ENDOPROSTHESIS GRAFT AND METHOD OF MANUFACTURING AN ENDOPROSTHESIS GRAFT

Abstract

The present invention relates to an endoprosthesis graft, comprising: a base endoprosthesis having a first and a second longitudinal end, a lumen extending longitudinally through the base endoprosthesis, a coating material provided for covering the base endoprosthesis, the base endoprosthesis having a rough surface that is at least partially penetrated by the coating material to form a positive fit.

Description

ENDOPROSTHESIS GRAFT AND METHOD OF MANUFACTURING AN ENDOPROSTHESIS GRAFT FIELD OF INVENTION The present invention relates to endoprosthesis grafts and methods for manufacturing them. BACKGROUND OF THE INVENTION Endoprosthesis grafts, or covered endoprostheses, are frequently used in medicine for endovascular repairs and a range of other procedures, such as the placement of transjugular intrahepatic portosystemic shunts (TIPS). In contrast to uncovered endoprostheses, which are often used to keep occluded or restricted blood vessels open and have walls that blood can easily penetrate, endoprosthesis grafts are themselves tubular conduits that can, to some extent, replace the blood-conducting function of a blood vessel. A typical endoprosthesis graft consists of three layers. First, the base endoprosthesis, which provides structural integrity to the graft and defines its shape. Such base endoprostheses may be made of self-expanding materials such as nitinol, which expands to a delivery configuration when implanted in the body as it warms to the patient's body temperature. Alternatively, the base endoprosthesis may be balloon-expandable and expand to its final delivery configuration by means of a balloon that is inserted into it and then inflated. In the previous technique, endoprosthesis grafts are often covered inside and out with a coating layer made of a biocompatible lining material (e.g., ePTFE or FEP). This coating material transforms the scaffold provided by the base endoprosthesis into a tubular structure that can serve as a blood conduit. With such stent grafts, a common challenge is improving the graft's flexibility and reducing its delivery profile. Simply put, greater flexibility is advantageous for implanting the stent graft in potentially tortuous vessels. A reduced delivery profile facilitates delivery into narrow blood vessels and helps minimize vessel trauma and patient discomfort. In prior art devices, these two objectives have been achieved either by constructing the outer coating layer not as a single, integral layer, but as a ribbon-like band arranged helically around the outer surface of the base stent, or by reducing the thickness of both layers to some extent, which entails some processing disadvantages.Therefore, since the effective wall thickness of the outer wall is reduced, the endoprosthesis graft is more flexible and has a reduced delivery profile. However, with such endoprosthesis grafts, it is necessary to ensure that the coating material is firmly bonded to the endoprosthesis graft. Furthermore, having a structure where a coating layer is provided both inside and outside the base endoprosthesis can lead to wear, friction, and fatigue at the bond. Increasing the adhesion of the coating material to the base stent is also a general point of concern. It is important to ensure that the coating material is firmly bonded to the base stent. If it is not, the stent graft is not suitable for implantation and needs to be discarded. BRIEF DESCRIPTION OF THE INVENTION The present invention aims to solve or alleviate one or more of the aforementioned problems and, in particular, aims to provide an endoprosthesis graft that improves the adhesion of the coating material to the base endoprosthesis, while also improving flexibility and reducing the delivery profile. The invention also aims to provide a method for manufacturing an endoprosthesis graft that has such advantages. The present invention is defined by claim 1 and claim 7. The embodiments are defined in the dependent claims. According to the invention, the endoprosthesis graft comprises a base endoprosthesis. This base endoprosthesis, which could be a self-expanding or balloon-expandable base endoprosthesis, has a first and a second longitudinal end. A lumen extends longitudinally through the base endoprosthesis between the first and second longitudinal ends, so that, in general, the base endoprosthesis is tubular. A coating material is provided to cover the base stent. This coating material transforms the base stent into a graft capable of conducting blood flow. The coating material is fixed to the base stent so that the base stent and the coating material can be treated as a single mechanical unit. According to the invention, the base endoprosthesis has a rough surface that is at least partially penetrated by the covering material to form a positive fit. That is, there are recesses and / or protrusions formed by the base endoprosthesis material with which the covering material engages and which help to secure the covering material to the base endoprosthesis. Having a rough surface thus leads to better adhesion of the covering material to the base endoprosthesis. By a rough surface, it is understood that the surface is not smooth and is therefore structured, with the structure being formed to allow the covering material to penetrate it. The rough surface can be provided on all parts of the base endoprosthesis, i.e., on both the struts and the connectors. In some models, the coating material is provided only on the inside of the base stent, without covering the outside. Although it cannot be ruled out that small amounts of the coating material may be pushed onto the outside of the base stent during production, the outside of the base stent remains largely uncovered. This arrangement, where the coating material is provided only on the inside of the base stent, improves both the flexibility of the stent graft and its delivery profile. This is because the cross-sectional area of ​​the stent graft is reduced, increasing flexibility (due to lower flexural rigidity), and the reduced cross-section also improves the delivery profile. czc / nn / eznz / e / Yi Similarly, in other configurations, the coating material is applied only to the exterior of the base stent, without covering the interior. Again, while it cannot be ruled out that small amounts of the coating material may be pushed into the stent during manufacturing, the interior remains largely uncovered. This configuration improves flexibility and the delivery profile. Furthermore, compared to the configuration where the coating material is applied only to the interior of the base stent, this type of stent graft is easier to fabricate, as it is generally simpler to create the microcavities for coating material adhesion on the exterior of the base stent rather than the interior.For example, it is easier to clean a base endoprosthesis from the outside, rather than the inside, to create those microcavities, and the same applies to other ways of creating them, such as using a laser (which is easier to irradiate on the outer surface of the base endoprosthesis). In some models, the coating material forms a tube that, in some models, extends the entire length of the base stent. Because the tube extends the entire length of the base stent, no part of the base stent is left exposed. That is, there are no exposed portions of the base stent that could interfere with blood flow. Consequently, the usable length of the base stent is maximized. In some models, the surface has been roughened by sandblasting. Such a rough surface is particularly advantageous when it comes to adhering the base endoprosthesis. This method is also relatively easy to implement. In some models, the rough surface contains microcavities. These microcavities are particularly beneficial for adhering the veneering material. Such microcavities can be understood as pores or holes in the surface with a length significantly smaller than the thickness of the components they cover. For example, the length (diameter) of these irregularities could be less than 50% of the thickness, preferably less than 20%. In some models, these microcavities are blind holes. With blind holes, the veneering material does not have to penetrate the entire base prosthesis, thus preventing weakening of the veneering material in areas where it flows into the base prosthesis (since the amount of veneering material flowing into the holes is limited). In some modalities, the endoprosthesis graft comprises holes that penetrate the entirety of the base endoprosthesis material. These penetration holes, extending from the inside of the base endoprosthesis to the outside, allow the covering material to fully penetrate the base endoprosthesis and reach the other surface. This leads to particularly strong adhesion of the covering material to the base endoprosthesis due to the material flowing through these holes, producing a rivet effect. Such penetration holes can also be combined with blind holes (i.e., some of the holes in the base endoprosthesis could be blind holes, while others are penetration holes). czc / nn / eznz / e / Yi In another aspect of the invention, a method for manufacturing an endoprosthesis graft is provided. According to this method, a base endoprosthesis is provided having first and second longitudinal ends and a lumen extending longitudinally through it. The endoprosthesis has a rough surface facing the lumen. Subsequently, a tubular liner material is placed on the endoprosthesis. It can be slid into the endoprosthesis, or it could be slid over it so that the liner material aligns with the internal lumen of the base endoprosthesis or, at least in theory, also with the periphery of the base endoprosthesis. The tubular liner material is then made to penetrate, at least partially, the roughened surface to form a positive fit by anchoring the liner material to the base endoprosthesis. To achieve this penetration, pressure is applied to the liner material to push it into the microcavities. For example, a tape can be tightly wrapped around the liner material to apply pressure, or an inflatable balloon can be inserted into the lumen of the base endoprosthesis and then expanded in that position.If the coating material softens when heated, it is generally advisable to heat it beyond its softening temperature. For a coating material such as ePTFE, a temperature of approximately 335 °C, slightly above its melting point of 327 °C, has proven effective. This method yields an endoprosthesis graft with improved adhesion of the coating material to the base endoprosthesis. Applying the coating material only to the inside or outside of the base endoprosthesis also improves the delivery profile and flexibility of the fabricated endoprosthesis graft. In some modalities, the endoprosthesis base involves intentionally roughening the surface facing the lumen. That is, a previously smooth endoprosthesis is roughened. This can improve adhesion, as a surface roughening method can be chosen that leads to better penetration of the lining material. It is worth noting that the roughening stage can also be used on a prefabricated, already roughened endoprosthesis base, so it does not imply that the surface of the endoprosthesis base before roughening is smooth. In some models, the roughness stage comprises one or more micro-grinding stages, pressure shaping and / or sandblasting of the surface facing the lumen. These stages result in a particularly good surface roughness. In some methods, the roughening stage involves applying a laser to the surface to be roughened. This laser roughens the surface in a highly controlled manner. Because a good degree of control can be exercised over how the surface is roughened, the resulting adhesion properties can be precisely adjusted. In some versions, the rough surface includes blind holes into which the coating material penetrates at least partially. These blind holes limit the amount of coating material that can penetrate them. This prevents undue weakening of the coating material in those holes. czc / nn / eznz / e / Yi In some models, the roughened surface comprises holes that penetrate the entire material of the base endoprosthesis, from the luminal side to the abluminal side. As mentioned previously, adhesion is improved with this configuration. BRIEF DESCRIPTION OF THE FIGURES Figure 1 shows an endoprosthesis graft according to one embodiment of the invention. Figure 2 shows a method for manufacturing an endoprosthesis graft according to one embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION Figure 1 shows, in a perspective view, an endoprosthesis graft according to one embodiment of the invention. An endoprosthesis graft 10 is provided comprising a base endoprosthesis 12 having three rings 13 made of zigzag struts 15. These rings 13 are connected by means of connectors 17. Inside the base endoprosthesis 12, an inner cover 14 is provided that lines the lumen 16 of the endoprosthesis graft 10. As can be seen in the figure, the base endoprosthesis 12 further comprises through-holes 18 arranged so as to extend radially from a luminal surface of the base endoprosthesis 12 to an abluminal surface of the base endoprosthesis 12 and penetrated at least partially by the cover material 14. The cover material, which could be PTFE, flows into these holes during sintering and, as a result, creates adhesion and mechanical grip between the endoprosthesis graft 12 and the cover material 14. The through-holes 18 are provided in both the connectors 17 and the struts 15 of the rings 13. Figure 2 shows in a flowchart one way to produce the graft endoprosthesis 10 shown in Figure 1. In stage S10, a base 12 endoprosthesis is provided. Subsequently, in stage S12, this base 12 endoprosthesis is roughened. This roughness could be achieved using micro-grinding, which provides a higher surface roughness than pre-polished base endoprostheses (the standard surface treatment for such endoprostheses). Alternatively, using a porous nitinol material before cutting the endoprosthesis could be an option. Other methods include sandblasting the surface of the base endoprosthesis or using other mechanical surface treatment techniques, such as pressing. Alternatively, laser microcavities could be created, or a laser could be used to produce blind holes. Through-holes 18, which completely cut through the base 12 endoprosthesis from the luminal to the abluminal side, as shown in Figure 1, could also be created.In the case of using micro-rectification and using a porous nititinol material, steps S10 and S12 can be a single step, so that a separate roughness step is not needed beyond providing a sufficiently porous base endoprosthesis 12. In a subsequent stage S14 of coating material placement 14, the coating material 14 is placed on the base endoprosthesis. It may be placed in the lumen 16 of the base endoprosthesis 12 or it may be placed to surround the base endoprosthesis. czc / nn / eznz / e / Yi Finally, through a sintering process similar to that used in the prior art, the coating material 14 is bonded to the base endoprosthesis 12 (step S16). In this step, in some modalities, sufficiently high pressure could be used to force the coating material 14, such as PTFE, to flow into the roughened surface and, if present, the holes in the surface of the base endoprosthesis to increase the adhesion of the coating material 14. This improves mechanical fixation and, in the case of through-holes, can lead to the lining material flowing through these through-holes 18 to the opposite surface, thus resulting in particularly strong mechanical fixation of the lining material to that of the base endoprosthesis. The bonding stage is otherwise similar to the bonding stage 10 performed during the manufacturing processes of endoprosthesis grafts using the prior technique.

Claims

1. An endoprosthesis graft, characterized in that it comprises: - a base endoprosthesis (12) having a first and a second longitudinal end, a lumen (16) extending longitudinally through the base endoprosthesis (12), - a coating material (14) provided to coat the base endoprosthesis (12), the base endoprosthesis (12) having a rough surface that is at least partially penetrated by the coating material (14) to form a positive fit, wherein the surface comprises microcavities that are blind holes.

2. The endoprosthesis graft according to claim 1, further characterized in that the covering material (14) is provided inside the base endoprosthesis (12) without covering the outside of the base endoprosthesis (12).

3. The endoprosthesis graft according to claim 1, further characterized in that the covering material (14) is provided on the outside of the base endoprosthesis (12) without covering the inside of the base endoprosthesis (12).

4. The endoprosthesis graft according to one of the preceding claims, further characterized in that the covering material (14) forms a tube that extends along the entire length of the base endoprosthesis (12).

5. The endoprosthesis graft according to one of the preceding claims, further characterized in that the rough surface has been roughened by sandblasting.

6. The endoprosthesis graft according to one of the preceding claims, further characterized in that the endoprosthesis graft comprises holes (18) penetrating through the base endoprosthesis (12).

7. The method of manufacturing an endoprosthesis graft, characterized in that it comprises: - providing a base endoprosthesis (12), the base endoprosthesis (12) having a first and a second longitudinal end and a lumen (16) extending longitudinally therethrough, the base endoprosthesis (12) having a rough surface oriented towards the lumen (16), wherein the rough surface comprises microcavities that are blind holes, - disposing of a tubular covering material (14) within the base endoprosthesis (12) and causing it to penetrate at least partially into the rough surface to form a positive fit.

8. The method according to claim 7, further characterized in that the step of providing a base endoprosthesis (12) comprises roughening the surface to be penetrated by the coating material (14).

9. The method according to claim 8, further characterized in that the roughening step comprises micro-rectification, pressing and / or sandblasting of the surface to be roughened.

10. The method according to claim 8 or 9, further characterized in that the roughening step comprises applying a laser to the surface to be roughened. czc / nn / eznz / e / Yi 11. The method according to one of claims 7 to 10, further characterized in that the rough surface comprises through holes (18) penetrating through the base endoprosthesis (12).

Images