MEDICAL IMPLANT FOR THE TREATMENT OF ANEURYSMS

Description

[0001] The invention relates to a medical implant for the treatment of aneurysms according to the preamble of claim 1. Such an implant is known, for example, from EP 2 678 466 B1, US 2014 / 358221 A1 or DE 10 2018 131269 A1.

[0002] EP 2 678 466 B1 relates to a stent for neurovascular applications covered with a fibrous fleece. The fleece is produced by electrospinning and comprises several layers, with an inner layer being fluid-impermeable and an outer layer having a sponge-like structure. The inner layer serves to encapsulate an aneurysm from the blood flow within a blood vessel. The outer, sponge-like layer is intended to allow the deposition of endothelial cells and / or medication. The disadvantage of the known implant is that it can only be used for aneurysms located far from a branching blood vessel, arteries, or arterioles. When using the known implant on aneurysms located near a vascular branch, there is a risk that the branching blood vessel will also be isolated from the blood flow.

[0003] As a result, a significant supply shortage can occur in tissue areas that are supposed to be supplied with oxygen and nutrients by the branching blood vessel.

[0004] Against this background, the invention is based on the objective of providing a medical implant for the treatment of aneurysms that, on the one hand, enables efficient coverage of an aneurysm and, on the other hand, ensures that the blood supply to branching blood vessels continues to be guaranteed.

[0005] This problem is solved by the subject matter of claim 1.

[0006] The invention is based on the concept of providing a medical implant for the treatment of aneurysms with a support structure comprising a compressible and expandable lattice structure made of lattice elements that define lattice openings. The lattice structure is at least partially covered by a membrane formed or consisting of fibers. The membrane comprises at least one luminal functional layer and at least one abluminal support layer, each of which has pores. The porosity of the functional layer is lower than that of the support layer.According to the invention, the membrane is configured such that at least the pores of the luminal functional layer of the membrane open to increase the fluid flow through the membrane as a result of a pressure gradient that arises between a fluid pressure in an inner passage channel of the support structure and a fluid pressure outside the abluminal support layer.

[0007] The invention is based on the idea of ​​making the membrane act intelligently, so that it becomes more permeable to fluid when a pressure gradient exists between the fluid pressure in the inner channel of the support structure and the fluid pressure outside the membrane. In the implanted state, the pores of the membrane, particularly in the functional layer, open when the membrane, which is inserted into a main blood vessel along with the implant, spans a branching blood vessel, thus creating a pressure gradient between the main blood vessel, in particular an artery, and a branching artery or arteriole. The blood flowing through the main vessel into the branching blood vessel, in particular the branching artery or arteriole, has a fluid pressure that forces the blood into the branching blood vessel or arteriole.The inner membrane is designed so that this fluid pressure is sufficient to open the pores of at least the functional layer of the membrane locally to such an extent that it becomes permeable to blood at points where blood vessels, especially arteries or arterioles, branch off. In particular, the membrane is adapted to be sufficiently permeable to ensure that tissue areas connected by the branching blood vessels or arterioles are adequately supplied with oxygen and nutrients.

[0008] In areas where the implant covers an aneurysm, such a pressure gradient is not present, so the membrane pores remain closed, thus efficiently shielding the aneurysm from blood flow within the blood vessel. In any case, the shielding is intended to be more efficient than with previously known or conventional flow diverter implants.

[0009] The occlusion does not need to create a complete fluid barrier. Rather, a significantly reduced fluid exchange between the blood within the aneurysm and the blood within the main vessel can be maintained. However, occlusion of the aneurysm is sufficient to reduce blood flow within the aneurysm to such an extent that the blood clots within the aneurysm, forming a thrombus. In this way, the aneurysm is effectively sealed off, with the implant membrane preventing the thrombus from leaving the aneurysm. The formation of a thrombus reduces the pressure on the aneurysm wall, thus reducing the risk of aneurysm rupture and the associated blood loss or hemorrhagic stroke.

[0010] The advantage of the implant according to the invention is obvious. When treating aneurysms, particularly cerebral aneurysms, using the implant according to the invention, it is not essential for the surgeon to precisely determine the implant's position. In particular, the surgeon does not need to ensure that an implant of a specific length is used to prevent the covering of branching blood vessels. This applies especially to smaller branching blood vessels, the so-called "perforating arteries," which typically have a diameter between 300 µm and 850 µm, and branching arterioles, which usually have a diameter between 50 µm and 300 µm. Rather, it is possible to use the medical implant in a standard length for any type of aneurysm, since the implant allows blood flow into branching blood vessels, particularly arteries.This allows for the treatment of aneurysms even when the implant covers the branching blood vessel, particularly arteries and branching arterioles. This significantly facilitates and speeds up the treatment of aneurysms.

[0011] Preferably, the membrane comprises an electrospun fabric forming the fibers. The fabric is preferably multilayered and composed of fibers with different properties. In particular, the fabric can comprise the support layer and the functional layer, each composed of fibers exhibiting different properties, especially different elasticities and / or fiber thicknesses. The membrane preferably has a relatively low porosity on the luminal side, i.e., the side facing the main vessel lumen, which increases under a pressure gradient (thus constituting the actual functionality), and a relatively higher porosity on the abluminal side, i.e., the side facing the vessel wall, which provides support.In this respect, the present application distinguishes between the luminal functional layer, which determines the functionality of the intelligent membrane, and the abluminal support layer, which supports the functional layer. The support layer's porosity remains essentially unchanged, or at least minimally so, under the influence of a pressure gradient created by a branching blood vessel or arteriole. Furthermore, the support layer can be designed to prevent the fibers of the functional layer from migrating radially.

[0012] The functional layer and the support layer can differ, in particular, in the type of fiber arrangement. Preferably, the support layer comprises or consists of fibers that are predominantly cross-linked, thus forming a stable layer. The freedom of movement of the fibers in the support layer is limited by this cross-linking. The functional layer, on the other hand, can be formed from or comprise fibers that are predominantly loosely arranged. This allows for greater freedom of movement of the fibers, so that larger pores can be formed by fiber displacement. Preferably, the fibers of the support layer have a relatively larger diameter and a relatively higher tensile strength or Shore hardness, whereas the fibers of the functional layer can have a relatively smaller diameter and a relatively lower tensile strength or Shore hardness.

[0013] In principle, the functional layer and the support layer can be designed to form clearly distinct layers. However, it is also possible that the functional layer and the support layer are not clearly distinguishable, but rather that these areas of differing porosity merge seamlessly into one another. The membrane preferably represents a compromise between functionality (opening or not opening the pores through movement or deformation of the fibers) and support function. In this case, the areas of differing porosity, particularly the functional layer and the support layer, can blend together to such an extent that the functional layer and the support layer are indistinguishable in the direction of the pressure gradient. Instead, the membrane as a whole can exhibit an almost uniform porosity in the direction of the pressure gradient. The above applies to the unloaded state of the membrane, i.e., without the influence of the pressure gradient.Under the influence of the pressure gradient, some of the fibers in the functional layer of the membrane move or deform, creating larger pores. This makes the membrane sufficiently permeable to blood, allowing branching blood vessels to deliver adequate oxygen and nutrients to downstream tissue areas. The deformation can be elastic or plastic. In any case, the formation of the larger pores is intended to occur without fiber tearing. Rather, the enlargement of the pores can occur non-destructively and can be reversed just as non-destructively, for example, if the pressure gradient between the fluid pressure in the inner channel of the supporting structure and the fluid pressure outside the supporting layer decreases.

[0014] Preferably, the functional layer and the support layer are bonded together. In particular, individual fibers of the functional layer and the support layer can cross over or under each other, forming a uniform membrane. The luminal functional layer and the abluminal support layer preferably differ in their porosity and the associated function. While the abluminal support layer is primarily intended to stabilize the membrane as a whole and hold the fibers of the luminal functional layer in their predetermined position, the functional layer serves to efficiently shield an aneurysm from blood flow. At the same time, however, the functional layer can open to allow blood flow into a branching blood vessel, thus ensuring the blood supply to downstream tissue areas.

[0015] The membrane preferably comprises a functional layer and a support layer. However, this does not preclude the membrane from also having further layers, for example, two or more functional layers and / or two or more support layers and / or other layers. Furthermore, the membrane can have a coating, for example, with antithrombogenic properties. This coating is designed such that each individual fiber of the membrane is encased in the coating.

[0016] To ensure blood flow through the functional layer at points where a blood vessel branches off from the main vessel into which the implant is inserted, a preferred embodiment of the invention provides that the fibers of the membrane, in particular at least the fibers of the functional layer, are loosely arranged one on top of the other at intersection points, so that intersecting fibers are movable relative to each other at these intersection points. In other words, the intersecting fibers of the inner membrane can slide against each other, allowing the pores defined by the fibers to open due to the pressure gradient described above. This creates a flow area through which blood can be directed into a branching blood vessel.

[0017] Alternatively or additionally, the fibers of the membrane, in particular at least the fibers of the functional layer, can be elastic and / or plastically deformable in order to deflect in the event of a pressure gradient and form enlarged pores, so that locally sufficient blood flow for the blood supply of downstream tissue areas is achieved into a branching blood vessel, in particular an artery or a branching arteriole.

[0018] For the advantageous function according to the invention, namely that the luminal functional layer can open section by section or locally to allow blood or fluid passage, it is advantageous if the functional layer exhibits high flexibility. In particular, the fibers of the functional layer should be as flexible as possible to allow deformation that leads to an enlargement of the pores of the functional layer. The enlargement of the pores preferably occurs non-destructively or without the formation of fiber cracks. In this respect, it is preferred if the fibers of the functional layer have a particularly small fiber thickness. The fiber thickness can be, in particular, less than 500 nm, in particular at most 400 nm, in particular at most 300 nm, in particular at most 200 nm, and in particular at most 100 nm. The abluminal support layer, which has a stabilizing function, should, on the other hand, comprise more stable fibers.This can be achieved by ensuring that the fibers of the support layer have a fiber thickness of at least 500 nm, in particular at least 750 nm, in particular at least 1000 nm, in particular at least 1250 nm, in particular at least 1500 nm.

[0019] A preferred design of the medical implant also contributes to the function of the functional layer, which allows blood flow into branching blood vessels while simultaneously efficiently shielding an aneurysm from blood flow in the main vessel. In this design, the functional layer has a thickness of at most, and in particular less than, 10 µm, in particular at most 8 µm, in particular at most 6 µm, in particular at most 4 µm, and in particular at most 2 µm. Similarly, the stabilizing function of the support layer is enhanced if it has a thickness of at least 3 µm, in particular at least 5 µm, in particular at least 6 µm, in particular at least 7 µm, and in particular at least 8 µm.

[0020] To effectively shield an aneurysm, a particularly low porosity of the functional layer is advantageous. Therefore, in a preferred embodiment of the invention, the functional layer is provided to have a porosity of less than 50%, in particular at most 40%, and in particular at most 30%. The supporting layer, which is intended to be permanently permeable to blood, can, on the other hand, have a porosity of at least 50%, in particular at least 60%, in particular at least 70%, in particular at least 80%, and in particular at least 90%. For the purposes of this application, porosity is understood to be the ratio between the open area of ​​a tissue, i.e., the sum of the areas of all pores, and the total area of ​​that tissue.

[0021] Particularly preferred is a variant of the medical implant in which the functional layer comprises at least 10 pores on an area of ​​100,000 µm 2< having an incircle diameter of at most 10 µm, in particular at most 8 µm, in particular at most 6 µm, in particular at most 4 µm, in particular at most 2 µm, in particular at most 1 µm. Alternatively or additionally, the support layer can comprise at least 5 pores, in particular at least 10 pores, on an area of ​​100,000 µm 2<, which have an incircle diameter of at least, in particular more than, 10 µm, in particular at least 15 µm, in particular at least 20 µm, in particular at least 25 µm, in particular at least 30 µm, in particular at least 40 µm, in particular at least 50 µm, in particular at least 60 µm.

[0022] With regard to the different functions of the functional layer and the support layer, whereby the functional layer should have a flexibility that allows blood flow through it under a corresponding pressure gradient, and the support layer should stabilize the functional layer so that it does not detach from the support structure, it is advantageous if the fibers of the functional layer have a smaller fiber thickness than the fibers of the support layer.

[0023] Therefore, it is also preferred if the functional layer or its fibers have a higher elasticity than the support layer or its fibers.

[0024] The fibers of the functional layer may be made of a material with a lower Shore hardness than the material of the fibers of the support layer. In particular, the material of the fibers of the functional layer may have a Shore hardness of at most 90A, in particular at most 80A, in particular at most 70A, in particular at most 60A, in particular at most 50A, and / or the material of the fibers of the support layer may have a Shore hardness of at least 90A, in particular at least 100A, in particular at least 60D, in particular at least 70D, in particular at least 80D.

[0025] The membrane, in particular the functional layer and the support layer, can be made of a thermoplastic polyurethane. This does not preclude the functional layer and / or the support layer from each comprising other plastic materials. In a preferred embodiment, however, the functional layer and the support layer are made of a thermoplastic polyurethane. It is also possible for the functional layer or the support layer, in particular the functional layer and the support layer, or the membrane as a whole, to be made of an absorbable or resorbable material. In this respect, it can be provided that the functional layer and / or the support layer dissolve over a certain period of time through contact with blood, so that after this period only the support structure remains in the blood vessel. Preferably, the absorbable or resorbable material is selected or...It is designed to dissolve after or within a period during which the aneurysm shielded by the functional layer is occluded. In other words, the functional layer and / or the supporting layer should not dissolve until the aneurysm has been occluded.

[0026] The fibers of the functional layer can also be configured as concentric fibers. Such concentric fibers comprise a fiber core and a fiber sheath. The fiber core is preferably made of a softer material than the fiber sheath, which is also thinner. The fiber sheath can be made of a relatively harder material. In this way, high flexibility of the individual fibers can be achieved via the fiber core, allowing the fibers to deform readily to create pores when a pressure gradient is applied to the membrane.The fiber core can be made of a material with a Shore hardness of at most 90A, in particular at most 80A, in particular at most 70A, in particular at most 60A, in particular at most 50A, and / or the material of the fiber sheath can have a Shore hardness greater than 90A, in particular at least 100A, in particular at least 60D, in particular at least 70D, in particular at least 80D. The relatively harder material of the fiber sheath, on the other hand, serves to enable good sliding of the fibers against each other, so that good pore enlargement is also achieved via fiber displacement.

[0027] In a preferred embodiment of the invention, the membrane can extend completely around the circumference of the support structure. While it is also conceivable that the membrane extends only partially around the circumference of the support structure, for example, to allow blood flow from the afferent blood vessel to the two branching vessels in bifurcation aneurysms, the preferred embodiment in which the membrane extends completely around the circumference of the support structure offers particular advantages. Firstly, in such an embodiment, the medical implant can be manufactured particularly easily in series production. Secondly, the circumferentially closed membrane inherently provides stabilization, ensuring that the membrane adheres to the support structure and does not detach from it. In particular, the support structure can thus perform its stabilizing function with exceptional efficiency.

[0028] Several variations are conceivable with regard to the support structure. On the one hand, the support structure can be monolithic, with the grid elements forming webs that define the grid openings, which are configured as cells. In other words, the support structure can have a grid structure cut from a tubular material. This can be done, for example, by laser cutting. Cutting the tubular material creates webs that define the cells. On the other hand, the support structure can also consist of interwoven wires, with the wires forming the grid elements and defining the grid openings, which are configured as meshes. In this variation, the support structure thus has a network of interwoven wires that forms the grid structure.The wires cross over and under each other, forming meshes between the intersecting wires. It is also possible for the support structure to consist of wire elements or to comprise wire elements that do not cross (wire forming). Alternatively, the wire elements can be arranged in a common circumferential plane and connected to each other, for example, by spot welds. It is also possible to produce a monolithic support structure using a combination of lithography and a sputtering process, such as physical vapor deposition (PVD), particularly magnetron sputtering.

[0029] It is advantageous for the use of the medical implant according to the invention if it exhibits good flexural flexibility and can expand readily from a minimally compressed state to a maximally expanded state. This expansion can preferably occur automatically by using suitable superelastic materials, for example, shape memory alloys. In this respect, the support structure can, in particular, be self-expanding. The implant can also incorporate or consist of shape memory polymers.

[0030] Although in a preferred embodiment of the invention the lattice elements of the support structure comprise or consist of a self-expanding shape-memory alloy such as Nitinol, it is also conceivable to manufacture the support structure from balloon-expandable materials such as stainless steel or CoCr alloys. The latter is particularly advantageous if the support structure is to have a particularly short length and / or a particularly high radial force.

[0031] Good flexibility of the implant, both in terms of bending flexibility and expansion capacity, can be achieved by appropriately adjusting the ratio between the total thickness of the membrane and the height of the grid elements or the wall thickness of the support structure. In a particularly preferred embodiment, the membrane has a thickness that is at most 40%, more specifically at most 30%, more specifically at most 20%, more specifically at most 10%, of the height of the grid elements, in particular the bars or wires.

[0032] In a monolithic support structure, the height of the grid elements corresponds to the height of the webs or the wall thickness of the support structure. In a support structure formed by interwoven wires, the height of the grid elements corresponds to the wire diameter. The overall wall thickness of the support structure differs from this, as the wires cross over each other in places, so that the wall thickness of the support structure is twice the height of the grid elements, i.e., the wire diameter. In any case, the overall thickness of the membrane is limited to ensure that the membrane has high flexibility to readily accommodate curvature or expansion of the support structure.

[0033] Furthermore, it is beneficial for the overall flexibility of the implant if, as is preferably provided, the grid elements, in particular the bars or the wires, have a height between 40 µm and 160 µm, in particular between 40 µm and 150 µm, in particular between 40 µm and 130 µm, in particular between 40 µm and 110 µm, in particular between 40 µm and 100 µm, in particular between 50 µm and 90 µm, in particular between 50 µm and 80 µm.

[0034] In general, for preferred variants of the implant according to the invention, it can be specified that the ratio between the thickness of the membrane and the height of the grid elements, in particular the struts or the wires, is at most 1 / 3, in particular at most 1 / 4, in particular at most 1 / 5, in particular at most 1 / 8, in particular at most 1 / 10, in particular at most 1 / 12, in particular at most 1 / 15, in particular at most 1 / 20. In other words, the grid elements are preferably two to ten times, in particular three to eight times, in particular four to six times, as high as the total thickness of the membrane.

[0035] Furthermore, it is advantageous if the implant is clearly visible under X-ray guidance. This makes it easier for the surgeon to determine the implant's position within the blood vessel and to verify that the membrane is functioning correctly (protecting an aneurysm while simultaneously ensuring good perfusion of branching blood vessels or arterioles). Therefore, the implant may be designed to be at least partially or locally coated with radiopaque materials. Such materials can include gold, platinum, or tantalum, as well as alloys thereof.

[0036] For example, radiopaque markers, such as loops, coils, or sleeves, can be arranged at the longitudinal ends of the support structure. Three radiopaque markers per longitudinal end are particularly advantageous for making the implant detectable. It is also possible for such radiopaque markers to be arranged additionally or alternatively in a central region of the support structure. Additional threads with enhanced radiolucency can also be woven into the support structure. In particular, such a thread can be wound around a series of aligned grid elements. This thread can be made of a so-called DFT (drawn-filled tube) wire.

[0037] Furthermore, it is conceivable that at least individual grid elements of the support structure comprise a radiopaque core material encased in a shape-memory material (DFT wire). Likewise, at least some, preferably all, fibers of the membrane can be provided with a radiopaque core material and a sheathing of another material, e.g., polyurethane. To improve radiopaqueness, radiopaque materials can also be arranged between the functional layer and the support layer. For example, at least one radiopaque nonwoven or at least one radiopaque tape can be arranged between the functional layer and the support layer. Finally, it is also possible to apply or integrate the radiopaque material, in particular tantalum, niobium, platinum, or gold, onto or into the support structure using sputtering technology (especially magnetron sputtering).The fibers can also be made from a plastic mixed with an X-ray-resistant material. For example, a plastic can be mixed with at least 20% barium sulfate, so that the membrane is visible at least in still X-ray images.

[0038] In a further embodiment of the invention, the implant is provided with an antithrombogenic coating, such that each fiber of the membrane is encased in this coating. Such a coating has the advantage that the pores of the membrane, which are created by the movement of the membrane fibers, remain open and are not closed by the deposition of platelets.

[0039] Preferably, the coating comprises a layer thickness of at most 10 nm. The coating may comprise fibrin and / or heparin. In particular, the coating may have heparin covalently bonded to fibrin. Such a coating is described in DE 10 2018 110 591 A1, which is attributed to the applicant and to which reference is made regarding the composition of the coating.

[0040] In general, the membrane described here can be used not only (as part of the implant according to the invention) for the treatment of aneurysms, but also for other cerebral vascular diseases. An example of this is the treatment of arteriovenous malformations (AVMs) and arteriovenous fistulas. The porosity and flexibility of the membrane can be adjusted so that the arteriovenous shunt still supplies the veins with blood, but the inflow and thus the pressure build-up in the veins no longer leads to their rupture.

[0041] The membrane can be manufactured entirely using an electrospinning process. For example, the functional layer and the support layer can be produced independently of each other by electrospinning and then joined together on a substrate. Due to the nonwoven-like structure of the electrospun functional layer and the electrospun support layer, the two layers bond to form a single membrane, as fibers from the support layer are directly applied to the fibers of the functional layer via electrospinning, thus creating a material bond. The process parameters and / or materials for the production of the functional layer and the support layer differ to reflect their respective functions. However, it is also possible for the functional layer and the support layer to be produced in a single manufacturing step.An electrospinning process can be used for this purpose, in which different materials are deposited simultaneously, so that the membrane is created directly, fulfilling the functions of both the functional layer and the support layer. It is generally desirable that the overall thickness of the membrane, as well as the thicknesses of the functional and support layers, remain essentially constant along the membrane's length. However, it can also be advantageous to vary these thicknesses along the membrane's length.

[0042] In a preferred embodiment of the invention, the functional layer is perforated in the area of ​​the grid openings. The perforation can, in particular, consist of holes, straight slots, curved slots, and / or T-shaped slots. The perforation creates openings in the functional layer that facilitate the local opening of the functional layer in the event of a pressure difference between the fluid pressure in the inner channel of the support structure and the fluid pressure outside the support layer. The support layer arranged above limits the opening process, preventing the opening or perforation from expanding too far. This ensures that opening occurs even with small pressure gradients.The perforation is preferably designed such that a local opening of the functional layer occurs in areas exposed to a pressure gradient that typically exists between a main blood vessel and a branching blood vessel or a perforator vessel. In particular, the perforation is configured so that an opening of the functional layer is avoided in areas where a lower pressure gradient is present, for example, the pressure gradient that typically forms between a main blood vessel and an aneurysm. However, a local opening of the functional layer should still occur to allow blood to flow into a perforator vessel.

[0043] The perforation can be produced by laser processing of the membrane, especially the functional layer, and / or by solvent spraying.

[0044] During laser processing, the functional layer can be perforated with a pattern, particularly using a UV laser or a femtosecond or picosecond infrared laser. Suitable perforation patterns include holes, straight slits or cuts, gill-like curved slits, and / or T-shaped slits or cuts. A patterned distribution of the perforation over a larger area of ​​the membrane is generally preferred. This ensures that, when the implant is inserted, a perforation is positioned in front of any covered lateral vessel, thus allowing fluid to pass through the membrane into the vessel.

[0045] Solvent spraying generates a mist of fine droplets of a solvent or solvent-polymer mixture of a defined size. When the mist hits the functional layer, the fibers of the functional layer are dissolved, thus creating holes in the functional layer.

[0046] Furthermore, it is conceivable to create perforations by masking during the production of the membrane, particularly the functional layer. The functional layer can be masked in such a way that a perforation pattern is created or preserved during its formation through a spraying process. This manufacturing method is particularly suitable for creating holes as perforation patterns.

[0047] The medical implant according to the invention is preferably producible by a method comprising the following steps: a. Providing the support structure; b. Applying the functional layer to the support structure; c. Perforating the functional layer by a laser cutting process or by solvent spraying; and d. Applying the support layer to the functional layer.

[0048] As an alternative to creating perforations using a laser cutting process or solvent spraying, the functional layer can also be perforated by leaving certain areas unperforated during application. This can be achieved, for example, by using a mask that is placed on the substrate before the functional layer is sprayed and then removed afterward.

[0049] The described method enables the simple and efficient production of an implant with an intelligent membrane that can open in certain areas as a result of a sufficiently high pressure gradient to allow fluid passage.

[0050] Furthermore, it may be provided that an additional support layer is arranged between the support structure and the functional layer. This additional support layer may have fibers with a greater thickness than the fibers of the functional layer. Moreover, the density of the fibers in the support layer may be lower than the density of the fibers in the functional layer.

[0051] The invention is explained in more detail below with reference to exemplary embodiments and the accompanying schematic drawings. These show: Figure 1 shows a section of a blood vessel system in which a medical implant according to the invention is inserted; Figure 2 shows a detailed section of the implant according to the invention. Figure 1 in the case of covering an aneurysm; Figure 3 shows a detailed section of the implant according to Figure 1 in the case of covering a branching blood vessel; and Figs. 4 to 7 each show a side view of a medical implant according to the invention in preferred embodiments, in which the functional layer has a different perforation.

[0052] Figure 1 Figure 1 shows a section of a blood vessel system with a main vessel MV and three lateral vessels BV1, BV2, and BV3 branching off from the main vessel MV. The main vessel MV also has an aneurysm AN located between the second lateral vessel BV2 and the third lateral vessel BV3. In particular, the aneurysm is positioned close to the third lateral vessel BV3.

[0053] The medical implant according to the invention is used to treat aneurysm AN. The medical implant comprises a support structure 1 formed by a lattice structure 10 made up of lattice elements. The lattice elements can be webs 12 that are integrally connected to each other, thus forming the lattice structure 10. The webs 12 define cells 13 of the lattice structure 10. Alternatively, the lattice structure 10 can also be formed by interwoven wires. To make the lattice structure 10 or the support structure 1 visible under X-ray guidance during insertion of the implant into the blood vessel system or into the main vessel MV, X-ray markers 11 are provided at each longitudinal end of the lattice structure 10. Preferably, several X-ray markers 11 are arranged at each longitudinal end of the lattice structure 10, positioned at regular intervals along the circumference of the lattice structure 10.

[0054] The implant further comprises a membrane 2, which includes a luminal functional layer 4 and an abluminal support layer 3. The functional layer 4 and the support layer 3 preferably overlap completely, i.e., they have the same length in the longitudinal direction of the lattice structure 10. However, it is preferred if the support layer 3 extends beyond the functional layer 4 at least at its longitudinal ends, preferably by a few millimeters. As in Figure 1 As can be seen, the lattice structure can be 10 times longer than the membrane 2.

[0055] The implant is positioned in the main vessel MV in such a way that the implant, in particular the membrane 2, completely covers the neck of the aneurysm AN. An embolizing agent 30 can also be placed in the aneurysm AN. Specifically, the medical implant can be offered as a unit or as a set together with an embolizing agent 30. The embolizing agent 30 can, for example, be a gel. Alternatively, the embolizing agent 30 can also be formed by coils, i.e., chaotically winding microwires. The embolizing agent 30 can be introduced into the aneurysm AN after the implant has been inserted into the main vessel MV. For example, coils can be introduced into the aneurysm through the membrane 2 via a microcatheter. The membrane 2, or rather its fibers, are flexible enough that the microcatheter can widen the pores of the membrane 2 and thus create a path into the aneurysm AN.

[0056] As in the Figure 1As is also evident, membrane 2 spans not only the aneurysm AN, but also the second lateral vessel BV2 and the third lateral vessel BV3. This is where the special function of membrane 2 comes into play. Membrane 2 encompasses the abluminal support layer 3, which has a greater porosity than the luminal functional layer 4. The support layer 3 is so porous that it is permanently permeable to blood. The functional layer 4, on the other hand, is essentially only slightly permeable to blood, in particular semipermeable, and especially less permeable than the support layer 3. At the same time, however, the functional layer 4 is flexible enough that it becomes permeable to blood, or even more permeable, when subjected to a corresponding force. Such a required force can arise from the pressure gradient that develops between the blood pressure in the main vessel MV and the decreasing blood pressure in one of the lateral vessels BV1, BV2, or BV3.

[0057] Since the functional layer initially reduces blood flow into a lateral vessel BV1, BV2, BV3, a pressure gradient, or a greater pressure gradient, is created between the blood pressure in the main vessel MV and the corresponding lateral vessel BV1, BV2, BV3. This pressure gradient generates a force sufficient to widen the pores of the functional layer 4. This occurs because the fibers of the functional layer 4 are elastically and / or plastically deformed and / or slide against each other, so that the functional layer 4 becomes permeable to blood, or more permeable to blood, only in the area of ​​the branching blood vessel, i.e., locally in the area of ​​the opening into the corresponding lateral vessel BV1, BV2, BV3. The membrane 2 is "intelligent" in that it only allows blood flow at those points where the pressure gradient between the blood pressure in the main vessel MV and a pressure outside the outer membrane 50 is sufficiently high.This threshold is regularly exceeded locally at points on membrane 2 that cover lateral vessels BV1, BV2, and BV3 branching off from the main vessel MV. At the point on membrane 2 that spans the aneurysm AN, which opens from the main vessel MV, the pressure threshold is not exceeded; that is, the pressure gradient between the blood pressure in the main vessel MV and the pressure within the aneurysm AN is not large enough to dilate the pores of functional layer 4. Thus, the aneurysm AN remains shielded from the blood flow, so that the blood remaining in the aneurysm AN clots within a short time, and the aneurysm AN is thus occluded.

[0058] If, as in the exemplary embodiment according Figure 1Since an embolizing agent 30 is additionally placed in the aneurysm, the supporting layer 3, which essentially has a stabilizing function, also ensures that the embolizing agent 30 is retained in the aneurysm AN and thus does not move back into the main vessel MV. This further ensures that the aneurysm AN is occluded in a timely manner.

[0059] The Figures 2 and 3 Each figure shows a section of the implant with a support structure 1 and a membrane 2. The support structure 1 is formed by a lattice structure 10, wherein in the Figures 2 and 3Several struts 12 of the grid structure are shown. The struts 12 form cells 13 of the grid structure 10. In the illustrated embodiment, the struts 12 are monolithically connected to one another. The grid structure 10 is therefore formed in one piece. However, it is also possible for the grid structure 10 to be formed by wires that are intertwined or woven together.

[0060] Cell 13 is spanned by membrane 2. Membrane 2 comprises at least two layers, each formed by electrospun fibers. The layers differ in the thickness and density of the fibers.

[0061] Specifically, the membrane 2 has a support layer 3, which has a relatively lower density of threads with a relatively higher thread thickness. The support layer 3 thus differs from a functional layer 4, whose threads have a smaller thread thickness. Furthermore, the density of the threads in the functional layer 4 is higher than the density of the threads in the support layer 3. In other words, both the support layer 3 and the functional layer 4 have thread-bounded pores 5, which are larger in the support layer 3 than in the functional layer 4. This is true, at least, for the implant in its resting state, i.e., without external force being applied.

[0062] The functional layer 4 has the task of obstructing or at least slowing down blood flow through membrane 2. In this respect, functional layer 4 acts as a flow diverter, diverting blood flow along its surface. Due to its thin thread, the functional layer is relatively flexible. The support layer 3 stabilizes functional layer 4, thus preventing it from bulging radially and ensuring that it lies close to the support structure 1.

[0063] Figure 2This illustrates the principle of blood flow diversion. Membrane 2, which extends over cell 13, spans an aneurysm AN. There is hardly any relevant pressure gradient between the aneurysm AN and the main vessel MV, into which the implant is inserted, so that functional layer 4 essentially remains in its resting state. Consequently, functional layer 4 has a small pore size, so that the blood flow is mainly directed along functional layer 4 and does not penetrate significantly into the aneurysm AN. The aneurysm AN is thus largely decoupled from the blood flow in the main vessel MV and can be occluded by coagulation of the blood remaining in the aneurysm AN. Nevertheless, a small amount of blood can flow into the aneurysm through the pores of the membrane so that the coagulation process and the formation of a solid thrombus within the aneurysm are not interrupted.

[0064] Figure 3This illustrates the function of functional layer 4 when it spans a branching blood vessel, such as the second lateral vessel BV2. The pressure difference that arises between the main vessel MV and the second lateral vessel BV2 causes the fibers of functional layer 4 to deflect or deform locally. This enlarges the pores of functional layer 4 at the orifice of the second lateral vessel BV2. The fibers of supporting layer 3, on the other hand, are more stable and largely retain their position. However, the pores of supporting layer 3 are already large enough to allow blood flow through it. Thus, the enlargement of the pores of functional layer 4 at the orifice of the second lateral vessel BV2 is sufficient to enable adequate blood flow from the main vessel MV to the second lateral vessel BV2.

[0065] In the Figures 4 to 7Various embodiments of medical implants are shown, the functional layer 4 of which is equipped with a perforation 14. For the sake of clarity, the Figures 4 to 7 The support layer 3 is not shown.

[0066] Specifically, the Figures 4 to 7 Each stent has a support structure 1 designed as a lattice structure 10. The lattice structure 10 comprises several integrally coupled struts 12 that delimit cells 13. X-ray markers 11 are arranged at the longitudinal ends of the lattice structure 10. A membrane 2 with a functional layer 4 is provided in a central region of the lattice structure 10. The membrane 2 extends over the entire circumference of the lattice structure 10 and completely covers the cells 13. The membrane 2 is connected to the struts 12 of the lattice structure 10.

[0067] The Figures 4 to 7The functional layer 4 shown has a perforation 14. The perforation 14 is preferably arranged in a pattern across the functional layer 4. In particular, the perforation 14 is located in the area of ​​grid openings or cells 13 of the support structure 1. With regard to the patterned arrangement of the perforation 14, there are commonalities in the embodiments according to Figures 4 to 7In the illustrated embodiments, the density of the perforations 14 is provided for in cells 13 located near the longitudinal end of the functional layer 4, rather than in cells 13 of a central region of the functional layer 4. When positioning the implant in the region of an aneurysm AN, it is essential to ensure that blood flow into the aneurysm AN is interrupted to a certain degree. A local opening of the functional layer 4 in the region of the aneurysm AN is therefore undesirable. Typically, the implant is positioned so that the central region of the implant, particularly the functional layer 4, lies within the region of the aneurysm AN. Because perforations 14 are still present in this region, albeit less densely packed, lateral vessels BV1, BV2, and BV3 branching off from the aneurysm AN can still be adequately supplied with nutrients, as the perforation 14 allows an opening in the functional layer 4.In the peripheral areas of functional layer 4, there is a higher probability that a side vessel BV1, BV2, BV3 will be covered. The perforation 14 provided there has a greater permeability.

[0068] The embodiments 4 to 7 differ in the type of perforation 14 of the functional layer 4. Thus, it shows Figure 4 An embodiment in which the functional layer 4 has a perforation 14 formed by holes 14a. The holes 14a are located essentially in areas of the functional layer 4 that cover the grid openings or cells 13. The number of holes 14a is greater in the cells 13 located at the longitudinal ends of the functional layer 4 than in a central area of ​​the functional layer 4.

[0069] In the embodiment according to Figure 5The perforation 14 is formed by straight slots 14b extending parallel to the longitudinal axis of the grid structure 10. Other orientations of the straight slots 14b are possible. In particular, the straight slots 14b can be arranged at an angle between 0° and 180° with respect to a longitudinal axis of the implant projected into the wall plane of the implant.

[0070] The length of the slots 14b is, in the embodiment according to Figure 5 The slots 14b are adapted to the available space between adjacent webs 12 in the longitudinal direction of the grid structure 10, such that they have different lengths. The spacing of the slots 14b in the circumferential direction of the grid structure 10 also varies, with a smaller spacing in the edge regions of the functional layer 4 than in the central region of the functional layer 4.

[0071] The exemplary embodiment according to Figure 6Figure 1 shows an implant with a functional layer 4 that has a perforation 14 consisting of curved slots 14c. The curved slots 14c extend essentially in the circumferential direction of the lattice structure 10. In the peripheral regions of the functional layer 4, two curved slots 14c are arranged in each cell 13, while in a central region of the functional layer 4, each cell 13 is assigned one curved slot 14c. A different number and distribution of the perforations 14 is possible.

[0072] The curved slots 14c are preferably aligned in the same direction, and in particular in the direction of blood flow. In other words, the implant is oriented according to Figure 6 preferably placed in a blood vessel such that the blood flows from the longitudinal ends of the curved slits 14c to the apex of their curvature. In the illustration according to Figure 6The blood would therefore flow from the left end of lattice structure 10 to the right end of lattice structure 10. The curved slits 14c thus form gill-like openings in functional layer 4.

[0073] In general, for all embodiments in which a perforation 14 is provided, the support layer 3 has a retention function for the opening of the perforation 14. In particular, in the gill-like design of the openings, the perforation opens by deflecting a portion of the functional layer 4. This deflection is limited by the support layer 3, which thus has a retention function for the valve-like opening of the perforation 14. The retention function of the support layer 3 and the perforation 14 of the functional layer 4 are therefore coordinated such that the perforation 14 only opens when a predetermined pressure gradient exists between the inside and outside of the membrane 2.

[0074] Figure 7 Figure 1 shows an embodiment in which the perforation 14 of the functional layer 4 is formed by T-shaped slots 14d. In this embodiment as well, more T-shaped slots 14d per cell 13 are provided in the edge regions of the functional layer 4 than in a central region of the functional layer 4. The T-shaped slots 14d are preferably oriented in the same direction. Each T-shaped slot 14d comprises, in particular, a stem slot 14d' and a bar slot 14d", wherein the stem slot 14d' extends parallel to the longitudinal axis of the lattice structure 10 and the bar slot 14d" extends perpendicular to it. The bar slot 14d" adjoins a distal longitudinal end of the stem slot 14d'. The implant is preferably placed in the blood vessel such that the blood flows from the proximal end of the stem slot 14d' to the bar slot 14d". Reference symbol list

[0075] 1 Support structure 2 Membrane 3 Support layer 4 Functional layer 5 Pore 10 Lattice structure 11 X-ray marker 12 Bridge 13 Cell 14 Perforation 14a Hole 14b Straight slit 14c Curved slit 14d T-shaped slit 14d' Stem slit 14d' Beam slit 30 Embolizing agent AN Aneurysm BV1 First lateral vessel BV2 Second lateral vessel BV3 Third lateral vessel MV Main vessel

Claims

1. A medical implant for the treatment of aneurysms, with a carrier structure (1) which has a compressible and expandable mesh structure (10) produced from mesh elements which delimit mesh openings, wherein the mesh structure (10) is covered, at least in sections, with a membrane (2) which is produced from fibres and which in particular is electrospun and which comprises at least one luminal functional layer (4) and at least one abluminal support layer (3) which respectively have pores, wherein the porosity of the functional layer (4) is smaller than the porosity of the support layer (3), wherein the membrane (2) is configured in a manner such that, as a consequence of a pressure gradient which occurs between a liquid pressure in an inner through channel of the carrier structure (1) and a liquid pressure outside the support layer (3), at least the pores of the functional layer (4) open in order to increase the flow of liquid through the membrane (2).

2. The medical implant as claimed in claim 1, characterized in that the fibres of the membrane (2), in particular of the luminal functional layer (4), are disposed loosely on top of one another at points of intersection, so that intersecting fibres are movable with respect to each other at the points of intersection, and / or in that at least the fibres of the functional layer (4) of the membrane (2) are elastically and / or plastically deformable.

3. The medical implant as claimed in one of the preceding claims, characterized in that the fibres of the functional layer (4) of the membrane (2) have a fibre thickness of less than 500 nm, in particular at most 400 nm, in particular at most 300 nm, in particular at most 200 nm, in particular at most 100 nm, and / or in that the fibres of the support layer (3) of the membrane (2) have a fibre thickness of at least 500 nm, in particular at least 750 nm, in particular at least 1000 nm, in particular at least 1250 nm, in particular at least 1500 nm.

4. The medical implant as claimed in one of the preceding claims, characterized in that the functional layer (4) of the membrane (2) has a thickness of at most, in particular less than, 10 µm, in particular at most 8 µm, in particular at most 6 µm, in particular at most 4 µm, in particular at most 2 µm, and / or in that the support layer (3) of the membrane (2) has a thickness of at least 3 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.

5. The medical implant as claimed in one of the preceding claims, characterized in that the functional layer (4) of the membrane (2) has a porosity of less than 50 %, in particular at most 40 %, in particular at most 30 %, and / or in that the support layer (3) of the membrane (2) has a porosity of at least 50 %, in particular at least 60 %, in particular at least 70 %, in particular at least 80 %, in particular at least 90%.

6. The medical implant as claimed in one of the preceding claims, characterized in that the functional layer (4) of the membrane (2) comprises at least 10 pores which have an inscribed circle diameter of at most 10 µm, in particular at most 8 µm, in particular at most 6 µm, in particular at most 4 µm, in particular at most 2 µm, in particular at most 1 µm, over a surface area of 100000 µm2, and / or in that the support layer (3) of the membrane (2) comprises at least 5 pores which have an inscribed circle diameter of at least, in particular more than, 10 µm, in particular at least 15 µm, in particular at least 20 µm, in particular at least 25 µm, in particular at least 30 µm, in particular at least 40 µm, in particular at least 50 µm, in particular at least 60 µm, over a surface area of 100000 µm2.

7. The medical implant as claimed in one of the preceding claims, characterized in that the thickness of the fibres of the functional layer (4) is smaller than the fibres of the support layer (3), and / or in that the fibres of the functional layer (4) have a higher ductility than the support layer (3).

8. The medical implant as claimed in one of the preceding claims, characterized in that the fibres of the functional layer (4) are formed from a material which has a lower Shore hardness than the material of the fibres of the support layer (3), in particular wherein the material of the fibres of the functional layer (4) has a Shore hardness of at most 90A, in particular at most 80A, in particular at most 70A, in particular at most 60A, in particular at most 50A, and / or the material of the fibres of the support layer (3) has a Shore hardness of at least 90A, in particular at least 100A, in particular at least 60D, in particular at least 70D, in particular at least 80D.

9. The medical implant as claimed in one of the preceding claims, characterized in that the membrane (2), in particular the functional layer (4) and the support layer (3) respectively, comprise or consist of a thermoplastic polyurethane, wherein the membrane (2) preferably extends around the entire circumference of the carrier structure (1).

10. The medical implant as claimed in one of the preceding claims, characterized in that the carrier structure (1) is monolithic in configuration, wherein the mesh elements of the mesh structure (10) form webs (12) which delimit mesh openings of the mesh structure (10) which are formed as cells (13).

11. The medical implant as claimed in one of the preceding claims, characterized in that the carrier structure (1) has interwoven wires, wherein the wires form the mesh elements of the mesh structure (10) and delimit mesh openings of the mesh structure (10) which are formed as loops.

12. The medical implant as claimed in claim 11, characterized in that the membrane (2) has a total layer thickness which is at most 40 %, in particular at most 30 %, in particular at most 20 %, in particular at most 10 % of the height of the mesh elements, in particular the webs (12) or the wires, and / or the height of the mesh elements, in particular the webs (12) or the wires, is preferably a height of between 40 µm and 160 µm, in particular between 40 µm and 150 µm, in particular between 40 µm and 130 µm, in particular between 40 µm and 110 µm, in particular between 40 µm and 100 µm, in particular between 50 µm and 90 µm, in particular between 50 µm and 80 µm, and wherein a ratio between the thickness of the membrane (2) and the height of the mesh elements, in particular the webs (12) or the wires, is preferably at most 1 / 3, in particular at most 1 / 4, in particular at most 1 / 5, in particular at most 1 / 8, in particular at most 1 / 10, in particular at most 1 / 12, in particular at most 1 / 15, in particular at most 1 / 20.

13. The medical implant as claimed in one of the preceding claims, characterized in that the functional layer (4) has a perforation in the region of mesh openings.

14. The medical implant as claimed in claim 13, characterized in that the perforation is formed by holes (14a), straight slits (14b), curved slits (14c) and / or cross-slits.

15. A method for the production of a medical implant as claimed in one of the preceding claims, with the following steps: a. providing the carrier structure (1); b. applying the functional layer (4) to the carrier structure; c. perforating the functional layer (4) by a laser cutting process; and d. applying the support layer (3) to the functional layer (4).