores is at most 750 μm.sup.2, in particular at most 500 μm.sup.2, in particular at most 300 μm.sup.2.

8. The medical device as claimed in claim 1, wherein the covering is securely, in particular cohesively, connected to the mesh structure.

9. The medical device as claimed in claim 8, wherein the mesh elements are sheathed by a bonding agent, in particular polyurethane, in particular wherein the bonding agent forms the cohesive connection of the covering with the mesh structure.

10. The medical device as claimed in claim 1, wherein at least sections of the mesh structure form a cylindrical and/or funnel-shaped hollow body.

11. The medical device as claimed in claim 10, wherein the hollow body is entirely perfusible along the longitudinal axis.

12. The medical device as claimed in claim 10, wherein the covering is disposed on an outer face of the mesh structure, in particular of the hollow body.

13. The medical device as claimed in claim 1, wherein the covering is formed from a synthetic material, in particular from a polyurethane.

14. The medical device as claimed in claim 1, wherein the covering is formed from filaments disposed in an irregular network and which have a filament thickness of between 0.1 μm and 3 μm, in particular between 0.2 μm and 2 μm, in particular between 0.5 μm and 1.5 μm, in particular between 0.8 μm and 1.2 μm.

15. The medical device as claimed in claim 1, wherein the medical device is a stent for the treatment of aneurysms in arterial, in particular neurovascular, blood vessels.

16. The medical device as claimed in claim 1, wherein at least 60%, in particular at least 70%, in particular at least 80% of the area of the covering is formed by pores with a size of at least 10 μm.sup.2.

17. The medical device as claimed in claim 1, wherein at least 30% of the area of the covering is formed by pores with a size of at least 30 μm.sup.2.

18. The medical device as claimed in claim 1, wherein at most 20% of the area of the covering is formed by pores with a size of at least 500 μm.sup.2.

19. The medical device as claimed in claim 1, wherein at most 50% of the area of the covering is formed by pores with a size of at least 300 μm.sup.2.

20. The medical device as claimed in claim 1, wherein the mesh elements form webs which are coupled together into one piece by means of web connectors, or form wires which are braided together.

21. The medical device as claimed in claim 1, wherein the covering has a ductility in accordance with ASTM 412 of between 300% and 550%, in particular between 350% and 500%, in particular between 375% and 450%.

22. The medical device as claimed in claim 1, wherein the covering has an elastic modulus in accordance with ASTM 412 as follows: at 50% extension: >15-21 MPa (psi) at 100% extension: >18<26 MPa (psi) at 300% extension: >32<41 MPa (psi).

23. The medical device as claimed in claim 1, wherein the covering has a Shore hardness in accordance with ASTM D 2240 of between 80 A and 85 D, in particular between 90 A and 80 D, in particular between 55 D and 75 D.

24. The medical device as claimed in claim 1, wherein after compression and renewed deployment of the mesh structure, the covering is capable of returning its original configuration, in particular its non-folded configuration.

25. The medical device as claimed in claim 1, wherein the filaments of the fabric are cohesively connected to each other at their points of intersection in the fabric.

26. The medical device as claimed in claim 1, wherein in addition to the pores formed by electrospinning, the fabric is also perforated by further pores which are formed in the electrospun fabric by processing the fabric, in particular by laser cutting.

27. The medical device as claimed in claim 26, characterized in wherein the fabric is perforated by the further pores over at least 25%, in particular at least 40%, in particular at least 50% of the circumference of the mesh structure.

28. The medical device as claimed in claim 26, wherein at least 25%, in particular at least 40%, in particular at least 50% of the circumference of the mesh structure is free from further pores.

29. The medical device as claimed in claim 26, wherein starting from the axial centre of the mesh structure, the further pores are formed in both axial directions.

30. The medical device as claimed in claim 26, wherein the size of the further pores is at least 50 μm, in particular at least 100 μm, in particular at least 200 μm, in particular at least 300 μm.

31. The medical device as claimed in claim 26, wherein the separation of the further pores with respect to each other is at least 1 multiple, in particular at least 1.5 multiples, in particular at least 2 multiples, in particular at least 2.5 multiples of the diameter of the further pores.

32. The medical device as claimed in claim 1, wherein on expansion of the mesh structure, the fabric remains at least 0.25 mm, in particular at least 0.5 mm, in particular at least 1 mm within the internal profile of the mesh structure.

33. The medical device as claimed in claim 1, wherein on expansion of the mesh structure, the fabric protrudes into the overall lumen by at most 10% of the overall lumen, in particular by at most 5% of the overall lumen, in particular by at most 2% of the overall lumen.

34. The medical device as claimed in claim 1, wherein the circumferential contour of the covering is marked at least in sections, preferably around the full circumference, by a radiopaque agent.

35. The medical device as claimed in claim 1, wherein the fabric itself contains a radiopaque agent.

36. A medical set for the treatment of aneurysms, with a main catheter, a medical device as claimed in claim 1 for covering an aneurysm which can be moved through the main catheter to a treatment site, wherein the device is connected to or can be connected to a transport wire, wherein the mesh structure of the device comprises webs which are connected together into one piece and which define inner cells as well as edge cells, wherein the edge cells form a closed edge cell ring at a longitudinal end of the mesh structure and which is connected to inner cells on only one side, wherein at least one inner cell of the mesh structure is at least partially, preferably to a major extent, without a covering.

37. A method for the production of a medical device for introduction into a hollow body organ, in particular as claimed in claim 1, wherein the method comprises the following steps: a providing a compressible and expandable mesh structure formed from mesh elements, which delimit closed cells of the mesh structure, wherein each closed cell is delimited by four respective mesh elements; b. coating the mesh structure with a bonding agent, in particular produced front polyurethane; and c. applying a covering to the mesh structure by means of an electrospinning process.

38. The method as claimed in claim 37, characterized in wherein coating of the mesh structure is carried out with the bonding agent by means of a dip coating process.

39. The method as claimed in claim 37, wherein the bonding agent and the covering respectively comprise a synthetic material, in particular from the same group of materials, preferably polyurethane.

Description

[0075] The invention will now be explained in more detail with the aid of exemplary embodiments and with reference to the accompanying drawings, in which:

[0076] FIG. 1 shows a side view of a medical device in accordance with the invention according to a preferred exemplary embodiment;

[0077] FIG. 2 shows a scanning electron microscope image of a covering of a medical device in accordance with the invention according to a preferred exemplary embodiment;

[0078] FIG. 3 shows a scanning electron microscope image of a covering of a medical device in accordance with the invention according to a further exemplary embodiment;

[0079] FIG. 4 shows a perspective view of a mesh structure of a medical device in accordance with the invention according to a further preferred exemplary embodiment;

[0080] FIG. 5 shows a scanning electron microscope image of a covering of a medical device in accordance with the invention according to a further preferred exemplary embodiment, at 500× magnification;

[0081] FIG. 6 shows a scanning electron microscope image of the covering of FIG. 5, under 3500× magnification;

[0082] FIG. 7 shows a diagrammatic representation of a medical device in accordance with the invention according to a further preferred exemplary embodiment with a partially applied fabric in the implanted state; and

[0083] FIG. 8 shows a diagrammatic representation of a medical device in accordance with the invention according to a further preferred exemplary embodiment with a partially perforated fabric, in the implanted state.

[0084] The accompanying figures show a medical device which is suitable for introduction into a hollow body organ. The medical device in this regard in particular has a mesh structure 10 which is compressible and expandable. In other words, the mesh structure 10 may take up a delivery state, in which the mesh structure 10 has a relatively small cross sectional diameter. The mesh structure 10 is preferably self-expandable, so that the mesh structure 10 can expand by itself to a maximum cross sectional diameter without the influence of external forces. The state in which the mesh structure 10 has a maximum cross sectional diameter corresponds to the expanded state. In this state, the mesh structure 10 does not exert any radial forces.

[0085] Preferably, the mesh structure 10 is one-piece in configuration. In particular, at least portions of the mesh structure 10 may be cylindrical. Preferably, the mesh structure 10 is produced from, a tubular blank by laser cutting. In this regard, individual mesh elements or webs 11, 12, 14 of the mesh structure 10 are exposed by the laser cutting process. The regions removed from the blank form, cells 30 of the mesh structure 10.

[0086] The cells 30 have a substantially diamond-shaped basic shape. In particular, the cells 30 are delimited by four respective webs 11, 12, 13, 14. The webs 11, 12, 13, 14 in the exemplary embodiment that is depicted here have an at least partially curved profile, in particular S-shaped. Other shapes for the webs are possible.

[0087] The cells 30 each have cell tips 31, 32 which form the corner points of the diamond-shaped basic shape. The cell tips 31, 32 are respectively disposed at web connectors 20 which each connect four webs 11, 12, 13, 14 together into one piece. Four respective webs 11, 12, 13, 14 extend from each web connector 20, whereupon two cells 30 are associated with each web 11, 12, 13, 14. The respective webs 12, 13, 14 delimit the cell 30.

[0088] FIG. 1 shows the mesh structure 10 in the expanded state. It can readily be seen that the web connectors 20 are substantially respectively disposed on a common circumferential line. Overall, then, a plurality of cells 30 form a cell ring 34 in the circumferential direction of the mesh structure 10. A plurality of cell rings 34 connected together in the longitudinal direction form the entire mesh structure 10. In the exemplary embodiment shown, the cell rings 34 each comprise six cells 30.

[0089] In this regard, it should be noted here that the mesh structure 10 may be formed by interconnected cell rings which have the same cross sectional diameter only in sections. Rather, it is also possible for sections of the mesh structure 10 to have a geometry which differs from that of a cylinder. As an example, the mesh structure may be funnel-shaped at least at a proximal end. A configuration of this type is advantageous in medical devices which are employed to capture thrombi or, more generally as thrombectomy devices. In these cases, the mesh structure 10 may essentially form a basket-like structure.

[0090] Mesh structures 10 which are completely cylindrical in configuration are in particular used in medical devices which form a stent. Stents can be used to support blood vessels or, more generally, hollow body organs and/or for covering aneurysms.

[0091] When the mesh structure 10 is deployed from a catheter or, more generally, a feeding system, the mesh structure 10 expands radially outwards by itself. In this regard, the mesh structure 10 passes through a plurality of levels of expansion until the mesh structure 10 reaches the implanted state. In the implanted state, the mesh structure 10 preferably exerts a radial force on the surrounding vessel walls. In the implanted state, the mesh structure 10 preferably has a cross sectional diameter which is approximately 10%-30%, in particular approximately 20% smaller than the cross sectional diameter of the mesh structure 10 in the expanded state. The implanted state is also described as the “intended use configuration”.

[0092] As can readily be seen in FIG. 1, radiographic markers 50 are provided in the medical device. The radiographic markers 50 are disposed at cell tips 31, 32 on the edge cells 30 of the mesh structure 10. Specifically, the radiographic markers 50 may be formed as radiopaque sleeves, for example produced from platinum or gold, which are crimped onto the cell tips 31, 32 of the edge cells 30. In FIG. 1, it can be seen that each longitudinal end of the mesh structure 10 has three respective radiographic markers 50.

[0093] The mesh structure 10 of FIG. 1 can be divided into three sections. Two edge sections, which are each formed by two cell rings 34, are connected via a central section which comprises five cell rings 34. The cells 30 of the central section essentially have a diamond-shaped geometry, wherein all of the webs 11, 12, 13, 14 of the cells 30 of the central section have essentially the same length. The edge cell rings 34 each have cells 30 in which two of the directly adjacent webs 11, 12, 13, in the circumferential direction are each longer in configuration than the two webs 11, 12, 13, 14 of the same cell 30 which are adjacent in the axial direction. In this manner, the edge cells 30 essentially form a kite-like basic shape.

[0094] The medical device of FIG. 1 furthermore comprises a covering 40 which is disposed on an outer face of the mesh structure 10. The covering 40 bridges the entire mesh structure 10 and in particular covers the cells 30. The covering 40 is formed from an electrospun fabric and is therefore characterized by a particularly thin wall. At the same time, the covering 40 is sufficiently stable to follow an expansion of the mesh structure 10. Preferably, the covering 40 is completely and securely connected to the mesh structure 10. Specifically, the covering 40 is preferably bonded to the webs 11, 12, 13, 14, for example by means of a bonding agent which is applied to the mesh structure 10 by means of a dip coating process.

[0095] The covering 40 may extend over the entire mesh structure 10, as can be seen in FIG. 1. Alternatively, it is possible for the covering 40 to extend over only a portion of the mesh structure 10. As an example, edge cells at one axial end or at both axial ends of the mesh structure 10 may be without a covering. In this regard, the covering 40 may stop before the last or penultimate cell ring 34 of the mesh structure 10. The cell rings 34 which are without a covering allow for good coupling to a transport wire. In addition, the edge cells, which in any case barely participate in covering an aneurysm but ought to serve as anchors in a blood vessel, provide a high permeability in this mariner, so that the internal wails of the vessel can be properly supplied with nutrients in this region. The region of the medical device which has the covering 40 can be highlighted by radiographic markers.

[0096] The configuration of the covering 40 can readily be discerned from the scanning electron microscope images of FIGS. 2 and 3. These show that the covering 40 has a plurality of irregularly sized pores 41 which are each delimited by filaments 42. By means of the electrospinning process, a plurality of filaments 42 are formed which are orientated in an irregular manner with respect to each other. This forms the pores 41. FIG. 2 also shows that the pores 41 have comparatively small pore sizes, wherein some pores 41 are sufficiently large, however, to ensure blood permeability. Specifically, in FIG. 2, four pores 41 have been graphically highlighted with a size of more than 30 μm.sup.2. The density of the pores 41 with a size of more than 30 μm.sup.2 indicates that the covering has at least 10 pores 41 of this type over an area of 100,000 μm.sup.2.

[0097] FIG. 3 shows a further exemplary embodiment of a covering 40, in which a generally larger pore size has been set. It can be seen that some pores 41 have a size of more than 30 μm.sup.2 wherein, however, a pore size of 300 μm.sup.2 is not exceeded.

[0098] Perfusion of covered side branches (vessels) can be significantly influenced by the coating duration during production. As an example, a stent which is coated for 1 minute results in a side branch flow reduction of approximately 10-40%. As an example, a stent which is coated for 2 minutes results in a side branch flow reduction of approximately 40-70%. As an example, a stent which is coated for 4 minutes results is a side branch flow reduction of approximately 70-93%. The longer the fabric is applied to the mesh structure 10 by electrospinning using the spinning process, the denser and less porous will the fabric become. In this manner, the perfusion of side branches (vessels) can be deliberately influenced.

[0099] FIGS. 2 and 3 respectively show that the filaments 42 of the covering 40 intersect multiple times. A particular feature of the electrospinning process is, however, that in the covering 40, sites are present at which exclusively, i.e. not more than, two filaments 42 intersect. It is clear from this that the covering 40 overall has very thin walls and is therefore highly flexible.

[0100] The high flexibility of the covering 40 in combination with the high flexibility of the mesh structure 10 means that a medical device, in particular a scent, can be provided which can be introduced into a blood vessel by means of very small delivery catheters. In particular, delivery catheters can be used with a size of 6 French, in particular at most 5 French, in particular at most 4 French, in particular at most 3 French, in particular at most 2 French. Specifically, in the exemplary embodiments described herein, the medical devices can be used in catheters which have an internal diameter of at most 1.6 mm, in particular at most 1.0 mm, in particular at most 0.7 mm, in particular at most 0.4 mm.

[0101] The layer thickness of the covering 40 in particularly preferred variations is at most 10 μm, in particular at most 8 μm, in particular at most 6 μm, in particular at most 4 μm. In this, at most 4, in particular at most 3, in particular at most 2 filaments 42 intersect. In general, within the electrospun structure of the covering 40, intersecting points are present in which only 2 filaments 42 intersect. Preferably, the mesh structure 10 has a cross sectional diameter of between 2.5 mm and 8 mm, in particular between 4.5 mm and 6 mm.

[0102] FIG. 4 shows a braided mesh structure 10 which, in a preferred exemplary embodiment, can form a support for a covering 40. The braided mesh structure 10 is formed by a single wire 16 which is braided into a tube. The wire ends are connected within the mesh structure 10 with a connecting element 18.

[0103] The wire 16 has a plurality of sections which are described as the mesh elements 11, 12, 13, 14. Each section of the wire 16 which runs between two intersecting points 19 is described as an autonomous mesh element 12, 13, 14. Clearly, four respective mesh elements 11, 12, 13, 14 delimit a mesh or cell 30.

[0104] The braided mesh structure 10 has flaring axial ends which are described as flares 17. The wire 16 is turned around in each flare 17 and forms end loops 15. Overall, in the exemplary embodiment shown, six end loops 15 are provided at each flare 17. Alternate end loops 15 carry a radiographic marker 50 in the form of a crimp sleeve. Thus, three respective radiographic markers 50 are present on each axial end of the mesh structure 10.

[0105] FIGS. 5 and 6 show an exemplary embodiment of the device in accordance with the invention in different magnifications of a scanning electron microscope image. The device comprises a mesh structure 10 in accordance with FIG. 4 which is formed with a covering 40 produced from an electrospun fabric. The covering 40 is disposed on an outer face of the tubular mesh structure 10.

[0106] FIG. 5 shows a 500× magnification of a region of the device which comprises a cell tip 32 of the mesh structure 10. At the cell tip 32, two mesh elements or webs 11, 13, of a cell 30 meet. The covering 40 covers the webs 11, 12. It can be seen that the covering 40 has a plurality of pores 41, i.e. completely free through openings, of different sizes. The porosity is adjusted in this regard so that the covering 40 forms a good barrier to perfusion, but at the same time allows the passage of nutrients.

[0107] The 3500× magnification of FIG. 6 shows a section of the covering 40 of FIG. 5 in detail. The profile of the individual filaments 42 of the electrospun fabric can clearly be seen. The filaments 42 delimit pores 41, wherein the pores 41 are irregular in configuration. In each case it can be seen that some pores 41 have a larger through area than other pores 41. The larger pores 41 allow the passage of nutrients through the covering 40.

[0108] FIG. 7 shows the mesh structure 10 of an exemplary embodiment (stent) in accordance with the invention in the implanted state, wherein the covering 40 is disposed on the mesh structure 10 in the region of the aneurysm neck and bridges it. The covering 40 is disposed on a part circumference or on an angled segment of the mesh structure 10. In the example, the fabric or the covering covers approximately half the circumference of the mesh structure 10 or the stent. Another level of coverage, i.e. more or less than half the circumference of the mesh structure 10, is possible. As can be seen in FIG. 7—in contrast to FIG. 8—there are no other pores provided in the fabric apart from the pores formed by electrospinning. The properties of the fabric are therefore determined only by the pores formed during the electrospinning production process.

[0109] FIG. 8 shows a further exemplary embodiment of the invention in which, as in FIG. 7, the mesh structure 10 is implanted for the treatment of an aneurysm. In contrast to FIG. 7, the covering 40, in particular the fabric, is applied entirely around the circumference of the mesh structure 10 and in fact by electrospinning. A portion of the covering 40, specifically the portion of the covering 40 which is opposite the aneurysm neck, is perforated in addition to the pores formed by electrospinning. This is achieved by a secondary treatment of the fabric, for example by laser cutting. The further pores 43 which are formed in the fabric in this manner are larger than the pores formed by electrospinning, as can be seen in FIG. 8. In the example of FIG. 8, four further pores 43 are formed per cell. The number of further pores 43 can vary. In contrast to the pores formed by electrospinning, the further pores 43 are geometrically defined, and are circular, for example. This is made possible because of the laser cutting.

[0110] The additional perforation of the fabric enables the perfusibility of the fabric to be specifically influenced, for example in order to improve the blood supply to the side branches, without in any way compromising the treatment of the aneurysm.

REFERENCE LIST

[0111] 10 mesh structure

[0112] 11, 12, 13, 14 web or mesh element

[0113] 15 end loop

[0114] 16 wire

[0115] 17 flare

[0116] 18 connecting element

[0117] 19 intersecting point

[0118] 20 web connector

[0119] 30 cell

[0120] 31, 32 cell tip

[0121] 34 cell ring

[0122] 40 covering

[0123] 41 pore

[0124] 42 filament

[0125] 43 further pores

[0126] 50 radiographic marker